EyeLink Usability / Applied Publications
All EyeLink usability and applied research publications up until 2023 (with some early 2024s) are listed below by year. You can search the publications using keywords such as Driving, Sport, Workload, etc. You can also search for individual author names. If we missed any EyeLink usability or applied article, please email us!
2010 |
Thérèse Collins Visual target selection and motor planning define attentional enhancement at perceptual processing stages Journal Article In: Frontiers in Human Neuroscience, vol. 4, pp. 14, 2010. @article{Collins2010, Extracting information from the visual field can be achieved by covertly orienting attention to different regions, or by making saccades to bring areas of interest onto the fovea. While much research has shown a link between covert attention and saccade preparation, the nature of that link remains a matter of dispute. Covert presaccadic orienting could result from target selection or from planning a motor act toward an object. We examined the contribution of visual target selection and motor preparation to attentional orienting in humans by dissociating these two habitually aligned processes with saccadic adaptation. Adaptation introduces a discrepancy between the visual target evoking a saccade and the motor metrics of that saccade, which, unbeknownst to the participant, brings the eyes to a different spatial location. We examined attentional orienting by recording event-related potentials (ERPs) to task-irrelevant visual probes flashed during saccade preparation at four equidistant locations including the visual target location and the upcoming motor endpoint. ERPs as early as 130-170 ms post-probe were modulated by attention at both the visual target and motor endpoint locations. These results indicate that both target selection and motor preparation determine the focus of spatial attention, resulting in enhanced processing of stimuli at early visual-perceptual stages. |
Hans Peter Frey; Shane P. Kelly; Edmund C. Lalor; John J. Foxe Early spatial attentional modulation of inputs to the fovea Journal Article In: Journal of Neuroscience, vol. 30, no. 13, pp. 4547–4551, 2010. @article{Frey2010, Attending to a specific spatial location modulates responsivity of neurons with receptive fields processing that part of the environment. A major outstanding question is whether attentional modulation operates differently for the foveal (central) representation of the visual field than it does for the periphery. Indeed, recent animal electrophysiological recordings suggest that attention differentially affects spatial integration for central and peripheral receptive fields in primary visual cortex. In human electroencephalographic recordings, spatial attention to peripheral locations robustly modulates activity in early visual regions, but it has been claimed that this mechanism does not operate in foveal vision. Here, however, we show clear early attentional modulation of foveal stimulation with the same timing and cortical sources as seen for peripheral stimuli, demonstrating that attentional gain control operates similarly across the entire field of view. These results imply that covertly attending away from the center of gaze, which is a common paradigm in behavioral and electrophysiological studies of attention, results in a precisely timed push–pull mechanism. While the amplitude of the initial response to stimulation at attended peripheral locations is significantly increased beginning at 80 ms, the amplitude of the response to foveal stimulation begins to be attenuated. |
José P. Ossandón; Andrea Helo; Rodrigo Montefusco-Siegmund; Pedro E. Maldonado Superposition model predicts EEG occipital activity during free viewing of natural scenes Journal Article In: Journal of Neuroscience, vol. 30, no. 13, pp. 4787–4795, 2010. @article{Ossandon2010, Visual event-related potentials (ERPs) produced by a stimulus are thought to reflect either an increase of synchronized activity or a phase realignment of ongoing oscillatory activity, with both mechanisms sharing the assumption that ERPs are independent of the current state of the brain at the time of stimulation. In natural viewing, however, visual inputs occur one after another at specific subject-paced intervals through unconstrained eye movements. We conjecture that during natural viewing, ERPs generated after each fixation are better explained by a superposition of ongoing oscillatory activity related to the processing of previous fixations, with new activity elicited by the visual input at the current fixation. We examined the electroencephalography (EEG) signals that occur in humans at the onset of each visual fixation, both while subjects freely viewed natural scenes and while they viewed a black or gray background. We found that the fixation ERPs show visual components that are absent when subjects move their eyes on a homogeneous gray or black screen. Single-trial EEG signals that comprise the ERP are predicted more accurately by a model of superposition than by either phase resetting or the addition of evoked responses and stimulus-independent noise. The superposition of ongoing oscillatory activity and the visually evoked response results in a modification of the ongoing oscillation phase. The results presented suggest that the observed EEG signals reflect changes occurring in a common neuronal substrate rather than a simple summation at the scalp of signals from independent sources. |
Keith J. Yoder; Matthew K. Belmonte Combining computer game-based behavioural experiments with high-density EEG and infrared gaze tracking Journal Article In: Journal of Visualized Experiments, vol. 46, pp. 1–10, 2010. @article{Yoder2010, Experimental paradigms are valuable insofar as the timing and other parameters of their stimuli are well specified and controlled, and insofar as they yield data relevant to the cognitive processing that occurs under ecologically valid conditions. These two goals often are at odds, since well controlled stimuli often are too repetitive to sustain subjects' motivation. Studies employing electroencephalography (EEG) are often especially sensitive to this dilemma between ecological validity and experimental control: attaining sufficient signal-to-noise in physiological averages demands large numbers of repeated trials within lengthy recording sessions, limiting the subject pool to individuals with the ability and patience to perform a set task over and over again. This constraint severely limits researchers' ability to investigate younger populations as well as clinical populations associated with heightened anxiety or attentional abnormalities. Even adult, non-clinical subjects may not be able to achieve their typical levels of performance or cognitive engagement: an unmotivated subject for whom an experimental task is little more than a chore is not the same, behaviourally, cognitively, or neurally, as a subject who is intrinsically motivated and engaged with the task. A growing body of literature demonstrates that embedding experiments within video games may provide a way between the horns of this dilemma between experimental control and ecological validity. The narrative of a game provides a more realistic context in which tasks occur, enhancing their ecological validity (Chaytor & Schmitter-Edgecombe, 2003). Moreover, this context provides motivation to complete tasks. In our game, subjects perform various missions to collect resources, fend off pirates, intercept communications or facilitate diplomatic relations. In so doing, they also perform an array of cognitive tasks, including a Posner attention-shifting paradigm (Posner, 1980), a go/no-go test of motor inhibition, a psychophysical motion coherence threshold task, the Embedded Figures Test (Witkin, 1950, 1954) and a theory-of-mind (Wimmer & Perner, 1983) task. The game software automatically registers game stimuli and subjects' actions and responses in a log file, and sends event codes to synchronise with physiological data recorders. Thus the game can be combined with physiological measures such as EEG or fMRI, and with moment-to-moment tracking of gaze. Gaze tracking can verify subjects' compliance with behavioural tasks (e.g. fixation) and overt attention to experimental stimuli, and also physiological arousal as reflected in pupil dilation (Bradley et al., 2008). At great enough sampling frequencies, gaze tracking may also help assess covert attention as reflected in microsaccades - eye movements that are too small to foveate a new object, but are as rapid in onset and have the same relationship between angular distance and peak velocity as do saccades that traverse greater distances. The distribution of directions of microsaccades correlates with the (otherwise) covert direction of attention (Hafed & Clark, 2002). |
Tjerk P. Gutteling; Helene M. Ettinger-Veenstra; J. Leon Kenemans; Sebastiaan F. W. Neggers In: Journal of Cognitive Neuroscience, vol. 22, no. 9, pp. 1931–1943, 2010. @article{Gutteling2010, When an eye movement is prepared, attention is shifted toward the saccade end-goal. This coupling of eye movements and spatial attention is thought to be mediated by cortical connections between the FEFs and the visual cortex. Here, we present evidence for the existence of these connections. A visual discrimination task was performed while recording the EEG. Discrimination performance was significantly improved when the discrimination target and the saccade target matched. EEG results show that frontal activity precedes occipital activity contralateral to saccade direction when the saccade is prepared but not yet executed; these effects were absent in fixation conditions. This is consistent with the idea that the FEF exerts a direct modulatory influence on the visual cortex and enhances perception at the saccade end-goal. |
Ben M. Harvey; O. J. Braddick; A. Cowey In: Journal of Vision, vol. 10, no. 5, pp. 1–15, 2010. @article{Harvey2010, Our recent psychophysical experiments have identified differences in the spatial summation characteristics of pattern detection and position discrimination tasks performed with rotating, expanding, and contracting stimuli. Areas MT and MST are well established to be involved in processing these stimuli. fMRI results have shown retinotopic activation of area V3A depending on the location of the center of radial motion in vision. This suggests the possibility that V3A may be involved in position discrimination tasks with these motion patterns. Here we use repetitive transcranial magnetic stimulation (rTMS) over MT+ and a dorsomedial extrastriate region including V3A to try to distinguish between TMS effects on pattern detection and position discrimination tasks. If V3A were involved in position discrimination, we would expect to see effects on position discrimination tasks, but not pattern detection tasks, with rTMS over this dorsomedial extrastriate region. In fact, we could not dissociate TMS effects on the two tasks, suggesting that they are performed by the same extrastriate area, in MT+. |
Simon P. Kelly; John J. Foxe; Geoffrey Newman; Jay A. Edelman Prepare for conflict: EEG correlates of the anticipation of target competition during overt and covert shifts of visual attention Journal Article In: European Journal of Neuroscience, vol. 31, no. 9, pp. 1690–1700, 2010. @article{Kelly2010a, When preparing to make a saccadic eye movement in a cued direction, perception of stimuli at the target location is enhanced, just as it is when attention is covertly deployed there. Accordingly, the timing and anatomical sources of preparatory brain activity accompanying shifts of covert attention and saccade preparation tend to exhibit a large degree of overlap. However, there is evidence that preparatory processes are modulated by the foreknowledge of visual distractor competition during covert attention, and it is unknown whether eye movement preparation undergoes equivalent modulation. Here we examine preparatory processes in the electroencephalogram of human participants during four blocked versions of a spatial cueing task, requiring either covert detection or saccade execution, and either containing a distractor or not. As in previous work, a typical pattern of spatially selective occipital, parietal and frontal activity was seen in all task versions. However, whereas distractor presence called on an enhancement of spatially selective visual cortical modulation during covert attention, it instead called on increased activity over frontomedial oculomotor areas in the case of overt saccade preparation. We conclude that, although advance orienting signals may be similar in character during overt and covert conditions, the pattern by which these signals are modulated to ameliorate the behavioral costs of distractor competition is highly distinct, pointing to a degree of separability between the overt and covert systems. |
Alon S. Keren; Shlomit Yuval-Greenberg; Leon Y. Deouell Saccadic spike potentials in gamma-band EEG : Characterization , detection and suppression Journal Article In: NeuroImage, vol. 49, no. 3, pp. 2248–2263, 2010. @article{Keren2010, Analysis of high-frequency (gamma-band) neural activity by means of non-invasive EEG is gaining increasing interest. However, we have recently shown that a saccade-related spike potential (SP) seriously confounds the analysis of EEG induced gamma-band responses (iGBR), as the SP eludes traditional EEG artifact rejection methods. Here we provide a comprehensive profile of the SP and evaluate methods for its detection and suppression, aiming to unveil true cerebral gamma-band activity. The SP appears consistently as a sharp biphasic deflection of about 22 ms starting at the saccade onset, with a frequency band of ∼ 20-90 Hz. On the average, larger saccades elicit higher SP amplitudes. The SP amplitude gradually changes from the extra-ocular channels towards posterior sites with the steepest gradients around the eyes, indicating its ocular source. Although the amplitude and the sign of the SP depend on the choice of reference channel, the potential gradients remain the same and non-zero for all references. The scalp topography is modulated almost exclusively by the direction of saccades, with steeper gradients ipsilateral to the saccade target. We discuss how the above characteristics impede attempts to remove these SPs from the EEG by common temporal filtering, choice of different references, or rejection of contaminated trials. We examine the extent to which SPs can be reliably detected without an eye tracker, assess the degree to which scalp current density derivation attenuates the effect of the SP, and propose a tailored ICA procedure for minimizing the effect of the SP. |
Yosuke Kita; Atsuko Gunji; Kotoe Sakihara; Masumi Inagaki; Makiko Kaga; Eiji Nakagawa; Toru Hosokawa Scanning strategies do not modulate face identification: Eye-tracking and near-infrared spectroscopy study Journal Article In: PLoS ONE, vol. 5, no. 6, pp. e11050, 2010. @article{Kita2010, BACKGROUND: During face identification in humans, facial information is sampled (seeing) and handled (processing) in ways that are influenced by the kind of facial image type, such as a self-image or an image of another face. However, the relationship between seeing and information processing is seldom considered. In this study, we aimed to reveal this relationship using simultaneous eye-tracking measurements and near-infrared spectroscopy (NIRS) in face identification tasks. METHODOLOGY/PRINCIPAL FINDINGS: 22 healthy adult subjects (8 males and 14 females) were shown facial morphing movies in which an initial facial image gradually changed into another facial image (that is, the subject's own face was changed to a familiar face). The fixation patterns on facial features were recorded, along with changes in oxyhemoglobin (oxyHb) levels in the frontal lobe, while the subjects identified several faces. In the self-face condition (self-face as the initial image), hemodynamic activity around the right inferior frontal gyrus (IFG) was significantly greater than in the familiar-face condition. On the other hand, the scanning strategy was similar in almost all conditions with more fixations on the eyes and nose than on other areas. Fixation time on the eye area did not correlate with changes in oxyHb levels, and none of the scanning strategy indices could estimate the hemodynamic changes. CONCLUSIONS/SIGNIFICANCE: We conclude that hemodynamic activity, i.e., the means of processing facial information, is not always modulated by the face-scanning strategy, i.e., the way of seeing, and that the right IFG plays important roles in both self-other facial discrimination and self-evaluation. |
Steven L. Prime; Michael Vesia; J. Douglas Crawford TMS over human frontal eye fields disrupts trans-saccadic memory of multiple objects Journal Article In: Cerebral Cortex, vol. 20, no. 4, pp. 759–772, 2010. @article{Prime2010, We recently showed that transcranial magnetic stimulation (TMS) over the right parietal eye fields disrupts memory of object features and locations across saccades. We applied TMS over the frontal eye fields (FEF) as subjects compared the feature details of visual targets presented either within a single eye fixation (Fixation Task) or across a saccade (Saccade Task). TMS pulses were randomly delivered at one of 3 time intervals around the time of the saccade, or at equivalent times in the Fixation Task. A No-TMS control confirmed that subjects could normally retain approximately 3 visual features. TMS in the Fixation Task had no effect compared with No-TMS, but differences among TMS times were found during right FEF stimulation. TMS over either the right or left FEF disrupted memory performance in the Saccade Task when stimulation coincided most closely with the saccade. The capacity to compare pre-and postsaccadic features was reduced to 1-2 objects, as expected if the spatial aspect of memory was disrupted. These findings suggest that the FEF plays a role in the spatial processing involved in trans-saccadic memory of visual features. We propose that this process employs saccade-related feedback signals similar to those observed in spatial updating. |
Pia Rämä; Thierry Baccino Eye fixation-related potentials (EFRPs) during object identification Journal Article In: Visual Neuroscience, vol. 27, no. 5-6, pp. 187–192, 2010. @article{Raemae2010, Eye fixation-related potential (EFRP) measures electrical brain activity in response to eye fixations. The aim of the current study was to investigate whether the EFRPs vary during consecutive eye fixations while subjects were performing an object identification task. Eye fixations evoked P1 and N1 components at the occipital and parietal recording sites. The latency of P1 component increased during consecutive fixations. The amplitude of P1 increased and the amplitude of N1 decreased during consecutive fixations. The results indicate that EFRPs are modulated during consecutive fixations, suggesting that the current technique may provide a useful tool to study temporal dynamics of visual perception and processes underlying object identification. |
Victor Sander; Brian Soper; Stefan Everling Nonhuman primate event-related potentials associated with pro- and anti-saccades Journal Article In: NeuroImage, vol. 49, no. 2, pp. 1650–1658, 2010. @article{Sander2010, Non-invasive event-related potential (ERP) recordings have become a popular technique to study neural activity associated with saccades in humans. To date, it is not known whether nonhuman primates exhibit similar saccade-related ERPs. Here, we recorded ERPs associated with the performance of randomly interleaved pro- and anti-saccades in macaque monkeys. Stimulus-aligned ERPs showed short-latency visual component with more negative P2 and N2 peak amplitudes on anti- than on pro-saccade trials. Saccade-aligned ERPs showed a larger presaccadic negativity on anti- than pro-saccade trials, and a presaccadic positivity on pro-saccade trials, which was attenuated or absent on anti-saccade trials. This was followed by sharp negative spike potential immediately prior to the movement. Overall, these findings demonstrate that macaque monkeys, like humans, exhibit task-related differences of visual ERPs associated with pro- and anti-saccades and furthermore share presaccadic positivity as well as a spike potential prior to these tasks. We suggest that the presaccadic positivity on pro-saccade trials is generated by a source in the contralateral frontal eye fields and that the more negative voltage on anti-saccade trials is the result of additional sources of opposite polarity in neighboring frontal areas. |
Michael Vesia; Steven L. Prime; Xiaogang Yan; Lauren E. Sergio; J. Douglas Crawford Specificity of human parietal saccade and reach regions during transcranial magnetic stimulation Journal Article In: Journal of Neuroscience, vol. 30, no. 39, pp. 13053–13065, 2010. @article{Vesia2010, Single-unit recordings in macaque monkeys have identified effector-specific regions in posterior parietal cortex (PPC), but functional neuroimaging in the human has yielded controversial results. Here we used on-line repetitive transcranial magnetic stimulation (rTMS) to determine saccade and reach specificity in human PPC. A short train of three TMS pulses (separated by an interval of 100 ms) was delivered to superior parieto-occipital cortex (SPOC), a region over the midposterior intraparietal sulcus (mIPS), and a site close to caudal IPS situated over the angular gyrus (AG) during a brief memory interval while subjects planned either a saccade or reach with the left or right hand. Behavioral measures then were compared to controls without rTMS. Stimulation of mIPS and AG produced similar patterns: increased end-point variability for reaches and decreased saccade accuracy for contralateral targets. In contrast, stimulation of SPOC deviated reach end points toward visual fixation and had no effect on saccades. Contralateral-limb specificity was highest for AG and lowest for SPOC. Visual feedback of the hand negated rTMS-induced disruptions of the reach plan for mIPS and AG, but not SPOC. These results suggest that human SPOC is specialized for encoding retinally peripheral reach goals, whereas more anterior-lateral regions (mIPS and AG) along the IPS possess overlapping maps for saccade and reach planning and are more closely involved in motor details (i.e., planning the reach vector for a specific hand). This work provides the first causal evidence for functional specificity of these parietal regions in healthy humans. |
Michael L. Waterston; Christopher C. Pack Improved discrimination of visual stimuli following repetitive transcranial magnetic stimulation Journal Article In: PLoS ONE, vol. 5, no. 4, pp. e10354, 2010. @article{Waterston2010, Repetitive transcranial magnetic stimulation (rTMS) at certain frequencies increases thresholds for motor-evoked potentials and phosphenes following stimulation of cortex. Consequently rTMS is often assumed to introduce a “virtual lesion” in stimulated brain regions, with correspondingly diminished behavioral performance. Here we investigated the effects of rTMS to visual cortex on subjects' ability to perform visual psychophysical tasks. Contrary to expectations of a visual deficit, we find that rTMS often improves the discrimination of visual features. For coarse orientation tasks, discrimination of a static stimulus improved consistently following theta-burst stimulation of the occipital lobe. Using a reaction-time task, we found that these improvements occurred throughout the visual field and lasted beyond one hour post-rTMS. Low-frequency (1 Hz) stimulation yielded similar improvements. In contrast, we did not find consistent effects of rTMS on performance in a fine orientation discrimination task. Overall our results suggest that rTMS generally improves or has no effect on visual acuity, with the nature of the effect depending on the type of stimulation and the task. We interpret our results in the context of an ideal-observer model of visual perception. |
2009 |
Naoyuki Sato; Yoko Yamaguchi A computational predictor of human episodic memory based on a theta phase precession network Journal Article In: PLoS ONE, vol. 4, no. 10, pp. e7536, 2009. @article{Sato2009, In the rodent hippocampus, a phase precession phenomena of place cell firing with the local field potential (LFP) theta is called "theta phase precession" and is considered to contribute to memory formation with spike time dependent plasticity (STDP). On the other hand, in the primate hippocampus, the existence of theta phase precession is unclear. Our computational studies have demonstrated that theta phase precession dynamics could contribute to primate-hippocampal dependent memory formation, such as object-place association memory. In this paper, we evaluate human theta phase precession by using a theory-experiment combined analysis. Human memory recall of object-place associations was analyzed by an individual hippocampal network simulated by theta phase precession dynamics of human eye movement and EEG data during memory encoding. It was found that the computational recall of the resultant network is significantly correlated with human memory recall performance, while other computational predictors without theta phase precession are not significantly correlated with subsequent memory recall. Moreover the correlation is larger than the correlation between human recall and traditional experimental predictors. These results indicate that theta phase precession dynamics are necessary for the better prediction of human recall performance with eye movement and EEG data. In this analysis, theta phase precession dynamics appear useful for the extraction of memory-dependent components from the spatio-temporal pattern of eye movement and EEG data as an associative network. Theta phase precession may be a common neural dynamic between rodents and humans for the formation of environmental memories. |
Helene M. Ettinger-Veenstra; W. Huijbers; Tjerk P. Gutteling; M. Vink; J. Leon Kenemans; Sebastiaan F. W. Neggers In: Journal of Neurophysiology, vol. 102, no. 6, pp. 3469–3480, 2009. @article{EttingerVeenstra2009, It is well known that parts of a visual scene are prioritized for visual processing, depending on the current situation. How the CNS moves this focus of attention across the visual image is largely unknown, although there is substantial evidence that preparation of an action is a key factor. Our results support the view that direct corticocortical feedback connections from frontal oculomotor areas to the visual cortex are responsible for the coupling between eye movements and shifts of visuospatial attention. Functional magnetic resonance imaging (fMRI)-guided transcranial magnetic stimulation (TMS) was applied to the frontal eye fields (FEFs) and intraparietal sulcus (IPS). A single pulse was delivered 60, 30, or 0 ms before a discrimination target was presented at, or next to, the target of a saccade in preparation. Results showed that the known enhancement of discrimination performance specific to locations to which eye movements are being prepared was enhanced by early TMS on the FEF contralateral to eye movement direction, whereas TMS on the IPS resulted in a general performance increase. The current findings indicate that the FEF affects selective visual processing within the visual cortex itself through direct feedback projections. |
Rolf Verleger; Andreas Sprenger; Sina Gebauer; Michaela Fritzmannova; Monique Friedrich; Stefanie Kraft; Piotr Jaśkowski; Piotr Jas On why left events are the right ones: Neural mechanisms underlying the left-hemifield advantage in rapid serial visual presentation Journal Article In: Journal of Cognitive Neuroscience, vol. 21, no. 3, pp. 474–488, 2009. @article{Verleger2009, When simultaneous series of stimuli are rapidly presented left and right, containing two target stimuli T1 and T2, T2 is much better identified when presented in the left than in the right hemifield. Here, this effect was replicated, even when shifts of gaze were controlled, and was only partially compensated when T1 side provided the cue where to expect T2. Electrophysiological measurement revealed earlier latencies of T1- and T2-evoked N2(pc) peaks at the right than at the left visual cortex, and larger right-hemisphere T2-evoked N2(pc) amplitudes when T2 closely followed T1. These findings suggest that the right hemisphere was better able to single out the targets in time. Further, sustained contralateral slow shifts remained active after T1 for longer time at the right than at the left visual cortex, and developed more consistently at the right visual cortex when expecting T2 on the contralateral side. These findings might reflect better capacity of right-hemisphere visual working memory. These findings about the neurophysiological underpinnings of the large right-hemisphere advantage in this complex visual task might help elucidating the mechanisms responsible for the severe disturbance of hemineglect following damage to the right hemisphere. |
Robin Walker; Puncharat Techawachirakul; Patrick Haggard Frontal eye field stimulation modulates the balance of salience between target and distractors Journal Article In: Brain Research, vol. 1270, pp. 54–63, 2009. @article{Walker2009, Natural scenes generally include several possible objects that can be the target for a shift of gaze and attention. The oculomotor system may select a single target by boosting neural activation representing the target, and also by inhibiting neural activity associated with competing alternatives (distractors). We examine the role of the frontal eye field (FEF) in these processes through the effects of single-pulse transcranial magnetic stimulation (TMS) on the distractor-related modulation of saccade trajectories. Participants made voluntary saccades to peripheral locations specified by a central arrow-cue. On some trials, visual distractors appeared remote from the target location. The competing distractor produced a deviation of saccade trajectory, away from the distractor location. Single-pulse TMS stimulation of the right frontal eye field increased this distractor-related deviation compared that observed when stimulation was applied to a control site (vertex). The increase in distractor-related deviation of trajectory, following FEF stimulation, was observed for saccades made in both the left and right visual fields and could not be attributed to an effect of TMS on saccade latency. The enhanced distractor-related deviation following FEF stimulation could reflect increased inhibition of the competing distractor, or reduced salience of the endogenous saccade goal. The results are interpreted in light of neurophysiological evidence that the human FEF is involved in the dynamic interaction between competing stimuli for the selection of a candidate target. |
Ulrich Nuding; Roger Kalla; Neil G. Muggleton; Ulrich Büttner; Vincent Walsh; Stefan Glasauer TMS evidence for smooth pursuit gain control by the frontal eye fields Journal Article In: Cerebral Cortex, vol. 19, no. 5, pp. 1144–1150, 2009. @article{Nuding2009, Smooth pursuit eye movements are used to continuously track slowly moving visual objects. A peculiar property of the smooth pursuit system is the nonlinear increase in sensitivity to changes in target motion with increasing pursuit velocities. We investigated the role of the frontal eye fields (FEFs) in this dynamic gain control mechanism by application of transcranial magnetic stimulation. Subjects were required to pursue a slowly moving visual target whose motion consisted of 2 components: a constant velocity component at 4 different velocities (0, 8, 16, and 24 deg/s) and a superimposed high-frequency sinusoidal oscillation (4 Hz, +/-8 deg/s). Magnetic stimulation of the FEFs reduced not only the overall gain of the system, but also the efficacy of the dynamic gain control. We thus provide the first direct evidence that the FEF population is significantly involved in the nonlinear computation necessary for continuously adjusting the feedforward gain of the pursuit system. We discuss this with relation to current models of smooth pursuit. |
Ming Qian; