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!
2008 |
Harold T. Nefs; J. M. Harris Induced motion in depth and the effects of vergence eye movements Journal Article In: Journal of Vision, vol. 8, no. 3, pp. 1–16, 2008. @article{Nefs2008, Induced motion is the false impression that physically stationary objects move when in the presence of other objects that really move. In this study, we investigated this motion illusion in the depth dimension. We raised three related questions, as follows: (1) What cues in the stimulus are responsible for this motion illusion in depth? (2) Is the size of this illusion affected by vergence eye movements? And (3) are the effects of eye movements different for motion in depth and for motion in the frontoparallel plane? To answer these questions, we measured the point of subjective stationarity. Observers viewed an inducer target that oscillated in depth and a test target that was located directly above it. The test target moved in phase or out of phase with the inducer, but with a smaller amplitude. Observers had to indicate whether the test target and the inducer target moved in phase or out of phase with one another. They were asked to keep their eyes either on the test target or on the inducer. For motion in depth, created by binocular disparity and retinal size change or by binocular disparity alone, we found that when the eyes followed the inducer, subjective stationarity occurred at approximately 40-45% of the inducer's amplitude. When the eyes were kept fixated on the test target, the bias decreased tenfold to around 4%. When size change was the only cue to motion in depth, there was no illusory motion. When the eyes were kept on an inducer moving in the frontoparallel plane, induced motion was of the same order as for induced motion in depth, namely, approximately 44%. When the induced motion was in the frontoparallel plane, we found that perceived stationarity occurred at approximately 23% of inducer's amplitude when the eyes were kept on the test target. |
Jorge Otero-Millan; Xoana G. Troncoso; Stephen L. Macknik; Ignacio Serrano-Pedraza; Susana Martinez-Conde Saccades and microsaccades during visual fixation, exploration, and search: Foundations for a common saccadic generator Journal Article In: Journal of Vision, vol. 8, no. 14, pp. 1–18, 2008. @article{OteroMillan2008, Microsaccades are known to occur during prolonged visual fixation, but it is a matter of controversy whether they also happen during free-viewing. Here we set out to determine: 1) whether microsaccades occur during free visual exploration and visual search, 2) whether microsaccade dynamics vary as a function of visual stimulation and viewing task, and 3) whether saccades and microsaccades share characteristics that might argue in favor of a common saccade-microsaccade oculomotor generator. Human subjects viewed naturalistic stimuli while performing various viewing tasks, including visual exploration, visual search, and prolonged visual fixation. Their eye movements were simultaneously recorded with high precision. Our results show that microsaccades are produced during the fixation periods that occur during visual exploration and visual search. Microsaccade dynamics during free-viewing moreover varied as a function of visual stimulation and viewing task, with increasingly demanding tasks resulting in increased microsaccade production. Moreover, saccades and microsaccades had comparable spatiotemporal characteristics, including the presence of equivalent refractory periods between all pair-wise combinations of saccades and microsaccades. Thus our results indicate a microsaccade-saccade continuum and support the hypothesis of a common oculomotor generator for saccades and microsaccades. |
N. Alahyane; V. Fonteille; C. Urquizar; Roméo Salemme; Norbert Nighoghossian; Denis Pelisson; C. Tilikete Separate neural substrates in the human cerebellum for sensory-motor adaptation of reactive and of scanning voluntary saccades Journal Article In: Cerebellum, vol. 7, no. 4, pp. 595–601, 2008. @article{Alahyane2008, Sensory-motor adaptation processes are critically involved in maintaining accurate motor behavior throughout life. Yet their underlying neural substrates and task-dependency bases are still poorly understood. We address these issues here by studying adaptation of saccadic eye movements, a well-established model of sensory-motor plasticity. The cerebellum plays a major role in saccadic adaptation but it has not yet been investigated whether this role can account for the known specificity of adaptation to the saccade type (e.g., reactive versus voluntary). Two patients with focal lesions in different parts of the cerebellum were tested using the double-step target paradigm. Each patient was submitted to two separate sessions: one for reactive saccades (RS) triggered by the sudden appearance of a visual target and the second for scanning voluntary saccades (SVS) performed when exploring a more complex scene. We found that a medial cerebellar lesion impaired adaptation of reactive-but not of voluntary-saccades, whereas a lateral lesion affected adaptation of scanning voluntary saccades, but not of reactive saccades. These findings provide the first evidence of an involvement of the lateral cerebellum in saccadic adaptation, and extend the demonstrated role of the cerebellum in RS adaptation to adaptation of SVS. The double dissociation of adaptive abilities is also consistent with our previous hypothesis of the involvement in saccadic adaptation of partially separated cerebellar areas specific to the reactive or voluntary task (Alahyane et al. Brain Res 1135:107-121 (2007)). |
Nadia Alahyane; Anne-Dominique Devauchelle; Roméo Salemme; Denis Pélisson Spatial transfer of adaptation of scanning voluntary saccades in humans Journal Article In: Neuroreport, vol. 19, no. 1, pp. 37–41, 2008. @article{Alahyane2008a, The properties and neural substrates of the adaptive mechanisms that maintain over time the accuracy of voluntary, internally triggered saccades are still poorly understood. Here, we used transfer tests to evaluate the spatial properties of adaptation of scanning voluntary saccades. We found that an adaptive reduction of the size of a horizontal rightward 7 degrees saccade transferred to other saccades of a wide range of amplitudes and directions. This transfer decreased as tested saccades increasingly differed in amplitude or direction from the trained saccade, being null for vertical and leftward saccades. Voluntary saccade adaptation thus presents bounded, but large adaptation fields, suggesting that at least part of the underlying neural substrate encodes saccades as vectors. |
Naseem Al-aidroos; Jos J. Adam; Martin H. Fischer; Jay Pratt Structured perceptual arrays and the modulation of Fitts's Law: Examining saccadic eye movements Journal Article In: Journal of Motor Behavior, vol. 40, no. 2, pp. 155–164, 2008. @article{Alaidroos2008, On the basis of recent observations of a modulation of Fitts's law for manual pointing movements in structured visual arrays (J. J. Adam, R. Mol, J. Pratt, & M. H. Fischer, 2006; J. Pratt, J. J. Adam, & M. H. Fischer, 2007), the authors examined whether a similar modulation occurs for saccadic eye move- ments. Healthy participants (N = 19) made horizontal saccades to targets that appeared randomly in 1 of 4 positions, either on an empty background or within 1 of 4 placeholder boxes. Whereas in previous studies, placeholders caused a decrease in movement time (MT) without the normal decrease in movement accuracy predicted by Fitts's law, placeholders in the present experiment increased saccadic accuracy (decreased endpoint variability) with- out an increase in MT. The present results extend the findings of J. J. Adam et al. of a modulation of Fitts's law from the temporal domain to the spatial domain and from manual movements to eye movements. |
R. Contreras; Rachel Kolster; Henning U. Voss; Jamshid Ghajar; M. Suh; S. Bahar Eye-target synchronization in mild traumatic brain-injured patients Journal Article In: Journal of Biological Physics, vol. 34, no. 3-4, pp. 381–392, 2008. @article{Contreras2008, Eye-target synchronization is critical for effective smooth pursuit of a moving visual target. We apply the nonlinear dynamical technique of stochastic-phase synchronization to human visual pursuit of a moving target, in both normal and mild traumatic brain-injured (mTBI) patients. We observe significant fatigue effects in all subject populations, in which subjects synchronize better with the target during the first half of the trial than in the second half. The fatigue effect differed, however, between the normal and the mTBI populations and between old and young subpopulations of each group. In some cases, the younger (</=40 years old) normal subjects performed better than mTBI subjects and also better than older (>40 years old) normal subjects. Our results, however, suggest that further studies will be necessary before a standard of "normal" smooth pursuit synchronization can be developed. |
Adele Diederich; Hans Colonius Crossmodal interaction in saccadic reaction time: Separating multisensory from warning effects in the time window of integration model Journal Article In: Experimental Brain Research, vol. 186, no. 1, pp. 1–22, 2008. @article{Diederich2008, In a focused attention task saccadic reaction time (SRT) to a visual target stimulus (LED) was measured with an auditory (white noise burst) or tactile (vibration applied to palm) non-target presented in ipsi- or contralateral position to the target. Crossmodal facilitation of SRT was observed under all configurations and stimulus onset asynchrony (SOA) values ranging from -500 (non-target prior to target) to 0 ms, but the effect was larger for ipsi- than for contralateral presentation within an SOA range from -200 ms to 0. The time-window-of-integration (TWIN) model (Colonius and Diederich in J Cogn Neurosci 16:1000, 2004) is extended here to separate the effect of a spatially unspecific warning effect of the non-target from a spatially specific and genuine multisensory integration effect. |
Adele Diederich; Hans Colonius; Adele Diederich In: Brain Research, vol. 1242, pp. 219–230, 2008. @article{Diederich2008a, In a focused attention task saccadic reaction time (SRT) to a visual target stimulus (LED) was measured with an auditory (white noise burst) or tactile (vibration applied to palm) nontarget presented in ipsi- or contralateral position to the target. Crossmodal facilitation of SRT was observed under all configurations and stimulus onset asynchrony (SOA) values ranging from - 250 ms (nontarget prior to target) to 50 ms. This study specifically addressed the effect of varying nontarget intensity. While facilitation effects for auditory nontargets are somewhat more pronounced than for tactile ones, decreasing intensity slightly reduced facilitation for both types of nontargets. The time course of crossmodal mean SRT over SOA and the pattern of facilitation observed here suggest the existence of two distinct underlying mechanisms: (a) a spatially unspecific crossmodal warning triggered by the nontarget being detected early enough before the arrival of the target plus (b) a spatially specific multisensory integration mechanism triggered by the target processing time terminating within the time window of integration. It is shown that the time window of integration (TWIN) model introduced by the authors gives a reasonable quantitative account of the data relating observed SRT to the unobservable probability of integration and crossmodal warning for each SOA value under a high and low intensity level of the nontarget. |
Tyler W. Garaas; Tyson Nieuwenhuis; Marc Pomplun A gaze-contingent paradigm for studying continuous saccadic adaptation Journal Article In: Journal of Neuroscience Methods, vol. 168, no. 2, pp. 334–340, 2008. @article{Garaas2008a, Saccadic eye movements are used to quickly and accurately orient our fovea within our visual field to obtain detailed information from various locations. The accuracy of these eye movements is maintained throughout life despite constant pressure on oculomotor muscles and neuronal structures by growth and aging; this maintenance appears to be a product of an adaptive mechanism that continuously accounts for consistent post-saccadic visual error, and is referred to as saccadic adaptation. In this paper, we present a new paradigm to test saccadic adaptation under circumstances that more closely resemble natural visual error in everyday vision, whereas previous saccadic adaptation paradigms study adaptation in a largely restricted form. The paradigm achieves this by positioning a stimulus panel atop an identically colored background relative to the gaze position of the participant. We demonstrate the paradigm by successfully decreasing participants' saccadic amplitudes during a common visual search task by shifting the stimulus panel in the opposite direction of the saccade by 50% of the saccadic amplitude. Participants' adaptation reached approximately 60% of the 50% back-shift during the adaptation phase, and was uniformly distributed across saccadic direction. The adaptation time-course found using the new paradigm is consistent with that achieved using previous paradigms. Task-performance results and the manner in which eye movements changed during adaptation were also analyzed. |
Valérie Gaveau; Denis Pélisson; Annabelle Blangero; Christian Urquizar; Claude Prablanc; Alain Vighetto; Laure Pisella Saccade control and eye-hand coordination in optic ataxia Journal Article In: Neuropsychologia, vol. 46, no. 2, pp. 475–486, 2008. @article{Gaveau2008, The aim of this work was to investigate ocular control in patients with optic ataxia (OA). Following a lesion in the posterior parietal cortex (PPC), these patients exhibit a deficit for fast visuo-motor control of reach-to-grasp movements. Here, we assessed the fast visuo-motor control of saccades as well as spontaneous eye-hand coordination in two bilateral OA patients and five neurologically intact controls in an ecological "look and point" paradigm. To test fast saccadic control, trials with unexpected target-jumps synchronised with saccade onset were randomly intermixed with stationary target trials. Results confirmed that control subjects achieved visual capture (foveation) of the displaced targets with the same timing as stationary targets (fast saccadic control) and began their hand movement systematically at the end of the primary saccade. In contrast, the two bilateral OA patients exhibited a delayed visual capture, especially of displaced targets, resulting from an impairment of fast saccadic control. They also exhibited a peculiar eye-hand coordination pattern, spontaneously delaying their hand movement onset until the execution of a final corrective saccade, which allowed target foveation. To test whether this pathological behaviour results from a delay in updating visual target location, we had subjects perform a second experiment in the same control subjects in which the target-jump was synchronised with saccade offset. With less time for target location updating, the control subjects exhibited the same lack of fast saccadic control as the OA patients. We propose that OA corresponds to an impairment of fast updating of target location, therefore affecting both eye and hand movements. |
Robert D. Gordon; Sarah D. Vollmer; Megan L. Frankl Object continuity and the transsaccadic representation of form Journal Article In: Perception and Psychophysics, vol. 70, no. 4, pp. 667–679, 2008. @article{Gordon2008, Transsaccadic object file representations were investigated in three experiments. Subjects moved their eyes from a central fixation cross to a location between two peripheral objects. During the saccade, this preview display was replaced with a target display containing a single object to be named. On trials on which the target identity matched one of the preview objects, its orientation either matched or did not match the previewed orientation. The results of Experiments 1 and 2 revealed that orientation changes disrupt perceptual continuity for objects located near fixation, but not for objects located further from fixation. The results of Experiment 3 confirmed that orientation changes do not disrupt continuity for distant objects, while showing that subjects nevertheless maintain an object-specific representation of the orientation of such objects. Together, the results suggest that object files represent orientation but that whether or not orientation plays a role in the processes that determine continuity depends on the quality of the perceptual representation. While |
Eric Matheron; Qing Yang; Thanh Thuan Lê; Zoï Kapoula Effects of ocular dominance on the vertical vergence induced by a 2-diopter vertical prism during standing Journal Article In: Neuroscience Letters, vol. 444, no. 2, pp. 176–180, 2008. @article{Matheron2008, This study examined the eye movement responses to vertical disparity induced by a 2-diopter vertical prism base down while in standing position. Vertical vergence movements are known to be small requiring accurate measurement with the head stabilized, and was done with the EyeLink 2. The 2-diopter vertical prism, base down, was inserted in front of either the non-dominant eye (NDE) or dominant eye (DE) at 40 and 200 cm. The results showed that vertical vergence was stronger and excessive relative to the required value (i.e. 1.14°) when the prism was on the NDE for both distances, but more appropriate when the prism was on the DE. The results suggest that sensory disparity process and vertical vergence responses are modulated by eye dominance. |
Andre Kaminiarz; Bart Krekelberg; Frank Bremmer Expansion of visual space during optokinetic afternystagmus (OKAN) Journal Article In: Journal of Neurophysiology, vol. 99, no. 5, pp. 2470–2478, 2008. @article{Kaminiarz2008, The mechanisms underlying visual perceptual stability are usually investigated using voluntary eye movements. In such studies, errors in perceptual stability during saccades and pursuit are commonly interpreted as mismatches between actual eye position and eye-position signals in the brain. The generality of this interpretation could in principle be tested by investigating spatial localization during reflexive eye movements whose kinematics are very similar to those of voluntary eye movements. Accordingly, in this study, we determined mislocalization of flashed visual targets during optokinetic afternystagmus (OKAN). These eye movements are quite unique in that they occur in complete darkness and are generated by subcortical control mechanisms. We found that during horizontal OKAN slow phases, subjects mislocalize targets away from the fovea in the horizontal direction. This corresponds to a perceived expansion of visual space and is unlike mislocalization found for any other voluntary or reflexive eye movement. Around the OKAN fast phases, we found a bias in the direction of the fast phase prior to its onset and opposite to the fast-phase direction thereafter. Such a biphasic modulation has also been reported in the temporal vicinity of saccades and during optokinetic nystagmus (OKN). A direct comparison, however, showed that the modulation during OKAN was much larger and occurred earlier relative to fast-phase onset than during OKN. A simple mismatch between the current eye position and the eye-position signal in the brain is unlikely to explain such disparate results across similar eye movements. Instead, these data support the view that mislocalization arises from errors in eye-centered position information. |
