EyeLink Clinical and Oculomotor Eye-Tracking Publications
EyeLink clinical and oculomotor research publications up until 2023 (with some early 2024s) are listed below by year. You can search the publications using keywords such as Saccadic Adaptation, Schizophrenia, Nystagmus, etc. You can also search for individual author names, and limit searches by year (choose the year then click the search button). If we missed any EyeLink clinical or oculomotor articles, please email us!
2016 |
Markku Kilpeläinen; Jan Theeuwes Efficient avoidance of the penalty zone in human eye movements Journal Article In: PLoS ONE, vol. 11, no. 12, pp. e0167956, 2016. @article{Kilpelaeinen2016, People use eye movements extremely effectively to find objects of interest in a cluttered visual scene. Distracting, task-irrelevant attention capturing regions in the visual field should be avoided as they jeopardize the efficiency of search. In the current study, we used eye tracking to determine whether people are able to avoid making saccades to a predetermined visual area associated with a financial penalty, while making fast and accurate saccades towards stimuli placed near the penalty area. We found that in comparison to the same task without a penalty area, the introduction of a penalty area immediately affected eye movement behaviour: the proportion of saccades to the penalty area was immediately reduced. Also, saccadic latencies increased, but quite modestly, and mainly for saccades towards stimuli near the penalty area. We conclude that eye movement behaviour is under efficient cognitive control and thus quite flexible: it can immediately be adapted to changing environ- mental conditions to improve reward outcome. |
Tomas Knapen; Jascha D. Swisher; Frank Tong; Patrick Cavanagh Oculomotor remapping of visual information to foveal retinotopic cortex Journal Article In: Frontiers in Systems Neuroscience, vol. 10, pp. 54, 2016. @article{Knapen2016a, Our eyes continually jump around the visual scene to bring the high-resolution, central part of our vision onto objects of interest. We are oblivious to these abrupt shifts, perceiving the visual world to appear reassuringly stable. A process called remapping has been proposed to mediate this perceptual stability for attended objects by shifting their retinotopic representation to compensate for the effects of the upcoming eye movement. In everyday vision, observers make goal-directed eye movements towards items of interest bringing them to the fovea and, for these items, the remapped activity should impinge on foveal regions of the retinotopic maps in visual cortex. Previous research has focused instead on remapping for targets that were not saccade goals, where activity is remapped to a new peripheral location rather than to the foveal representation. We used functional MRI and a phase-encoding design to investigate remapping of spatial patterns of activity towards the fovea/parafovea for saccade targets that were removed prior to completion of the eye movement. We found strong evidence of foveal remapping in retinotopic visual areas, which failed to occur when observers merely attended to the same peripheral target without making eye movements toward it. Significantly, the spatial profile of the remapped response matched the orientation and size of the saccade target, and was appropriately scaled to reflect the retinal extent of the stimulus had it been foveated. We conclude that this remapping of spatially structured information to the fovea may serve as an important mechanism to support our world-centered sense of location across goal-directed eye movements under natural viewing conditions. |
Rebecca M. Krock; Tirin Moore Visual sensitivity of frontal eye field neurons during the preparation of saccadic eye movements Journal Article In: Journal of Neurophysiology, vol. 116, no. 6, pp. 2882–2891, 2016. @article{Krock2016, Primate vision is continuously disrupted by saccadic eye movements, and yet this disruption goes unperceived. One mechanism thought to reduce perception of this self-generated movement is saccadic suppression, a global loss of visual sensitivity just before, during, and after saccadic eye movements. The frontal eye field (FEF) is a candidate source of neural correlates of saccadic suppression previously observed in visual cortex, because it contributes to the generation of visually guided saccades and modulates visual cortical responses. However, whether the FEF exhibits a perisaccadic reduction in visual sensitivity that could be transmitted to visual cortex is unknown. To determine whether the FEF exhibits a signature of saccadic suppression, we recorded the visual responses of FEF neurons to brief, full-field visual probe stimuli presented during fixation and before onset of saccades directed away from the receptive field in rhesus macaques (Macaca mulatta). We measured visual sensitivity during both epochs and found that it declines before saccade onset. Visual sensitivity was significantly reduced in visual but not visuomotor neurons. This reduced sensitivity was also present in visual neurons with no movement-related modulation during visually guided saccades and thus occurred independently from movement-related activity. Across the population of visual neurons, sensitivity began declining similar to 80 ms before saccade onset. We also observed a similar presaccadic reduction in sensitivity to isoluminant, chromatic stimuli. Our results demonstrate that the signaling of visual information by FEF neurons is reduced during saccade preparation, and thus these neurons exhibit a signature of saccadic suppression. |
Hannah M. Krüger; Thérèse Collins; Bernhard Englitz; Patrick Cavanagh Saccades create similar mislocalizations in visual and auditory space Journal Article In: Journal of Neurophysiology, vol. 115, no. 4, pp. 2237–2245, 2016. @article{Krueger2016, Orienting our eyes to a light, a sound, or a touch occurs effortlessly, despite the fact that sound and touch have to be converted from head- and body-based coordinates to eye-based coordinates to do so. We asked whether the oculomotor representation is also used for localization of sounds even when there is no saccade to the sound source. To address this, we examined whether saccades introduced similar errors of localization judgments for both visual and auditory stimuli. Sixteen subjects indicated the direction of a visual or auditory apparent motion seen or heard between two targets presented either during fixation or straddling a saccade. Compared with the fixation baseline, saccades introduced errors in direction judgments for both visual and auditory stimuli: in both cases, apparent motion judgments were biased in direction of the saccade. These saccade-induced effects across modalities give rise to the possibility of shared, cross-modal location coding for perception and action. |
Kaitlin E. W. Laidlaw; Mona J. H. Zhu; Alan Kingstone Looking away: Distractor influences on saccadic trajectory and endpoint in prosaccade and antisaccade tasks Journal Article In: Experimental Brain Research, vol. 234, no. 6, pp. 1637–1648, 2016. @article{Laidlaw2016, Successful target selection often occurs concurrently with distractor inhibition. A better understanding of the former thus requires a thorough study of the competition that arises between target and distractor representations. In the present study, we explore whether the presence of a distractor influences saccade processing via interfering with visual target and/or saccade goal representations. To do this, we asked participants to make either pro- or antisaccade eye movements to a target and measured the change in their saccade trajectory and landing position (collectively referred to as deviation) in response to distractors placed near or far from the saccade goal. The use of an antisaccade paradigm may help to distinguish between stimulus- and goal-related distractor interference, as unlike with prosaccades, these two features are dissociated in space when making a goal-directed antisaccade response away from a visual target stimulus. The present results demonstrate that for both pro- and antisaccades, distractors near the saccade goal elicited the strongest competition, as indicated by greater saccade trajectory deviation and landing position error. Though distractors far from the saccade goal elicited, on average, greater deviation away in antisaccades than in prosaccades, a time-course analysis revealed a significant effect of far-from-goal distractors in prosaccades as well. Considered together, the present findings support the view that goal-related representations most strongly influence the saccade metrics tested, though stimulus-related representations may play a smaller role in determining distractor-based interference effects on saccade execution under certain circumstances. Further, the results highlight the advantage of considering temporal changes in distractor-based interference. |
Caroline Landelle; Anna Montagnini; Laurent Madelain; Frederic R. Danion Eye tracking a self-moved target with complex hand-target dynamics Journal Article In: Journal of Neurophysiology, vol. 116, no. 4, pp. 1859–1870, 2016. @article{Landelle2016, Previous work has shown that the ability to track with the eye a moving target is substantially improved when the target is self-moved by the subject's hand compared with when being externally moved. Here, we explored a situation in which the mapping between hand movement and target motion was perturbed by simulating an elastic relationship between the hand and target. Our objective was to determine whether the predictive mechanisms driving eye-hand coordination could be updated to accommodate this complex hand-target dynamics. To fully appreciate the behavioral effects of this perturbation, we compared eye tracking performance when self-moving a target with a rigid mapping (simple) and a spring mapping as well as when the subject tracked target trajectories that he/she had previously generated when using the rigid or spring mapping. Concerning the rigid mapping, our results confirmed that smooth pursuit was more accurate when the target was self-moved than externally moved. In contrast, with the spring map- ping, eye tracking had initially similar low spatial accuracy (though shorter temporal lag) in the self versus externally moved conditions. However, within ⬃5 min of practice, smooth pursuit improved in the self-moved spring condition, up to a level similar to the self-moved rigid condition. Subsequently, when the mapping unexpectedly switched from spring to rigid, the eye initially followed the expected target trajectory and not the real one, thereby suggesting that subjects used an internal representation of the new hand-target dynamics. Overall, these results emphasize the stunning adaptability of smooth pursuit when self-maneuvering objects with complex dynamics. |
Christelle Lemoine-Lardennois; Nadia Alahyane; Coline Tailhefer; Thérèse Collins; Jacqueline Fagard; Karine Doré-Mazars Saccadic adaptation in 10–41 month-old children Journal Article In: Frontiers in Human Neuroscience, vol. 10, pp. 241, 2016. @article{LemoineLardennois2016, When saccade amplitude becomes systematically inaccurate, adaptation mechanisms gradually decrease or increase it until accurate saccade targeting is recovered. Adaptive shortening and adaptive lengthening of saccade amplitude rely on separate mechanisms in adults. When these adaptation mechanisms emerge during development is poorly known except that adaptive shortening processes are functional in children above 8 years of age. Yet, saccades in infants are consistently inaccurate (hypometric) as if adaptation mechanisms were not fully functional in early childhood. Here, we tested reactive saccade adaptation in 10–41 month-old children compared to a group of 20–30 year-old adults. A visual target representing a cartoon character appeared at successive and unpredictable locations 10◦ apart on a computer screen. During the eye movement toward the target, it systematically stepped in the direction opposite to the saccade to induce an adaptive shortening of saccade amplitude (Experiment 1). In Experiment 2, the target stepped in the same direction as the ongoing saccade to induce an adaptive lengthening of saccade amplitude. In both backward and forward adaptation experiments, saccade adaptation was compared to a control condition where there was no intrasaccadic target step. Analysis of baseline performance revealed both longer saccade reaction times and hypometric saccades in children compared to adults. In both experiments, children on average showed gradual changes in saccade amplitude consistent with the systematic intrasaccadic target steps. Moreover, the amount of amplitude change was similar between children and adults for both backward and forward adaptation. Finally, adaptation abilities in our child group were not related to age. Overall the results suggest that the neural mechanisms underlying reactive saccade adaptation are in place early during development. |
Delphine Lévy-Bencheton; Aarlenne Zein Khan; Denis Pélisson; Caroline Tilikete; Laure Pisella Adaptation of saccadic sequences with and without remapping Journal Article In: Frontiers in Human Neuroscience, vol. 10, pp. 359, 2016. @article{LevyBencheton2016, It is relatively easy to adapt visually-guided saccades because the visual vector and the saccade vector match. The retinal error at the saccade landing position is compared to the prediction error, based on target location and efference copy. If these errors do not match, planning processes at the level(s) of the visual and/or motor vector processing are assumed to be inaccurate and the saccadic response is adjusted. In the case of a sequence of two saccades, the final error can be attributed to the last saccade vector or to the entire saccadic displacement. Here, we asked whether and how adaptation can occur in the case of remapped saccades, such as during the classic double-step saccade paradigm, where the visual and motor vectors of the second saccade do not coincide and so the attribution of error is ambiguous. Participants performed saccades sequences to two targets briefly presented prior to first saccade onset. The second saccade target was either briefly re-illuminated (sequential visually-guided task) or not (remapping task) upon first saccade offset. To drive adaptation, the second target was presented at a displaced location (backward or forward jump condition or control-no jump) at the end of the second saccade. Pre- and post-adaptation trials were identical, without the re-appearance of the target after the second saccade. For the 1st saccade endpoints, there was no change as a function of adaptation. For the 2nd saccade, there was a similar increase in gain in the forward jump condition (52% and 61% of target jump) in the two tasks, whereas the gain decrease in the backward condition was much smaller for the remapping task than for the sequential visually-guided task (41% vs. 94%). In other words, the absolute gain change was similar between backward and forward adaptation for remapped saccades. In conclusion, we show that remapped saccades can be adapted, suggesting that the error is attributed to the visuo-motor transformation of the remapped visual vector. The mechanisms by which adaptation takes place for remapped saccades may be similar to those of forward sequential visually-guided saccades, unlike those involved in adaptation for backward sequential visually-guided saccades. |
Nathaniel Lizak; Meaghan Clough; Lynette Millist; Tomas Kalincik; Owen B. White; Joanne Fielding Impairment of smooth pursuit as a marker of early multiple sclerosis Journal Article In: Frontiers in Neurology, vol. 7, pp. 206, 2016. @article{Lizak2016, Background: Multiple sclerosis (MS) is a diffuse disease that disrupts wide-ranging cerebral networks. The control of saccades and smooth pursuit are similarly dependent upon widespread networks, with the assessment of pursuit offering an opportunity to examine feedback regulation. We sought to characterize pursuit deficits in MS and to examine their relationship with disease duration. Methods: 20 healthy controls, 20 patients with a clinically isolated syndrome (CIS), and 40 patients with clinically definite MS (CDMS) participated. 36 trials of Rashbass' step-ramp paradigm of smooth pursuit, evenly split by velocity (8.65°/s, 17.1°/s, and 25.9°/s) and ramp direction (left/right), were performed. Four parameters were measured: latency of pursuit onset, closed-loop pursuit gain, number of saccades, and summed saccade amplitudes during pursuit. For CDMS patients, these were correlated with disease duration and Expanded Disability Status Scale (EDSS) score. Results: Closed-loop pursuit gain was significantly lower in CIS than controls at all speeds. CDMS gain was lower than controls at medium pursuit velocity. CDMS patients also displayed longer pursuit latency than controls at all velocities. All patients accumulated increased summed saccade amplitudes at slow and medium pursuit speeds, and infrequent high-amplitude saccades at the fast speed. No pursuit variable significantly correlated with EDSS or disease duration in CDMS patients. Conclusions: Smooth pursuit is significantly compromised in MS from onset. Low pursuit gain and increased saccadic amplitudes may be robust markers of disseminated pathology in CIS and in more advanced MS. Pursuit may be useful in measuring early disease. |
Guido Maiello; William J. Harrison; Peter J. Bex Monocular and binocular contributions to oculomotor plasticity Journal Article In: Scientific Reports, vol. 6, pp. 31861, 2016. @article{Maiello2016, Most eye movements in the real-world redirect the foveae to objects at a new depth and thus require the co-ordination of monocular saccade amplitudes and binocular vergence eye movements. Additionally to maintain the accuracy of these oculomotor control processes across the lifespan, ongoing calibration is required to compensate for errors in foveal landing positions. Such oculomotor plasticity has generally been studied under conditions in which both eyes receive a common error signal, which cannot resolve the long-standing debate regarding whether both eyes are innervated by a common cortical signal or by a separate signal for each eye. Here we examine oculomotor plasticity when error signals are independently manipulated in each eye, which can occur naturally owing to aging changes in each eye's orbit and extra-ocular muscles, or in oculomotor dysfunctions. We find that both rapid saccades and slow vergence eye movements are continuously recalibrated independently of one another and corrections can occur in opposite directions in each eye. Whereas existing models assume a single cortical representation of space employed for the control of both eyes, our findings provide evidence for independent monoculomotor and binoculomotor plasticities and dissociable spatial mapping for each eye. |
Maria Matziridi; Eli Brenner; Jeroen B. J. Smeets Moving your head reduces perisaccadic compression Journal Article In: Journal of Vision, vol. 16, no. 13, pp. 1–8, 2016. @article{Matziridi2016, Flashes presented around the time of a saccade appear to be closer to the saccade endpoint than they really are. The resulting compression of perceived positions has been found to increase with the amplitude of the saccade. In most studies on perisaccadic compression the head is static, so the eye-in-head movement is equal to the change in gaze. What if moving the head causes part of the change in gaze? Does decreasing the eye-in-head rotation by moving the head decrease the compression of perceived positions? To find out, we asked participants to shift their gaze between two positions, either without moving their head or with the head contributing to the change in gaze. Around the time of the saccades we flashed bars that participants had to localize. When the head contributed to the change in gaze, the duration of the saccade was shorter and compression was reduced. We interpret this reduction in compression as being caused by a reduction in uncertainty about gaze position at the time of the flash. We conclude that moving one's head can reduce the systematic mislocalization of flashes presented around the time of saccades. |
Brónagh McCoy; Jan Theeuwes Effects of reward on oculomotor control Journal Article In: Journal of Neurophysiology, vol. 116, no. 5, pp. 2453–2466, 2016. @article{McCoy2016, The present study examines the extent to which distractors that signal the availability of monetary reward on a given trial affect eye movements. We used a novel eye movement task in which observers had to follow a target around the screen while ignoring distractors presented at varying locations. We examined the effects of reward magnitude and distractor location on a host of oculomotor properties, including saccade latency, amplitude, landing position, curvature, and erroneous saccades toward the distractor. We found consistent effects of reward magnitude on classic oculomotor phenomena such as the remote distractor effect, the global effect, and oculomotor capture by the distractor. We also show that a distractor in the visual hemifield opposite to the target had a larger effect on oculomotor control than an equidistant distractor in the same hemifield as the target. Bayesian hierarchical drift diffusion modeling revealed large differences in drift rate depending on the reward value, location, and visual hemifield of the distractor stimulus. Our findings suggest that high reward distractors not only capture the eyes but also affect a multitude of oculomotor properties associated with oculomotor inhibition and control. |
Eugene McSorley; Rachel McCloy; Louis Williams The concurrent programming of saccades Journal Article In: PLoS ONE, vol. 11, no. 12, pp. e0168724, 2016. @article{McSorley2016, Sequences of saccades have been shown to be prepared concurrently however it remains unclear exactly what aspects of those saccades are programmed in parallel. To examine this participants were asked to make one or two target-driven saccades: a reflexive sac- cade; a voluntary saccade; a reflexive then a voluntary saccade; or vice versa. During the first response the position of a second target was manipulated. The new location of the sec- ond saccade target was found to impact on second saccade latencies and second saccade accuracy showing that some aspects of the second saccade program are prepared in paral- lel with the first. However, differences were found in the specific pattern of effects for each sequence type. These differences fit well within a general framework for saccade control in which a common priority map for saccade control is computed and the influence of saccade programs on one another depends not so much on the types of saccade being produced but rather on the rate at which their programs develop. |
Annegret Meermeier; Svenja Gremmler; Markus Lappe The influence of image content on oculomotor plasticity Journal Article In: Journal of Vision, vol. 16, no. 8, pp. 1–12, 2016. @article{Meermeier2016, When we observe a scene, we shift our gaze to different points of interest via saccadic eye movements. Saccades provide high resolution views of objects and are essential for vision. The successful view of an interesting target might constitute a rewarding experience to the oculomotor system. We measured the influence of image content on learning efficiency in saccade control. We compared meaningful pictures to luminance and spatial frequency-matched random noise images in a saccadic adaptation paradigm. In this paradigm a shift of the target during the saccades results in a gradual increase of saccade amplitude. Stimuli were masked at different times after saccade onset. For immediate masking of the stimuli, as well as for their permanent visibility, saccadic adaptation was similar for both types of targets. However, when stimuli were masked 200 ms after saccade onset, adaptation of saccades directed toward the meaningful target stimuli was significantly greater than that of saccades directed toward noise targets. Thus, the percept of a meaningful image at the saccade landing position facilitates learning of the appropriate parameters for saccadic motor control when time constraints exist. We conclude that oculomotor learning, which is traditionally considered a low-level and highly automatized process, is modulated by the visual content of the image. |
Muriel T. N. Panouillères; Valérie Gaveau; Jeremy Debatisse; Patricia Jacquin; Marie LeBlond; Denis Pélisson Oculomotor adaptation elicited by intra-saccadic visual stimulation: Time-course of efficient visual target perturbation Journal Article In: Frontiers in Human Neuroscience, vol. 10, pp. 91, 2016. @article{Panouilleres2016, Perception of our visual environment strongly depends on saccadic eye movements, which in turn are calibrated by saccadic adaptation mechanisms elicited by systematic movement errors. Current models of saccadic adaptation assume that visual error signals are acquired only after saccade completion, because the high speed of saccade execution disturbs visual processing (saccadic “suppression” and “mislocalization”). Complementing a previous study from our group, here we report that visual information presented during saccades can drive adaptation mechanisms and we further determine the critical time window of such error processing. In 15 healthy volunteers, shortening adaptation of reactive saccades toward a ±8° visual target was induced by flashing the target for 2 msec less eccentrically than its initial location either near saccade peak velocity (‘PV' condition) or peak deceleration (‘PD') or saccade termination (‘END'). Results showed that, as compared to the ‘CONTROL' condition (target flashed at its initial location upon saccade termination), saccade amplitude decreased all throughout the ‘PD' and ‘END' conditions, reaching significant levels in the second adaptation and post- adaptation blocks. The results of 9 other subjects tested in a saccade lengthening adaptation paradigm with the target flashing near peak deceleration (‘PD' and ‘CONTROL' conditions) revealed no significant change of gain, confirming that saccade shortening adaptation is easier to elicit. Also, together with this last result, the stable gain observed in the ‘CONTROL' conditions of both experiments suggests that mislocalization of the target flash is not responsible for the saccade shortening adaptation demonstrated in the first group. Altogether, these findings reveal that the visual “suppression” and “mislocalization” phenomena related to saccade execution do not prevent brief visual information delivered ‘in-flight' from being processed to elicit oculomotor adaptation. |
Jeroen Atsma; Femke Maij; Mathieu Koppen; David E. Irwin; W. Pieter Medendorp Causal inference for spatial constancy across saccades Journal Article In: PLoS Computational Biology, vol. 12, no. 3, pp. e1004766, 2016. @article{Atsma2016, Our ability to interact with the environment hinges on creating a stable visual world despite the continuous changes in retinal input. To achieve visual stability, the brain must distinguish the retinal image shifts caused by eye movements and shifts due to movements of the visual scene. This process appears not to be flawless: during saccades, we often fail to detect whether visual objects remain stable or move, which is called saccadic suppression of displacement (SSD). How does the brain evaluate the memorized information of the presaccadic scene and the actual visual feedback of the postsaccadic visual scene in the computations for visual stability? Using a SSD task, we test how participants localize the presaccadic position of the fixation target, the saccade target or a peripheral non-foveated target that was displaced parallel or orthogonal during a horizontal saccade, and subsequently viewed for three different durations. Results showed different localization errors of the three targets, depending on the viewing time of the postsaccadic stimulus and its spatial separation from the presaccadic location. We modeled the data through a Bayesian causal inference mechanism, in which at the trial level an optimal mixing of two possible strategies, integration vs. separation of the presaccadic memory and the postsaccadic sensory signals, is applied. Fits of this model generally outperformed other plausible decision strategies for producing SSD. Our findings suggest that humans exploit a Bayesian inference process with two causal structures to mediate visual stability. |
Pablo A. Barrionuevo; Dingcai Cao Luminance and chromatic signals interact differently with melanopsin activation to control the pupil light response Journal Article In: Journal of Vision, vol. 16, no. 11, pp. 29, 2016. @article{Barrionuevo2016, Intrinsically photosensitive retinal ganglion cells (ipRGCs) express the photopigment melanopsin. These cells receive afferent inputs from rods and cones, which provide inputs to the postreceptoral visual pathways. It is unknown, however, how melanopsin activation is integrated with postreceptoral signals to control the pupillary light reflex. This study reports human flicker pupillary responses measured using stimuli generated with a five-primary photostimulator that selectively modulated melanopsin, rod, S-, M-, and L-cone excitations in isolation, or in combination to produce postreceptoral signals. We first analyzed the light adaptation behavior of melanopsin activation and rod and cones signals. Second, we determined how melanopsin is integrated with postreceptoral signals by testing with cone luminance, chromatic blue-yellow, and chromatic red-green stimuli that were processed by magnocellular (MC), koniocellular (KC), and parvocellular (PC) pathways, respectively. A combined rod and melanopsin response was also measured. The relative phase of the postreceptoral signals was varied with respect to the melanopsin phase. The results showed that light adaptation behavior for all conditions was weaker than typical Weber adaptation. Melanopsin activation combined linearly with luminance, S-cone, and rod inputs, suggesting the locus of integration with MC and KC signals was retinal. The melanopsin contribution to phasic pupil responses was lower than luminance contributions, but much higher than S-cone contributions. Chromatic red-green modulation interacted with melanopsin activation nonlinearly as described by a "winner-takes-all" process, suggesting the integration with PC signals might be mediated by a postretinal site. |
Alessandro Benedetto; Paola Binda Dissociable saccadic suppression of pupillary and perceptual responses to light Journal Article In: Journal of Neurophysiology, vol. 115, no. 3, pp. 1243–1251, 2016. @article{Benedetto2016, We measured pupillary constrictions in response to full-screen flashes of variable luminance, occurring either at the onset of a saccadic eye movement or well before/after it. A large fraction of perisaccadic flashes were undetectable to the subjects, consistent with saccadic suppression of visual sensitivity. Likewise, pupillary responses to perisaccadic flashes were strongly suppressed. However, the two phenomena appear to be dissociable. Across subjects and luminance levels of the flash stimulus, there were cases in which conscious perception of the flash was completely depleted yet the pupillary response was clearly present, as well as cases in which the opposite occurred. On one hand, the fact that pupillary light responses are subject to saccadic suppression reinforces evidence that this is not a simple reflex but depends on the integration of retinal illumination with complex "extraretinal" cues. On the other hand, the relative independence of pupillary and perceptual responses suggests that suppression acts separately on these systems-consistent with the idea of multiple visual pathways that are differentially affected by saccades. |
Brittany Benjamin; Christopher Macomb; Alisha Martin; Aaron L. Cecala Can color act as a contextual cue in human saccadic adaptation? Journal Article In: Bios, vol. 87, no. 1, pp. 9–20, 2016. @article{Benjamin2016, When the head does not move, rapid movements of the eyes called saccades are used to redirect the line of sight. Saccades are defined by a series of metrical and kinematic (evolution of a movement as a function of time) relationships. For example, the amplitude of a saccade made from one visual target to another is roughly 90% of the distance between the initial fixation point (T0) and the peripheral target (T1). However, this stereotypical relationship between saccade amplitude and initial retinal error (jT1-Initial Eye Positionj) may be altered, either increased or decreased, by surreptitiously displacing a visual target during an ongoing saccade. This form of saccadic adaptation has been described in both humans and monkeys. We investigated the effects of a contextual cue (target color) on the magnitude of human saccadic adaptation using an eye tracker to measure our subjects' eye position. Our results indicate that target color cannot be used by the eye movement control system to elicit differential changes in motor output regardless of whether the color cues are randomly intermixed or presented sequentially. |
Jutta Billino; Jürgen Hennig; Karl R. Gegenfurtner The role of dopamine in anticipatory pursuit eye movements: Insights from genetic polymorphisms in healthy adults Journal Article In: eNeuro, vol. 3, no. 6, pp. 1–13, 2016. @article{Billino2016, There is a long history of eye movement research in patients with psychiatric diseases for which dysfunctions of neurotransmission are considered to be the major pathologic mechanism. However, neuromodulation of oculomotor control is still hardly understood. We aimed to investigate in particular the impact of dopamine on smooth pursuit eye movements. Systematic variability in dopaminergic transmission due to genetic polymorphisms in healthy subjects offers a noninvasive opportunity to determine functional associations. We measured smooth pursuit in 110 healthy subjects genotyped for two well-documented polymorphisms, the COMT Val158Met polymorphism and the SLC6A3 3′-UTR-VNTR polymorphism. Pursuit paradigms were chosen to particularly assess the ability of the pursuit system to initiate tracking when target motion onset is blanked, reflecting the impact of extraretinal signals. In contrast, when following a fully visible target sensory, retinal signals are available. Our results highlight the crucial functional role of dopamine for anticipatory, but not for sensory-driven, pursuit processes. We found the COMT Val158Met polymorphism specifically associated with anticipatory pursuit parameters, emphasizing the dominant impact of prefrontal dopamine activity on complex oculomotor control. In contrast, modulation of striatal dopamine activity by the SLC6A3 3′-UTR-VNTR polymorphism had no significant functional effect. Though often neglected so far, individual differences in healthy subjects provide a promising approach to uncovering functional mechanisms and can be used as a bridge to understanding deficits in patients. |
Yoram S. Bonneh; Yael Adini; Uri Polat Contrast sensitivity revealed by spontaneous eyeblinks: Evidence for a common mechanism of oculomotor inhibition Journal Article In: Journal of Vision, vol. 16, no. 7, pp. 1–15, 2016. @article{Bonneh2016, Spontaneous eyeblinks are known to serve important physiological functions, and recent evidence shows that they are also linked to cognitive processes. It is yet unclear whether this link reflects a crude rate modulation or, alternatively, an automatic and precise process, tightly linked to the low-level properties of sensory stimuli. We have recently reported (Y. S. Bonneh, Adini, & Polat, 2015) that, for microsaccades, the onset and release from inhibition in response to transient stimuli depend systematically on the low-level stimulus parameters. Here we reanalyzed our previous data for both microsaccades and eyeblinks for observers with sufficient blinking (.10% of trials, 18 of 23 observers tested) who watched and silently counted sequences of Gabor patches at 1 Hz with varied contrast and spatial frequency. We found that spontaneous eyeblinks, although less frequent, were similar to microsaccades in their modulation pattern in response to transient stimuli, demonstrating inhibition and rebound, which were dependent on the contrast and spatial frequency of the stimuli. The average blink response time, measured as the latency of the first blink following its release from inhibition, was longer for lower contrast and higher spatial frequency. Importantly, it was highly correlated with a similar measure for microsaccades as well as with psychophysical measures of contrast sensitivity. These results suggest that both eyeblinks and microsaccades are linked to the same inhibitory mechanism that presumably turns off oculomotor events while processing previous events and generates a rebound effect upon its release. The onset of both eyeblinks and microsaccades may thus reflect the time course of this mechanism and the associated cognitive process. |
Paul J. Boon; Artem V. Belopolsky; Jan Theeuwes The role of the oculomotor system in updating visual-spatial working memory across saccades Journal Article In: PLoS ONE, vol. 11, no. 9, pp. e0161829, 2016. @article{Boon2016, Visual-spatial workingmemory (VSWM) helps us to maintain and manipulate visual infor- mation in the absence of sensory input. It has been proposed thatVSWMis an emergent property of the oculomotor system. In the present study we investigated the role of the ocu- lomotor system in updating of spatial working memory representations across saccades. Participants had to maintain a location in memory while making a saccade to a different location. During the saccade the target was displaced, which went unnoticed by the partici- pants. After executing the saccade, participants had to indicate the memorized location. If memory updating fully relies on cancellation driven by extraretinal oculomotor signals, the displacement should have no effect on the perceived location of thememorized stimulus. However, if postsaccadic retinal information about the location of the saccade target is used, the perceived location will be shifted according to the target displacement. As it has been suggested thatmaintenance of accurate spatial representations across saccades is especially important for action control, we used different ways of reporting the location held in memory; amatch-to-sample task, a mouse click or by making another saccade. The results showed a small systematic target displacement bias in all response modalities. Parametric manipulation of the distance between the to-be-memorized stimulus and sac- cade target revealed that target displacement bias increased over time and changed its spa- tial profile from being initially centered on locations around the saccade target to becoming spatially global. Taken together results suggest that we neither rely exclusively on extraret- inal nor on retinal information in updating working memory representations across sac- cades. The relative contribution of retinal signals is not fixed but depends on both the time available to integrate these signals as well as the distance between the saccade target and the remembered location. |
Sabine Born; Hannah M. Krüger; Eckart Zimmermann; Patrick Cavanagh Compression of space for low visibility probes Journal Article In: Frontiers in Systems Neuroscience, vol. 10, pp. 1–13, 2016. @article{Born2016, Stimuli briefly flashed just before a saccade are perceived closer to the saccade target, a phenomenon known as perisaccadic compression of space (Ross, Morrone, & Burr, 1997). More recently, we have demonstrated that brief probes are attracted towards a visual reference when followed by a mask, even in the absence of saccades (Zimmermann, Born, Fink, & Cavanagh, 2014). Here, we ask whether spatial compression depends on the transient disruptions of the visual input stream caused by either a mask or a saccade. Both of these degrade the probe visibility but we show that low probe visibility alone causes compression in the absence of any disruption. In a first experiment, we varied the regions of the screen covered by a transient mask, including areas where no stimulus was presented and a condition without masking. In all conditions, we adjusted probe contrast to make the probe equally hard to detect. Compression effects were found in all conditions. To obtain compression without a mask, the probe had to be presented at much lower contrasts than with masking. Comparing mislocalizations at different probe detection rates across masking, saccades and low contrast conditions without mask or saccade, Experiment 2 confirmed this observation and showed a strong influence of probe contrast on compression. Finally, in Experiment 3, we found that compression decreased as probe duration increased both for masks and saccades although here we did find some evidence that factors other than simply visibility as we measured it contribute to compression. Our experiments suggest that compression reflects how the visual system localizes weak targets in the context of highly visible stimuli. |
Doris I. Braun; Karl R. Gegenfurtner Dynamics of oculomotor direction discrimination Journal Article In: Journal of Vision, vol. 16, no. 13, pp. 1–26, 2016. @article{Braun2016, Successful foveation of a dynamic target depends on good predictions of its movement direction and speed. We measured and compared the temporal dynamics of directional precision of both saccades and smooth pursuit and their interactions. We also compared the directional precision of both eye movements to psychophysical direction discrimination thresholds. Directional thresholds of pure pursuit responses improved rapidly and reached asymptotic values of 1.5°-3° within 300 ms after target motion onset, both for trained and untrained observers and irrespective of the speed of the stimuli. Psychophysical thresholds were in the same range. Directional thresholds for saccades in the ramp paradigm were just slightly higher, but these occurred significantly earlier in time at around 200 ms after target motion onset. At the equivalent time during pure pursuit initiation, thresholds were typically higher by 2°-3°. The rise in directional precision-or decrease in thresholds-over time was more pronounced for trials with longer latencies. As an effect, precision depended mainly on time since stimulus motion onset rather than pursuit onset. Directional precision for saccades to static targets was slightly better than to moving targets, at even shorter latencies. We conclude that directional precision is higher for the saccadic system at saccade onset than for the pursuit system, presumably due to additional position signals that are not available to the pursuit system at that point in time. The pursuit response improves rapidly due to refined sensory processing and motor planning. The combination of initial saccades and pursuit to track moving targets is a good strategy for the oculomotor system to reduce directional errors during the phase of initiation. The target speed has very little effects on the directional precision of both eye movements. |
Antimo Buonocore; Robert D. McIntosh; David Melcher Beyond the point of no return: Effects of visual distractors on saccade amplitude and velocity Journal Article In: Journal of Neurophysiology, vol. 115, no. 2, pp. 752–762, 2016. @article{Buonocore2016a, Visual transients, such as a bright flash, reduce the proportion of saccades executed, ∼60–125 ms after flash onset, a phenomenon known as saccadic inhibition (SI). Across three experiments, we apply a similar time-course analysis to the amplitudes and velocities of saccades. Alongside the expected reduction of saccade frequency in the key time period, we report two perturbations of the “main sequence”: one before and one after the period of SI. First, saccades launched between 30 and 70 ms, following the flash, were hypometric, with peak speed exceeding that expected for a saccade of similar amplitude. This finding was in contrast to the common idea that saccades have passed a “point of no return,” ∼60 ms before launching, escaping interference from distractors. The early hypometric saccades observed were not a consequence of spatial averaging between target and distractor locations, as they were found not only following a localized central flash (experiment 1) but also following a spatially generalized flash (experiment 2). Second, across experiments, saccades launched at 110 ms postflash, toward the end of SI, had normal amplitude but a peak speed higher than expected for that amplitude, suggesting increased collicular excitation at the time of launching. Overall, the results show that saccades that escape inhibition following a visual transient are not necessarily unaffected but instead, can reveal interference in spatial and kinematic measures. |
Damien Camors; Yves Trotter; Pierre Pouget; Sophie Gilardeau; Jean-Baptiste Durand Visual straight-ahead preference in saccadic eye movements Journal Article In: Scientific Reports, vol. 6, pp. 23124, 2016. @article{Camors2016, Ocular saccades bringing the gaze toward the straight-ahead direction (centripetal) exhibit higher dynamics than those steering the gaze away (centrifugal). This is generally explained by oculomotor determinants: centripetal saccades are more efficient because they pull the eyes back toward their primary orbital position. However, visual determinants might also be invoked: elements located straight-ahead trigger saccades more efficiently because they receive a privileged visual processing. Here, we addressed this issue by using both pro- and anti-saccade tasks in order to dissociate the centripetal/centrifugal directions of the saccades, from the straight-ahead/eccentric locations of the visual elements triggering those saccades. Twenty participants underwent alternating blocks of pro- and anti-saccades during which eye movements were recorded binocularly at 1 kHz. The results confirm that centripetal saccades are always executed faster than centrifugal ones, irrespective of whether the visual elements have straight-ahead or eccentric locations. However, by contrast, saccades triggered by elements located straight-ahead are consistently initiated more rapidly than those evoked by eccentric elements, irrespective of their centripetal or centrifugal direction. Importantly, this double dissociation reveals that the higher dynamics of centripetal pro-saccades stem from both oculomotor and visual determinants, which act respectively on the execution and initiation of ocular saccades. |
Valeria C. Caruso; Daniel S. Pages; Marc A. Sommer; Jennifer M. Groh In: Journal of Neurophysiology, vol. 115, no. 6, pp. 3162–3173, 2016. @article{Caruso2016, Saccadic eye movements can be elic- ited by more than one type of sensory stimulus. This implies substantial transformations of signals originating in different sense organs as they reach a common motor output pathway. In this study, we compared the prevalence and magnitude of auditory- and visually evoked activity in a structure implicated in oculomotor processing, the primate frontal eye fields (FEF). We recorded from 324 single neurons while 2 monkeys performed delayed saccades to visual or auditory targets. We found that 64% of FEF neurons were active on presenta- tion of auditory targets and 87% were active during auditory-guided saccades, compared with 75 and 84% for visual targets and saccades. As saccade onset approached, the average level of population activity in the FEF became indistinguishable on visual and auditory trials. FEF activity was better correlated with the movement vector than with the target location for both modalities. In summary, the large proportion of auditory-responsive neurons in the FEF, the similarity between visual and auditory activity levels at the time of the saccade, and the strong correlation between the activity and the saccade vector suggest that auditory signals undergo tailoring to match roughly the strength of visual signals present in the FEF, facilitating accessing of a common motor output pathway. |
Carlos R. Cassanello; Sven Ohl; Martin Rolfs Saccadic adaptation to a systematically varying disturbance Journal Article In: Journal of Neurophysiology, vol. 116, no. 2, pp. 336–350, 2016. @article{Cassanello2016, Saccadic adaptation maintains the correct mapping between eye movements and their targets, yet the dynamics of saccadic gain changes in the presence of systematically varying disturbances has not been extensively studied. Here, we assessed changes in the gain of saccade amplitudes induced by continuous and periodic post-saccadic visual feedback. Observers made saccades following a sequence of target steps either along the horizontal meridian (Two-way adaptation) or with unconstrained saccade directions (Global adaptation). An intra-saccadic step-following a sinusoidal variation as a function of the trial number (with three different frequencies tested in separate blocks)-consistently displaced the target along its vector. The oculomotor system responded to the resulting feedback error by modifying saccade amplitudes in a periodic fashion with similar frequency of variation but lagging the disturbance by a few trials. This periodic response was superimposed on a drift towards stronger hypometria with similar asymptotes and decay rates across stimulus conditions. The magnitude of the periodic response decreased with increasing frequency and was smaller and more delayed for Global than Two-way adaptation. These results suggest that-in addition to the well-characterized return-to-the-baseline response observed in protocols using constant visual feedback-the oculomotor system attempts to minimize the feedback error by integrating its variation across trials. This process resembles a convolution with an internal response function, whose structure would be determined by coefficients of the learning model. Our protocol reveals this fast learning process in single short experimental sessions, qualifying it for the study of sensorimotor learning in health and disease. |
Bob McMurray; Ashley Farris-Trimble; Michael Seedorff; Hannah Rigler The effect of residual acoustic hearing and adaptation to uncertainty on speech perception in cochlear implant users: Evidence from eye-tracking Journal Article In: Ear & Hearing, vol. 37, no. 1, pp. e37–e51, 2016. @article{McMurray2016, OBJECTIVES: While outcomes with cochlear implants (CIs) are generally good, performance can be fragile. The authors examined two factors that are crucial for good CI performance. First, while there is a clear benefit for adding residual acoustic hearing to CI stimulation (typically in low frequencies), it is unclear whether this contributes directly to phonetic categorization. Thus, the authors examined perception of voicing (which uses low-frequency acoustic cues) and fricative place of articulation (s/ʃ, which does not) in CI users with and without residual acoustic hearing. Second, in speech categorization experiments, CI users typically show shallower identification functions. These are typically interpreted as deriving from noisy encoding of the signal. However, psycholinguistic work suggests shallow slopes may also be a useful way to adapt to uncertainty. The authors thus employed an eye-tracking paradigm to examine this in CI users. DESIGN: Participants were 30 CI users (with a variety of configurations) and 22 age-matched normal hearing (NH) controls. Participants heard tokens from six b/p and six s/ʃ continua (eight steps) spanning real words (e.g., beach/peach, sip/ship). Participants selected the picture corresponding to the word they heard from a screen containing four items (a b-, p-, s- and ʃ-initial item). Eye movements to each object were monitored as a measure of how strongly they were considering each interpretation in the moments leading up to their final percept. RESULTS: Mouse-click results (analogous to phoneme identification) for voicing showed a shallower slope for CI users than NH listeners, but no differences between CI users with and without residual acoustic hearing. For fricatives, CI users also showed a shallower slope, but unexpectedly, acoustic + electric listeners showed an even shallower slope. Eye movements showed a gradient response to fine-grained acoustic differences for all listeners. Even considering only trials in which a participant clicked "b" (for example), and accounting for variation in the category boundary, participants made more looks to the competitor ("p") as the voice onset time neared the boundary. CI users showed a similar pattern, but looked to the competitor more than NH listeners, and this was not different at different continuum steps. CONCLUSION: Residual acoustic hearing did not improve voicing categorization suggesting it may not help identify these phonetic cues. The fact that acoustic + electric users showed poorer performance on fricatives was unexpected as they usually show a benefit in standardized perception measures, and as sibilants contain little energy in the low-frequency (acoustic) range. The authors hypothesize that these listeners may overweight acoustic input, and have problems when this is not available (in fricatives). Thus, the benefit (or cost) of acoustic hearing for phonetic categorization may be complex. Eye movements suggest that in both CI and NH listeners, phoneme categorization is not a process of mapping continuous cues to discrete categories. Rather listeners preserve gradiency as a way to deal with uncertainty. CI listeners appear to adapt to their implant (in part) by amplifying competitor activation to preserve their flexibility in the face of potential misperceptions. |
Raika Pancaroglu; Charlotte S. Hills; Alla Sekunova; Jayalakshmi Viswanathan; Brad Duchaine; Jason J. S. Barton Seeing the eyes in acquired prosopagnosia Journal Article In: Cortex, vol. 81, pp. 251–265, 2016. @article{Pancaroglu2016, Case reports have suggested that perception of the eye region may be impaired more than that of other facial regions in acquired prosopagnosia. However, it is unclear how frequently this occurs, whether such impairments are specific to a certain anatomic subtype of prosopagnosia, and whether these impairments are related to changes in the scanning of faces. We studied a large cohort of 11 subjects with this rare disorder, who had a variety of occipitotemporal or anterior temporal lesions, both unilateral and bilateral. Lesions were characterized by functional and structural imaging. Subjects performed a perceptual discrimination test in which they had to discriminate changes in feature position, shape, or external contour. Test conditions were manipulated to stress focused or divided attention across the whole face. In a second experiment we recorded eye movements while subjects performed a face memory task. We found that greater impairment for eye processing was more typical of subjects with occipitotemporal lesions than those with anterior temporal lesions. This eye selectivity was evident for both eye position and shape, with no evidence of an upper/lower difference for external contour. A greater impairment for eye processing was more apparent under attentionally more demanding conditions. Despite these perceptual deficits, most subjects showed a normal tendency to scan the eyes more than the mouth. We conclude that occipitotemporal lesions are associated with a partially selective processing loss for eye information and that this deficit may be linked to loss of the right fusiform face area, which has been shown to have activity patterns that emphasize the eye region. |
Angelina Paolozza; Douglas P. Munoz; Donald Brien; James N. Reynolds Immediate neural plasticity involving reaction time in a saccadic eye movement task is intact in children with fetal alcohol spectrum disorder Journal Article In: Alcoholism: Clinical and Experimental Research, vol. 40, no. 11, pp. 2351–2358, 2016. @article{Paolozza2016, Background: Saccades are rapid eye movements that bring an image of interest onto the retina. Previous research has found that in healthy individuals performing eye movement tasks, the location of a previous visual target can influence performance of the saccade on the next trial. This rapid behavioral adaptation represents a form of immediate neural plasticity within the saccadic circuitry. Our studies have shown that children with fetal alcohol spectrum disorder (FASD) are impaired on multiple saccade measures. We therefore investigated these previous trial effects in typically developing children and children with FASD to measure sensory neural plasticity and how these effects vary with age and pathology. Methods: Both typically developing control children (n = 102; mean age = 10.54 +/- 3.25; 48 males) and children with FASD (n = 66; mean age = 11.85 +/- 3.42; 35 males) were recruited from 5 sites across Canada. Each child performed a visually guided saccade task. Reaction time and saccade amplitude were analyzed and then assessed based on the previous trial. Results: There was a robust previous trial effect for both reaction time and amplitude, with both the control and FASD groups displaying faster reaction times and smaller saccades during alternation trials (visual target presented on the opposite side to the previous trial). Children with FASD exhibited smaller overall mean amplitude and smaller amplitude selectively on alternation trials compared with controls. The effect of the previous trial on reaction time and amplitude did not differ across childhood and adolescent development. Conclusions: Children with FASD did not display any significant reaction time differences, despite exhibiting numerous deficits in motor and higher level cognitive control over saccades in other studies. These results suggest that this form of immediate neural plasticity in response to sensory information before saccade initiation remains intact in children with FASD. In contrast, the previous trial effect on amplitude suggests that the motor component of saccades may be affected, signifying differential vulnerability to prenatal alcohol exposure. |
Andrea Phillipou; Larry Allen Abel; David Jonathan Castle; Matthew Edward Hughes; Richard Grant Nibbs; Caroline T. Gurvich; Susan Lee Rossell Resting state functional connectivity in anorexia nervosa Journal Article In: Psychiatry Research: Neuroimaging, vol. 251, pp. 45–52, 2016. @article{Phillipou2016, Anorexia Nervosa (AN) is a serious psychiatric illness characterised by a disturbance in body image, a fear of weight gain and significantly low body weight. The factors involved in the genesis and maintenance of AN are unclear, though the potential neurobiological underpinnings of the condition are of increasing interest. Through the investigation of functional connectivity of the brain at rest, information relating to neuronal communication and integration of information that may relate to behaviours and cognitive symptoms can be explored. The aim of this study was to investigate functional connectivity of the default mode network, and sensorimotor and visual networks in AN. 26 females with AN and 27 healthy control participants matched for age, gender and premorbid intelligence underwent a resting state functional magnetic resonance imaging scan. Default mode network functional connectivity did not differ between groups. AN participants displayed reduced functional connectivity between the sensorimotor and visual networks, in comparison to healthy controls. This finding is discussed in terms of differences in visuospatial processing in AN and the distortion of body image experienced by these individuals. Overall, the findings suggest that sensorimotor and visual network connectivity may be related to visuospatial processing in AN, though, further research is required. |
Andrea Phillipou; Susan Lee Rossell; Caroline T. Gurvich; David Jonathan Castle; Nikolaus F. Troje; Larry Allen Abel Body image in anorexia nervosa: Body size estimation utilising a biological motion task and eyetracking Journal Article In: European Eating Disorders Review, vol. 24, no. 2, pp. 131–138, 2016. @article{Phillipou2016a, OBJECTIVE: Anorexia nervosa (AN) is a psychiatric condition characterised by a distortion of body image. However, whether individuals with AN can accurately perceive the size of other individuals' bodies is unclear. METHOD: In the current study, 24 women with AN and 24 healthy control participants undertook two biological motion tasks while eyetracking was performed: to identify the gender and to indicate the walkers' body size. RESULTS: Anorexia nervosa participants tended to 'hyperscan' stimuli but did not demonstrate differences in how visual attention was directed to different body areas, relative to controls. Groups also did not differ in their estimation of body size. DISCUSSION: The hyperscanning behaviours suggest increased anxiety to disorder-relevant stimuli in AN. The lack of group difference in the estimation of body size suggests that the AN group was able to judge the body size of others accurately. The findings are discussed in terms of body image distortion specific to oneself in AN. |
Andrea Phillipou; Susan Lee Rossell; Caroline T. Gurvich; Matthew Edward Hughes; David Jonathan Castle; Richard Grant Nibbs; Larry Allen Abel Saccadic eye movements in Anorexia Nervosa Journal Article In: PLoS ONE, vol. 11, no. 3, pp. e0152338, 2016. @article{Phillipou2016b, Background: Anorexia Nervosa (AN) has a mortality rate among the highest of any mental illness, though the factors involved in the condition remain unclear. Recently, the potential neurobiological underpinnings of the condition have become of increasing interest. Saccadic eye movement tasks have proven useful in our understanding of the neurobiology of some other psychiatric illnesses as they utilise known brain regions, but to date have not been examined in AN. The aim of this study was to investigate whether individuals with AN differ from healthy individuals in performance on a range of saccadic eye movements tasks. Methods: 24 females with AN and 25 healthy individuals matched for age, gender and premorbid intelligence participated in the study. Participants were required to undergo memory-guided and self-paced saccade tasks, and an interleaved prosaccade/antisaccade/no-go saccade task while undergoing functional magnetic resonance imaging (fMRI). Results: AN participants were found to make prosaccades of significantly shorter latency than healthy controls. AN participants also made an increased number of inhibitory errors on the memory-guided saccade task. Groups did not significantly differ in antisaccade, no-go saccade or self-paced saccade performance, or fMRI findings. Discussion: The results suggest a potential role of GABA in the superior colliculus in the psychopathology of AN. |
F. Pieruccini-Faria; J. A. Jones; Q. J. Almeida Insight into dopamine-dependent planning deficits in Parkinson's disease: A sharing of cognitive & sensory resources Journal Article In: Neuroscience, vol. 318, pp. 219–229, 2016. @article{PierucciniFaria2016, Cognitive and sensorimotor processes are both needed for successful planning of footsteps during complex gait situations, but the interaction between these factors during motor planning, as well as their response to dopaminergic treatment is poorly understood in Parkinson's disease (PD). In the current study, we evaluated walking and gaze behaviors of individuals with PD while planning an approach toward an obstacle to be stepped over. The obstacle clearance task was completed both ON and OFF dopaminergic medication by individuals with Parkinson's disease (n = 20) and compared to healthy age-matched control participants (n = 19), as well as with and without an auditory digit monitoring dual task. In this novel protocol of synchronized gaze and gait data collection, each trial was split into an early and late phase prior to the obstacle, providing a unique opportunity to examine dopamine-dependent planning deficits in PD. Interestingly, only patients in the OFF medication state showed greater deceleration in the late phase (i.e., just before the obstacle) (F(1,37) = 45.42, p < 0.001), as well as an increase in step time variability (also in this late phase) with the additional demands of a dual task (F(2,74) = 3.49 |
Malcolm Proudfoot; Ricarda A. L. Menke; Rakesh Sharma; Claire M. Berna; Stephen L. Hicks; Christopher Kennard; Kevin Talbot; Martin R. Turner Eye-tracking in amyotrophic lateral sclerosis: A longitudinal study of saccadic and cognitive tasks Journal Article In: Amyotrophic Lateral Sclerosis and Frontotemporal Degeneration, vol. 17, no. 1-2, pp. 101–111, 2016. @article{Proudfoot2016, A relative preservation of eye movements is notable in ALS, but saccadic functions have not been studied longitudinally. ALS overlaps with FTD, typically involving executive dysfunction, and eye-tracking offers additional potential for the assessment of extramotor pathology where writing and speaking are both impaired. Eye-tracking measures (including anti- saccade, trail-making and visual search tasks) were assessed at six-monthly intervals for up to two years in a group of ALS (n ? 61) and primary lateral sclerosis (n ? 7) patients, compared to healthy age-matched controls (n ? 39) assessed on a single occasion. Task performance was explored speculatively in relation to resting-state functional MRI (R-FMRI) network connectivity. Results showed that ALS patients were impaired on executive and visual search tasks despite normal basic saccadic function, and impairments in the PLS patients were unexpectedly often more severe. No significant progression was detected longitudinally in either group. No changes in R-FMRI network connectivity were identified in relation to patient performance. In conclusion, eye-tracking offers an objective means to assess extramotor cerebral involvement in ALS. The relative resistance of pure oculomotor function is confirmed, and higher-level executive impairments do not follow the same rate of decline as physical disability. PLS patients may have more cortical dysfunction than has been previously appreciated. |
Mary Vining Radomski; Mattie Anheluk; M. Penny Bartzen; Joette Zola In: American Journal of Occupational Therapy, vol. 70, no. 3, pp. 1–9, 2016. @article{Radomski2016, OBJECTIVE: To determine the effectiveness of interventions addressing cognitive impairments to improve occupational performance for people with traumatic brain injury. METHOD: A total of 37 studies met inclusion criteria: 9 Level I systematic reviews, 14 Level I studies, 5 Level II studies, and 9 Level III studies. RESULTS: Strong evidence supports use of direct attention training, dual-task training, and strategy training to optimize executive functioning, encoding, and use of memory compensations, including assistive technology. However, in most studies, occupational performance was a secondary outcome, if it was evaluated at all. CONCLUSION: Although evidence supports many intervention approaches used by occupational therapy practitioners to address cognitive impairments of adults with traumatic brain injury, more studies are needed in which occupational performance is the primary outcome of cognitive intervention. |
Benedikt Reuter; Björn Elsner; David Möllers; Norbert Kathmann In: Psychophysiology, vol. 53, no. 11, pp. 1712–1720, 2016. @article{Reuter2016, Clinical and theoretical models suggest deficient volitional initiation of action in schizophrenia patients. Recent research provided an experimental model of testing this assumption using saccade tasks. However, inconsistent findings necessitate a specification of conditions on which the deficit may occur. The present study sought to detect mechanisms that may contribute to poor performance. Sixteen schizophrenia patients and 16 healthy control participants performed visually guided and two types of volitional saccade tasks. All tasks varied as to whether the initial fixation stimulus disappeared (fixation stimulus offset) or continued during saccade initiation, and whether a direction cue allowed motor preparation of the specific saccade. Saccade latencies of the two groups were differentially affected by task type, fixation stimulus offset, and cueing, suggesting abnormal volitional saccade generation, fixation release, and motor preparation in schizophrenia. However, substantial performance deficits may only occur if all affected processes are required in a task. |
John-Ross Rizzo; Todd E. Hudson; Weiwei Dai; Joel Birkemeier; Rosa M. Pasculli; Ivan Selesnick; Laura J. Balcer; Steven L. Galetta; Janet C. Rucker Rapid number naming in chronic concussion: Eye movements in the King–Devick test Journal Article In: Annals of Clinical and Translational Neurology, vol. 3, no. 10, pp. 801–811, 2016. @article{Rizzo2016, Objective: The King–Devick (KD) test, which is based on rapid number nam- ing speed, is a performance measure that adds vision and eye movement assess- ments to sideline concussion testing. We performed a laboratory-based study to characterize ocular motor behavior during the KD test in a patient cohort with chronic concussion to identify features associated with prolonged KD reading times. Methods: Twenty-five patients with a concussion history (mean age: 31) were compared to control participants with no concussion history (n = 42, mean age: 32). Participants performed a computerized KD test under infrared- based video-oculography. Results: Average intersaccadic intervals for task-speci- fic saccades were significantly longer among concussed patients compared to controls (324.4 ? 85.6 msec vs. 286.1 ? 49.7 msec |
Mariel Roberts; Rachel Cymerman; R. Theodore Smith; Lynne Kiorpes; Marisa Carrasco Covert spatial attention is functionally intact in amblyopic human adults Journal Article In: Journal of Vision, vol. 16, no. 15, pp. 1–19, 2016. @article{Roberts2016, Certain abnormalities in behavioral performance and neural signaling have been attributed to a deficit of visual attention in amblyopia, a neurodevelopmental disorder characterized by a diverse array of visual deficits following abnormal binocular childhood experience. Critically, most have inferred attention's role in their task without explicitly manipulating and measuring its effects against a baseline condition. Here, we directly investigate whether human amblyopic adults benefit from covert spatial attention—the selective processing of visual information in the absence of eye movements—to the same degree as neurotypical observers. We manipulated both involuntary (Experiment 1) and voluntary (Experiment 2) attention during an orientation discrimination task for which the effects of covert spatial attention have been well established in neurotypical and special populations. In both experiments, attention significantly improved accuracy and decreased reaction times to a similar extent (a) between the eyes of the amblyopic adults and (b) between the amblyopes and their age- and gender- matched controls. Moreover, deployment of voluntary attention away from the target location significantly impaired task performance (Experiment 2). The magnitudes of the involuntary and voluntary attention benefits did not correlate with amblyopic depth or severity. Both groups of observers showed canonical performance fields (better performance along the horizontal than vertical meridian and at the lower than upper vertical meridian) and similar effects of attention across locations. Despite their characteristic low-level vision impairments, covert spatial attention remains functionally intact in human amblyopic adults. |
Yu Li; Yangyang Xu; Mengqing Xia; Tianhong Zhang; Junjie Wang; Xu Liu; Yongguang He; Jijun Wang Eye movement indices in the study of depressive disorder Journal Article In: Shanghai Archives of Psychiatry, vol. 28, no. 6, pp. 326–334, 2016. @article{Li2016, Background: Impaired cognition is one of the most common core symptoms of depressive disorder. Eye movement testing mainly reflects patients' cognitive functions, such as cognition, memory, attention, recognition, and recall. This type of testing has great potential to improve theories related to cognitive functioning in depressive episodes as well as potential in its clinical application. Aims: This study investigated whether eye movement indices of patients with unmedicated depressive disorder were abnormal or not, as well as the relationship between these indices and mental symptoms. Methods: Sixty patients with depressive disorder and sixty healthy controls (who were matched by gender, age and years of education) were recruited, and completed eye movement tests including three tasks: fixation task, saccade task and free-view task. The EyeLink desktop eye tracking system was employed to collect eye movement information, and analyze the eye movement indices of the three tasks between the two groups. Results: (1) In the fixation task, compared to healthy controls, patients with depressive disorder showed more fixations, shorter fixation durations, more saccades and longer saccadic lengths; (2) In the saccade task, patients with depressive disorder showed longer anti-saccade latencies and smaller anti-saccade peak velocities; (3) In the free-view task, patients with depressive disorder showed fewer saccades and longer mean fixation durations; (4) Correlation analysis showed that there was a negative correlation between the pro-saccade amplitude and anxiety symptoms, and a positive correlation between the anti-saccade latency and anxiety symptoms. The depression symptoms were negatively correlated with fixation times, saccades, and saccadic paths respectively in the free-view task; while the mean fixation duration and depression symptoms showed a positive correlation. Conclusion: Compared to healthy controls, patients with depressive disorder showed significantly abnormal eye movement indices. In addition patients' anxiety and depression symptoms and eye movement indices were correlated. The pathological meaning of these phenomena deserve further exploration. |
Judith Lunn; Tim Donovan; Damien Litchfield; Charlie Lewis; Robert Davies; Trevor J. Crawford Saccadic eye movement abnormalities in children with epilepsy Journal Article In: PLoS ONE, vol. 11, no. 8, pp. e0160508, 2016. @article{Lunn2016, Childhood onset epilepsy is associated with disrupted developmental integration of sensorimotor and cognitive functions that contribute to persistent neurobehavioural comorbidities. The role of epilepsy and its treatment on the development of functional integration of motor and cognitive domains is unclear. Oculomotor tasks can probe neurophysiological and neurocognitive mechanisms vulnerable to developmental disruptions by epilepsy-related factors. The study involved 26 patients and 48 typically developing children aged 8–18 years old who performed a prosaccade and an antisaccade task. Analyses compared medicated chronic epilepsy patients and unmedicated controlled epilepsy patients to healthy control children on saccade latency, accuracy and dynamics, errors and correction rate, and express saccades. Patients with medicated chronic epilepsy had impaired and more variable processing speed, reduced accuracy, increased peak velocity and a greater number of inhibitory errors, younger unmedicated patients also showed deficits in error monitoring. Deficits were related to reported behavioural problems in patients. Epilepsy factors were significant predictors of oculomotor functions. An earlier age at onset predicted reduced latency of prosaccades and increased express saccades, and the typical relationship between express saccades and inhibitory errors was absent in chronic patients, indicating a persistent reduction in tonic cortical inhibition and aberrant cortical connectivity. In contrast, onset in later childhood predicted altered antisaccade dynamics indicating disrupted neurotransmission in frontoparietal and oculomotor networks with greater demand on inhibitory control. The observed saccadic abnormalities are consistent with a dysmaturation of subcortical-cortical functional connectivity and aberrant neurotransmission. Eye movements could be used to monitor the impact of epilepsy on neurocognitive development and help assess the risk for poor neurobehavioural outcomes. |
Wayne E. Mackey; Orrin Devinsky; Werner K. Doyle; John G. Golfinos; Clayton E. Curtis Human parietal cortex lesions impact the precision of spatial working memory Journal Article In: Journal of Neurophysiology, vol. 116, no. 3, pp. 1049–1054, 2016. @article{Mackey2016, The neural mechanisms that support working memory (WM) depend on persistent neural activity. Within topographically organized maps of space in dorsal parietal cortex, spatially selective neural activity persists during WM for location. However, to date the necessity of these topographic subregions of human parietal cortex for WM remain unknown. To test the causal relationship of these areas to WM, we compared the performance of patients with lesions to topographically organized parietal cortex to controls on a memory-guided saccade (MGS) task as well as a visually-guided saccade (VGS) task. The MGS task allowed us to measure WM precision continuously with great sensitivity, while the VGS task allowed us to control for any deficits in general spatial or visuomotor processing. Compared to controls, patients generated memory-guided saccades that were significantly slower and less accurate, while visually-guided saccades were unaffected. These results provide key missing evidence for the causal role of topographic areas in human parietal cortex for WM, as well as the neural mechanisms supporting WM. |
Sanjay G. Manohar; Masud Husain Human ventromedial prefrontal lesions alter incentivisation by reward Journal Article In: Cortex, vol. 76, pp. 104–120, 2016. @article{Manohar2016, Although medial frontal brain regions are implicated in valuation of rewards, evidence from focal lesions to these areas is scant, with many conflicting results regarding motivation and affect, and no human studies specifically examining incentivisation by reward. Here, 19 patients with isolated, focal damage in ventral and medial prefrontal cortex were selected from a database of 453 individuals with subarachnoid haemorrhage. Using a speeded saccadic task based on the oculomotor capture paradigm, we manipulated the maximum reward available on each trial using an auditory incentive cue. Modulation of behaviour by motivation permitted quantification of reward sensitivity. At the group level, medial frontal damage was overall associated with significantly reduced effects of reward on invigorating saccadic velocity and autonomic (pupil) responses compared to age-matched, healthy controls. Crucially, however, some individuals instead showed abnormally strong incentivisation effects for vigour. Increased sensitivity to rewards within the lesion group correlated with damage in subgenual ventromedial prefrontal cortex (vmPFC) areas, which have recently become the target for deep brain stimulation (DBS) in depression. Lesion correlations with clinical apathy suggested that the apathy associated with prefrontal damage is in fact reduced by damage at those coordinates. Reduced reward sensitivity showed a trend to correlate with damage near nucleus accumbens. Lesions did not, on the other hand, influence reward sensitivity of cognitive control, as measured by distractibility. Thus, although medial frontal lesions may generally reduce reward sensitivity, damage to key subregions paradoxically protect from this effect. |
Jun Maruta; Eva M. Palacios; Robert D. Zimmerman; Jamshid Ghajar; Pratik Mukherjee Chronic post-concussion neurocognitive deficits . I . Relationship with white matter integrity Journal Article In: Frontiers in Human Neuroscience, vol. 10, pp. 35, 2016. @article{Maruta2016, We previously identified visual tracking deficits and associated degradation of integrity in specific white matter tracts as characteristics of concussion. We re-explored these characteristics in adult patients with persistent post-concussive symptoms using independent new data acquired during 2009–2012. Thirty-two patients and 126 normal controls underwent cognitive assessments and MR-DTI. After data collection, a subset of control subjects was selected to be individually paired with patients based on gender and age. We identified patients' cognitive deficits through pairwise comparisons between patients and matched control subjects. Within the remaining 94 normal subjects, we identified white matter tracts whose integrity correlated with metrics that indicated performance degradation in patients. We then tested for reduced integrity in these white matter tracts in patients relative to matched controls. Most patients showed no abnormality in MR images unlike the previous study. Patients' visual tracking was generally normal. Patients' response times in an attention task were slowed, but could not be explained as reduced integrity of white matter tracts relating to normal response timing. In the present patient cohort, we did not observe behavioral or anatomical deficits that we previously identified as characteristic of concussion. The recent cohort likely represented those with milder injury compared to the earlier cohort. The discrepancy may be explained by a change in the patient recruitment pool circa 2007 associated with an increase in public awareness of concussion. |
Jun Maruta; Lisa A. Spielman; Brett B. Yarusi; Yushi Wang; Jonathan M. Silver; Jamshid Ghajar Chronic post-concussion neurocognitive deficits. II. Relationship with persistent symptoms Journal Article In: Frontiers in Human Neuroscience, vol. 10, pp. 45, 2016. @article{Maruta2016a, Individuals who sustain a concussion may continue to experience problems long after their injury. However, it has been postulated in the literature that the relationship between a concussive injury and persistent complaints attributed to it is mediated largely by the development of symptoms associated with posttraumatic stress disorder (PTSD) and depression. We sought to characterize cognitive deficits of adult patients who had persistent symptoms after a concussion and determine whether the original injury retains associations with these deficits after accounting for the developed symptoms that overlap with PTSD and depression. We compared the results of neurocognitive testing from 33 patients of both genders aged 18-55 at 3 months to 5 years post-injury with those from 140 control subjects. Statistical comparisons revealed that patients generally produced accurate responses on reaction time-based tests, but with reduced efficiency. On visual tracking, patients increased gaze position error variability following an attention demanding task, an effect that may reflect greater fatigability. When neurocognitive performance was examined in the context of demographic- and symptom-related variables, the original injury retained associations with reduced performance at a statistically significant level. For some patients, reduced cognitive efficiency and fatigability may represent key elements of interference when interacting with the environment, leading to varied paths of recovery after a concussion. Poor recovery may be better understood when these deficits are taken into consideration. |
Kathleen Thomaes; Iris M. Engelhard; Marit Sijbrandij; Danielle C. Cath; Odile A. Heuvel Degrading traumatic memories with eye movements: A pilot functional MRI study in PTSD Journal Article In: European Journal of Psychotraumatology, vol. 7, no. 1, pp. 1–10, 2016. @article{Thomaes2016, Background: Eye movement desensitization and reprocessing (EMDR) is an effective treatment for post-traumatic stress disorder (PTSD). During EMDR, the patient recalls traumatic memories while making eye movements (EMs). Making EMs during recall is associated with decreased vividness and emotionality of traumatic memories, but the underlying mechanism has been unclear. Recent studies support a ''working-memory'' (WM) theory, which states that the two tasks (recall and EMs) compete for limited capacity of WM resources. However, prior research has mainly relied on self-report measures. Methods: Using functional magnetic resonance imaging, we tested whether ''recall with EMs,''relative to a ''recall-only'' control condition, was associated with reduced activity of primary visual and emotional processing brain regions, associatedwith vividness and emotionality respectively, and increased activity of the dorsolateral prefrontal cortex (DLPFC), associated with working memory. We used a randomized, controlled, crossover experimental design in eight adult patients with a primary diagnosis of PTSD. A script-driven imagery (SDI) procedure was used to measure responsiveness to an audio-script depicting the participant's traumatic memory before and after conditions. Results: SDI activated mainly emotional processing-related brain regions (anterior insula, rostral anterior cingulate cortex (ACC), and dorsomedial prefrontal cortex), WM-related (DLPFC), and visual (association) brain regions before both conditions. Although predicted pre-to post-test decrease in amygdala activation after "recall with EMs" was not significant, SDI activated less right amygdala and rostral ACC activity after "recall with EMs" compared to post-"recall-only." Furthermore, functional connectivity from the right amygdala to the rostral ACC was decreased after "recall with EMs" compared with after "recall-only." Conclusions: These preliminary results in a small sample suggest that making EMs during recall, which is part of the regular EMDR treatment protocol, might reduce activity and connectivity in emotional processing-related areas. This study warrants replication in a larger sample. |
Shin-ichi Tokushige; Yasuo Terao; Shun-ichi Matsuda; Satomi Inomata-Terada; Takahiro Shimizu; Nobuyuki Tanaka; Masashi Hamada; Akihiro Yugeta; Ritsuko Hanajima; Harushi Mori; Shoji Tsuji; Yoshikazu Ugawa Motor neuron disease with saccadic abnormalities similar to progressive supranuclear palsy Journal Article In: Neurology and Clinical Neuroscience, vol. 4, pp. 146–152, 2016. @article{Tokushige2016, Background: In recent years, a variety of clinical types of amyotrophic lateral sclerosis have come to be recognized. As some patients present with oculomotor abnormalities both clinically and pathologically, the progressive supranuclear palsy variant of amyotrophic lateral sclerosis has been proposed. Aim: To describe atypical cases of motor neuron disease with abnormal extraocular movements mimicking progressive supranuclear palsy. Methods: We present three motor neuron disease patients with slow saccades, who were aged 57, 63 and 62 years. Neurological examinations found vertical gaze palsy in two patients. The two patients who presented extrapyramidal signs were regarded as motor neuron disease with parkinsonism, whereas the other was diagnosed with amyotrophic lateral sclerosis. Their saccades were investigated by visually-guided saccade and memory-guided saccade tasks, and were compared with those of 14 age-matched normal participants (60.3 +/- 1.9 years). Results: In all these patients, the visually-guided saccade latencies were significantly prolonged compared with normal participants, whereas the memory-guided saccade latencies were not. The velocity and amplitude of saccades of the patients were significantly reduced in visually-guided saccade and memory-guided saccade in comparison with normal participants. Conclusion: The patterns of saccadic abnormalities in the patients were similar to those of progressive supranuclear palsy patients, suggesting that some patients with motor neuron disease show saccade abnormalities similar to those of progressive supranuclear palsy patients from the clinical and physiological perspective. Motor neuron disease with slow saccades and parkinsonism, as reported here, suggest the existence of progressive supranuclear palsy-variant amyotrophic lateral sclerosis. |
Preeti Verghese; Terence L. Tyson; Saeideh Ghahghaei; Donald C. Fletcher Depth perception and grasp in central field loss Journal Article In: Investigative Ophthalmology & Visual Science, vol. 57, no. 3, pp. 1476–1487, 2016. @article{Verghese2016, PURPOSE: We set out to determine whether individuals with central field loss benefit from using two eyes to perform a grasping task. Specifically, we tested the hypothesis that this advantage is correlated with coarse stereopsis, in addition to binocular summation indices of visual acuity, contrast sensitivity, and binocular visual field. METHODS: Sixteen participants with macular degeneration and nine age-matched controls placed pegs on a pegboard, while their eye and hand movements were recorded. Importantly, the pegboard was placed near eye height, to minimize the contribution of monocular cues to peg position. All participants performed this task binocularly and monocularly. Before the experiment, we performed microperimetry to determine the profile of field loss in each eye and the locations of eccentric fixation (if applicable). In addition, we measured both acuity and contrast sensitivity monocularly and binocularly, and stereopsis by using both a RanDot test and a custom stereo test. RESULTS: Peg-placement time was significantly shorter and participants made significantly fewer errors with binocular than with monocular viewing in both the patient and control groups. Among participants with measurable stereopsis, binocular advantage in peg-placement time was significantly correlated with stereoacuity (ρ = -0.78; P = 0.003). In patients without measurable stereopsis, the binocular advantage was related significantly to the overlap in the scotoma between the two eyes (ρ = -0.81; P = 0.032). CONCLUSIONS: The high correlation between grasp performance and stereoacuity indicates that coarse stereopsis may benefit tasks of daily living for individuals with central field loss. |
W. C. Walker; W. Carne; L. M. Franke; T. Nolen; S. D. Dikmen; D. X. Cifu; K. Wilson; H. G. Belanger; R. Williams In: Brain Injury, vol. 30, no. 12, pp. 1469–1480, 2016. @article{Walker2016, PRIMARY OBJECTIVES To establish and comprehensively evaluate a large cohort of US veterans who served in recent military conflicts in order to better understand possible chronic and late-life effects of mild traumatic brain injury (mTBI), including those that may stem from neurodegeneration. RESEARCH DESIGN Cross-sectional and prospective longitudinal. METHODS AND PROCEDURES Inclusion criteria are prior combat exposure and deployment(s) in Operation Enduring Freedom, Operation Iraqi Freedom or one of their follow-on conflicts (collectively OEF/OIF). Effects of mTBI will be assessed by enrolling participants across the entire spectrum of mTBI, from entirely negative to many mTBIs. Longitudinal assessments consist of in-person comprehensive testing at least every 5 years, with interval annual telephonic testing. The primary outcome is the composite score on the NIH Toolbox neuropsychological test battery. Assessments also include structured interviews, questionnaires, traditional neuropsychological testing, motor, sensory and vestibular functions, neuroimaging, electrophysiology, genotypes and biomarkers. MAIN OUTCOMES AND RESULTS The authors fully describe the study methods and measures and report demographic and exposure characteristics from the early portion of the cohort of OEF/OIF veterans. CONCLUSIONS This centrepiece observational study of the Chronic Effects of Neurotrauma Consortium (CENC) is successfully launched and, within several years, should provide fertile data to begin investigating its aims. |
Tiffany Hon; Ravi K. Das; Sunjeev K. Kamboj The effects of cognitive reappraisal following retrieval-procedures designed to destabilize alcohol memories in high-risk drinkers Journal Article In: Psychopharmacology, vol. 233, no. 5, pp. 851–861, 2016. @article{Hon2016, RATIONALE: Addiction is a disorder of motivational learning and memory. Maladaptive motivational memories linking drug-associated stimuli to drug seeking are formed over hundreds of reinforcement trials and accompanied by aberrant neuroadaptation in the mesocorticolimbic reward system. Such memories are resistant to extinction. However, the discovery of retrieval-dependent memory plasticity has opened up the possibility of permanent modification of established (long-term) memories during 'reconsolidation'.$backslash$n$backslash$nOBJECTIVES: Here, we investigate whether reappraisal of maladaptive alcohol cognitions performed after procedures designed to destabilize alcohol memory networks affected subsequent alcohol memory, craving, drinking and attentional bias.$backslash$n$backslash$nMETHODS: Forty-seven at-risk drinkers attended two sessions. On the first lab session, participants underwent one of two prediction error-generating procedures in which outcome expectancies were violated while retrieving alcohol memories (omission and value prediction error groups). Participants in a control group retrieved non-alcohol memories. Participants then reappraised personally relevant maladaptive alcohol memories and completed measures of reappraisal recall, alcohol verbal fluency and craving. Seven days later, they repeated these measures along with attentional bias assessment.$backslash$n$backslash$nRESULTS: Omission prediction error (being unexpectedly prevented from drinking beer), but not a value prediction error (drinking unexpectedly bitter-tasting beer) or control procedure (drinking unexpectedly bitter orange juice), was associated with significant reductions in verbal fluency for positive alcohol-related words. No other statistically robust outcomes were detected.$backslash$n$backslash$nCONCLUSIONS: This study provides partial preliminary support for the idea that a common psychotherapeutic strategy used in the context of putative memory retrieval-destabilization can alter accessibility of alcohol semantic networks. Further research delineating the necessary and sufficient requirements for producing alterations in alcohol memory performance based on memory destabilization is still required. |
Bianca Huurneman; F. Nienke Boonstra; Jeroen Goossens Perceptual learning in children with infantile nystagmus: Effects on visual performance Journal Article In: Investigative Ophthalmology & Visual Science, vol. 57, no. 10, pp. 4216–4228, 2016. @article{Huurneman2016a, PURPOSE: To evaluate whether computerized training with a crowded or uncrowded letter-discrimination task reduces visual impairment (VI) in 6- to 11-year-old children with infantile nystagmus (IN) who suffer from increased foveal crowding, reduced visual acuity, and reduced stereopsis. METHODS: Thirty-six children with IN were included. Eighteen had idiopathic IN and 18 had oculocutaneous albinism. These children were divided in two training groups matched on age and diagnosis: a crowded training group (n = 18) and an uncrowded training group (n = 18). Training occurred two times per week during 5 weeks (3500 trials per training). Eleven age-matched children with normal vision were included to assess baseline differences in task performance and test-retest learning. Main outcome measures were task-specific performance, distance and near visual acuity (DVA and NVA), intensity and extent of (foveal) crowding at 5 m and 40 cm, and stereopsis. RESULTS: Training resulted in task-specific improvements. Both training groups also showed uncrowded and crowded DVA improvements (0.10 ± 0.02 and 0.11 ± 0.02 logMAR) and improved stereopsis (670 ± 249″). Crowded NVA improved only in the crowded training group (0.15 ± 0.02 logMAR), which was also the only group showing a reduction in near crowding intensity (0.08 ± 0.03 logMAR). Effects were not due to test-retest learning. CONCLUSIONS: Perceptual learning with or without distractors reduces the extent of crowding and improves visual acuity in children with IN. Training with distractors improves near vision more than training with single optotypes. Perceptual learning also transfers to DVA and NVA under uncrowded and crowded conditions and even stereopsis. Learning curves indicated that improvements may be larger after longer training. |
Seon-Kyeong Jang; Sujin Kim; Chai-Youn Kim; Hyeon-Seung Lee; Kee-Hong Choi Attentional processing of emotional faces in schizophrenia: Evidence from eye tracking Journal Article In: Journal of Abnormal Psychology, vol. 125, no. 7, pp. 894–906, 2016. @article{Jang2016, Severe emotional disturbances such as anxiety and depression have been closely related to aberrant attentional processing of emotional stimuli. However, this has been little studied in schizophrenia, which is also characterized by marked emotional impairments such as heightened negative affect and anhedonia. In the current study, we investigated temporal dynamics of motivated attention to emotional stimuli in schizophrenia. For this purpose, we tracked eye movements of 22 individuals with schizophrenia or schizoaffective disorder (ISZs) and 19 healthy controls (HCs) to emotional (i.e., happy, sad, angry) and neutral face pairs presented either for 500 ms or 1,500 ms. Initial fixation direction and viewing time at 3 successive intervals (0–500, 500–1,000, 1,000–1,500 ms) were calculated. The results showed that both ISZs and HCs were more likely to orient initial fixations and exhibited longer viewing times to emotional than neutral faces. However, compared with HCs, ISZs allocated less attention to overall faces during the late stage (1,000–1,500 ms) when one of the paired faces displayed negative emotions. Furthermore, positive symptoms were highly associated with initial fixation avoidance to angry faces while depressive symptoms were related to later avoidance of angry faces. Both social amotivation and poor interpersonal functioning were closely related to diminished sustained attention to happy faces. This suggests that early attentional capture of emotional salience may be relatively preserved in schizophrenia, but the people with this disorder display an atypical late attentional process characterized by generalized attentional avoidance of negative stimuli. Of note, aberrant attentional processes of social threat and reward were closely associated with major symptoms and functioning in this disorder. |
Christian P. Janssen; Preeti Verghese Training eye movements for visual search in individuals with macular degeneration Journal Article In: Journal of Vision, vol. 16, no. 15, pp. 1–20, 2016. @article{Janssen2016, We report a method to train individuals with central field loss due to macular degeneration to improve the efficiency of visual search. Our method requires participants to make a same/different judgment on two simple silhouettes. One silhouette is presented in an area that falls within the binocular scotoma while they are fixating the center of the screen with their preferred retinal locus (PRL); the other silhouette is presented diametrically opposite within the intact visual field. Over the course of 480 trials (approximately 6 hr), we gradually reduced the amount of time that participants have to make a saccade and judge the similarity of stimuli. This requires that they direct their PRL first toward the stimulus that is initially hidden behind the scotoma. Results from nine participants show that all participants could complete the task faster with training without sacrificing accuracy on the same/different judgment task. Although a majority of participants were able to direct their PRL toward the initially hidden stimulus, the ability to do so varied between participants. Specifically, six of nine participants made faster saccades with training. A smaller set (four of nine) made accurate saccades inside or close to the target area and retained this strategy 2 to 3 months after training. Subjective reports suggest that training increased awareness of the scotoma location for some individuals. However, training did not transfer to a different visual search task. Nevertheless, our study suggests that increasing scotoma awareness and training participants to look toward their scotoma may help them acquire missing information. |
Manon W. Jones; Margaret J. Snowling; Kristina Moll What automaticity deficit? Activation of lexical information by readers with dyslexia in a rapid automatized naming Stroop-switch task Journal Article In: Journal of Experimental Psychology: Learning, Memory, and Cognition, vol. 42, no. 3, pp. 465–474, 2016. @article{Jones2016, Reading fluency is often predicted by rapid automatized naming (RAN) speed, which as the name implies, measures the automaticity with which familiar stimuli (e.g., letters) can be retrieved and named. Readers with dyslexia are considered to have less "automatized" access to lexical information, reflected in longer RAN times compared with nondyslexic readers. We combined the RAN task with a Stroop-switch manipulation to test the automaticity of dyslexic and nondyslexic readers' lexical access directly within a fluency task. Participants named letters in 10 × 4 arrays while eye movements and speech responses were recorded. Upon fixation, specific letter font colors changed from black to a different color, whereupon the participant was required to rapidly switch from naming the letter to naming the letter color. We could therefore measure reading group differences on "automatic" lexical processing, insofar as it was task-irrelevant. Readers with dyslexia showed obligatory lexical processing and a timeline for recognition that was overall similar to typical readers, but a delay emerged in the output (naming) phase. Further delay was caused by visual-orthographic competition between neighboring stimuli. Our findings outline the specific processes involved when researchers speak of "impaired automaticity" in dyslexic readers' fluency, and are discussed in the context of the broader literature in this field. |
Esther S. Kim; Shannon F. Lemke Behavioural and eye-movement outcomes in response to text-based reading treatment for acquired alexia Journal Article In: Neuropsychological Rehabilitation, vol. 26, no. 1, pp. 60–86, 2016. @article{Kim2016, Text-based reading treatments, such as Multiple Oral Rereading (MOR) and Oral Reading for Language in Aphasia (ORLA) have been used successfully to remediate reading impairments in individuals with acquired alexia, but the mechanisms underlying such improvements are not well understood. In this study, an individual with acquired alexia who demonstrated reliance on a sub-lexical reading strategy (i.e., presence of spelling regularity effect and phonologically plausible errors) underwent 12 weeks of text-based reading treatment combining MOR and ORLA procedures. Behavioural assessments of single-word and text reading, along with eye-tracking assessments were conducted pre-treatment, post-treatment and at 5 month follow-up. Improved reading fluency (rate, accuracy) was observed for both trained and untrained passages. Evidence from behavioural and eye-tracking assessment suggested text-based reading treatment facilitated use of a lexical-semantic reading strategy. Increased frequency and lexicality effects, as well as a shift in initial landing position towards the centre of the word (the "optimal viewing position") were observed at post-treatment and follow-up assessments. These results demonstrate the potential utility of using eye movements as a parameter of interest in addition to traditional behavioural outcomes when investigating response to reading treatment. |
Makoto Kobayashi Delayed saccade to perceptually demanding locations in Parkinson's disease: Analysis from the perspective of the speed–accuracy trade-off Journal Article In: Neurological Sciences, vol. 37, no. 11, pp. 1841–1848, 2016. @article{Kobayashi2016, Parkinson's disease (PD) patients reportedly have shortened, normal, or prolonged latency of visually guided saccades (VGSs). This inconsistency seems to be partly derived from differences in experimental conditions, such as target eccentricity and direction. Another etiology may be a physiological saccade property, the speed-accuracy trade-off. VGS latency tends to increase along with its gain in certain conditions; however, this relationship has not been addressed in PD saccade studies. In this study, we measured VGS latency and gain in 47 PD patients and 48 normal controls (NCs). VGS was evoked by a target, which was presented at the central position initially and pseudo-randomly jumped to the horizontal (10° or 20° eccentricity) or vertical (10° or 15°) meridian. For each target location, the logarithm of the latency (log-latency) was modeled with subject type (PD or NC), age, and gain in the linear-mixed regression analysis. Subsequently, for target locations where PD patients showed an abnormality, the log-latency was similarly modeled with additional clinical variables measured by the mini-mental state examination (MMSE) and unified Parkinson's disease rating scale Part III. PD saccade latency was prolonged and influenced by the MMSE score when targets were presented at the 20° horizontal and upper vertical meridians. Furthermore, gain was a consistently significant variable in all models. The target locations of the delayed saccade corresponded to perceptually demanding locations, indicating that PD subclinical visual dysfunction prolonged the latency. The influence of the MMSE score supports this reasoning. Moreover, the speed-accuracy trade-off appeared to contribute to the accurate saccade analysis. |
Ivan Koychev; Dan Joyce; E. Barkus; Ulrich Ettinger; Anne Schmechtig; Colin T. Dourish; G. R. Dawson; Kevin J. Craig; J. F. William Deakin Cognitive and oculomotor performance in subjects with low and high schizotypy: Implications for translational drug development studies Journal Article In: Translational Psychiatry, vol. 6, pp. e811, 2016. @article{Koychev2016, The development of drugs to improve cognition in patients with schizophrenia is a major unmet clinical need. A number of promising compounds failed in recent clinical trials, a pattern linked to poor translation between preclinical and clinical stages of drug development. Seeking proof of efficacy in early Phase 1 studies in surrogate patient populations (for example, high schizotypy individuals where subtle cognitive impairment is present) has been suggested as a strategy to reduce attrition in the later stages of drug development. However, there is little agreement regarding the pattern of distribution of schizotypal features in the general population, creating uncertainty regarding the optimal control group that should be included in prospective trials. We aimed to address this question by comparing the performance of groups derived from the general population with low, average and high schizotypy scores over a range of cognitive and oculomotor tasks. We found that tasks dependent on frontal inhibitory mechanisms (N-Back working memory and anti-saccade oculomotor tasks), as well as a smooth-pursuit oculomotor task were sensitive to differences in the schizotypy phenotype. In these tasks the cognitive performance of 'low schizotypes' was significantly different from 'high schizotypes' with 'average schizotypes' having an intermediate performance. These results indicate that for evaluating putative cognition enhancers for treating schizophrenia in early-drug development studies the maximum schizotypy effect would be achieved using a design that compares low and high schizotypes. |
Chin-An Wang; Hailey McInnis; Donald C. Brien; Giovanna Pari; Douglas P. Munoz Disruption of pupil size modulation correlates with voluntary motor preparation deficits in Parkinson's disease Journal Article In: Neuropsychologia, vol. 80, pp. 176–184, 2016. @article{Wang2016c, Pupil size is an easy-to-measure, non-invasive method to index various cognitive processes. Although a growing number of studies have incorporated measures of pupil size into clinical investigation, there have only been limited studies in Parkinson's disease (PD). Convergent evidence has suggested PD patients exhibit cognitive impairment at or soon after diagnosis. Here, we used an interleaved pro- and anti-saccade paradigm while monitoring pupil size with saccadic eye movements to examine the relationship between executive function deficits and pupil size in PD patients. Subjects initially fixated a central cue, the color of which instructed them to either look at a peripheral stimulus automatically (pro-saccade) or suppress the automatic response and voluntarily look in the opposite direction of the stimulus (anti-saccade). We hypothesized that deficits of voluntary control should be revealed not only on saccadic but also on pupil responses because of the recently suggested link between the saccade and pupil control circuits. In elderly controls, pupil size was modulated by task preparation, showing larger dilation prior to stimulus appearance in preparation for correct anti-saccades, compared to correct pro-saccades, or erroneous pro-saccades made in the anti-saccade condition. Moreover, the size of pupil dilation correlated negatively with anti-saccade reaction times. However, this profile of pupil size modulation was significantly blunted in PD patients, reflecting dysfunctional circuits for anti-saccade preparation. Our results demonstrate disruptions of modulated pupil responses by voluntary movement preparation in PD patients, highlighting the potential of using low-cost pupil size measurement to examine executive function deficits in early PD. |
David E. Warren; Daniel Tranel; Melissa C. Duff Impaired acquisition of new words after left temporal lobectomy despite normal fast-mapping behavior Journal Article In: Neuropsychologia, vol. 80, pp. 165–175, 2016. @article{Warren2016a, Word learning has been proposed to rely on unique brain regions including the temporal lobes, and the left temporal lobe appears to be especially important. In order to investigate the role of the left temporal lobe in word learning under different conditions, we tested whether patients with left temporal lobectomies (N=6) could learn novel words using two distinct formats. Previous research has shown that word learning in contrastive fast mapping conditions may rely on different neural substrates than explicit encoding conditions (Sharon et al., 2011). In the current investigation, we used a previously reported word learning task that implemented two distinct study formats (Warren and Duff, 2014): a contrastive fast mapping condition in which a picture of a novel item was displayed beside a picture of a familiar item while the novel item's name was presented aurally ("Click on the numbat."); and an explicit encoding (i.e., control) condition in which a picture of a novel item was displayed while its name was presented aurally ("This is a numbat."). After a delay, learning of the novel words was evaluated with memory tests including three-alternative forced-choice recognition, free recall, cued recall, and familiarity ratings. During the fast-mapping study condition both the left temporal lobectomy and healthy comparison groups performed well, but at test only the comparison group showed evidence of novel word learning. Our findings indicate that unilateral resection of the left temporal lobe including the hippocampus and temporal pole can severely impair word learning, and that fast-mapping study conditions do not promote subsequent word learning in temporal lobectomy populations. |
Nilly Weiss; Elite Mardo; Galia Avidan Visual expertise for horses in a case of congenital prosopagnosia Journal Article In: Neuropsychologia, vol. 83, pp. 63–75, 2016. @article{Weiss2016a, A major question in the domain of face perception is whether faces comprise a distinct visual category that is processed by specialized mechanisms, or whether face processing merely represents an extreme case of visual expertise. Here, we examined O.H, a 22 years old woman with congenital prosopagnosia (CP), who despite her severe deficits in face processing, acquired superior recognition skills for horses. To compare the nature of face and horse processing, we utilised the inversion manipulation, known to disproportionally affect faces compared to other objects, with both faces and horses. O.H's performance was compared to data obtained from two control groups that were either horse experts, or non-experts. As expected, both control groups exhibited the face inversion effect, while O.H did not show the effect, but importantly, none of the participants showed an inversion effect for horses. Finally, gaze behaviour toward upright and inverted faces and horses was indicative of visual skill but in a distinct fashion for each category. Particularly, both control groups showed different gaze patterns for upright compared to inverted faces, while O.H presented a similar gaze pattern for the two orientations that differed from that of the two control groups. In contrast, O.H and the horse experts exhibited a similar gaze pattern for upright and inverted horses, while non-experts showed different gaze patterns for different orientations. Taken together, these results suggest that visual expertise can be acquired independently from the mechanisms mediating face recognition. |
Kyoko Yoshida; Yasuhiro Go; Itaru Kushima; Atsushi Toyoda; Asao Fujiyama; Hiroo Imai; Nobuhito Saito; Atsushi Iriki; Norio Ozaki; Masaki Isoda Single-neuron and genetic correlates of autistic behavior in macaque Journal Article In: Science Advances, vol. 2, no. 9, pp. e1600558, 2016. @article{Yoshida2016, Atypical neurodevelopment in autism spectrum disorder is a mystery, defying explanation despite increasing attention. We report on a Japanese macaque that spontaneously exhibited autistic traits, namely, impaired social ability as well as restricted and repetitive behaviors, along with our single-neuron and genomic analyses. Its social ability was measured in a turn-taking task, where two monkeys monitor each other's actions for adaptive behavioral planning. In its brain, the medial frontal neurons responding to others' actions, abundant in the controls, were almost nonexistent. In its genes, whole-exome sequencing and copy number variation analyses identified rare coding variants linked to human neuropsychiatric disorders in 5-hydroxytryptamine (serotonin) receptor 2C (HTR2C) and adenosine triphosphate (ATP)–binding cassette subfamily A13 (ABCA13). This combination of systems neuroscience and cognitive genomics in macaques suggests a new, phenotype-to-genotype approach to studying mental disorders. |
Alexandre Zénon; Yann Duclos; Romain Carron; Tatiana Witjas; Christelle Baunez; Jean Régis; Jean Philippe Azulay; Peter Brown; Alexandre Eusebio The human subthalamic nucleus encodes the subjective value of reward and the cost of effort during decision-making Journal Article In: Brain, vol. 139, no. 6, pp. 1830–1843, 2016. @article{Zenon2016a, Adaptive behaviour entails the capacity to select actions as a function of their energy cost and expected value and the disruption of this faculty is now viewed as a possible cause of the symptoms of Parkinsons disease. Indirect evidence points to the involvement of the subthalamic nucleus–the most common target for deep brain stimulation in Parkinsons disease–in cost-benefit computation. However, this putative function appears at odds with the current view that the subthalamic nucleus is important for adjusting behaviour to conflict. Here we tested these contrasting hypotheses by recording the neuronal activity of the subthalamic nucleus of patients with Parkinsons disease during an effort-based decision task. Local field potentials were recorded from the subthalamic nucleus of 12 patients with advanced Parkinsons disease (mean age 63.8 years +/- 6.8; mean disease duration 9.4 years +/- 2.5) both OFF and ON levodopa while they had to decide whether to engage in an effort task based on the level of effort required and the value of the reward promised in return. The data were analysed using generalized linear mixed models and cluster-based permutation methods. Behaviourally, the probability of trial acceptance increased with the reward value and decreased with the required effort level. Dopamine replacement therapy increased the rate of acceptance for efforts associated with low rewards. When recording the subthalamic nucleus activity, we found a clear neural response to both reward and effort cues in the 1-10 Hz range. In addition these responses were informative of the subjective value of reward and level of effort rather than their actual quantities, such that they were predictive of the participants decisions. OFF levodopa, this link with acceptance was weakened. Finally, we found that these responses did not index conflict, as they did not vary as a function of the distance from indifference in the acceptance decision. These findings show that low-frequency neuronal activity in the subthalamic nucleus may encode the information required to make cost-benefit comparisons, rather than signal conflict. The link between these neural responses and behaviour was stronger under dopamine replacement therapy. Our findings are consistent with the view that Parkinsons disease symptoms may be caused by a disruption of the processes involved in balancing the value of actions with their associated effort cost. |
Gabriela Rosenblau; Dorit Kliemann; Benjamin Lemme; Henrik Walter; Hauke R. Heekeren; Isabel Dziobek The role of the amygdala in naturalistic mentalising in typical development and in autism spectrum disorder Journal Article In: British Journal of Psychiatry, vol. 208, no. 6, pp. 556–564, 2016. @article{Rosenblau2016, Background: The substantial discrepancy between mentalising in experimental settings v. real-life social interactions hinders the understanding of the neural basis of real-life social cognition and of social impairments in psychiatric disorders. Aims: To determine the neural mechanisms underlying naturalistic mentalising in individuals with and without autism spectrum disorder. Method: We investigated mentalising with a new video-based functional magnetic resonance imaging task in 20 individuals with autism spectrum disorder and 22 matched healthy controls. Results: Naturalistic mentalising implicated regions of the traditional mentalising network (medial prefrontal cortex, temporoparietal junction), and additionally the insula and amygdala. Moreover, amygdala activity predicted implicit mentalising performance on an independent behavioural task. Compared with controls, the autism spectrum disorder group did not show differences in neural activity within classical mentalising regions. They did, however, show reduced amygdala activity and a reduced correlation between amygdala activity and mentalising accuracy on the behavioural task, compared with controls. Conclusions: These findings highlight the crucial role of the amygdala in making accurate implicit mental state inferences in typical development and in the social cognitive impairments of individuals with autism spectrum disorder. |
Paul Roux; Pauline Smith; Christine Passerieux; Franck Ramus Preserved implicit mentalizing in schizophrenia despite poor explicit performance: Evidence from eye tracking Journal Article In: Scientific Reports, vol. 6, pp. 34728, 2016. @article{Roux2016, Schizophrenia has been characterized by an impaired mentalizing. It has been suggested that distinguishing implicit from explicit processes is crucial in social cognition, and only the latter might be affected in schizophrenia. Two other questions remain open: (1) Is schizophrenia characterized by an hypo- or hyper attribution of intentions? (2) Is it characterized by a deficit in the attribution of intention or of contingency? To test these three questions, spontaneous mentalizing was tested in 29 individuals with schizophrenia and 29 control subjects using the Frith-Happé animations, while eye movements were recorded. Explicit mentalizing was measured from participants' verbal descriptions and was contrasted with implicit mentalizing measured through eye tracking. As a group, patients made less accurate and less intentional descriptions of the goal-directed and theory of mind animations. No group differences were found in the attribution of contingency. Eye tracking results revealed that patients and controls showed a similar modulation of eye movements in response to the mental states displayed in the Frith-Happé animations. To conclude, in this paradigm, participants with schizophrenia showed a dissociation between explicit and implicit mentalizing, with a decrease in the explicit attribution of intentions, whereas their eye movements suggested a preserved implicit perception of intentions. |
Cristina Rubino; Sherryse L. Corrow; Jeffrey C. Corrow; Brad Duchaine; Jason J. S. Barton Word and text processing in developmental prosopagnosia Journal Article In: Cognitive Neuropsychology, vol. 33, no. 5-6, pp. 315–328, 2016. @article{Rubino2016a, The many-to-many hypothesis proposes that visual object processing is supported by distributed circuits that overlap for different object categories. For faces and words the hypothesis posits that both posterior fusiform regions contribute to both face and visual word perception and predicts that unilateral lesions impairing one will affect the other. However, studies testing this hypothesis have produced mixed results. We evaluated visual word processing in subjects with developmental prosopagnosia, a condition linked to right posterior fusiform abnormalities. Ten developmental prosopagnosic subjects performed a word-length effect task and a task evaluating the recognition of word content across variations in text style, and the recognition of style across variations in word content. All subjects had normal word-length effects. One had prolonged sorting time for word recognition in handwritten stimuli. These results suggest that the deficit in developmental prosopagnosia is unlikely to affect visual word processing, contrary to predictions of the many-to-many hypothesis. |
Nicolas Ruffieux; Meike Ramon; Junpeng Lao; Françoise Colombo; Lisa Stacchi; François-Xavier Borruat; Ettore Accolla; Jean-Marie Annoni; Roberto Caldara Residual perception of biological motion in cortical blindness Journal Article In: Neuropsychologia, vol. 93, pp. 301–311, 2016. @article{Ruffieux2016, From birth, the human visual system shows a remarkable sensitivity for perceiving biological motion. This visual ability relies on a distributed network of brain regions and can be preserved even after damage of high-level ventral visual areas. However, it remains unknown whether this critical biological skill can withstand the loss of vision following bilateral striate damage. To address this question, we tested the categorization of human and animal biological motion in BC, a rare case of cortical blindness after anoxia-induced bilateral striate damage. The severity of his impairment, encompassing various aspects of vision (i.e., color, shape, face, and object recognition) and causing blind-like behavior, contrasts with a residual ability to process motion. We presented BC with static or dynamic point-light displays (PLDs) of human or animal walkers. These stimuli were presented either individually, or in pairs in two alternative forced choice (2AFC) tasks. When confronted with individual PLDs, the patient was unable to categorize the stimuli, irrespective of whether they were static or dynamic. In the 2AFC task, BC exhibited appropriate eye movements towards diagnostic information, but performed at chance level with static PLDs, in stark contrast to his ability to efficiently categorize dynamic biological agents. This striking ability to categorize biological motion provided top-down information is important for at least two reasons. Firstly, it emphasizes the importance of assessing patients' (visual) abilities across a range of task constraints, which can reveal potential residual abilities that may in turn represent a key feature for patient rehabilitation. Finally, our findings reinforce the view that the neural network processing biological motion can efficiently operate despite severely impaired low-level vision, positing our natural predisposition for processing dynamicity in biological agents as a robust feature of human vision. |
Gerardo Salvato; Eva Z. Patai; Tayla Mccloud; Anna C. Nobre In: Cortex, vol. 82, pp. 206–216, 2016. @article{Salvato2016, Apolipoprotein (APOE) ɛ4 genotype has been identified as a risk factor for late-onset Alzheimer disease (AD). The memory system is mostly involved in AD, and memory deficits represent its key feature. A growing body of studies has focused on the earlier identification of cognitive dysfunctions in younger and older APOE ɛ4 carriers, but investigation on middle-aged individuals remains rare. Here we sought to investigate if the APOE ɛ4 genotype modulates declarative memory and its influences on perception in the middle of the life span. We tested 60 middle-aged individuals recruited according to their APOE allele variants (ɛ3/ɛ3, ɛ3/ɛ4, ɛ4/ɛ4) on a long-term memory-based orienting of attention task. Results showed that the APOE ɛ4 genotype impaired neither explicit memory nor memory-based orienting of spatial attention. Interestingly, however, we found that the possession of the ɛ4 allele broke the relationship between declarative long-term memory and memory-guided orienting of visuo-spatial attention, suggesting an earlier modulation exerted by pure genetic characteristics on cognition. These findings are discussed in light of possible accelerated brain ageing in middle-aged ɛ4-carriers, and earlier structural changes in the brain occurring at this stage of the lifespan. |
Ricarda Schmidt; Patrick Lüthold; Rebekka Kittel; Anne Tetzlaff; Anja Hilbert Visual attentional bias for food in adolescents with binge-eating disorder Journal Article In: Journal of Psychiatric Research, vol. 80, pp. 22–29, 2016. @article{Schmidt2016, Evidence suggests that adults with binge-eating disorder (BED) are prone of having their attention interfered by food cues, and that food-related attentional biases are associated with calorie intake and eating disorder psychopathology. For adolescents with BED experimental evidence on attentional processing of food cues is lacking. Using eye-tracking and a visual search task, the present study examined visual orienting and disengagement processes of food in youth with BED. Eye-movement data and reaction times were recorded in 25 adolescents (12-20 years) with BED and 25 controls (CG) individually matched for sex, age, body mass index, and socio-economic status. During a free exploration paradigm, the BED group showed a greater gaze duration bias for food images than the CG. Groups did not differ in gaze direction biases. In a visual search task, the BED group showed a greater detection bias for food targets than the CG. Group differences were more pronounced for personally attractive than unattractive food images. Regarding clinical associations, only in the BED group the gaze duration bias for food was associated with increased hunger and lower body mass index, and the detection bias for food targets was associated with greater reward sensitivity. The study provided first evidence of an attentional bias to food in adolescents with BED. However, more research is needed for further specifying disengagement and orienting processes in adolescent BED, including overt and covert attention, and their prospective associations with binge-eating behaviors and associated psychopathology. |
Jillian M. Schuh; Inge Marie Eigsti; Daniel Mirman Discourse comprehension in autism spectrum disorder: Effects of working memory load and common ground Journal Article In: Autism Research, vol. 9, no. 12, pp. 1340–1352, 2016. @article{Schuh2016, Pragmatic language impairments are nearly universal in autism spectrum disorders (ASD). Discourse requires that we monitor information that is shared or mutually known, called "common ground." While many studies have examined the role of Theory of Mind (ToM) in such impairments, few have examined working memory (WM). Common ground impairments in ASD could reflect limitations in both WM and ToM. This study explored common ground use in youth ages 8-17 years with high-functioning ASD (n = 13) and typical development (n = 22); groups did not differ on age, gender, IQ, or standardized language. We tracked participants' eye movements while they performed a discourse task in which some information was known only to the participant (e.g., was privileged; a manipulation of ToM). In addition, the amount of privileged information varied (a manipulation of WM). All participants were slower to fixate the target when considering privileged information, and this effect was greatest during high WM load trials. Further, the ASD group was more likely to fixate competing (non-target) shapes. Predictors of fixation patterns included ASD symptomatology, language ability, ToM, and WM. Groups did not differ in ToM. Individuals with better WM fixated the target more rapidly, suggesting an association between WM capacity and efficient discourse. In addition to ToM knowledge, WM capacity constrains common ground representation and impacts pragmatic skills in ASD. Social impairments in ASD are thus associated with WM capacity, such that deficits in domain-general, nonsocial processes such as WM exert an influence during complex social interactions. |
Mustafa Seckin; M. Marsel Mesulam; Alfred W. Rademaker; Joel L. Voss; Sandra Weintraub; Emily J. Rogalski; Robert S. Hurley Eye movements as probes of lexico-semantic processing in a patient with primary progressive aphasia Journal Article In: Neurocase, vol. 22, no. 1, pp. 65–75, 2016. @article{Seckin2016, Eye movement trajectories during a verbally cued object search task were used as probes of lexico-semantic associations in an anomic patient with primary progressive aphasia. Visual search was normal on trials where the target object could be named but became lengthy and inefficient on trials where the object failed to be named. The abnormality was most profound if the noun denoting the object could not be recognized. Even trials where the name of the target object was recognized but not retrieved triggered abnormal eye movements, demonstrating that retrieval failures can have underlying associative components despite intact comprehension of the corresponding noun. |
Mustafa Seckin; M. Marsel Mesulam; Joel L. Voss; Wei Huang; Emily J. Rogalski; Robert S. Hurley Am I looking at a cat or a dog? Gaze in the semantic variant of primary progressive aphasia is subject to excessive taxonomic capture Journal Article In: Journal of Neurolinguistics, vol. 37, pp. 68–81, 2016. @article{Seckin2016a, Object naming impairments or anomias are the most frequent symptom in aphasia, and can be caused by a variety of underlying neurocognitive mechanisms. Anomia in neurodegenerative or primary progressive aphasias (PPA) often appears to be based on taxonomic blurring of word meaning: words such as "dog" and "cat" are still recognized generically as referring to animals, but are no longer conceptually differentiated from each other, leading to coordinate errors in word-object matching. This blurring is the hallmark symptom of the "semantic variant" of PPA, who invariably show focal atrophy in the left anterior temporal lobe. In this study we used eye tracking to characterize information processing online (in real time) as non-aphasic controls, semantic and non-semantic PPA participants completed a word-to-object matching task. All participants (including controls) showed taxonomic capture of gaze, spending more time viewing foils that were from the same category as the target compared to unrelated foils, but capture was more extreme in the semantic PPA group. The semantic group showed heightened capture even on trials where they ultimately pointed to the correct target, demonstrating the superiority of eye movements over traditional testing methods in detecting subtle processing impairments. Heightened capture was primarily driven by a tendency to direct gaze back and forth, repeatedly, between a set of related foils on each trial, a behavior almost never shown by controls or non-semantic participants. This suggests semantic PPA participants were accumulating and weighing evidence for a probabilistic rather than definitive mapping between the noun and several candidate objects. Neurodegeneration in PPA thus appears to distort lexical concepts prior to extinguishing them altogether, causing uncertainty in recognition and word-object matching. |
Matthew W. Self; Judith C. Peters; Jessy K. Possel; Joel Reithler; Rainer Goebel; Peterjan Ris; Danique Jeurissen; Leila Reddy; Steven Claus; Johannes C. Baayen; Pieter R. Roelfsema The effects of context and attention on spiking activity in human early visual cortex Journal Article In: PLoS Biology, vol. 14, no. 3, pp. e1002420, 2016. @article{Self2016, Here we report the first quantitative analysis of spiking activity in human early visual cortex. We recorded multi-unit activity from two electrodes in area V2/V3 of a human patient implanted with depth electrodes as part of her treatment for epilepsy. We observed well-localized multi-unit receptive fields with tunings for contrast, orientation, spatial frequency, and size, similar to those reported in the macaque. We also observed pronounced gamma oscillations in the local-field potential that could be used to estimate the underlying spiking response properties. Spiking responses were modulated by visual context and attention. We observed orientation-tuned surround suppression: responses were suppressed by image regions with a uniform orientation and enhanced by orientation contrast. Additionally, responses were enhanced on regions that perceptually segregated from the background, indicating that neurons in the human visual cortex are sensitive to figure-ground structure. Spiking responses were also modulated by object-based attention. When the patient mentally traced a curve through the neurons' receptive fields, the accompanying shift of attention enhanced neuronal activity. These results demonstrate that the tuning properties of cells in the human early visual cortex are similar to those in the macaque and that responses can be modulated by both contextual factors and behavioral relevance. Our results, therefore, imply that the macaque visual system is an excellent model for the human visual cortex. |
Aasef G. Shaikh; Jorge Otero-Millan; Priyanka Kumar; Fatema F. Ghasia Abnormal fixational eye movements in amblyopia Journal Article In: PLoS ONE, vol. 11, no. 3, pp. e0149953, 2016. @article{Shaikh2016, PURPOSE: Fixational saccades shift the foveal image to counteract visual fading related to neural adaptation. Drifts are slow eye movements between two adjacent fixational saccades. We quantified fixational saccades and asked whether their changes could be attributed to pathologic drifts seen in amblyopia, one of the most common causes of blindness in childhood. METHODS: Thirty-six pediatric subjects with varying severity of amblyopia and eleven healthy age-matched controls held their gaze on a visual target. Eye movements were measured with high-resolution video-oculography during fellow eye-viewing and amblyopic eye-viewing conditions. Fixational saccades and drifts were analyzed in the amblyopic and fellow eye and compared with controls. RESULTS: We found an increase in the amplitude with decreased frequency of fixational saccades in children with amblyopia. These alterations in fixational eye movements correlated with the severity of their amblyopia. There was also an increase in eye position variance during drifts in amblyopes. There was no correlation between the eye position variance or the eye velocity during ocular drifts and the amplitude of subsequent fixational saccade. Our findings suggest that abnormalities in fixational saccades in amblyopia are independent of the ocular drift. DISCUSSION: This investigation of amblyopia in pediatric age group quantitatively characterizes the fixation instability. Impaired properties of fixational saccades could be the consequence of abnormal processing and reorganization of the visual system in amblyopia. Paucity in the visual feedback during amblyopic eye-viewing condition can attribute to the increased eye position variance and drift velocity. |
Martha M. Shiell; François Champoux; Robert J. Zatorre The right hemisphere planum temporale supports enhanced visual motion detection ability in deaf people: Evidence from cortical thickness Journal Article In: Neural Plasticity, vol. 2016, pp. 7217630, 2016. @article{Shiell2016, After sensory loss, the deprived cortex can reorganize to process information from the remaining modalities, a phenomenon known as cross-modal reorganization. In blind people this cross-modal processing supports compensatory behavioural enhancements in the nondeprived modalities. Deaf people also show some compensatory visual enhancements, but a direct relationship between these abilities and cross-modally reorganized auditory cortex has only been established in an animal model, the congenitally deaf cat, and not in humans. Using T1-weighted magnetic resonance imaging, we measured cortical thickness in the planum temporale, Heschl's gyrus and sulcus, the middle temporal area MT+, and the calcarine sulcus, in early-deaf persons. We tested for a correlation between this measure and visual motion detection thresholds, a visual function where deaf people show enhancements as compared to hearing. We found that the cortical thickness of a region in the right hemisphere planum temporale, typically an auditory region, was greater in deaf individuals with better visual motion detection thresholds. This same region has previously been implicated in functional imaging studies as important for functional reorganization. The structure-behaviour correlation observed here demonstrates this area's involvement in compensatory vision and indicates an anatomical correlate, increased cortical thickness, of cross-modal plasticity. |
Stephen Soncin; Donald C. Brien; Brian C. Coe; Alina Marin; Douglas P. Munoz Contrasting emotion processing and executive functioning in attention-Deficit/hyperactivity disorder and bipolar disorder Journal Article In: Behavioral Neuroscience, vol. 130, no. 5, pp. 531–543, 2016. @article{Soncin2016, Attention-deficit/hyperactivity disorder (ADHD) and bipolar disorder (BD) are highly comorbid and share executive function and emotion processing deficits, complicating diagnoses despite distinct clinical features. We compared performance on an oculomotor task that assessed these processes to capture subtle differences between ADHD and BD. The interaction between emotion processing and executive functioning may be informative because, although these processes overlap anatomically, certain regions that are compromised in each network are different in ADHD and BD. Adults, aged 18-62, with ADHD ( = 22), BD ( = 20), and healthy controls ( = 21) performed an interleaved pro- and antisaccade task (looking toward vs. looking away from a visual target, respectively). Task irrelevant emotional faces (fear, happy, sad, neutral) were presented on a subset of trials either before or with the target. The ADHD group made more direction errors (looked in the wrong direction) than controls. Presentation of negatively valenced (fear, sad) and ambiguous (neutral) emotional faces increased saccadic reaction time in BD only compared to controls, whereas longer presentation of sad faces modestly increased group differences. The antisaccade task differentiated ADHD from controls. Emotional processing further impaired processing speed in BD. We propose that the dorsolateral prefrontal cortex is critical in both processing systems, but the inhibitory signal this region generates is impacted by dysfunction in the emotion processing network, possibly at the orbitofrontal cortex, in BD. These results suggest there are differences in how emotion processing and executive functioning interact, which could be utilized to improve diagnostic specificity. |
Petra Fischer; José P. Ossandón; Johannes Keyser; Alessandro Gulberti; Niklas Wilming; Wolfgang Hamel; Johannes Köppen; Carsten Buhmann; Manfred Westphal; Christian Gerloff; Christian K. E. Moll; Andreas K. Engel; Peter König STN-DBS reduces saccadic hypometria but not visuospatial bias in Parkinson's disease patients Journal Article In: Frontiers in Behavioral Neuroscience, vol. 10, pp. 85, 2016. @article{Fischer2016, In contrast to its well-established role in alleviating skeleto-motor symptoms in Parkinson's disease, little is known about the impact of deep brain stimulation (DBS) of the subthalamic nucleus (STN) on oculomotor control and attention. Eye-tracking data of 17 patients with left-hemibody symptom onset was compared with 17 age-matched control subjects. Free-viewing of natural images was assessed without stimulation as baseline and during bilateral DBS. To examine the involvement of ventral STN territories in oculomotion and spatial attention, we employed unilateral stimulation via the left and right ventralmost contacts respectively. When DBS was off, patients showed shorter saccades and a rightward viewing bias compared with controls. Bilateral stimulation in therapeutic settings improved saccadic hypometria but not the visuospatial bias. At a group level, unilateral ventral stimulation yielded no consistent effects. However, the evaluation of electrode position within normalized MNI coordinate space revealed that the extent of early exploration bias correlated with the precise stimulation site within the left subthalamic area. These results suggest that oculomotor impairments "but not higher-level exploration patterns" are effectively ameliorable by DBS in therapeutic settings. Our findings highlight the relevance of the STN topography in selecting contacts for chronic stimulation especially upon appearance of visuospatial attention deficits. |
Phillip D. Fletcher; Jennifer M. Nicholas; Laura E. Downey; Hannah L. Golden; Camilla N. Clark; Carolina Pires; Jennifer L. Agustus; Catherine J. Mummery; Jonathan M. Schott; Jonathan D. Rohrer; Sebastian J. Crutch; Jason D. Warren A physiological signature of sound meaning in dementia Journal Article In: Cortex, vol. 77, pp. 13–23, 2016. @article{Fletcher2016, The meaning of sensory objects is often behaviourally and biologically salient and decoding of semantic salience is potentially vulnerable in dementia. However, it remains unclear how sensory semantic processing is linked to physiological mechanisms for coding object salience and how that linkage is affected by neurodegenerative diseases. Here we addressed this issue using the paradigm of complex sounds. We used pupillometry to compare physiological responses to real versus synthetic nonverbal sounds in patients with canonical dementia syndromes (behavioural variant frontotemporal dementia - bvFTD, semantic dementia - SD; progressive nonfluent aphasia - PNFA; typical Alzheimer's disease - AD) relative to healthy older individuals. Nonverbal auditory semantic competence was assessed using a novel within-modality sound classification task and neuroanatomical associations of pupillary responses were assessed using voxel-based morphometry (VBM) of patients' brain MR images. After taking affective stimulus factors into account, patients with SD and AD showed significantly increased pupil responses to real versus synthetic sounds relative to healthy controls. The bvFTD, SD and AD groups had a nonverbal auditory semantic deficit relative to healthy controls and nonverbal auditory semantic performance was inversely correlated with the magnitude of the enhanced pupil response to real versus synthetic sounds across the patient cohort. A region of interest analysis demonstrated neuroanatomical associations of overall pupil reactivity and differential pupil reactivity to sound semantic content in superior colliculus and left anterior temporal cortex respectively. Our findings suggest that autonomic coding of auditory semantic ambiguity in the setting of a damaged semantic system may constitute a novel physiological signature of neurodegenerative diseases. |
Alessio Fracasso; Yvonne Koenraads; Giorgio L. Porro; Serge O. Dumoulin Bilateral population receptive fields in congenital hemihydranencephaly Journal Article In: Ophthalmic and Physiological Optics, vol. 36, no. 3, pp. 324–334, 2016. @article{Fracasso2016a, PURPOSE: Congenital hemihydranencephaly (HH) is a very rare disorder characterised by prenatal near-complete unilateral loss of the cerebral cortex. We investigated a patient affected by congenital right HH whose visual field extended significantly into the both visual hemifields, suggesting a reorganisation of the remaining left visual hemisphere. We examined the early visual cortex reorganisation using functional MRI (7T) and population receptive field (pRF) modelling. METHODS: Data were acquired by means of a 7T MRI while the patient affected by HH viewed conventional population receptive field mapping stimuli. Two possible pRF reorganisation schemes were evaluated: where every cortical location processed information from either (i) a single region of the visual field or (ii) from two bilateral regions of the visual field. RESULTS: In the patient affected by HH, bilateral pRFs in single cortical locations of the remaining hemisphere were found. In addition, using this specific pRF reorganisation scheme, the biologically known relationship between pRF size and eccentricity was found. CONCLUSIONS: Bilateral pRFs were found in the remaining left hemisphere of the patient affected by HH, indicating reorganisation of intra-cortical wiring of the early visual cortex and confirming brain plasticity and reorganisation after an early cerebral damage in humans. |
Mallory Frayn; Christopher R. Sears; Kristin M. Ranson A sad mood increases attention to unhealthy food images in women with food addiction Journal Article In: Appetite, vol. 100, pp. 55–63, 2016. @article{Frayn2016, Food addiction and emotional eating both influence eating and weight, but little is known of how negative mood affects the attentional processes that may contribute to food addiction. The purpose of this study was to compare attention to food images in adult women (N = 66) with versus without food addiction, before and after a sad mood induction (MI). Participants' eye fixations were tracked and recorded throughout 8-s presentations of displays with healthy food, unhealthy food, and non-food images. Food addiction was self-reported using the Yale Food Addiction Scale. The sad MI involved watching an 8-min video about a young child who passed away from cancer. It was predicted that: (1) participants in the food addiction group would attend to unhealthy food significantly more than participants in the control group, and (2) participants in the food addiction group would increase their attention to unhealthy food images following the sad MI, due to increased emotional reactivity and poorer emotional regulation. As predicted, the sad MI had a different effect for those with versus without food addiction: for participants with food addiction, attention to unhealthy images increased following the sad MI and attention to healthy images decreased, whereas for participants without food addiction the sad MI did not alter attention to food. These findings contribute to researchers' understanding of the cognitive factors underlying food addiction. |
Fatema F. Ghasia; George Wilmot; Anwar Ahmed; Aasef G. Shaikh Strabismus and micro-opsoclonus in Machado-Joseph disease Journal Article In: Cerebellum, vol. 15, no. 4, pp. 491–497, 2016. @article{Ghasia2016, We describe novel deficits ofgaze holding and ocular alignment in patients with spinocerebellar ataxia type 3, also known as Machado-Joseph disease (MJD). Twelve MJD patients were studied. Clinical assessments and quantitative ocular alignment measures were performed. Eye movements were quantitatively assessed with corneal curvature tracker and video-oculography. Strabismus was seen in ten MJD patients. Four patients had mild to moderate intermittent exotropia, three had esotropia, one had skew deviation, one had hypotropia, and one patient had moderate exophoria. Three strabismic patients had V-pattern. Near point ofconvergence was normal in two out ofthree patients with exotropia. Gaze holding deficits were also common. Eight patients had gaze-evoked nystagmus, and five had micro-opsoclonus. Other ocular motor deficits included saccadic dysmetria in eight patients, whereas all had saccadic interruption ofsmooth pursuit. Strabismus and micro-opsoclonus are common in MJD. Coexisting ophthalmoplegia or vergence abnormalities in our patients with exotropia that comprised 50 % of the cohort could not explain the type ofstrabismus in our patients. Therefore, it is possible that involvement ofthe brainstem, the deep cerebellar nuclei, and the superior cerebellar peduncle are the physiological basis for exotropia in these patients. Micro-opsoclonus was also common in MJD. Brainstem and deep cerebellar nuclei lesion also explains micro-opsoclonus, whereas brainstem deficits can describe slow saccades seen in our patients with MJD. |
Lauren R. Godier; Jessica C. Scaife; Sven Braeutigam; Rebecca J. Park Enhanced early neuronal processing of food pictures in Anorexia Nervosa: A magnetoencephalography study Journal Article In: Psychiatry Journal, vol. 2016, pp. 1–13, 2016. @article{Godier2016, Neuroimaging studies in Anorexia Nervosa (AN) have shown increased activation in reward and cognitive control regions in response to food, and a behavioral attentional bias (AB) towards food stimuli is reported. This study aimed to further investigate the neural processing of food using magnetoencephalography (MEG). Participants were 13 females with restricting-type AN, 14 females recovered from restricting-type AN, and 15 female healthy controls. MEG data was acquired whilst participants viewed high- and low-calorie food pictures. Attention was assessed with a reaction time task and eye tracking. Time-series analysis suggested increased neural activity in response to both calorie conditions in the AN groups, consistent with an early AB. Increased activity was observed at 150 ms in the current AN group. Neuronal activity at this latency was at normal level in the recovered group; however, this group exhibited enhanced activity at 320 ms after stimulus. Consistent with previous studies, analysis in source space and behavioral data suggested enhanced attention and cognitive control processes in response to food stimuli in AN. This may enable avoidance of salient food stimuli and maintenance of dietary restraint in AN. A later latency of increased activity in the recovered group may reflect a reversal of this avoidance, with source space and behavioral data indicating increased visual and cognitive processing of food stimuli. |
Gil Gonen-Yaacovi; Ayelet Arazi; Nitzan Shahar; Anat Karmon; Shlomi Haar; Nachshon Meiran; Ilan Dinstein Increased ongoing neural variability in ADHD Journal Article In: Cortex, vol. 81, pp. 50–63, 2016. @article{GonenYaacovi2016, Attention Deficit Hyperactivity Disorder (ADHD) has been described as a disorder where frequent lapses of attention impair the ability of an individual to focus/attend in a sustained manner, thereby generating abnormally large intra-individual behavioral variability across trials. Indeed, increased reaction time (RT) variability is a fundamental behavioral characteristic of individuals with ADHD found across a large number of cognitive tasks. But what is the underlying neurophysiology that might generate such behavioral instability? Here, we examined trial-by-trial EEG response variability to visual and auditory stimuli while subjects' attention was diverted to an unrelated task at the fixation cross. Comparisons between adult ADHD and control participants revealed that neural response variability was significantly larger in the ADHD group as compared with the control group in both sensory modalities. Importantly, larger trial-by-trial variability in ADHD was apparent before and after stimulus presentation as well as in trials where the stimulus was omitted, suggesting that ongoing (rather than stimulus-evoked) neural activity is continuously more variable (noisier) in ADHD. While the patho-physiological mechanisms causing this increased neural variability remain unknown, they appear to act continuously rather than being tied to a specific sensory or cognitive process. |
Claudia C. Gonzalez; Mark Mon-Williams; Siobhan Burke; Melanie R. Burke Cognitive control of saccadic eye movements in children with developmental coordination disorder Journal Article In: PLoS ONE, vol. 11, no. 11, pp. e0165380, 2016. @article{Gonzalez2016b, The ability to use advance information to prepare and execute a movement requires cognitive control of behaviour (e.g., anticipation and inhibition). Our aim was to explore the integrity of saccadic eye movement control in developmental coordination disorder (DCD) and typically developing (TD) children (8–12 years) and assess how these children plan and inhibit saccadic responses, the principal mechanisms within visual attention control. Eye movements and touch responses were measured (separately and concurrently) in Cued and Non-Cued conditions. We found that children with DCD had similar saccade kinematics to the TD group during saccade initiation. Advance information decreased hand movement duration in both groups during Cued trials, but decrements in accuracy were significantly worse in the DCD group. In addition, children with DCD exhibited greater inhibitory errors and inaccurate fixation during the Cued trials. Thus, children with DCD were reasonably proficient in executing saccades during reflexive (Non-Cued) conditions, but showed deficits in more complex control processes involving prediction and inhibition. These findings have implications for our understanding of motor control in children with DCD. |
Martin Gorges; Hans Peter Müller; Dorothée Lulé; LANDSCAPE Consortium; Elmar H. Pinkhardt; Albert C. Ludolph; Jan Kassubek The association between alterations of eye movement control and cerebral intrinsic functional connectivity in Parkinson's disease Journal Article In: Brain Imaging and Behavior, vol. 10, no. 1, pp. 79–91, 2016. @article{Gorges2016, Patients with Parkinson's disease (PD) present with eye movement disturbances that accompany the cardinal motor symptoms. Previous studies have consistently found evidence that large-scale functional networks are critically involved in eye movement control. We challenged the hypothesis that altered eye movement control in patients with PD is closely related to alterations of whole-brain functional connectivity in association with the neurodegenerative process. Saccadic and pursuit eye movements by video-oculography and 'resting-state' functional MRI (3 Tesla) were recorded from 53 subjects, i.e. 31 patients with PD and 22 matched healthy controls. Video-oculographically, a broad spectrum of eye movement impairments was demonstrated in PD patients vs. controls, including interrupted smooth pursuit, hypometric saccades, and a high distractibility in anti-saccades. Significant correlations between altered oculomotor parameters and functional connectivity measures were observed, i.e. the worse the oculomotor performance was, the more the regional functional connectivity in cortical, limbic, thalamic, cerebellar, and brainstem areas was decreased. Remarkably, decreased connectivity between major nodes of the default mode network was tightly correlated with the prevalence of saccadic intrusions as a measure for distractability. In conclusion, dysfunctional eye movement control in PD seems to be primarily associated with (cortical) executive deficits, rather than being related to the ponto-cerebellar circuits or the oculomotor brainstem nuclei. Worsened eye movement performance together with the potential pathophysiological substrate of decreased intrinsic functional connectivity in predominantly oculomotor-associated cerebral functional networks may constitute a behavioral marker in PD. |
Ziad M. Hafed; Katarina Stingl; Karl Ulrich Bartz-Schmidt; Florian Gekeler; Eberhart Zrenner Oculomotor behavior of blind patients seeing with a subretinal visual implant Journal Article In: Vision Research, vol. 118, pp. 119–131, 2016. @article{Hafed2016, Electronic implants are able to restore some visual function in blind patients with hereditary retinal degenerations. Subretinal visual implants, such as the CE-approved Retina Implant Alpha IMS (Retina Implant AG, Reutlingen, Germany), sense light through the eye's optics and subsequently stimulate retinal bipolar cells via ~1500 independent pixels to project visual signals to the brain. Because these devices are directly implanted beneath the fovea, they potentially harness the full benefit of eye movements to scan scenes and fixate objects. However, so far, the oculomotor behavior of patients using subretinal implants has not been characterized. Here, we tracked eye movements in two blind patients seeing with a subretinal implant, and we compared them to those of three healthy controls. We presented bright geometric shapes on a dark background, and we asked the patients to report seeing them or not. We found that once the patients visually localized the shapes, they fixated well and exhibited classic oculomotor fixational patterns, including the generation of microsaccades and ocular drifts. Further, we found that a reduced frequency of saccades and microsaccades was correlated with loss of visibility. Last, but not least, gaze location corresponded to the location of the stimulus, and shape and size aspects of the viewed stimulus were reflected by the direction and size of saccades. Our results pave the way for future use of eye tracking in subretinal implant patients, not only to understand their oculomotor behavior, but also to design oculomotor training strategies that can help improve their quality of life. |
Jarkko Hautala; Otto Loberg; Piia Astikainen; Lauri Nummenmaa; Jari K. Hietanen Effects of conversation content on viewing dyadic conversations Journal Article In: Journal of Eye Movement Research, vol. 9, no. 7, pp. 1–12, 2016. @article{Hautala2016, People typically follow conversations closely with their gaze. We asked whether this viewing is influenced by what is actually said in the conversation and by the viewer's psychological condition. We recorded the eye movements of healthy (N = 16) and de- pressed (N = 25) participants while they were viewing video clips. Each video showed two people, each speaking one line of dialogue about socio-emotionally important (i.e., per- sonal) or unimportant topics (matter-of-fact). Between the spoken lines, the viewers made more saccadic shifts between the discussants, and looked more at the second speaker, in personal vs. matter-of-fact conversations. Higher depression scores were correlated with less looking at the currently speaking discussant. We conclude that subtle social attention dynamics can be detected from eye movements and that these dynamics are sensitive to the observer's psychological condition, such as depression. |
R. A. Hayes; Michael Walsh Dickey; Tessa Warren Looking for a location: Dissociated effects of event-related plausibility and verb–argument information on predictive processing in aphasia Journal Article In: American Journal of Speech-Language Pathology, vol. 25, no. 3, pp. S758–S775, 2016. @article{Hayes2016a, PURPOSE: This study examined the influence of verb-argument information and event-related plausibility on prediction of upcoming event locations in people with aphasia, as well as older and younger, neurotypical adults. It investigated how these types of information interact during anticipatory processing and how the ability to take advantage of the different types of information is affected by aphasia. METHOD: This study used a modified visual-world task to examine eye movements and offline photo selection. Twelve adults with aphasia (aged 54-82 years) as well as 44 young adults (aged 18-31 years) and 18 older adults (aged 50-71 years) participated. RESULTS: Neurotypical adults used verb argument status and plausibility information to guide both eye gaze (a measure of anticipatory processing) and image selection (a measure of ultimate interpretation). Argument status did not affect the behavior of people with aphasia in either measure. There was only limited evidence of interaction between these 2 factors in eye gaze data. CONCLUSIONS: Both event-related plausibility and verb-based argument status contributed to anticipatory processing of upcoming event locations among younger and older neurotypical adults. However, event-related likelihood had a much larger role in the performance of people with aphasia than did verb-based knowledge regarding argument structure. |
Amanda J. Connolly; Nicole J. Rinehart; Joanne Fielding Saccade adaptation in young people diagnosed with Attention Deficit Hyperactivity Disorder Combined Type Journal Article In: Neuroscience, vol. 333, pp. 27–34, 2016. @article{Connolly2016, Growing evidence suggests Attention Deficit Hyperactivity Disorder (ADHD) often co-occurs with Autism Spectrum Disorder (ASD), and a better understanding of the nature of their overlap, including at a neurobiological level, is needed. Research has implicated cerebellar-networks as part of the neural-circuitry disrupted in ASD, but little research has been carried out to investigate this in ADHD. We investigated cerebellar integrity using a double-step saccade adaptation paradigm in a group of male children age 8–15 (n = 12) diagnosed with ADHD-Combined Type (-CT). Their performance was compared to a group of age and IQ-matched typically developing (TD) controls (n = 12). Parent reported symptoms of ADHD-CT and ASD were measured, along with motor proficiency (Movement ABC-2). We found, on average, the adaptation of saccade gain was reduced for the ADHD-CT group compared to the TD group. Greater saccadic gain change (adaptation) was also positively correlated with higher Movement ABC-2 total and balance scores among the ADHD-CT participants. These differences suggest cerebellar networks underlying saccade adaptation may be disrupted in young people with ADHD-CT. Though our findings require further replication with larger samples, they suggest further research into cerebellar dysfunction in ADHD-CT, and as a point of neurobiological overlap with ASD, may be warranted. |
Amanda J. Connolly; Nicole J. Rinehart; Beth P. Johnson; Nicole Papadopoulos; Joanne Fielding In: Neuroscience, vol. 334, pp. 47–54, 2016. @article{Connolly2016a, Although there is little overlap in core diagnostic criteria for ADHD and Autism Spectrum Disorder (ASD), ASD symptoms are estimated to co-occur in children with ADHD in 20–50% of cases. As motor control deficits are common to both disorders, we investigated the impact of ASD symptoms on ocular motor control in children with Attention Deficit Hyperactivity Disorder-Combined Type (ADHD-CT), using a cued saccade paradigm sensitive to cerebellar ocular motor impairment in ASD. Basic saccade metrics (latency, velocity and accuracy), trial-to-trial variability, and main sequences relationships (saccade velocity for a given amplitude) were assessed, for 14 males with ADHD-CT and 14 typically developing (TD) males (aged 8–14, IQ > 80). Our results revealed that saccade profiles of the ADHD-CT group showed a pattern of hypermetria and altered main sequence. As the cerebellum is crucially involved in the regulation of saccade parameters, we propose that this pattern of deficit in ADHD-CT is consistent with the widely reported morphological abnormalities in ocular motor vermis (cerebellar lobules VI-VII) in ADHD-CT and ASD. |
Katri K. Cornelissen; Piers L. Cornelissen; Peter J. B. Hancock; Martin J. Tovée Fixation patterns, not clinical diagnosis, predict body size over-estimation in eating disordered women and healthy controls Journal Article In: International Journal of Eating Disorders, vol. 49, no. 5, pp. 507–518, 2016. @article{Cornelissen2016, OBJECTIVE: A core feature of anorexia nervosa (AN) is an over-estimation of body size. Women with AN have a different pattern of eye-movements when judging bodies, but it is unclear whether this is specific to their diagnosis or whether it is found in anyone over-estimating body size. METHOD: To address this question, we compared the eye movement patterns from three participant groups while they carried out a body size estimation task: (i) 20 women with recovering/recovered anorexia (rAN) who had concerns about body shape and weight and who over-estimated body size, (ii) 20 healthy controls who had normative levels of concern about body shape and who estimated body size accurately (iii) 20 healthy controls who had normative levels of concern about body shape but who did over-estimate body size. RESULTS: Comparisons between the three groups showed that: (i) accurate body size estimators tended to look more in the waist region, and this was independent of clinical diagnosis; (ii) there is a pattern of looking at images of bodies, particularly viewing the upper parts of the torso and face, which is specific to participants with rAN but which is independent of accuracy in body size estimation. DISCUSSION: Since the over-estimating controls did not share the same body image concerns that women with rAN report, their over-estimation cannot be explained by attitudinal concerns about body shape and weight. These results suggest that a distributed fixation pattern is associated with over-estimation of body size and should be addressed in treatment programs. |
Hayley Crawford; Joanna Moss; Chris Oliver; Natasha Elliott; Giles M. Anderson; Joseph P. McCleery Visual preference for social stimuli in individuals with autism or neurodevelopmental disorders: An eye-tracking study Journal Article In: Molecular Autism, vol. 7, no. 1, pp. 1–12, 2016. @article{Crawford2016, Background: Recent research has identified differences in relative attention to competing social versus non-social video stimuli in individuals with autism spectrum disorder (ASD). Whether attentional allocation is influenced by the potential threat of stimuli has yet to be investigated. This is manipulated in the current study by the extent to which the stimuli are moving towards or moving past the viewer. Furthermore, little is known about whether such differences exist across other neurodevelopmental disorders. This study aims to determine if adolescents with ASD demonstrate differences in attentional allocation to competing pairs of social and non-social video stimuli, where the actor or object either moves towards or moves past the viewer, in comparison to individuals without ASD, and to determine if individuals with three genetic syndromes associated with differing social phenotypes demonstrate differences in attentional allocation to the same stimuli. Methods: In study 1, adolescents with ASD and control participants were presented with social and non-social video stimuli in two formats (moving towards or moving past the viewer) whilst their eye movements were recorded. This paradigm was then employed with groups of individuals with fragile X, Cornelia de Lange, and Rubinstein-Taybi syndromes who were matched with one another on chronological age, global adaptive behaviour, and verbal adaptive behaviour (study 2). Results: Adolescents with ASD demonstrated reduced looking-time to social versus non-social videos only when stimuli were moving towards them. Individuals in the three genetic syndrome groups showed similar looking-time but differences in fixation latency for social stimuli moving towards them. Across both studies, we observed within- and between-group differences in attention to social stimuli that were moving towards versus moving past the viewer. Conclusions: Taken together, these results provide strong evidence to suggest differential visual attention to competing social versus non-social video stimuli in populations with clinically relevant, genetically mediated differences in socio-behavioural phenotypes. |
Louis F. Dell'Osso; Faruk H. Orge; Jonathan B. Jacobs Effects of augmented tenotomy and reattachment in the infantile nystagmus syndrome Journal Article In: Digital Journal of Opthalmology, vol. 22, no. 1, pp. 12–24, 2016. @article{DellOsso2016, PURPOSE: To test the hypothesis that augmented tenotomy and reattachment surgery (AT-R), which involves placing an additional suture in each distal tendon during the 4-muscle tenotomy and reattachment (T-R) or other infantile nystagmus syndrome (INS) procedures, could increase the beneficial effects of many types of extraocular muscle (EOM) surgery to treat INS. METHODS: Both infrared reflection and high-speed digital video systems were used to record the eye movements in 4 patients with INS before and after AT-R surgery. Data were analyzed using the eXpanded Nystagmus Acuity Function (NAFX) that is part of the OMtools software. RESULTS: Placement of the augmentation suture did not interfere with Kestenbaum, Anderson, bilateral medial rectus muscle recession, or T-R surgeries. The therapeutic effects of AT-R were similar to but not equal to those from the traditional single-suture surgeries (ie, broadening longest foveation domain [LFD] but no improvement of NAFX peak). The average of the NAFX percent improvements after AT-R was within 31% of those estimated from NAFX values before T-R; the average of the percent broadenings of the LFD values after AT-R was within 16%. CONCLUSIONS: The AT-R does not improve the foveation quality in INS above the traditional T-R surgery. It is not improved by an additional suture; indeed, some improvements may be diminished by the added suture. The hypothesized augmented-tendon suture technique (sans tenotomy) has been modified and remains to be tested. |
Yun Ding; Jing Zhao; Tao He; Yufei Tan; Lingshuang Zheng; Zhiguo Wang Selective impairments in covert shifts of attention in Chinese dyslexic children Journal Article In: Dyslexia, vol. 22, no. 4, pp. 362–378, 2016. @article{Ding2016a, Reading depends heavily on the efficient shift of attention. Mounting evidence has suggested that dyslexics have deficits in covert attentional shift. However, it remains unclear whether dyslexics also have deficits in overt attentional shift. With the majority of relevant studies carried out in alphabetic writing systems, it is also unknown whether the attentional deficits observed in dyslexics are restricted to a particular writing system. The present study examined inhibition of return (IOR)-a major driving force of attentional shifts-in dyslexic children learning to read a logographic script (i.e., Chinese). Robust IOR effects were observed in both covert and overt attentional tasks in two groups of typically developing children, who were age- or reading ability-matched to the dyslexic children. In contrast, the dyslexic children showed IOR in the overt but not in the covert attentional task. We conclude that covert attentional shift is selectively impaired in dyslexic children. This impairment is not restricted to alphabetic writing systems, and it could be a significant contributor to the difficulties encountered by children learning to read. |
Muriel Dysli; Mathias Abegg Nystagmus does not limit reading ability in albinism Journal Article In: PLoS ONE, vol. 11, no. 7, pp. e0158815, 2016. @article{Dysli2016, PURPOSE: Subjects with albinism usually suffer from nystagmus and reduced visual acuity, which may impair reading performance. The contribution of nystagmus to decreased reading ability is not known. Low vision and nystagmus may have an additive effect. We aimed to address this question by motion compensation of the nystagmus in affected subjects and by simulating nystagmus in healthy controls. METHODS: Reading speed and eye movements were assessed in 9 subjects with nystagmus associated with albinism and in 12 healthy controls. We compared the reading ability with steady word presentation and with words presented on a gaze contingent display where words move in parallel to the nystagmus and thus correct for the nystagmus. As the control, healthy subjects were asked to read words and texts in steady reading conditions as well as text passages that moved in a pattern similar to nystagmus. RESULTS: Correcting nystagmus with a gaze contingent display neither improved nor reduced the reading speed for single words. Subjects with nystagmus and healthy participants achieved comparable reading speed when reading steady texts. However, movement of text in healthy controls caused a significantly reduced reading speed and more regressive saccades. CONCLUSIONS: Our results argue against nystagmus as the rate limiting factor for reading speed when words were presented in high enough magnification and support the notion that other sensory visual impairments associated with albinism (for example reduced visual acuity) might be the primary causes for reading impairment. |
Joris A. Elshout; Freekje Asten; Carel B. Hoyng; Douwe P. Bergsma; Albert V. Van den Berg Visual rehabilitation in chronic cerebral blindness: A randomized controlled crossover study Journal Article In: Frontiers in Neurology, vol. 7, pp. 92, 2016. @article{Elshout2016, The treatment of patients suffering from cerebral blindness following stroke is a topic of much recent interest. Several types of treatment are under investigation, such as substitution with prisms and compensation training of saccades. A third approach, aimed at vision restitution is controversial, as a proper controlled study design is missing. In the current study, 27 chronic stroke patients with homonymous visual field defects were trained at home with a visual training device. We used a discrimination task for two types of stimuli: a static point stimulus and a new optic flow-discontinuity stimulus. Using a randomized controlled crossover design, each patient received two successive training rounds, one with high contrast stimuli in their affected hemifield (test) and one round with low-contrast stimuli in their intact hemifield (control). Goldmann and Humphrey perimetry were performed at the start of the study and following each training round. In addition, reading performance was measured. Goldmann perimetry revealed a statistically significant reduction of the visual field defect after the test training, but not after the control training or after no intervention. For both training rounds combined, Humphrey perimetry revealed that the effect of a directed training (sensitivity change in trained hemifield) exceeded that of an undirected training (sensitivity change in untrained hemifield). The interaction between trained and tested hemifield was just above the threshold of significance (p = 0.058). Interestingly, reduction of the field defect assessed by Goldmann perimetry increases with the difference between defect size as measured by Humphrey and Goldmann perimetry prior to training. Moreover, improvement of visual sensitivity measured by Humphrey perimetry increases with the fraction of non-responsive elements (i.e., more relative field loss) in Humphrey perimetry prior to training. Reading speed revealed a significant improvement after training. Our findings demonstrate that our training can result in reduction of the visual field. Improved reading performance after defect training further supports the significance of our training for improvement in daily life activities. |
Gerardo Fernández; Salvador Guinjoan; Marcelo Sapognikoff; David Orozco; Osvaldo Agamennoni Contextual predictability enhances reading performance in patients with schizophrenia Journal Article In: Psychiatry Research, vol. 241, pp. 333–339, 2016. @article{Fernandez2016, In the present work we analyzed fixation duration in 40 healthy individuals and 18 patients with chronic, stable SZ during reading of regular sentences and proverbs. While they read, their eye movements were recorded. We used lineal mixed models to analyze fixation durations. The predictability of words N-1, N, and N+1 exerted a strong influence on controls and SZ patients. The influence of the predictabilities of preceding, current, and upcoming words on SZ was clearly reduced for proverbs in comparison to regular sentences. Both controls and SZ readers were able to use highly predictable fixated words for an easier reading. Our results suggest that SZ readers might compensate attentional and working memory deficiencies by using stored information of familiar texts for enhancing their reading performance. The predictabilities of words in proverbs serve as task-appropriate cues that are used by SZ readers. To the best of our knowledge, this is the first study using eyetracking for measuring how patients with SZ process well-defined words embedded in regular sentences and proverbs. Evaluation of the resulting changes in fixation durations might provide a useful tool for understanding how SZ patients could enhance their reading performance. |
Gerardo Fernández; Facundo Manes; Luis E. Politi; David Orozco; Marcela Schumacher; Liliana Castro; Osvaldo Agamennoni; Nora P. Rotstein Patients with mild Alzheimer's disease fail when using their working memory: Evidence from the eye tracking technique Journal Article In: Journal of Alzheimer's Disease, vol. 50, no. 3, pp. 827–838, 2016. @article{Fernandez2016a, Patients with Alzheimer's disease (AD) develop progressive language, visuoperceptual, attentional, and oculomotor changes that can have an impact on their reading comprehension. However, few studies have examined reading behavior in AD, and none have examined the contribution of predictive cueing in reading performance. For this purpose we analyzed the eye movement behavior of 35 healthy readers (Controls) and 35 patients with probable AD during reading of regular and highpredictable sentences. The cloze predictability of words N- 1, and N+ 1 exerted an influence on the reader's gaze duration. The predictabilities of preceding words in high-predictable sentences served as task-appropriate cues that were used by Control readers. In contrast, these effects were not present in AD patients. In Controls, changes in predictability significantly affected fixation duration along the sentence; noteworthy, these changes did not affect fixation durations in AD patients. Hence, only in healthy readers did predictability of upcoming words influence fixation durations via memory retrieval. Our results suggest that Controls used stored information of familiar texts for enhancing their reading performance and imply that contextual-word predictability, whose processing is proposed to require memory retrieval, only affected reading behavior in healthy subjects. In AD patients, this loss reveals impairments in brain areas such as those corresponding to working memory and memory retrieval. These findings might be relevant for expanding the options for the early detection and monitoring in the early stages of AD. Furthermore, evaluation of eye movements during reading could provide a new tool for measuring drug impact on patients' behavior. |
Gerardo Fernández; Marcelo Sapognikoff; Salvador Guinjoan; David Orozco; Osvaldo Agamennoni Word processing during reading sentences in patients with schizophrenia: Evidences from the eyetracking technique Journal Article In: Comprehensive Psychiatry, vol. 68, pp. 193–200, 2016. @article{Fernandez2016b, Purpose: The current study analyze the effect of word properties (i.e., word length, word frequency and word predictability) on the eye movement behavior of patients with schizophrenia (SZ) compared to age-matched controls. Method: 18 SZ patients and 40 age matched controls participated in the study. Eye movements were recorded during reading regular sentences by using the eyetracking technique. Eye movement analyses were performed using linear mixed models. Findings: Analysis of eye movements revealed that patients with SZ decreased the amount of single fixations, increased their total number of second pass fixations compared with healthy individuals (Controls). In addition, SZ patients showed an increase in gaze duration, compared to Controls. Interestingly, the effects of current word frequency and current word length processing were similar in Controls and SZ patients. The high rate of second pass fixations and its low rate in single fixation might reveal impairments in working memory when integrating neighbor words. In contrast, word frequency and length processing might require less complex mechanisms, which were functioning in SZ patients. Conclusion: To the best of our knowledge, this is the first study measuring how patients with SZ process dynamically well-defined words embedded in regular sentences. The findings suggest that evaluation of the resulting changes in eye movement behavior may supplement current symptom-based diagnosis. |
Valerie Benson; Monica S. Castelhano; Philippa L. Howard; Nida Latif; Keith Rayner Looking, seeing and believing in autism: Eye movements reveal how subtle cognitive processing differences impact in the social domain Journal Article In: Autism Research, vol. 9, no. 8, pp. 879–887, 2016. @article{Benson2016, Adults with High Functioning Autism Spectrum Disorders (ASD) viewed scenes with people in them, while having their eye movements recorded. The task was to indicate, using a button press, whether the pictures were normal, or in some way weird or odd. Oddities in the pictures were categorized as violations of either perceptual or social norms. Compared to a Typically Developed (TD) control group, the ASD participants were equally able to categorize the scenes as odd or normal, but they took longer to respond. The eye movement patterns showed that the ASD group made more fixations and revisits to the target areas in the odd scenes compared with the TD group. Additionally, when the ASD group first fixated the target areas in the scenes, they failed to initially detect the social oddities. These two findings have clear implications for processing difficulties in ASD for the social domain, where it is important to detect social cues on-line, and where there is little opportunity to go back and recheck possible cues in fast dynamic interactions. |