Dirk Kerzel; Angélique Gauch; Blandine Ulmann Local motion inside an object affects pointing less than smooth pursuit Journal Article In: Experimental Brain Research, vol. 191, no. 2, pp. 187–195, 2008. @article{Kerzel2008, During smooth pursuit eye movements, briefly presented objects are mislocalized in the direction of motion. It has been proposed that the localization error is the sum of the pursuit signal and the retinal motion signal in a ~200 ms interval after flash onset. To evaluate contributions of retinal motion signals produced by the entire object (global motion) and elements within the object (local motion), we asked observers to reach to flashed Gabor patches (Gaussian-windowed sine-wave gratings). Global motion was manipulated by varying the duration of a stationary flash, and local motion was manipulated by varying the motion of the sine-wave. Our results confirm that global retinal motion reduces the localization error. The effect of local retinal motion on object localization was far smaller, even though local and global motion had equal effects on eye velocity. Thus, local retinal motion has differential access to manual and oculomotor control circuits. Further, we observed moderate correlations between smooth pursuit gain and localization error. |
Dirk Kerzel; David Souto; Nathalie E. Ziegler Effects of attention shifts to stationary objects during steady-state smooth pursuit eye movements Journal Article In: Vision Research, vol. 48, no. 7, pp. 958–969, 2008. @article{Kerzel2008a, A number of studies have shown that stationary backgrounds compromise smooth pursuit eye movements. It has been suggested that poor attentional selection of the pursuit target was responsible for reductions of pursuit gain. To quantify the detrimental effects of attention, we instructed observers to either pay attention to background objects or to ignore them. The to-be-attended object was indicated by peripheral or central cues. Strong reductions of pursuit gain occurred when the following conditions were met: (a) the subject payed attention to the object (b) a salient event was present, for instance the onset of the target or cue and (c) the attended target produced retinal motion. Removing any of the three conditions resulted in no or far smaller decreases of pursuit gain. Further, decreases in pursuit gain were present with perceptual discrimination and simple manual detection. |
Christopher M. Knapp; Irene Gottlob; Rebecca J. McLean; Frank A. Proudlock Horizontal and vertical look and stare optokinetic nystagmus symmetry in healthy adult volunteers Journal Article In: Investigative Ophthalmology & Visual Science, vol. 49, no. 2, pp. 581–588, 2008. @article{Knapp2008, PURPOSE: Look optokinetic nystagmus (OKN) consists of voluntary tracking of details in a moving visual field, whereas stare OKN is reflexive and consists of shorter slow phases of lower gain. Horizontal OKN is symmetrical in healthy adults, whereas symmetry of vertical OKN is controversial. Horizontal and vertical look and stare OKN symmetry was measured, and the consistency of individual asymmetries and the effect of varying stimulus conditions were investigated.METHODS: Horizontal and vertical look and stare OKN gains were recorded in 15 healthy volunteers (40 degrees /s) using new methods to delineate look and stare OKN. Responses with right and left eye viewing were compared to investigate consistency of individual OKN asymmetry. In a second experiment, the symmetry of stare OKN was measured in nine volunteers varying velocity (20 degrees /s and 40 degrees /s), contrast (50% and 100%), grating contrast profile (square or sine wave), and stimulus shape (full screen or circular vignetted).RESULTS: There was no horizontal or vertical asymmetry in look or stare OKN gain for all volunteers grouped together. However, individual vertical asymmetries were strongly correlated for left and right eye viewing (look: r = 0.77 |
Teresa D. Hernandez; Carmel A. Levitan; Martin S. Banks; Clifton M. Schor How does saccade adaptation affect visual perception? Journal Article In: Journal of Vision, vol. 8, no. 8, pp. 1–16, 2008. @article{Hernandez2008, Three signals are used to visually localize targets and stimulate saccades: (1) retinal location signals for intended saccade amplitude, (2) sensory-motor transform (SMT) of retinal signals to extra-ocular muscle innervation, and (3) estimates of eye position from extra-retinal signals. We investigated effects of adapting saccade amplitude to a double-step change in target location on perceived direction. In a flashed-pointing task, subjects pointed an unseen hand at a briefly displayed eccentric target without making a saccade. In a sustained-pointing task, subjects made a horizontal saccade to a double-step target. One second after the second step, they pointed an unseen hand at the final target position. After saccade-shortening adaptation, there was little change in hand-pointing azimuth toward the flashed target suggesting that most saccade adaptation was caused by changes in the SMT. After saccade-lengthening adaptation, there were small changes in hand-pointing azimuth to flashed targets, indicating that 1/3 of saccade adaptation was caused by changes in estimated retinal location signals and 2/3 by changes in the SMT. The sustained hand-pointing task indicated that estimates of eye position adapted inversely with changes of the SMT. Changes in perceived direction resulting from saccade adaptation are mainly influenced by extra-retinal factors with a small retinal component in the lengthening condition. |
L. Elliot Hong; Kathleen A. Turano; Hugh B. O'Neill; Lei Hao; Ikwunga Wonodi; Robert P. McMahon; Amie Elliott; Gunvant K. Thaker Refining the predictive pursuit endophenotype in schizophrenia. Journal Article In: Biological Psychiatry, vol. 63, no. 5, pp. 458–464, 2008. @article{Hong2008, Background: To utilize fully a schizophrenia endophenotype in gene search and subsequent neurobiological studies, it is critical that the precise underlying physiologic deficit is identified. Abnormality in smooth pursuit eye movements is one of the endophenotypes of schizophrenia. The precise nature of the abnormality is unknown. Previous work has shown a reduced predictive pursuit response to a briefly masked (i.e., invisible) moving object in schizophrenia. However, the overt awareness of target removal can confound the measurement. Methods: This study employed a novel method that covertly stabilized the moving target image onto the fovea. The foveal stabilization was implemented after the target on a monitor had oscillated at least for one cycle and near the change of direction when the eye velocity momentarily reached zero. Thus, the subsequent pursuit eye movements were completely predictive and internally driven. Eye velocity during this foveally stabilized smooth pursuit was compared among schizophrenia patients (n = 45), their unaffected first-degree relatives (n = 42), and healthy comparison subjects (n = 22). Results: Schizophrenia patients and their unaffected relatives performed similarly and both had substantially reduced predictive pursuit acceleration and velocity under the foveally stabilized condition. Conclusions: These findings show that inability to maintain internal representation of the target motion or integration of such information into a predictive response may be the specific brain deficit indexed by the smooth pursuit endophenotype in schizophrenia. Similar performance between patients and unaffected relatives suggests that the refined predictive pursuit measure may index a less complex genetic origin of the eye-tracking deficits in schizophrenia families. |
Jörg Hoormann; Stephanie Jainta; Wolfgang Jaschinski The effect of calibration errors on the accuracy of the eye movement recordings Journal Article In: Journal of Eye Movement Research, vol. 1, no. 2, pp. 1–7, 2008. @article{Hoormann2008, For calibrating eye movement recordings, a regression between spatially defined calibration points and corresponding measured raw data is performed. Based on this regression, a confidence interval (CI) of the actually measured eye position can be calculated in order to$backslash$nquantify the measurement error introduced by inaccurate calibration coefficients. For calculating this CI, a standard deviation (SD) - depending on the calibration quality and the$backslash$ndesign of the calibration procedure - is needed.$backslash$nExamples of binocular recordings with separate monocular calibrations illustrate that the SD is almost independent of the number and spatial separation between the calibration points – even though the later was expected from theoretical simulation. Our simulations and recordings demonstrate that the SD depends critically on residuals at certain calibration points, thus robust regressions are suggested. |
Wolfgang Jaschinski; Stephanie Jainta; Jörg Hoormann Comparison of shutter glasses and mirror stereoscope for measuring dynamic and static vergence Journal Article In: Journal of Eye Movement Research, vol. 1, no. 2, pp. 1–7, 2008. @article{Jaschinski2008, Vergence eye movement recordings in response to disparity step stimuli require to present different stimuli to the two eyes. The traditional method is a mirror stereoscope. Shutter glasses are more convenient, but have disadvantages as limited repetition rate, residual cross task, and reduced luminance. Therefore, we compared both techniques measuring (1) dynamic disparity step responses for stimuli of 1 and 3 deg and (2) fixation disparity, the static vergence error. Shutter glasses and mirror stereoscope gave very similar dynamic responses with correlations of about 0.95 for the objectively measured vergence velocity and for the response amplitude reached 400 ms after the step stimulus (measured objectively with eye movement recordings and subjectively with dichoptic nonius lines). Both techniques also provided similar amounts of fixation disparity, tested with dichoptic nonius lines. |
Larry Allen Abel; Zhong I. Wang; Louis F. Dell'Osso Wavelet analysis in infantile nystagmus syndrome: Limitations and abilities Journal Article In: Investigative Ophthalmology & Visual Science, vol. 49, no. 8, pp. 3413–3423, 2008. @article{Abel2008, PURPOSE: To investigate the proper usage of wavelet analysis in infantile nystagmus syndrome (INS) and determine its limitations and abilities. METHODS: Data were analyzed from accurate eye-movement recordings of INS patients. Wavelet analysis was performed to examine the foveation characteristics, morphologic characteristics and time variation in different INS waveforms. Also compared were the wavelet analysis and the expanded nystagmus acuity function (NAFX) analysis on sections of pre- and post-tenotomy data. RESULTS: Wavelet spectra showed some sensitivity to different features of INS waveforms and reflected their variations across time. However, wavelet analysis was not effective in detecting foveation periods, especially in a complicated INS waveform. NAFX, on the other hand, was a much more direct way of evaluating waveform changes after nystagmus treatments. CONCLUSIONS: Wavelet analysis is a tool that performs, with difficulty, some things that can be done faster and better by directly operating on the nystagmus waveform itself. It appears, however, to be insensitive to the subtle but visually important improvements brought about by INS therapies. Wavelet analysis may have a role in developing automated waveform classifiers where its time-dependent characterization of the waveform can be used. The limitations of wavelet analysis outweighed its abilities in INS waveform-characteristic examination. |
Sarah Bate; Catherine Haslam; Jeremy J. Tree; Timothy L. Hodgson Evidence of an eye movement-based memory effect in congenital prosopagnosia Journal Article In: Cortex, vol. 44, no. 7, pp. 806–819, 2008. @article{Bate2008, While extensive work has examined the role of covert recognition in acquired prosopagnosia, little attention has been directed to this process in the congenital form of the disorder. Indeed, evidence of covert recognition has only been demonstrated in one congenital case in which autonomic measures provided evidence of recognition (Jones and Tranel, 2001), whereas two investigations using behavioural indicators failed to demonstrate the effect (de Haan and Campbell, 1991; Bentin et al., 1999). In this paper, we use a behavioural indicator, an "eye movement-based memory effect" (Althoff and Cohen, 1999), to provide evidence of covert recognition in congenital prosopagnosia. In an initial experiment, we examined viewing strategies elicited to famous and novel faces in control participants, and found fewer fixations and reduced regional sampling for famous compared to novel faces. In a second experiment, we examined the same processes in a patient with congenital prosopagnosia (AA), and found some evidence of an eye movement-based memory effect regardless of his recognition accuracy. Finally, we examined whether a difference in scanning strategy was evident for those famous faces AA failed to explicitly recognise, and again found evidence of reduced sampling for famous faces. We use these findings to (a) provide evidence of intact structural representations in a case of congenital prosopagnosia, and (b) to suggest that covert recognition can be demonstrated using behavioural indicators in this disorder. |
Paul Reeve; James J. Clark; J. Kevin O'Regan Convergent flash localization near saccades without equivalent "compression" of perceived separation Journal Article In: Journal of Vision, vol. 8, no. 13, pp. 1–19, 2008. @article{Reeve2008, Visual space is sometimes said to be "compressed" before saccadic eye movements. The most central evidence for this hypothesis is a converging pattern of localization errors on single flashes presented close to saccade time under certain conditions. An intuitive version of the compression hypothesis predicts that the reported distance between simultaneous, spatially separated presaccadic flashes should contract in the same way as their individual locations. In our experiment we tested this prediction by having subjects perform one of two tasks on stimuli made up of two bars simultaneously flashed near saccade time: either localizing one of the bars or judging the separation between the two. Localization judgments showed the previously observed converging pattern over the 50-100 ms before saccades. Contractions in perceived separation between the two bars were not accurately predicted by this pattern: they occurred mainly during saccades and were much weaker than convergence in localization. Different forms of spatial information about flashed stimuli can be differentially modulated before, during, and after saccades. Structural alterations in the perceptual field around saccades may explain these different effects, but alternative hypotheses based on decision making under uncertainty and on the influence of other perisaccadic mechanisms are also consistent with this and other evidence. |
Frédéric P. Rey; Thanh Thuan Lê; René Bertin; Zoï Kapoula Saccades horizontal or vertical at near or at far do not deteriorate postural control Journal Article In: Auris Nasus Larynx, vol. 35, no. 2, pp. 185–191, 2008. @article{Rey2008, Objective: There is a discrepancy about the effect of saccades on postural control: some studies reported a stabilization effect, other studies the opposite. Perturbation of posture by saccades could be related to loss of vision during saccades (saccades suppression) due to high velocity retinal slip. On the other hand, efferent and afferent proprioceptive signals related to saccades can be used for obtaining spatial stability over saccades and maintaining good postural control. In natural conditions saccades can be horizontal, vertical and made at different distance. The present study examines all these parameters to provide a more complete view on the role of saccade on postural control in quiet stance. Methods: Horizontal or vertical saccades of 30° were made at 1 Hz and at two distances, 40 and 200 cm. Eye movements were recorded with video-oculograhpy (EyeLink II). Posturography was recorded with the TechnoConcept platform. The results from "saccade" conditions are compared to "fixation control" condition (at far and near). Results: The video oculography results show that subjects performed the fixation or the saccade task correctly. Execution of saccades (horizontal or vertical at near or at far distance) had no significant effect on the surface of center of pressure (CoP), neither on the standard deviation of the lateral body sway, nor on the variance of speed of the CoP. Moreover, whatever the distance, execution of saccades decreased significantly the standard deviation of the antero-posterior sway. Conclusion: We conclude that saccades, of either the direction and at either the distance, do not deteriorate postural control; rather they could reduce sway. Efferent and proprioceptive oculomotor signals as well as attention could contribute to maintain or improve postural stability while making saccades. |
Martin Rolfs; Reinhold Kliegl; Ralf Engbert Toward a model of microsaccade generation: The case of microsaccadic inhibition Journal Article In: Journal of Vision, vol. 8, no. 11, pp. 1–23, 2008. @article{Rolfs2008a, Microsaccades are one component of the small eye movements that constitute fixation. Their implementation in the oculomotor system is unknown. To better understand the physiological and mechanistic processes underlying microsaccade generation, we studied microsaccadic inhibition, a transient drop of microsaccade rate, in response to irrelevant visual and auditory stimuli. Quantitative descriptions of the time course and strength of inhibition revealed a strong dependence of microsaccadic inhibition on stimulus characteristics. In Experiment 1, microsaccadic inhibition occurred sooner after auditory than after visual stimuli and after luminance-contrast than after color-contrast visual stimuli. Moreover, microsaccade amplitude strongly decreased during microsaccadic inhibition. In Experiment 2, the latency of microsaccadic inhibition increased with decreasing luminance contrast. We develop a conceptual model of microsaccade generation in which microsaccades result from fixation-related activity in a motor map coding for both fixation and saccades. In this map, fixation is represented at the central site. Saccades are generated by activity in the periphery, their amplitude increasing with eccentricity. The activity at the central, fixation-related site of the map predicts the rate of microsaccades as well as their amplitude and direction distributions. This model represents a framework for understanding the dynamics of microsaccade behavior in a broad range of tasks. |
Martin Rolfs; Jochen Laubrock; Reinhold Kliegl Microsaccade-induced prolongation of saccadic latencies depends on microsaccade amplitude Journal Article In: Journal of Eye Movement Research, vol. 1, no. 3, pp. 1–8, 2008. @article{Rolfs2008, Fixations consist of small movements including microsaccades, i.e., rapid flicks in eye position that replace the retinal image by up to 1 degree of visual angle. Recently, we showed in a delayed-saccade task (1) that the rate of microsaccades decreased in the course of saccade preparation and (2) that microsaccades occurring around the time of a go signal were associated with prolonged saccade latencies (Rolfs et al., 2006). A re-analysis of the same data set revealed a strong dependence of these findings on microsaccade amplitude. First, microsaccade amplitude dropped to a minimum just before the generation of a saccade. Second, the delay of response saccades was a function of microsaccade amplitude: Microsaccades with larger amplitudes were followed by longer response latencies. These finding were predicted by a recently proposed model that attributes microsaccade generation to fixation-related activity in a saccadic motor map that is in competition with the generation of large saccades (Rolfs et al., 2008). We propose, therefore, that microsaccade statistics provide a behavioral correlate of fixation-related activity in the oculomotor system. |
Xoana G. Troncoso; Stephen L. Macknik; Susana Martinez-conde Microsaccades counteract perceptual filling-in Journal Article In: Journal of Vision, vol. 8, no. 14, pp. 1–9, 2008. @article{Troncoso2008, Artificial scotomas positioned within peripheral dynamic noise fade perceptually during visual fixation (that is, the surrounding dynamic noise appears to fill-in the scotoma). Because the scotomas' edges are continuously refreshed by the dynamic noise background, this filling-in effect cannot be explained by low-level adaptation mechanisms (such as those that may underlie classical Troxler fading). We recently showed that microsaccades counteract Troxler fading and drive first-order visibility during fixation (S. Martinez-Conde, S. L. Macknik, X. G. Troncoso, & T. A. Dyar, 2006). Here we set out to determine whether microsaccades may counteract the perceptual filling-in of artificial scotomas and thus drive second-order visibility. If so, microsaccades may not only counteract low-level adaptation but also play a role in higher perceptual processes. We asked subjects to indicate, via button press/release, whether an artificial scotoma presented on a dynamic noise background was visible or invisible at any given time. The subjects' eye movements were simultaneously measured with a high precision video system. We found that increases in microsaccade production counteracted the perception of filling-in, driving the visibility of the artificial scotoma. Conversely, decreased microsaccades allowed perceptual filling-in to take place. Our results show that microsaccades do not solely overcome low-level adaptation mechanisms but they also contribute to maintaining second-order visibility during fixation. |
Xoana G. Troncoso; Stephen L. Macknik; Jorge Otero-Millan; Susana Martinez-Conde Microsaccades drive illusory motion in the Enigma illusion Journal Article In: Proceedings of the National Academy of Sciences, vol. 105, no. 41, pp. 16033–16038, 2008. @article{Troncoso2008b, Visual images consisting of repetitive patterns can elicit striking illusory motion percepts. For almost 200 years, artists, psychologists, and neuroscientists have debated whether this type of illusion originates in the eye or in the brain. For more than a decade, the controversy has centered on the powerful illusory motion perceived in the painting Enigma, created by op-artist Isia Leviant. However, no previous study has directly correlated the Enigma illusion to any specific physiological mechanism, and so the debate rages on. Here, we show that microsaccades, a type of miniature eye movement produced during visual fixation, can drive illusory motion in Enigma. We asked subjects to indicate when illusory motion sped up or slowed down during the observation of Enigma while we simultaneously recorded their eye movements with high precision. Before "faster" motion periods, the rate of microsaccades increased. Before "slower/no" motion periods, the rate of microsaccades decreased. These results reveal a direct link between microsaccade production and the perception of illusory motion in Enigma and rule out the hypothesis that the origin of the illusion is purely cortical. |
Stefan Van der Stigchel; Wieske Zoest; Jan Theeuwes; Jason J. S. Barton The influence of "blind" distractors on eye movement trajectories in visual hemifield defects Journal Article In: Journal of Cognitive Neuroscience, vol. 20, no. 11, pp. 2025–2036, 2008. @article{VanderStigchel2008a, There is evidence that some visual information in blind regions may still be processed in patients with hemifield defects after cerebral lesions ("blindsight"). We tested the hypothesis that, in the absence of retinogeniculostriate processing, residual retinotectal processing may still be detected as modifications of saccades to seen targets by irrelevant distractors in the blind hemifield. Six patients were presented with distractors in the blind and intact portions of their visual field and participants were instructed to make eye movements to targets in the intact field. Eye movements were recorded to determine if blind-field distractors caused deviation in saccadic trajectories. No deviation was found in one patient with an optic chiasm lesion, which affect both retinotectal and retinogeniculostriate pathways. In five patients with lesions of the optic radiations or the striate cortex, the results were mixed, with two of the five patients showing significant deviations of saccadic trajectory away from the "blind" distractor. In a second experiment, two of the five patients were tested with the target and the distractor more closely aligned. Both patients showed a "global effect," in that saccades deviated toward the distractor, but the effect was stronger in the patient who also showed significant trajectory deviation in the first experiment. Although our study confirms that distractor effects on saccadic trajectory can occur in patients with damage to the retinogeniculostriate visual pathway but preserved retinotectal projections, there remain questions regarding what additional factors are required for these effects to manifest themselves in a given patient. |
Stan Van Pelt; W. Pieter Medendorp Updating target distance across eye movements in depth Journal Article In: Journal of Neurophysiology, vol. 99, no. 5, pp. 2281–2290, 2008. @article{VanPelt2008, We tested between two coding mechanisms that the brain may use to retain distance information about a target for a reaching movement across vergence eye movements. If the brain was to encode a retinal disparity representation (retinal model), i.e., target depth relative to the plane of fixation, each vergence eye movement would require an active update of this representation to preserve depth constancy. Alternatively, if the brain was to store an egocentric distance representation of the target by integrating retinal disparity and vergence signals at the moment of target presentation, this representation should remain stable across subsequent vergence shifts (nonretinal model). We tested between these schemes by measuring errors of human reaching movements (n = 14 subjects) to remembered targets, briefly presented before a vergence eye movement. For comparison, we also tested their directional accuracy across version eye movements. With intervening vergence shifts, the memory-guided reaches showed an error pattern that was based on the new eye position and on the depth of the remembered target relative to that position. This suggests that target depth is recomputed after the gaze shift, supporting the retinal model. Our results also confirm earlier literature showing retinal updating of target direction. Furthermore, regression analyses revealed updating gains close to one for both target depth and direction, suggesting that the errors arise after the updating stage during the subsequent reference frame transformations that are involved in reaching. |
Marine Vernet; Qing Yang; Gintautas Daunys; Christophe Orssaud; Zoï Kapoula Divergence influences triggering of both vertical and horizontal saccades Journal Article In: Optometry and Vision Science, vol. 85, no. 3, pp. 187–195, 2008. @article{Vernet2008b, Purpose. In real life, divergence is frequently combined with vertical saccades. The purpose of this study was to examine the initiation of vertical and horizontal saccades, pure or combined with divergence. Methods. We used a gap paradigm to elicit vertical or horizontal saccades (10 degrees), pure or combined with a predictable divergence (10 degrees). Eye movements from 12 subjects were recorded with EyeLink II. Results. The major results were (i) when combined with divergence, the latency of horizontal saccades increased but not the latency of vertical saccades; (ii) for both vertical and horizontal saccades, a tight correlation between the latency of saccade and divergence was found; (iii) when the divergence was anticipated, the saccade was delayed. Conclusion. We conclude that the initiation of both components of combined movements is interdependent. |
Robin Walker; Eugene McSorley The influence of distractors on saccade target selection: Saccade trajectory effects Journal Article In: Journal of Eye Movement Research, vol. 2, no. 3, pp. 1–13, 2008. @article{Walker2008, It has long been known that the path (trajectory) taken by the eye to land on a target is rarely straight (Yarbus, 1967). Furthermore, the magnitude and direction of this natural tendency for curvature can be modulated by the presence of a competing distractor stimulus presented along with the saccade target. The distractorrelated modulation of saccade trajectories provides a subtle measure of the underlying competitive processes involved in saccade target selection. Here we review some of our own studies into the effects distractors have on saccade trajectories, which can be regarded as a way of probing the competitive balance between target and distractor salience. |
Brian J. White; Martin Stritzke; Karl R. Gegenfurtner Saccadic facilitation in natural backgrounds Journal Article In: Current Biology, vol. 18, no. 2, pp. 124–128, 2008. @article{White2008, In visual systems with a fovea, only a small portion of the visual field can be analyzed with high accuracy. Saccadic eye movements shift that center of gaze around several times a second. Saccades have been characterized in great detail and depend critically on a number of visual properties of the stimuli [1-5]. However, typical experiments have used bright spots on dark backgrounds, while our natural environment has a highly characteristic rich spatial structure [6, 7]. Here we show that the saccadic system, unlike the perceptual system, is able to compensate for the masking caused by structured backgrounds. Consequently, saccadic latencies in the context of natural backgrounds are much faster than unstructured backgrounds at equal levels of visibility. The results suggest that whenever a structured background acts to mask the visibility of the saccade target, it simultaneously preactivates saccadic circuitry and thus ensures a fast reaction to potentially critical stimuli that are difficult to detect in our environment. © 2008 Elsevier Ltd. All rights reserved. |
D. A. Wismeijer; Raymond Van Ee; Casper J. Erkelens Depth cues, rather than perceived depth, govern vergence Journal Article In: Experimental Brain Research, vol. 184, no. 1, pp. 61–70, 2008. @article{Wismeijer2008, We studied the influence of perceived surface orientation on vergence accompanying a saccade while viewing an ambiguous stimulus. We used the slant rivalry stimulus, in which perspective foreshortening and disparity specified opposite surface orientations. This rivalrous configuration induces alternations of perceived surface orientation, while the slant cues remain constant. Subjects were able to voluntarily control their perceptual state while viewing the ambiguous stimulus. They were asked to make a saccade across the perceived slanted surface. Our data show that vergence responses closely approximated the vergence response predicted by the disparity cue, irrespective of voluntarily controlled perceived orientation. However, comparing the data obtained while viewing the ambiguous stimulus with data from an unambiguous stimulus condition (when disparity and perspective specified similar surface orientations) revealed an effect of perspective cues on vergence. Collectively our results show that depth cues rather than perceived depth govern vergence. |
Scott L. Davis; Teresa C. Frohman; C. J. Crandall; M. J. Brown; D. A. Mills; Phillip D. Kramer; O. Stuve; Elliot M. Frohman Modeling Uhthoff's phenomenon in MS patients with internuclear ophthalmoparesis Journal Article In: Neurology, vol. 70, pp. 1098–1106, 2008. @article{Davis2008, Objective: The goal of this investigation was to demonstrate that internuclear ophthalmoparesis (INO) can be utilized to model the effects of body temperature-induced changes on the fidelity of axonal conduction in multiple sclerosis (Uhthoff's phenomenon). Methods: Ocular motor function was measured using infrared oculography at 10-minute intervals in patients with multiple sclerosis (MS) with INO (MS-INO; n=8), patients with MS without INO (MS-CON; n=8), and matched healthy controls (CON; n=8) at normothermic baseline, during whole-body heating (increase in core temperature 0.8°C as measured by an ingestible temperature probe and transabdominal telemetry), and after whole-body cooling. The versional disconjugacy index (velocity-VDI), the ratio of abducting/adducting eye movements for velocity, was calculated to assess changes in interocular disconjugacy. The first pass amplitude (FPA), the position of the adducting eye when the abducting eye achieves a centrifugal fixation target, was also computed. Results: Velocity-VDI and FPA in MS-INO patients was elevated (p<0.001) following whole body heating with respect to baseline measures, confirming a compromise in axonal electrical impulse transmission properties. Velocity-VDI and FPA in MS-INO patients was then restored to baseline values following whole-body cooling, confirming the reversible and stereotyped nature of this characteristic feature of demyelination. Conclusions: We have developed a neurophysiologic model for objectively understanding temperature-related reversible changes in axonal conduction in multiple sclerosis. Our observations corroborate the hypothesis that changes in core body temperature (heating and cooling) are associated with stereotypic decay and restoration in axonal conduction mechanisms. |
Alexander C. Schütz; Doris I. Braun; Dirk Kerzel; Karl R. Gegenfurtner Improved visual sensitivity during smooth pursuit eye movements Journal Article In: Nature Neuroscience, vol. 11, no. 10, pp. 1211–1216, 2008. @article{Schuetz2008, When we view the world around us, we constantly move our eyes. This brings objects of interest into the fovea and keeps them there, but visual sensitivity has been shown to deteriorate while the eyes are moving. Here we show that human sensitivity for some visual stimuli is improved during smooth pursuit eye movements. Detection thresholds for briefly flashed, colored stimuli were 16% lower during pursuit than during fixation. Similarly, detection thresholds for luminance-defined stimuli of high spatial frequency were lowered. These findings suggest that the pursuit-induced sensitivity increase may have its neuronal origin in the parvocellular retino-thalamic system. This implies that the visual system not only uses feedback connections to improve processing for locations and objects being attended to, but that a whole processing subsystem can be boosted. During pursuit, facilitation of the parvocellular system may reduce motion blur for stationary objects and increase sensitivity to speed changes of the tracked object. |
Jan L. Souman; Tom C. A. Freeman Motion perception during sinusoidal smooth pursuit eye movements: Signal latencies and non-linearities Journal Article In: Journal of Vision, vol. 8, no. 14, pp. 1–14, 2008. @article{Souman2008, Smooth pursuit eye movements add motion to the retinal image. To compensate, the visual system can combine estimates of pursuit velocity and retinal motion to recover motion with respect to the head. Little attention has been paid to the temporal characteristics of this compensation process. Here, we describe how the latency difference between the eye movement signal and the retinal signal can be measured for motion perception during sinusoidal pursuit. In two experiments, observers compared the peak velocity of a motion stimulus presented in pursuit and fixation intervals. Both the pursuit target and the motion stimulus moved with a sinusoidal profile. The phase and amplitude of the motion stimulus were varied systematically in different conditions, along with the amplitude of pursuit. The latency difference between the eye movement signal and the retinal signal was measured by fitting the standard linear model and a non-linear variant to the observed velocity matches. We found that the eye movement signal lagged the retinal signal by a small amount. The non-linear model fitted the velocity matches better than the linear one and this difference increased with pursuit amplitude. The results support previous claims that the visual system estimates eye movement velocity and retinal velocity in a non-linear fashion and that the latency difference between the two signals is small. |
David Souto; Dirk Kerzel Dynamics of attention during the initiation of smooth pursuit eye movements Journal Article In: Journal of Vision, vol. 8, no. 14, pp. 3–1–16, 2008. @article{Souto2008, Many studies indicate that saccades are necessarily preceded by a shift of attention to the target location. There is no direct evidence for the same coupling during smooth pursuit. If smooth pursuit and attention were coupled, pursuit onset should be delayed whenever attention is focused on a stationary, non-target location. To test this hypothesis, observers were instructed to shift their attention to a peripheral location according to a location cue (Experiments 1 and 2) or a symbolic cue (Experiment 3) around the time of smooth pursuit initiation. Attending to static targets had only negligible effects on smooth pursuit latencies and the early open-loop response but lowered pursuit velocity substantially about the onset of closed-loop pursuit. Around this time, eye velocity reflected the competition between the to-be-tracked and to-be-attended object motion, entailing a reduction of eye velocity by 50% compared to the single task condition. The precise time course of attentional modulation of smooth pursuit initiation was at odds with the idea that an attention shift must precede any voluntary eye movement. Finally, the initial catch-up saccades were strongly delayed with attention diverted from the pursuit target. Implications for models of target selection for pursuit and saccades are discussed. |
Miriam Spering; Anna Montagnini; Karl R. Gegenfurtner Competition between color and luminance for target selection in smooth pursuit and saccadic eye movements Journal Article In: Journal of Vision, vol. 8, no. 15, pp. 1–19, 2008. @article{Spering, Visual processing of color and luminance for smooth pursuit and saccadic eye movements was investigated using a target selection paradigm. In two experiments, stimuli were varied along the dimensions color and luminance, and selection of the more salient target was compared in pursuit and saccades. Initial pursuit was biased in the direction of the luminance component whereas saccades showed a relative preference for color. An early pursuit response toward luminance was often reversed to color by a later saccade. Observers' perceptual judgments of stimulus salience, obtained in two control experiments, were clearly biased toward luminance. This choice bias in perceptual data implies that the initial short-latency pursuit response agrees with perceptual judgments. In contrast, saccades, which have a longer latency than pursuit, do not seem to follow the perceptual judgment of salience but instead show a stronger relative preference for color. These substantial differences in target selection imply that target selection processes for pursuit and saccadic eye movements use distinctly different weights for color and luminance stimuli. |
Rike Steenken; Adele Diederich; Hans Colonius Time course of auditory masker effects: Tapping the locus of audiovisual integration? Journal Article In: Neuroscience Letters, vol. 435, no. 1, pp. 78–83, 2008. @article{Steenken2008a, In a focused attention paradigm, saccadic reaction time (SRT) to a visual target tends to be shorter when an auditory accessory stimulus is presented in close temporal and spatial proximity. Observed SRT reductions typically diminish as spatial disparity between the stimuli increases. Here a visual target LED (500 ms duration) was presented above or below the fixation point and a simultaneously presented auditory accessory (2 ms duration) could appear at the same or the opposite vertical position. SRT enhancement was about 35 ms in the coincident and 10 ms in the disparate condition. In order to further probe the audiovisual integration mechanism, in addition to the auditory non-target an auditory masker (200 ms duration) was presented before, simultaneous to, or after the accessory stimulus. In all interstimulus interval (ISI) conditions, SRT enhancement went down both in the coincident and disparate configuration, but this decrement was fairly stable across the ISI values. If multisensory integration solely relied on a feed-forward process, one would expect a monotonic decrease of the masker effect with increasing ISI in the backward masking condition. It is therefore conceivable that the relatively high-energetic masker causes a broad excitatory response of SC neurons. During this state, the spatial audio-visual information from multisensory association areas is fed back and merged with the spatially unspecific excitation pattern induced by the masker. Assuming that a certain threshold of activation has to be achieved in order to generate a saccade in the correct direction, the blurred joint output of noise and spatial audio-visual information needs more time to reach this threshold prolonging SRT to an audio-visual object. |
T. Teichert; Steffen Klingenhoefer; T. Wachtler; Frank Bremmer Depth perception during saccades Journal Article In: Journal of Vision, vol. 8, no. 14, pp. 1–13, 2008. @article{Teichert2008, A number of studies have investigated the localization of briefly flashed targets during saccades to understand how the brain perceptually compensates for changes in gaze direction. Typical version saccades, i.e., saccades between two points of the horopter, are not only associated with changes in gaze direction, but also with large transient changes of ocular vergence. These transient changes in vergence have to be compensated for just as changes in gaze direction. We investigated depth judgments of perisaccadically flashed stimuli relative to continuously present references and report several novel findings. First, disparity thresholds increased around saccade onset. Second, for horizontal saccades, depth judgments were prone to systematic errors: Stimuli flashed around saccade onset were perceived in a closer depth plane than persistently shown references with the same retinal disparity. Briefly before and after this period, flashed stimuli tended to be perceived in a farther depth plane. Third, depth judgments for upward and downward saccades differed substantially: For upward, but not for downward saccades we observed the same pattern of mislocalization as for horizontal saccades. Finally, unlike localization in the fronto-parallel plane, depth judgments did not critically depend on the presence of visual references. Current models fail to account for the observed pattern of mislocalization in depth. |
D. A. Mills; Teresa C. Frohman; Scott L. Davis; A. R. Salter; Samuel M. McClure; I. Beatty; A. Shah; S. Galetta; E. Eggenberger; D. S. Zee; Elliot M. Frohman Break in binocular fusion during head turning in MS patients with INO Journal Article In: Neurology, vol. 71, pp. 457–460, 2008. @article{Mills2008, Internuclear ophthalmoparesis (INO) is the most common eye movement abnormality observed in pa- tients with multiple sclerosis (MS).1 While most MS patients with INO have no or little misalignment in the straight ahead position, significant disconjugacy occurs during horizontal saccades or with horizontal (yaw axis) head turning.2 A break in binocular fusion can produce a loss of stereopsis and depth percep- tion, transient diplopia (perceived as a double image or visual blur), oscillopsia, and disorientation.2 The purpose of this investigation was to confirm the hy- pothesis that a break in binocular fusion occurs in MS patients with INO during head or body turning, and that the magnitude of disconjugacy will be di- rectly correlated with the severity of this eye move- ment syndrome. |
Inger Montfoort; Josef N. Geest; Harm P. Slijper; Chris I. Zeeuw; Maarten A. Frens Adaptation of the cervico- and vestibulo-ocular reflex in whiplash injury patients Journal Article In: Journal of Neurotrauma, vol. 25, pp. 687–693, 2008. @article{Montfoort2008, The aim of this study was to investigate the underlying mechanisms of the increased gains of the cervico-ocular reflex (COR) and the lack of synergy between the COR and the vestibulo-ocular reflex (VOR) that have been previously observed in patients with whiplash-associated disorders (WAD). Eye movements during COR or VOR stimulation were recorded in four different experiments. The effect of restricted neck motion and the relationship between muscle activity and COR gain was examined in healthy controls. The adaptive ability of the COR and the VOR was tested in WAD patients and healthy controls. Reduced neck mobility yielded an increase in COR gain. No correlation between COR gain and muscle activity was observed. Adaptation of both the COR and VOR was observed in healthy controls, but not in WAD patients. The increased COR gain of WAD patients may stem from a reduced neck mobility. The lack of adaptation of the two stabilization reflexes may result in a lack of synergy between them. These abnormalities may underlie several of the symptoms frequently observed in WAD, such as vertigo and dizziness. |
2007 |
Caroline Paquette; J. Fung Temporal facilitation of gaze in the presence of postural reactions triggered by sudden surface perturbations Journal Article In: Neuroscience, vol. 145, no. 2, pp. 505–519, 2007. @article{Paquette2007, Saccadic reaction times can be shortened by an additional sensory modality (e.g. auditory, tactile) presented in temporal proximity to the triggering cue. Whereas somatosensory cues given by sudden perturbations of the support surface can trigger appropriate postural adjustments to maintain upright stance, it is not known how gaze executions are affected by the dual task of maintaining upright balance while redirecting gaze. It was hypothesized that the onset latency of gaze movements toward visual targets will be shortened by sudden surface perturbations following visual target shifts to prompt a stable visual anchor for postural stabilization. Eight subjects stood on a movable platform with gaze fixated on a central target 2 m directly in front, and were instructed to shift their gaze to lateral targets located along a 63° arc to the right and left. The trials began with the central target lit followed randomly by either the right, left or center target. Fifty or 250 ms following this target shift, balance was perturbed by a sudden yaw movement of the support surface (15.5° over 210 ms at 130°/s), with no stepping or large arm reactions observed. The latency of the gaze shifts was significantly shortened (by ∼72 ms) when executed simultaneously with a surface perturbation. A decrease in excitation latency was also observed in the cervical paraspinals and sternocleidomastoid muscles. Postural responses in the ankle and knee muscles were not affected by gaze shifts. Pelvic horizontal angular motion closely followed surface motion whereas head motion was influenced by gaze shifts. During the combined gaze shift and surface motion conditions, thorax movement excursion was larger and not correlated with either the surface motion or visual target shift. In conclusion, postural adjustments in response to sudden surface yaws facilitate voluntary gaze shift execution and this enhancement may result from the sensory fusion of somatosensory and visual information. |
Frank A. Proudlock; Irene Gottlob Physiology and pathology of eye-head coordination Journal Article In: Progress in Retinal and Eye Research, vol. 26, no. 5, pp. 486–515, 2007. @article{Proudlock2007, Human head movement control can be considered as part of the oculomotor system since the control of gaze involves coordination of the eyes and head. Humans show a remarkable degree of flexibility in eye-head coordination strategies, nonetheless an individual will often demonstrate stereotypical patterns of eye-head behaviour for a given visual task. This review examines eye-head coordination in laboratory-based visual tasks, such as saccadic gaze shifts and combined eye-head pursuit, and in common tasks in daily life, such as reading. The effect of the aging process on eye-head coordination is then reviewed from infancy through to senescence. Consideration is also given to how pathology can affect eye-head coordination from the lowest through to the highest levels of oculomotor control, comparing conditions as diverse as eye movement restrictions and schizophrenia. Given the adaptability of the eye-head system we postulate that this flexible system is under the control of the frontal cortical regions, which assist in planning, coordinating and executing behaviour. We provide evidence for this based on changes in eye-head coordination dependant on the context and expectation of presented visual stimuli, as well as from changes in eye-head coordination caused by frontal lobe dysfunction. |
Martin Rolfs On the limited role of target onset in the gap task: Support for the motor-preparation hypothesis Journal Article In: Journal of Vision, vol. 7, no. 10, pp. 1–20, 2007. @article{Rolfs2007, Saccade latency is reduced when the fixation stimulus is removed shortly before a saccade target appears (gap task) as compared to when the fixation stimulus remains present (overlap task). To test the assumption that this gap effect benefits from advanced motor preparation (M. Paré & D. P. Munoz, 1996), we manipulated target onset independently of the signal to launch a saccade (peripheral offset at the mirror location). In Experiment 1, we showed that, when the target appears at one of only two possible locations, target onset strongly improves performance (lower latency, higher accuracy) in the overlap task but not in the gap task. In Experiment 2, we found that the lack of an effect of target onset in the gap task was not due to inhibition of a reflexive response to the transient associated with the offset (go signal) in our task. In Experiment 3, we manipulated target onset and target uncertainty (two, four, or eight potential target locations) in gap and overlap tasks. As target uncertainty increased, the gap effect decreased, and the effect of target onset on saccade latency in the gap condition became greater. Overall, our results suggest, in line with the motor-preparation hypothesis, that saccade metrics in a gap task are computed before the target is actually displayed and that advanced motor preparation is enhanced when the location of the target is predictable. Analyses of anticipations and regular-latency errors corroborated this view. |
Philip J. Benson; Ute Leonards; Robert M. Lothian; David M. St. Clair; Marco C. G. Merlo Visual scan paths in first-episode schizophrenia and cannabis-induced psychosis Journal Article In: Journal of Psychiatry and Neuroscience, vol. 32, no. 4, pp. 267–274, 2007. @article{Benson2007, OBJECTIVE: Patterns of successive saccades and fixations (scan paths) that are made while viewing images are often spatially restricted in schizophrenia, but the relation with cannabis-induced psychosis has not been examined. We used higher-order statistical methods to examine spatiotemporal characteristics of scan paths to determine whether viewing behaviour was distinguishable on a continuum. METHODS: Patients with early acute first-episode paranoid schizophrenia (SCH; n = 11), cannabis-induced psychosis (CIP; n = 6) and unaffected control subjects (n = 22) undertook a task requiring free viewing of facial, fractal and landscape images for 5 seconds while their eye movements were recorded. Frequencies and distributions of saccades and fixations were calculated in relation to image regions examined during each trial. RESULTS: Findings were independent of image category, indicating generalized scanning deficits. Compared with control subjects, patients with SCH and CIP made fewer saccades and fewer fixations of longer duration. In turn, the spatial distribution of fixations in CIP patients was more clustered than in SCH and control subjects. The diversity of features fixated in subjects with CIP was also lower than in SCH patients and control subjects. CONCLUSION: A continuous approach to characterizing scan path changes in different phenotypes suggests that CIP shares some of the abnormalities of SCH but can be distinguished with measures that are sensitive to cognitive strategies active or inhibited during visual exploration. |
Alexander C. Schütz; Doris I. Braun; Karl R. Gegenfurtner Contrast sensitivity during the initiation of smooth pursuit eye movements Journal Article In: Vision Research, vol. 47, no. 21, pp. 2767–2777, 2007. @article{Schuetz2007, Eye movements challenge the perception of a stable world by inducing retinal image displacement. During saccadic eye movements visual stability is accompanied by a remapping of visual receptive fields, a compression of visual space and perceptual suppression. Here we explore whether a similar suppression changes the perception of briefly presented low contrast targets during the initiation of smooth pursuit eye movements. In a 2AFC design we investigated the contrast sensitivity for threshold-level stimuli during the initiation of smooth pursuit and during saccades. Pursuit was elicited by horizontal step-ramp and ramp stimuli. At any time from 200 ms before to 500 ms after pursuit stimulus onset, a blurred 0.3 deg wide horizontal line with low contrast just above detection threshold appeared for 10 ms either 2 deg above or below the pursuit trajectory. Observers had to pursue the moving stimulus and to indicate whether the target line appeared above or below the pursuit trajectory. In contrast to perceptual suppression effects during saccades, no pronounced suppression was found at pursuit onset for step-ramp motion. When pursuit was elicited by a ramp stimulus, pursuit initiation was accompanied by catch-up saccades, which caused saccadic suppression. Additionally, contrast sensitivity was attenuated at the time of pursuit or saccade stimulus onset. This attenuation might be due to an attentional deficit, because the stimulus required the focus of attention during the programming of the following eye movement. |
Alexander C. Schütz; Elias Delipetkos; Doris I. Braun; Dirk Kerzel; Karl R. Gegenfurtner Temporal contrast sensitivity during smooth pursuit eye movements Journal Article In: Journal of Vision, vol. 7, no. 13, pp. 1–15, 2007. @article{Schuetz2007a, During smooth pursuit eye movements, stimuli other than the pursuit target move across the retina, and this might affect their detectability. We measured detection thresholds for vertically oriented Gabor stimuli with different temporal frequencies (1, 4, 8, 12, 16, 20, and 24 Hz) of the sinusoids. Observers kept fixation on a small target spot that was either stationary or moved horizontally at a speed of 8 deg/s. The sinusoid of the Gabor stimuli moved either in the same or in the opposite direction as the pursuit target. Observers had to indicate whether the Gabor stimuli were displayed 4- above or below the target spot. Results show that contrast sensitivity was mainly determined by retinal-image motion but was slightly reduced during smooth pursuit eye movements. Moreover, sensitivity for motion opposite to pursuit direction was reduced in comparison to motion in pursuit direction. The loss in sensitivity for peripheral targets during pursuit can be interpreted in terms of space-based attention to the pursuit target. The loss of sensitivity for motion opposite to pursuit direction can be interpreted as feature-based attention to the pursuit direction. |
G. A. Spitzyna; Richard J. S. Wise; Scott A. McDonald; G. T. Plant; D. Kidd; H. Crewes; Alexander P. Leff Optokinetic therapy improves text reading in patients with hemianopic alexia: A controlled trial Journal Article In: Neurology, vol. 68, no. 22, pp. 1922–1930, 2007. @article{Spitzyna2007, OBJECTIVE: An acquired right-sided homonymous hemianopia can result in slowed left-to-right text reading, called hemianopic alexia (HA). Patients with HA lack essential visual information to help guide ensuing reading fixations. We tested two hypotheses: first, that practice with a visual rehabilitation method that induced small-field optokinetic nystagmus (OKN) would improve reading speeds in patients with HA when compared to a sham visual rehabilitation therapy; second, that this therapy would preferentially affect reading saccades into the blind field. METHODS: Nineteen patients with HA were entered into a two-armed study with two therapy blocks in each arm: one group practiced reading moving text (MT) that scrolled from right to left daily for two 4-week blocks (Group1), while the other had sham therapy (spot the difference) for the first block and then crossed over to MT for the second. RESULTS: Group 1 showed significant improvements in static text reading speed over both therapy blocks (18% improvement), while Group 2 did not significantly improve over the first block (5% improvement) but did when they crossed over to the MT block (23% improvement). MT therapy was associated with a direction-specific effect on saccadic amplitude for rightward but not leftward reading saccades. CONCLUSION: Optokinetic nystagmus inducing therapy preferentially affects reading saccades in the direction of the induced (involuntary) saccadic component. This is the first study to demonstrate the effectiveness of a specific eye movement based therapy in patients with hemianopic alexia (HA) in the context of a therapy-controlled trial. A free Web-based version of the therapy used in this study is available online to suitable patients with HA. |
James T. Todd; Karl R. Gegenfurtner; Lore Thaler; James T. Todd; Miriam Spering; Karl R. Gegenfurtner Illusory bending of a rigidly moving line segment: Effects of image motion and smooth pursuit eye movements. Journal Article In: Journal of Vision, vol. 7, no. 6, pp. 1–13, 2007. @article{Todd2007, Four experiments in which observers judged the apparent "rubberiness" of a line segment undergoing different types of rigid motion are reported. The results reveal that observers perceive illusory bending when the motion involves certain combinations of translational and rotational components and that the illusion is maximized when these components are presented at a frequency of approximately 3 Hz with a relative phase angle of approximately 120 degrees . Smooth pursuit eye movements can amplify or attenuate the illusion, which is consistent with other results reported in the literature that show effects of eye movements on perceived image motion. The illusion is unaffected by background motion that is in counterphase with the motion of the line segment but is significantly attenuated by background motion that is in-phase. This is consistent with the idea that human observers integrate motion signals within a local frame of reference, and it provides strong evidence that visual persistency cannot be the sole cause of the illusion as was suggested by J. R. Pomerantz (1983). An analysis of the motion patterns suggests that the illusory bending motion may be due to an inability of observers to accurately track the motions of features whose image displacements undergo rapid simultaneous changes in both space and time. A measure of these changes is presented, which is highly correlated with observers' numerical ratings of rubberiness. |
Massimo Turatto; Matteo Valsecchi; Luigi Tamè; Elena Betta Microsaccades distinguish between global and local visual processing Journal Article In: NeuroReport, vol. 18, no. 10, pp. 1015–1018, 2007. @article{Turatto2007, Much is known about the functional mechanisms involved in visual search. Yet, the fundamental question of whether the visual system can perform different types of visual analysis at different spatial resolutions still remains unsettled. In the visual-attention literature, the distinction between different spatial scales of visual processing corresponds to the distinction between distributed and focused attention. Some authors have argued that singleton detection can be performed in distributed attention, whereas others suggest that even such a simple visual operation involves focused attention. Here we showed that microsaccades were spatially biased during singleton discrimination but not during singleton detection. The results provide support to the hypothesis that some coarse visual analysis can be performed in a distributed attention mode. |
Matteo Valsecchi; Elena Betta; Massimo Turatto Visual oddballs induce prolonged microsaccadic inhibition Journal Article In: Experimental Brain Research, vol. 177, no. 2, pp. 196–208, 2007. @article{Valsecchi2007a, Eyes never stop moving. Even when asked to maintain the eyes at fixation, the oculomotor system produces small and rapid eye movements called microsaccades, at a frequency of about 1.5-2 s(-1). The frequency of microsaccades changes when a stimulus is presented in the visual field, showing a stereotyped response pattern consisting of an early inhibition of microsaccades followed by a rebound, before the baseline is reached again. Although this pattern of response has generally been considered as a sort of oculomotor reflex, directional biases in microsaccades have been recently linked to the orienting of spatial attention. In the present study, we show for the first time that regardless of any spatial bias, the pattern of absolute microsaccadic frequency is different for oddball stimuli compared to that elicited by standard stimuli. In a visual-oddball task, the oddball stimuli caused an initial prolonged inhibition of microsaccades, particularly when oddballs had to be explicitly recognized and remembered. The present findings suggest that high-order cognitive processes, other than spatial attention, can influence the frequency of microsaccades. Finally, we also introduce a new method for exploring the visual system response to oddball stimuli. |
Matteo Valsecchi; Massimo Turatto Microsaccadic response to visual events that are invisible to the superior colliculus Journal Article In: Behavioral Neuroscience, vol. 121, no. 4, pp. 786–793, 2007. @article{Valsecchi2007, Even when people think their eyes are still, tiny fixational eye movements, called microsaccades, occur at a rate of -1 Hz. Whenever a new (and potentially dangerous) event takes place in the visual field, the microsaccadic frequency is at first inhibited and then is followed by a rebound before the frequency returns to baseline. It has been suggested that this inhibition-rebound response is a type of oculomotor reflex mediated by the superior colliculus (SC), a midbrain structure involved in saccade programming. The present study investigated microsaccadic responses to visual events that were invisible to the SC; the authors recorded microsaccadic responses to visual oddballs when the latter were equiluminant with respect to the standard stimuli and when both oddballs and standards were equiluminant with respect to the background. Results showed that microsaccadic responses to oddballs and to standards were virtually identical both when the stimuli were visible to the SC and when they were invisible to it. Although the SC may be the generator of microsaccades, this research suggests that the specific fixational oculomotor activity in response to visual events can be controlled by other brain centers. |
Robert J. Beers The sources of variability in saccadic eye movements Journal Article In: Journal of Neuroscience, vol. 27, no. 33, pp. 8757–8770, 2007. @article{Beers2007, Our movements are variable, but the origin of this variability is poorly understood. We examined the sources of variability in human saccadic eye movements. In two experiments, we measured the spatiotemporal variability in saccade trajectories as a function of movement direction and amplitude. One of our new observations is that the variability in movement direction is smaller for purely horizontal and vertical saccades than for saccades in oblique directions. We also found that saccade amplitude, duration, and peak velocity are all correlated with one another. To determine the origin of the observed variability, we estimated the noise in motor commands from the observed spatiotemporal variability, while taking into account the variability resulting from uncertainty in localization of the target. This analysis revealed that uncertainty in target localization is the major source of variability in saccade endpoints, whereas noise in the magnitude of the motor commands explains a slightly smaller fraction. In addition, there is temporal variability such that saccades with a longer than average duration have a smaller than average peak velocity. This noise model has a large generality because it correctly predicts the variability in other data sets, which contain saccades starting from very different initial locations. Because the temporal noise most likely originates in movement planning, and the motor command noise in movement execution, we conclude that uncertainty in sensory signals and noise in movement planning and execution all contribute to the variability in saccade trajectories. These results are important for understanding how the brain controls movement. |
Henning U. Voss; Bruce D. McCandliss; Jamshid Ghajar; Minah Suh A quantitative synchronization model for smooth pursuit target tracking Journal Article In: Biological Cybernetics, vol. 96, no. 3, pp. 309–322, 2007. @article{Voss2007, We propose a quantitative model for human smooth pursuit tracking of a continuously moving visual target which is based on synchronization of an internal expectancy model of the target position coupled to the retinal target signal. The model predictions are tested in a smooth circular pursuit eye tracking experiment with transient target blanking of variable duration. In subjects with a high tracking accuracy, the model accounts for smooth pursuit and repeatedly reproduces quantitatively characteristic patterns of the eye dynamics during target blanking. In its simplest form, the model has only one free parameter, a coupling constant. An extended model with a second parameter, a time delay or memory term, accounts for predictive smooth pursuit eye movements which advance the target. The model constitutes an example of synchronization of a complex biological system with perceived sensory signals. |
Jeremy B. Wilmer; Ken Nakayama Two distinct visual motion mechanisms for smooth pursuit: evidence from individual differences Journal Article In: Neuron, vol. 54, no. 6, pp. 987–1000, 2007. @article{Wilmer2007, Smooth-pursuit eye velocity to a moving target is more accurate after an initial catch-up saccade than before, an enhancement that is poorly understood. We present an individual-differences-based method for identifying mechanisms underlying a physiological response and use it to test whether visual motion signals driving pursuit differ pre- and postsaccade. Correlating moment-to-moment measurements of pursuit over time with two psychophysical measures of speed estimation during fixation, we find two independent associations across individuals. Presaccadic pursuit acceleration is predicted by the precision of low-level (motion-energy-based) speed estimation, and postsaccadic pursuit precision is predicted by the precision of high-level (position-tracking) speed estimation. These results provide evidence that a low-level motion signal influences presaccadic acceleration and an independent high-level motion signal influences postsaccadic precision, thus presenting a plausible mechanism for postsaccadic enhancement of pursuit. © 2007 Elsevier Inc. All rights reserved. |
J. M. Hagen; Josef N. Geest; R. S. Giessen; Gerardina C. Lagers-van Haselen; H. J. F. M. M. Eussen; J. J. P. Gille; L. C. P. Govaerts; C. H. Wouters; I. F. M. Coo; C. C. Hoogenraad; Sebastiaan K. E. Koekkoek; Maarten A. Frens; N. Camp; A. Linden; M. C. E. Jansweijer; S. S. Thorgeirsson; Chris I. De Zeeuw Contribution of CYLN2 and GTF2IRD1 to neurological and cognitive symptoms in Williams Syndrome Journal Article In: Neurobiology of Disease, vol. 26, no. 1, pp. 112–124, 2007. @article{Hagen2007, Williams Syndrome (WS, [MIM 194050]) is a disorder caused by a hemizygous deletion of 25-30 genes on chromosome 7q11.23. Several of these genes including those encoding cytoplasmic linker protein-115 (CYLN2) and general transcription factors (GTF2I and GTF2IRD1) are expressed in the brain and may contribute to the distinct neurological and cognitive deficits in WS patients. Recent studies of patients with partial deletions indicate that hemizygosity of GTF2I probably contributes to mental retardation in WS. Here we investigate whether CYLN2 and GTF2IRD1 contribute to the motoric and cognitive deficits in WS. Behavioral assessment of a new patient in which STX1A and LIMK1, but not CYLN2 and GTF2IRD1, are deleted showed that his cognitive and motor coordination functions were significantly better than in typical WS patients. Comparative analyses of gene specific CYLN2 and GTF2IRD1 knockout mice showed that a reduced size of the corpus callosum as well as deficits in motor coordination and hippocampal memory formation may be attributed to a deletion of CYLN2, while increased ventricle volume can be attributed to both CYLN2 and GTF2IRD1. We conclude that the motor and cognitive deficits in Williams Syndrome are caused by a variety of genes and that heterozygous deletion of CYLN2 is one of the major causes responsible for such dysfunctions. |
Tobias Pflugshaupt; Urs P. Mosimann; Wolfgang J. Schmitt; Roman Wartburg; Pascal Wurtz; Mathias Lüthi; Thomas Nyffeler; Christian W. Hess; René M. Müri To look or not to look at threat? Scanpath differences within a group of spider phobics Journal Article In: Journal of Anxiety Disorders, vol. 21, no. 3, pp. 353–366, 2007. @article{Pflugshaupt2007, Predicting the behavior of phobic patients in a confrontational situation is challenging. While avoidance as a major clinical component of phobias suggests that patients orient away from threat, findings based on cognitive paradigms indicate an attentional bias towards threat. Here we present eye movement data from 21 spider phobics and 21 control subjects, based on 3 basic oculomotor tasks and a visual exploration task that included close-up views of spiders. Relative to the control group, patients showed accelerated reflexive saccades in one of the basic oculomotor tasks, while the fear-relevant exploration task evoked a general slowing in their scanning behavior and pronounced oculomotor avoidance. However, this avoidance strongly varied within the patient group and was not associated with the scores from spider avoidance-sensitive questionnaire scales. We suggest that variation of oculomotor avoidance between phobics reflects different strategies of how they cope with threat in confrontational situations. |
Tobias Pflugshaupt; Thomas Nyffeler; Roman Wartburg; Pascal Wurtz; Mathias Lüthi; Daniela Hubl; Klemens Gutbrod; Freimut D. Juengling; Christian W. Hess; René M. Müri When left becomes right and vice versa: Mirrored vision after cerebral hypoxia Journal Article In: Neuropsychologia, vol. 45, no. 9, pp. 2078–2091, 2007. @article{Pflugshaupt2007a, The combination of acquired mirror writing and reading is an extremely rare neurological disorder. It is encountered when brain damaged patients prefer horizontally mirrored over normal script in writing and reading. Previous theories have related this pathology to a disinhibition of mirrored engrams in the non-dominant hemisphere, possibly accompanied by a reversal of the preferred scanning direction. Here, we report the experimental investigation of PR, a patient who developed pronounced mirror writing and reading following septic shock that caused hypoxic brain damage. A series of five oculomotor experiments revealed that the patient's preferred scanning direction was indeed reversed. However, PR showed striking scanpath abnormalities and mirror reversals that cannot be explained by previous theories. Considered together with mirror phenomena she displayed in neuropsychological tasks and everyday activities, our findings suggest a horizontal reversal of visual information on a perceptual level. In addition, a systematic manipulation of visual variables within two further experiments had dramatic effects on her mirror phenomena. When confronted with moving, flickering or briefly presented stimuli, PR showed hardly any left-right reversals. Not only do these findings underline the perceptual nature of her disorder, but also allow interpretation of the pathology in terms of a dissociation between visual subsystems. We speculate that early visual cortices are crucially involved in this dissociation. More generally, her mirrored vision may represent an extreme clinical manifestation of the relative instability of the horizontal axis in spatial vision. |
Anouk Lamontagne; Caroline Paquette; Joyce Fung Stroke affects the coordination of gaze and posture during preplanned turns while walking Journal Article In: Neurorehabilitation and Neural Repair, vol. 21, no. 1, pp. 62–67, 2007. @article{Lamontagne2007, BACKGROUND: In healthy subjects, the act of walking and turning is accomplished by a sequential horizontal reorientation of gaze, head, and body toward the direction of the turn. Subjects with stroke, however, have difficulty altering their walking direction and present with loss of balance when performing a head turn or whole body rotation. OBJECTIVE: To study, in a pilot case study, the spatial and temporal coordination of gaze and posture during preplanned turns executed while walking in severely disabled and mildly disabled subjects with stroke as compared to a healthy control walking at slow speed. METHODS: Horizontal plane orientations of gaze, head, thorax, pelvis, and feet as well as the body's center of mass (CoM) trajectory were analyzed as subjects were walking straight or executing a 90-deg turn. RESULTS: Subjects with stroke revealed altered orientation and sequencing of gaze body segments. These alterations were more pronounced in the most severely disabled subject with stroke, especially when turning to the nonparetic side as compared to the paretic side. CONCLUSIONS: These findings suggest an altered coordination of gaze and posture during steering of locomotion in subjects with stroke. This altered coordination is likely due to a complex interaction of motor, sensory, and biomechanical factors that may explain the poor balance and poor control of heading direction during walking and turning in stroke. |
Mark F. Lenzenweger; Geoff McLachlan; Donald B. Rubin Resolving the latent structure of schizophrenia endophenotypes using expectation-maximization-based finite mixture modeling Journal Article In: Journal of Abnormal Psychology, vol. 116, no. 1, pp. 16–29, 2007. @article{Lenzenweger2007, Prior research has focused on the latent structure of endophenotypic markers of schizophrenia liability, or schizotypy. The work supports the existence of 2 relatively distinct latent classes and derives largely from the taxometric analysis of psychometric values. The present study used finite mixture modeling as a technique for discerning latent structure and the laboratory-measured endophenotypes of sustained attention deficits and eye-tracking dysfunction as endophenotype indexes. In a large adult community sample (N=311), finite mixture analysis of the sustained attention index d' and 2 eye-tracking indexes (gain and catch-up saccade rate) revealed evidence for 2 latent components. A putative schizotypy class accounted for 27% of the sample. A supplementary maximum covariance taxometric analysis yielded highly consistent results. Subjects in the schizotypy component displayed higher rates of schizotypal personality features and an increased rate of treated schizophrenia in their 1st-degree biological relatives compared with subjects in the other component. Implications of these results are examined in light of major theories of schizophrenia liability, and methodological advantages of finite mixture modeling for psychopathology research, with particular emphasis on genomic issues, are discussed. |
Rebecca J. McLean; Frank A. Proudlock; Shery Thomas; Christopher Degg; Irene Gottlob Congenital nystagmus: Randomized, controlled, double-masked trial of memantine/gabapentin Journal Article In: Annals of Neurology, vol. 61, no. 2, pp. 130–138, 2007. @article{McLean2007, OBJECTIVE: Nystagmus consists of involuntary to and fro movements of the eyes. Although studies have shown that memantine and gabapentin can reduce acquired nystagmus, no drug treatment has been systematically investigated in congenital nystagmus. METHODS: We performed a randomized, double-masked, placebo-controlled study investigating the effects of memantine and gabapentin on congenital nystagmus over a period of 56 days. The primary outcome measure was logarithmic minimum angle of resolution (logMAR) visual acuity; the secondary outcome measures were nystagmus intensity and foveation, subjective questionnaires about visual function (VF-14) and social function. Analyses were by intention to treat. RESULTS: Forty-eight patients were included in the study. One patient in the placebo group dropped out. Patients were randomized into either a memantine group (n=16), gabapentin group (n=16), or placebo group (n=15). Mean visual acuity improvements showed a significant effect between treatment groups (F=6.2; p=0.004, analysis of variance) with improvement in both memantine and gabapentin groups. Participants with afferent visual defects showed poorer improvements in visual acuity to medication than those with apparently normal visual systems. However, eye movement recordings showed that both nystagmus forms improved in nystagmus intensity (F=7.7; p=0.001) and foveation (F=8.7; p=0.0007). Participants subjectively reported an improvement in vision after memantine and gabapentin treatment more often than in the placebo group (p=0.03). However, there were no significant differences between the treatment groups with visual function (VF-14) or social function questionnaires because all groups reported improvements. INTERPRETATION: Our findings show that pharmacological agents such as memantine and gabapentin can improve visual acuity, reduce nystagmus intensity, and improve foveation in congenital nystagmus. |
J. Hübner; Andreas Sprenger; C. Klein; J. Hagenah; Holger Rambold; C. Zuhlke; D. Kompf; A. Rolfs; H. Kimmig; Christoph Helmchen Eye movement abnormalities in spinocerebellar ataxia type 17 (SCA17) Journal Article In: Neurology, vol. 69, no. 11, pp. 1160–1168, 2007. @article{Huebner2007, BACKGROUND: Spinocerebellar ataxia type 17 (SCA17) is associated with an expansion of CAG/CAA trinucleotide repeats in the gene encoding the TATA-binding protein. In this quantitative characterization of eye movements in SCA17 mutation carriers, we investigated whether eye movement abnormalities originate from multiple lesion sites as suggested by their phenotypic heterogeneity. METHODS: Eye movements (saccades, smooth pursuit) of 15 SCA17 mutation carriers (mean age 36.9 years, range 20 to 54 years; mean disease duration 7.3 years, range 0 to 20 years; 2 clinically unaffected, 13 affected) were compared with 15 age-matched control subjects using the video-based two-dimensional EYELINK II system. RESULTS: Smooth pursuit initiation (step-ramp paradigm) and maintenance were strongly impaired, i.e., pursuit latency was increased and acceleration decreased, whereas latency and position error of the first catch-up saccade were normal. Visually guided saccades were hypometric but had normal velocities. Gaze-evoked nystagmus was found in one-third of the mutation carriers, including downbeat and rebound nystagmus. There was a pathologic increase in error rates of antisaccades (52%) and memory-guided saccades (42%). Oculomotor disorders were not correlated with repeat length. Smooth pursuit impairment and saccadic disorders increased with disease duration. CONCLUSIONS: Several oculomotor deficits of spinocerebellar ataxia type 17 (SCA17) mutation carriers are compatible with cerebellar degeneration. This is consistent with histopathologic and imaging (morphometric) data. In contrast, increased error rates in antisaccades and memory-guided saccades point to a deficient frontal inhibition of reflexive movements, which is probably best explained by cortical dysfunction and may be related to other phenotypic SCA17 signs, e.g., dementia and parkinsonism. |
Vyv C. Huddy; Timothy L. Hodgson; Masuma Kapasi; Stanley H. Mutsatsa; Isobel Harrison; Thomas R. E. Barnes; Eileen M. Joyce Gaze strategies during planning in first-episode psychosis Journal Article In: Journal of Abnormal Psychology, vol. 116, no. 3, pp. 589–598, 2007. @article{Huddy2007, Eye movements were measured during the performance of a computerized Tower of London task to specify the source of planning abnormalities in patients with 1st-episode schizophrenia or schizoaffective disorder. Subjects viewed 2 arrays of colored balls in the upper and lower parts of the screen. They were asked to plan the shortest sequence of moves required to rearrange the balls in the lower screen to match the upper arrangement. Compared with healthy controls, patients made more planning errors, and decision times were longer. However, the patients showed the same gaze biases as controls prior to making a response, indicating that they understood the requirements of the task, approached the task in a strategic manner by identifying the nature of the problem, and used appropriate fixation strategies to plan and elaborate solutions. The patients showed increased duration of long-gaze periods toward both parts of the screen. This suggests that the patients had difficulty in encoding the essential features of the stimulus array. This finding is compatible with slowing of working memory consolidation. |
Rebecca L. Johnson; Keith Rayner Top-down and bottom-up effects in pure alexia: Evidence from eye movements Journal Article In: Neuropsychologia, vol. 45, no. 10, pp. 2246–2257, 2007. @article{Johnson2007, The eye movements of a patient with pure alexia, GJ, were recorded as he read sentences in order to explore the roles of top-down and bottom-up information during letter-by-letter reading. Specifically, the effects of word frequency and word predictability were examined. Additional analyses examined the interaction of these effects with the lower level influences of word length and letter confusability. The results indicate that GJ is sensitive to all four of these variables in sentence reading. These findings support an interactive account of reading where letter-by-letter readers use both bottom-up and top-down information to decode words. Due to the disrupted bottom-up processes caused by damage to the Visual Word Form Area or the input connections to it, pure alexic patients rely more heavily on intact top-down information in reading. |
Christoph Helmchen; Stefan Gottschalk; Thurid Sander; Peter Trillenberg; Holger Rambold; Andreas Sprenger Beneficial effects of 3,4-diaminopyridine on positioning downbeat nystagmus in a circumscribed uvulo-nodular lesion [6] Journal Article In: Journal of Neurology, vol. 254, no. 8, pp. 1126–1128, 2007. @article{Helmchen2007, Central positioning downbeat nystagmus (pDBN) presents with transient nystagmus in supine or the head hanging position in the absence of DBN in the head erect position. In contrast to central positional downbeat nystagmus, pDBN requires rapid head posi- tioning manoeuvres to be elicited. The pathomechanism and therapy of central pDBN is not yet known and circumscribed lesions are missing so far [1, 2]. We examined the effect of 3,4-diaminopyridine (DAP) [3, 4] on the oculomotor behavior of a patient with pDBN. |
Z. I. Wang; Louis F. Dell'Osso In: Vision Research, vol. 47, no. 11, pp. 1550–1560, 2007. @article{Wang2007, The objective of this study was to investigate the dynamic properties of infantile nystagmus syndrome (INS) that affect visual function; i.e., which factors influence latency of the initial reflexive saccade (Ls) and latency to target acquisition (Lt). We used our behavioral ocular motor system (OMS) model to simulate saccadic responses (in the presence of INS) to target jumps at different times within a single INS cycle and at random times during multiple cycles. We then studied the responses of 4 INS subjects with different waveforms to test the model's predictions. Infrared reflection was used for 1 INS subject, high-speed digital video for 3. We recorded and analyzed human responses to large and small target-step stimuli. We evaluated the following factors: stimulus time within the cycle (Tc), normalized Tc (Tc%), initial orbital position (Po), saccade amplitude, initial retinal error (ei), and final retinal error (ef). The ocular motor simulations were performed in MATLAB Simulink environment and the analysis was performed in MATLAB environment using OMLAB software. Both the OMS model and OMtools software are available from http://http:www.omlab.org. Our data analysis showed that for each subject, Ls was a fixed value that is typically higher than the normal saccadic latency. Although saccadic latency appears somewhat lengthened in INS, the amount is insufficient to cause the "slow-to-see" impression. For Lt, Tc% was the most influential factor for each waveform type. The main refixation strategies employed by INS subjects made use of slow and fast phases and catch-up saccades, or combinations of them. These strategies helped the subjects to foveate effectively after target movement, sometimes at the cost of increased target acquisition time. Foveating or braking saccades intrinsic to the nystagmus waveforms seemed to disrupt the OMS' ability to accurately calculate reflexive saccades' amplitude and refoveate. Our OMS model simulations demonstrated this emergent behavior and predicted the lengthy target acquisition times found in the patient data. |
Zhong I. Wang; Louis F. Dell'Osso; Robert L. Tomsak; Jonathan B. Jacobs In: Journal of AAPOS, vol. 11, no. 2, pp. 135–141, 2007. @article{Wang2007a, Purpose: To investigate the effects of combined tenotomy and recession procedures on both acquired downbeat nystagmus and horizontal infantile nystagmus. Methods: Patient 1 had downbeat nystagmus with a chin-down (upgaze) position, oscillopsia, strabismus, and diplopia. Asymmetric superior rectus recessions and inferior rectus tenotomies reduced right hypertropia and rotated both eyes downward. Patient 2 had horizontal infantile nystagmus, a 20° left-eye exotropia, and alternating (abducting-eye) fixation. Lateral rectus recessions and medial rectus tenotomies were performed. Horizontal and vertical eye movements were recorded pre- and postsurgically using high-speed digital video. The eXpanded Nystagmus Acuity Function (NAFX) and nystagmus amplitudes and frequencies were measured. Results: Patient 1: The NAFX peak moved from 10° up to primary position where NAFX values improved 17% and visual acuity increased 25%. Vertical NAFX increased across the -10° to +5° vertical range. Primary-position right hypertropia decreased ∼50%; foveation time per cycle increased 102%; vertical amplitude, oscillopsia, and diplopia were reduced, and frequency was unchanged. Patient 2: Two lateral, narrow high-NAFX regions (due to alternating fixation) became one broad region with a 43% increase in primary position (acuity increased ∼92.3%). Diplopia amplitude decreased; convergence and gaze holding were improved. Primary-position right exotropia was reduced; foveation time per cycle increased 257%; horizontal-component amplitude decreased 45.7%, and frequency remained unchanged. Conclusions: Combining tenotomy with nystagmus or strabismus recession procedures increased NAFX and visual acuities and reduced diplopia and oscillopsia in downbeat nystagmus and infantile nystagmus. |
Paul Sauleau; Pierre Pollak; Paul Krack; Denis Pélisson; Alain Vighetto; Alim Louis Benabid; Caroline Tilikete Contraversive eye deviation during stimulation of the subthalamic region Journal Article In: Movement Disorders, vol. 22, no. 12, pp. 1810–1813, 2007. @article{Sauleau2007, Contraversive eye deviation (CED) is most often observed intraoperatively during subthalamic nucleus implantation for Parkinson's disease and considered to result from wrong electrode positioning. We report on a woman, bilaterally implanted in the subthalamic nucleus for severe Parkinson's disease disclosing long-lasting CED only when the stimulators were activated separately. Clinical examination and eye movements recording in this patient showed that CED occurred when stimulation was applied at the site and at similar intensity used for the best antiparkinsonian effect. These results suggest that the subthalamic area may be involved in orienting movements, either through the subthalamic nucleus itself or the fibers from the Frontal Eye Fields. Interestingly, this report shows that CED may be corrected by bilateral stimulation and that CED may not necessarily implicate electrode repositioning. |
Daniel Smilek; Kelly A. Malcolmson; Jonathan S. A. Carriere; Meghan Eller; Donna Kwan; Michael G. Reynolds When "3" is a jerk and "E" is a king: Personifying inanimate objects in synesthesia Journal Article In: Journal of Cognitive Neuroscience, vol. 19, no. 6, pp. 981–992, 2007. @article{Smilek2007, We report a case study of an individual (TE) for whom inanimate objects, such as letters, numbers, simple shapes, and even furniture, are experienced as having rich and detailed personalities. TE reports that her object-personality pairings are stable over time, occur independent of her intentions, and have been there for as long as she can remember. In these respects, her experiences are indicative of synesthesia. Here we show that TE's object-personality pairings are very consistent across test-retest, even for novel objects. A qualitative analysis of TE's personality descriptions revealed that her personifications are extremely detailed and multi-dimensional, and that her personifications of familiar and novel objects differ in specific ways. We also found that TE's eye movements can be biased by the emotional associations she has with letters and numbers. These findings demonstrate that synesthesia can involve complex semantic personifications, which can influence visual attention. Finally, we propose a neural model of normal personification and the unusual personifications that accompany object-personality synesthesia. |
Michael L. Spezio; Ralph Adolphs; Robert S. Hurley; Joseph Piven Analysis of face gaze in autism using "Bubbles" Journal Article In: Neuropsychologia, vol. 45, no. 1, pp. 144–151, 2007. @article{Spezio2007a, One of the components of abnormal social functioning in autism is an impaired ability to direct eye gaze onto other people's faces in social situations. Here, we investigated the relationship between gaze onto the eye and mouth regions of faces, and the visual information that was present within those regions. We used the "Bubbles" method to vary the facial information available on any given trial by revealing only small parts of the face, and measured the eye movements made as participants viewed these stimuli. Compared to ten IQ- and age-matched healthy controls, eight participants with autism showed less fixation specificity to the eyes and mouth, a greater tendency to saccade away from the eyes when information was present in those regions, and abnormal directionality of saccades. The findings provide novel detail to the abnormal way in which people with autism look at faces, an impairment that likely influences all subsequent face processing. |
Michael L. Spezio; Ralph Adolphs; Robert S. Hurley; Joseph Piven Abnormal use of facial information in high-functioning autism Journal Article In: Journal of Autism and Developmental Disorders, vol. 37, no. 5, pp. 929–939, 2007. @article{Spezio2007, Altered visual exploration of faces likely contributes to social cognition deficits seen in autism. To investigate the relationship between face gaze and social cognition in autism, we measured both face gaze and how facial regions were actually used during emotion judgments from faces. Compared to IQ-matched healthy controls, nine high-functioning adults with autism failed to make use of information from the eye region of faces, instead relying primarily on information from the mouth. Face gaze accounted for the increased reliance on the mouth, and partially accounted for the deficit in using information from the eyes. These findings provide a novel quantitative assessment of how people with autism utilize information in faces when making social judgments. |
Bert Steenbergen; Julius Verrel; Andrew M. Gordon Motor planning in congenital hemiplegia Journal Article In: Disability and Rehabilitation, vol. 29, no. 1, pp. 13–23, 2007. @article{Steenbergen2007, PURPOSE: Cerebral Palsy (CP) is a broad definition of a neurological condition in which disorders in movement execution and postural control limit the performance of activities of daily living. In this paper, we first review studies on motor planning in hemiplegic CP. Second, preliminary data of a recent study on eye-hand coordination in participants with hemiplegic CP are presented. Here, the potential role of vision for online and prospective control of action was examined. METHOD: Review and presentation of preliminary data of an eye- and hand movement registration experiment in hemiplegic CP. RESULTS: Deficits in motor planning in hemiplegic CP contribute to limitations of activities of daily living. In the second part, exemplary plots of eye-hand coordination are presented for the affected and unaffected hand in one participant with hemiplegic CP, and for the preferred hand in controls, both as an illustration of the research methodology and to give an impression of the observed gaze patterns. CONCLUSION: Research on CP should not solely focus on low-level aspects of action execution, but also take into account the more high-level aspects of motor control, such as planning. Possible deviations therein may be sought in altered gaze patterns as illustrated in the paper. |
Timothy L. Hodgson; Marcia Chamberlain; Benjamin A. Parris; Martin James; Nicholas Gutowski; Masud Husain; Christopher Kennard The role of the ventrolateral frontal cortex in inhibitory oculomotor control Journal Article In: Brain, vol. 130, no. 6, pp. 1525–1537, 2007. @article{Hodgson2007, It has been proposed that the inferior/ventrolateral frontal cortex plays a critical role in the inhibitory control of action during cognitive tasks. However, the contribution of this region to the control of eye movements has not been clearly established. Here, we describe the performance of a group of 23 frontal lobe damaged patients in an oculomotor rule switching task for which the association between a centrally presented visual cue and the direction of a saccade could change from trial to trial. A subset of 16 patients also completed the standard antisaccade task. Ventrolateral damage was found to be a significant predictor of errors in both tasks. Analysis of the rate at which patients corrected errors in the rule switching task also revealed an important dissociation between left and right hemisphere damaged patients. Whilst patients with left ventrolateral damage usually corrected response errors with secondary saccades, those with right hemisphere lesions often failed to do so. The results suggest that the inferior frontal cortex forms part of a wider frontal network mediating inhibitory control over stimulus elicited eye movements. The critical role played by the right ventrolateral region in cognitive tasks may arise due to an additional functional specialization for the monitoring and updating of task rules. |
Amelia R. Hunt; Adrian Mühlenen; Alan Kingstone The time course of attentional and oculomotor capture reveals a common cause Journal Article In: Journal of Experimental Psychology: Human Perception and Performance, vol. 33, no. 2, pp. 271–284, 2007. @article{Hunt2007a, Eye movements are often misdirected toward a distractor when it appears abruptly, an effect known as oculomotor capture. Fundamental differences between eye movements and attention have led to questions about the relationship of oculomotor capture to the more general effect of sudden onsets on performance, known as attentional capture. This study explores that issue by examining the time course of eye movements and manual localization responses to targets in the presence of sudden-onset distractors. The results demonstrate that for both response types, the proportion of trials on which responses are erroneously directed to sudden onsets reflects the quality of information about the visual display at a given point in time. Oculomotor capture appears to be a specific instance of a more general attentional capture effect. Differences and similarities between the two types of capture can be explained by the critical idea that the quality of information about a visual display changes over time and that different response systems tend to access this information at different moments in time. |
Samuel B. Hutton; Brendan S. Weekes Low frequency rTMS over posterior parietal cortex impairs smooth pursuit eye tracking Journal Article In: Experimental Brain Research, vol. 183, no. 2, pp. 195–200, 2007. @article{Hutton2007, The role of the posterior parietal cortex in smooth pursuit eye movements remains unclear. We used low frequency repetitive transcranial magnetic stimulation (rTMS) to study the cognitive and neural systems involved in the control of smooth pursuit eye movements. Eighteen participants were tested on two separate occasions. On each occasion we measured smooth pursuit eye tracking before and after 6 min of 1 Hz rTMS delivered at 90% of motor threshold. Low frequency rTMS over the posterior parietal cortex led to a significant reduction in smooth pursuit velocity gain, whereas rTMS over the motor cortex had no effect on gain. We conclude that low frequency offline rTMS is a potentially useful tool with which to explore the cortical systems involved in oculomotor control. |
Stephanie Jainta; Jörg Hoormann; W. Jaschinski Objective and subjective measures of vergence step responses Journal Article In: Vision Research, vol. 47, no. 26, pp. 3238–3246, 2007. @article{Jainta2007, Dichoptic nonius lines are used for subjectively (psychophysically) measuring vergence states, but they have been questioned as valid indicators of vergence eye position. In a mirror-stereoscope, we presented convergent and divergent step-stimuli and estimated the vergence response with nonius lines flashed at fixed delays after the disparity step stimulus. For each delay, an adaptive psychophysical procedure was run to determine the physical nonius offset required for subjective alignment; these vergence states were compared with objective eye movement recordings. Between both measures of initial vergence, we calculated the maximal cross-correlation coefficient: the median in our sample was about 0.9 for convergence and divergence, suggesting a good agreement. Relative to the objective measures, the subjective method revealed a smaller vergence velocity and a larger vergence response in the final phase of the response, but both measures were well correlated. The dynamic nonius test is therefore considered to be useful to relatively evaluate a subject's ability in disparity vergence. |
Wolfgang Jaschinski; Stephanie Jainta; Jörg Hoormann; Nina Walper Objective vs subjective measurements of dark vergence Journal Article In: Ophthalmic and Physiological Optics, vol. 27, no. 1, pp. 85–92, 2007. @article{Jaschinski2007, Dark vergence is a resting position of vergence (tonic vergence), measured in a dark visual field to eliminate fusional, accommodative, and proximal stimuli. The vergence resting position is relevant for measures of phoria and fixation disparity. Dark vergence differs reliably among subjects: the average subject converges at a viewing distance of about 1 m, while the inter-individual range is from infinity to about 40 cm. In previous research, dark vergence was measured subjectively, i.e. observers adjusted the horizontal offset of dichoptically presented nonius targets to perceived alignment. Results of such subjective vergence tests do not necessarily agree with those of the objective measurements of eye position with eye trackers. Therefore, we made simultaneous subjective and objective measurements of dark vergence and found similar results with both methods in repeated tests in two sessions. Thus, the nonius test is sufficient for a subjective estimation of dark vergence. |
Thérèse Collins; Karine Doré-Mazars; Markus Lappe Motor space structures perceptual space: Evidence from human saccadic adaptation Journal Article In: Brain Research, vol. 1172, no. 1, pp. 32–39, 2007. @article{Collins2007, Saccadic adaptation is the progressive correction of systematic saccade targeting errors. When a saccade to a particular target is adapted, saccades within a spatial window around the target, the adaptation field, are affected as a function of their distance from the adapted target. Furthermore, previous studies suggest that saccadic adaptation might modify the perceptual localization of objects in space. We investigated the localization of visual probes before and after saccadic adaptation, and examined whether the spatial layout of the observed mislocalizations was structurally similar to the saccadic adaptation field. We adapted a horizontal saccade directed towards a target 12° to the right. Thirty-eight saccades towards the right visual hemifield were then used to measure the adaptation field. The adaptation field was asymmetric: transfer of adaptation to saccades larger than the adapted saccade was greater than transfer to smaller saccades. Subjects judged the localization of 39 visual probes both within and outside the adaptation field. The perceived localization of a probe at a given position was proportional to the amount of transfer from the adapted saccade to the saccade towards that position. This similar effect of saccadic adaptation on both the action and perception representations of space suggests that the system providing saccade metrics also contributes to the metric used for the perception of space. |
Julien Cotti; Alain Guillaume; Nadia Alahyane; Denis Pelisson; Jean-Louis Vercher Adaptation of voluntary saccades, but not of reactive saccades, transfers to hand pointing movements Journal Article In: Journal of Neurophysiology, vol. 98, no. 2, pp. 602–612, 2007. @article{Cotti2007, Studying the transfer of visuomotor adaptation from a given effector (e.g., the eye) to another (e.g., the hand) allows us to question whether sensorimotor processes influenced by adaptation are common to both effector control systems and thus to address the level where adaptation takes place. Previous studies have shown only very weak transfer of the amplitude adaptation of reactive saccades–i.e., produced automatically in response to the sudden appearance of visual targets–to hand pointing movements. Here we compared the amplitude of hand pointing movements recorded before and after adaptation of either reactive or voluntary saccades, produced either in a saccade sequence task or in a single saccade task. No transfer to hand pointing movements was found after adaptation of reactive saccades. In contrast, a substantial transfer to the hand was obtained following adaptation of voluntary saccades produced in sequence. Large amounts of transfer between the two saccade types were also found. These results demonstrate that the visuomotor processes influenced by saccadic adaptation depend on the type of saccades and that, in the case of voluntary saccades, they are shared by hand pointing movements. Implications for the neurophysiological substrates of the adaptation of reactive and voluntary saccades are discussed. |
Adele Diederich; Hans Colonius Why two "Distractors" are better than one: Modeling the effect of non-target auditory and tactile stimuli on visual saccadic reaction time Journal Article In: Experimental Brain Research, vol. 179, no. 1, pp. 43–54, 2007. @article{Diederich2007, Saccadic reaction time (SRT) was measured in a focused attention task with a visual target stimulus (LED) and auditory (white noise burst) and tactile (vibration applied to palm) stimuli presented as non-targets at five different onset times (SOAs) with respect to the target. Mean SRT was reduced (i) when the number of non-targets was increased and (ii) when target and non-targets were all presented in the same hemifield; (iii) this facilitation first increases and then decreases as the time point of presenting the non-targets is shifted from early to late relative to the target presentation. These results are consistent with the time-window-of-integration (TWIN) model (Colonius and Diederich in J Cogn Neurosci 16:1000-1009, 2004) which distinguishes a peripheral stage of independent sensory channels racing against each other from a second stage of neural integration of the input and preparation of an oculomotor response. Cross-modal interaction manifests itself in an increase or decrease of second stage processing time. For the first time, without making specific distributional assumptions on the processing times, TWIN is shown to yield numerical estimates for the facilitative effects of the number of non-targets and of the spatial configuration of target and non-targets. More generally, the TWIN model framework suggests that multisensory integration is a function of unimodal stimulus properties, like intensity, in the first stage and of cross-modal stimulus properties, like spatial disparity, in the second stage. |
Adele Diederich; Hans Colonius Modeling spatial effects in visual-tactile saccadic reaction time Journal Article In: Perception and Psychophysics, vol. 69, no. 1, pp. 56–67, 2007. @article{Diederich2007a, Saccadic reaction time (SRT) to visual targets tends to be shorter when nonvisual stimuli are presented in close temporal or spatial proximity, even when subjects are instructed to ignore the accessory input. Here, we investigate visual-tactile interaction effects on SRT under varying spatial configurations. SRT to bimodal stimuli was reduced by up to 30 msec, in comparison with responses to unimodal visual targets. In contrast to previous findings, the amount of multisensory facilitation did not decrease with increases in the physical distance between the target and the nontarget but depended on (1) whether the target and the nontarget were presented in the same hemifield (ipsilateral) or in different hemifields (contralateral), (2) the eccentricity of the stimuli, and (3) the frequency of the vibrotactile nontarget. The time-window-of-integration (TWIN) model for SRT (Colonius & Diederich, 2004) is shown to yield an explicit characterization of the observed multisensory spatial interaction effects through the removal of the peripheral-processing effects of stimulus location and tactile frequency. |
Jay A. Edelman; Árni Kristjánsson; Ken Nakayama The influence of object-relative visuomotor set on express saccades Journal Article In: Journal of Vision, vol. 7, no. 6, pp. 1–13, 2007. @article{Edelman2007, Express saccades are considered to have the shortest latency (70-110 ms) of all saccadic eye movements. The influence of visuomotor set, preparatory processes that spatially affect a sensorimotor response, on express saccades was examined by instructing human subjects to make a saccade to one of two simultaneously appearing spots defined by its position relative to the other. A temporal gap between fixation point disappearance and target appearance was used to facilitate the production of express saccades. For all subjects, the instruction influenced the vector of express saccades without increasing saccade latency. The effect on express saccades was only slightly weaker than that for longer latency saccades. Saccade curvature was minimal and did not depend strongly on task. Further experiments demonstrated that the effect of instruction on express saccade vector was much weaker when saccades were instructed to be made to one side of a single small spot, that the effect of instruction was equally strong when directing saccades to the less salient of two stimuli, and that an instruction could not only determine the direction of the effect but also modulate the effect's magnitude. The effect of instruction on saccade vector was no higher when blocked than when varied across trials. These results suggest that express saccades are influenced by object-relative spatial preparatory processes without increasing their reaction time and, thus, that high-level cognitive processes can influence the most reflexive of saccadic eye movements. |
Elena Betta; Giovanni Galfano; Massimo Turatto Microsaccadic response during inhibition of return in a target-target paradigm Journal Article In: Vision Research, vol. 47, no. 3, pp. 428–436, 2007. @article{Betta2007, This study examined the relationship between inhibition of return (IOR) in covert orienting and microsaccade statistics. Unlike a previous study [Galfano, G., Betta, E., & Turatto, M. (2004)], IOR was assessed by means of a target-target paradigm, and microsaccade dynamics were monitored as a function of both the first and the second visual event. In line with what has been reported with a cue-target paradigm, a significant directional modulation was observed opposite to the first visual event. Because participants were to respond to any stimulus, this rules out the possibility that the modulation resulted from a generic motor inhibition, showing instead that it is peculiarly coupled to the oculomotor system. Importantly, after the second visual event, a different response was observed in microsaccade orientation, whose direction critically depended of whether the second visual event appeared at the same location as the first visual event. The results are consistent with the notion that IOR is composed of both attentional and oculomotor components, and challenge the view that covert orienting paradigms engage the attentional component in isolation. |
François Bonnetblanc; Pierre Baraduc Saccadic adaptation without retinal postsaccadic error Journal Article In: NeuroReport, vol. 18, no. 13, pp. 1399–1402, 2007. @article{Bonnetblanc2007, Primary saccades undershoot their target. Corrective saccades are then triggered by retinal postsaccadic information. We tested whether primary saccades still undershoot when no postsaccadic visual information is available. Participants saccaded to five targets (10-34 degrees) that were either constantly illuminated (ON) or extinguished at saccade onset (OFF(Onset)). In OFF(Onset), few corrective saccades were observed. The saccadic gain increased over trials for the furthest (34 degrees) target. Terminal eye position after glissades or microsaccades progressively converged to the values observed in ON (targets over 16 degrees). Target extinction during the saccade only did not elicit any change. The results show that (i) postsaccadic retinal signals stabilize the saccadic gain and (ii) adaptive changes that reduce terminal error can take place without visual information. |
C. R. Camalier; A. Gotler; A. Murthy; K. G. Thompson; Gordon D. Logan; T. J. Palmeri; Jeffrey D. Schall Dynamics of saccade target selection: Race model analysis of double step and search step saccade production in human and macaque Journal Article In: Vision Research, vol. 47, no. 16, pp. 2187–2211, 2007. @article{Camalier2007, We investigated how saccade target selection by humans and macaque monkeys reacts to unexpected changes of the image. This was explored using double step and search step tasks in which a target, presented alone or as a singleton in a visual search array, steps to a different location on infrequent, random trials. We report that human and macaque monkey performance are qualitatively indistinguishable. Performance is stochastic with the probability of producing a compensated saccade to the final target location decreasing with the delay of the step. Compensated saccades to the final target location are produced with latencies relative to the step that are comparable to or less than the average latency of saccades on trials with no target step. Noncompensated errors to the initial target location are produced with latencies less than the average latency of saccades on trials with no target step. Noncompensated saccades to the initial target location are followed by corrective saccades to the final target location following an intersaccade interval that decreases with the interval between the target step and the initiation of the noncompensated saccade. We show that this pattern of results cannot be accounted for by a race between two stochastically independent processes producing the saccade to the initial target location and another process producing the saccade to the final target location. However, performance can be accounted for by a race between three stochastically independent processes-a GO process producing the saccade to the initial target location, a STOP process interrupting that GO process, and another GO process producing the saccade to the final target location. Furthermore, if the STOP process and second GO process start at the same time, then the model can account for the incidence and latency of mid-flight corrections and rapid corrective saccades. This model provides a computational account of saccade production when the image changes unexpectedly. |
C. S. Chapman; Amelia R. Hunt; Alan Kingstone Squeezing uncertainty from saccadic compression Journal Article In: Journal of Eye Movement Research, vol. 1, no. 1, pp. 1–5, 2007. @article{Chapman2007, Brief visual stimuli presented before and during a saccade are often mislocalized due to spatial compression. This saccadic compression effect is thought to have a perceptual basis, and results in visual objects being squeezed together and their number underestimated. Here we show that observers are also uncertain about their visual experiences just before and during a saccade. It is known that responses tend to be biased away from extreme values under conditions of uncertainty. Thus, a plausible alternative explanation of compression is that it reflects the uncertainty-bias to underestimate the number of items that were presented. We test this hypothesis and find that saccadic compression is independent of certainty, and is significantly modulated by orientation, with larger effects for stimuli oriented horizontally, in the direction of the saccade. These findings confirm that saccadic compression is a perceptual phenomenon that may enable seamless perceptual continuity across saccades. |
Konstantin Mergenthaler; Ralf Engbert Modeling the control of fixational eye movements with neurophysiological delays Journal Article In: Physical Review Letters, vol. 98, no. 13, pp. 1–4, 2007. @article{Mergenthaler2007, We propose a model for the control of fixational eye movements using time-delayed random walks. Fixational eye movements produce random displacements of the retinal image to prevent perceptual fading. First, we demonstrate that a transition from persistent to antipersistent correlations occurs in data recorded from a visual fixation task. Second, we propose and investigate a delayed random-walk model and get, by comparison of the transition points, an estimate of the neurophysiological delay. Differences between horizontal and vertical components of eye movements are found which can be explained neurophysiologically. Finally, we compare our numerical results with analytic approximations. |
David M. Milstein; Michael C. Dorris The influence of expected value on saccadic preparation Journal Article In: Journal of Neuroscience, vol. 27, no. 18, pp. 4810–4818, 2007. @article{Milstein2007, Basing higher-order decisions on expected value (reward probability x reward magnitude) maximizes an agent's accruement of reward over time. The goal of this study was to determine whether the advanced preparation of simple actions reflected the expected value of the potential outcomes. Human subjects were required to direct a saccadic eye movement to a visual target that was presented either to the left or right of a central fixation point on each trial. Expected value was manipulated by adjusting the probability of presenting each target and their associated magnitude of monetary reward across 15 blocks of trials. We found that saccadic reaction times (SRTs) were negatively correlated to the relative expected value of the targets. Occasionally, an irrelevant visual distractor was presented before the target to probe the spatial allocation of saccadic preparation. Distractor-directed errors (oculomotor captures) varied as a function of the relative expected value of, and the distance of distractors from, the potential valued targets. SRTs and oculomotor captures were better correlated to the relative expected value of actions than to reward probability, reward magnitude, or overall motivation. Together, our results suggest that the level and spatial distribution of competitive dynamic neural fields representing saccadic preparation reflect the relative expected value of the potential actions. |
Harold T. Nefs; Julie M. Harris Vergence effects on the perception of motion-in-depth Journal Article In: Experimental Brain Research, vol. 183, no. 3, pp. 313–322, 2007. @article{Nefs2007, When the eyes follow a target that is moving directly towards the head they make a vergence eye movement. Accurate perception of the target's motion requires adequate compensation for the movements of the eyes. The experiments in this paper address the issue of how well the visual system compensates for vergence eye movements when viewing moving targets. We show that there are small but consistent biases across observers: When the eyes follow a target that is moving in depth, it is typically perceived as slower than when the eyes are kept stationary. We also analysed the eye movements that were made by observers. We found that there are considerable differences between observers and between trials, but we did not find evidence that the gains and phase lags of the eye movements were related to psychophysical performance. |
Yasuki Noguchi; Shinsuke Shimojo; Ryusuke Kakigi; Minoru Hoshiyama Spatial contexts can inhibit a mislocalization of visual stimuli during smooth pursuit Journal Article In: Journal of Vision, vol. 7, no. 13, pp. 1–15, 2007. @article{Noguchi2007, The position of a flash presented during pursuit is mislocalized in the direction of the pursuit. Although this has been explained by a temporal mismatch between the slow visual processing of flash and fast efferent signals on eye positions, here we show that spatial contexts also play an important role in determining the flash position. We put various continuously lit objects (walls) between veridical and to-be-mislocalized positions of flash. Consequently, these walls significantly reduced the mislocalization of flash, preventing the flash from being mislocalized beyond the wall (Experiment 1). When the wall was shortened or had a hole in its center, the shape of the mislocalized flash was vertically shortened as if cutoff or funneled by the wall (Experiment 2). The wall also induced color interactions; a red wall made a green flash appear yellowish if it was in the path of mislocalization (Experiment 3). Finally, those flash-wall interactions could be induced even when the walls were presented after the disappearance of flash (Experiment 4). These results indicate that various features (position, shape, and color) of flash during pursuit are determined with an integration window that is spatially and temporally broad, providing a new insight for generating mechanisms of eye-movement mislocalizations. |
Nadia Alahyane; Roméo Salemme; Christian Urquizar; Julien Cotti; Alain Guillaume; Jean-Louis Vercher; Denis Pélisson Oculomotor plasticity: Are mechanisms of adaptation for reactive and voluntary saccades separate? Journal Article In: Brain Research, vol. 1135, no. 1, pp. 107–121, 2007. @article{Alahyane2007, Saccadic eye movements are permanently controlled and their accuracy maintained by adaptive mechanisms that compensate for physiological or pathological perturbations. In contrast to the adaptation of reactive saccades (RS) which are automatically triggered by the sudden appearance of a single target, little is known about the adaptation of voluntary saccades which allow us to intentionally scan our environment in nearly all our daily activities. In this study, we addressed this issue in human subjects by determining the properties of adaptation of scanning voluntary saccades (SVS) and comparing these features to those of RS. We also tested the reciprocal transfers of adaptation between the two saccade types. Our results revealed that SVS and RS adaptations disclosed similar adaptation fields, time course and recovery levels, with only a slightly lower after-effect for SVS. Moreover, RS and SVS main sequences both remained unaffected after adaptation. Finally and quite unexpectedly, the pattern of adaptation transfers was asymmetrical, with a much stronger transfer from SVS to RS (79%) than in the reverse direction (22%). These data demonstrate that adaptations of RS and SVS share several behavioural properties but at the same time rely on partially distinct processes. Based on these findings, it is proposed that adaptations of RS and SVS may involve a neural network including both a common site and two separate sites specifically recruited for each saccade type. |
Andre Kaminiarz; Bart Krekelberg; Frank Bremmer Localization of visual targets during optokinetic eye movements Journal Article In: Vision Research, vol. 47, no. 6, pp. 869–878, 2007. @article{Kaminiarz2007, We investigated localization of brief visual targets during reflexive eye movements (optokinetic nystagmus). Subjects mislocalized these targets in the direction of the slow eye movement. This error decreased shortly before a saccade and temporarily increased afterwards. The pattern of mislocalization differs markedly from mislocalization during voluntary eye movements in the presence of visual references, but (spatially) resembles mislocalization during voluntary eye movements in darkness. Because neither reflexive eye movements nor voluntary eye movements in darkness have explicit (visual) goals, these data support the view that visual goals support perceptual stability as an important link between pre- and post-saccadic scenes. |
Stephen J. Kerrigan; John F. Soechting Anisotropies in the gain of smooth pursuit during two-dimensional tracking as probed by brief perturbations Journal Article In: Experimental Brain Research, vol. 180, no. 3, pp. 435–448, 2007. @article{Kerrigan2007, Previous investigations suggest the gain of smooth pursuit is directionally anisotropic and is regulated in a task-dependent manner. Smooth pursuit is also known to be influenced by expectations concerning the target's motion, but the role of such expectations in modulating feedback gain is not known. In the present work, the gain of smooth pursuit was probed by applying brief perturbations to quasi-predictable two-dimensional target motion at multiple time points. The target initially moved in a straight line, then followed the circumference of a circle for distances ranging between 180 degrees and 270 degrees . Finally, the path reverted to linear motion. Perturbations consisted of a pulse of velocity 50 or 100 ms in duration, applied in one of eight possible directions. They were applied at the onset of the curve or after the target had traversed an arc of 45 degrees or 90 degrees . Pursuit gain was measured by computing the average amplitude of the response in smooth pursuit velocity over a 100 ms interval. To do so we used a coordinate system defined by the motion of the target at the onset of the perturbation, with directions tangential and normal to the path. Responses to the perturbations had two components: one that was modulated with the direction of the perturbation and one that was directionally nonspecific. For the directional response, on average the gain in the normal direction was slightly larger than the gain in the tangential direction, with a ratio ranging from 1.0 to 1.3. The directionally nonspecific response, which was more prominent for perturbations at curve onset or at 90 degrees , consisted of a transient decrease in pursuit speed. Perturbations applied at curve onset also delayed the tracking of the curved target motion. |
K. Konigs; J. Knoll; Frank Bremmer Localisation of auditory targets during optokinetic nystagmus Journal Article In: Perception, vol. 36, pp. 1507–1513, 2007. @article{Konigs2007, Previous studies have shown that the perceived location of visual stimuli briefly flashed during smooth pursuit, saccades, or optokinetic nystagmus (OKN) is not veridical. We investigated whether these mislocalisations can also be observed for brief auditory stimuli presented during OKN. Experiments were carried out in a lightproof sound-attenuated chamber. Participants performed eye movements elicited by visual stimuli. An auditory target (white noise) was presented for 5 ms. Our data clearly indicate that auditory targets are mislocalised during reflexive eye movements. OKN induces a shift of perceived location in the direction of the slow eye movement and is modulated in the temporal vicinity of the fast phase. The mislocalisation is stronger for look- as compared to stare-nystagmus. The size and temporal pattern of the observed mislocalisation are different from that found for visual targets. This suggests that different neural mechanisms are at play to integrate oculomotor signals and information on the spatial location of visual as well as auditory stimuli. |
2006 |
Dirk Kerzel; M. Pilar Aivar; Nathalie E. Ziegler; Eli Brenner Mislocalization of flashes during smooth pursuit hardly depends on the lighting conditions Journal Article In: Vision Research, vol. 46, no. 6-7, pp. 1145–1154, 2006. @article{Kerzel2006, Targets that are briefly flashed during smooth pursuit eye movements are mislocalized in the direction of motion (forward shift) and away from the fovea (spatial expansion). Hansen [Hansen, R. M. (1979). Spatial localization during pursuit eye movements. Vision Research 19(11), 1213-1221] reported that these errors are not present for fast motor responses in the dark, whereas Rotman et al. [Rotman, G., Brenner, E., Smeets, J. B. (2004). Quickly tapping targets that are flashed during smooth pursuit reveals perceptual mislocalizations. Experimental Brain Research 156(4), 409-414] reported that they are present for fast motor responses in the light. To evaluate whether the lighting conditions are the critical factor, we asked observers to point to the positions of flashed objects during smooth pursuit either in the dark or with the room lights on. In a first experiment, the flash, which could appear at 1 of 15 different positions, was always shown when the eye had reached a certain spatial position. We found a forward bias and spatial expansion that were independent of the target and ambient luminance. In a second experiment, the flash was always shown at the same retinal position, but the spatial position of the eye at the moment of flash presentation was varied. In this case we found differences between the luminance conditions, in terms of how the errors depended on the velocity and position on the trajectory. We also found specific conditions in which people did not mislocalize the target in the direction of pursuit at all. These findings may account for the above-mentioned discrepancy. We conclude that although the lighting conditions do influence the localization errors under some circumstances, it is certainly not so that such errors are absent whenever the experiment is conducted in the dark. |
Mark F. Lenzenweger; Gillian A. O'Driscoll Smooth pursuit eye movement and schizotypy in the community Journal Article In: Journal of Abnormal Psychology, vol. 115, no. 4, pp. 779–786, 2006. @article{Lenzenweger2006, Deficits in smooth pursuit eye movements are well documented in schizophrenia and schizotypic psychopathology. The status of eye tracking dysfunction (ETD) as an endophenotype for schizophrenia liability is relatively robust. However, the relation of ETD to schizophrenia-related deviance in the general population has not been confirmed. This study examined smooth pursuit eye tracking and schizotypal personality features in the general population. Smooth pursuit eye movement and schizotypal features were measured in 300 adult community subjects. The sample included both sexes, subjects with a wide age and educational range, and subjects with no prior history of psychosis. Primary outcome measures were peak gain (eye velocity/target velocity), catch-up saccade rate, and schizotypal feature scores. Total schizotypal features were significantly associated with decreased peak gain and were associated at the trend level with increased catch-up saccade rate. These associations were essentially unchanged after controlling for age, sex, and intellectual level effects. These data confirm a hypothesized association between schizotypal features and poorer eye tracking performance (principally, peak gain) in the general population as well as support the conceptualization of ETD as an endophenotype for schizophrenia liability. |
Elena Betta; Massimo Turatto Are you ready? I can tell by looking at your microsaccades Journal Article In: NeuroReport, vol. 17, no. 10, pp. 1001–1004, 2006. @article{Betta2006, The direction of microsaccades has been shown to be biased by the allocation of spatial attention. Here, we investigated whether the cognitive processes involved in preparing to respond to an upcoming target can modulate the microsaccadic response. Specifically, we found that optimal manual response preparation, reflected by faster response times, was associated with a reduction in the absolute frequency of microsaccades. The present results are consistent with previous studies suggesting a relationship between oculomotor activity and different sorts of motor responses. Our findings, however, surprisingly demonstrate that the effect of preparation and stimulus expectation extends to an automatic and unconscious oculomotor activity such as microsaccade execution. |
Ibrahim Dahlstrom-Hakki; Alexander Pollatsek Limits on integrating motion information across saccades Journal Article In: Perception and Psychophysics, vol. 68, no. 1, pp. 43–54, 2006. @article{DahlstromHakki2006, In two experiments, we investigated whether people could detect changes in the rotary motion of a cube. A rendering of a cube rotating at a constant angular velocity was presented on a video monitor and, at a key point in the trial, a cross was presented to one side of the cube as a cue for a saccade. On some trials, a change in the rotation occurred either about 100 msec before the saccade or during the saccade; on other trials, there was no change. The change consisted of moving the cube to a new position in the "rotation sequence," after which it continued to rotate at the same angular velocity as before. There was also a control on all trials to ensure that change detection was not due to the detection of low-level motion. Although detection of the change was well above chance when it occurred during the fixation, it was at chance when it occurred during the saccade, except in the case of one participant (who was in both experiments). This chance performance also occurred in Experiment 2 for (1) a slower rotation speed and (2) an axis of rotation that made the rotation planar. The participant who had above chance performance (and as good as that when the change occurred during a fixation) reported using a "strategy" that did not track the path of the cube. It thus appears that there is no natural way in which the visual system tracks this rotary motion, and that detection of change requires some sort of recoding. This finding raises the question of whether good performance in other, apparently similar, motion-detection tasks is a result of similar recoding. |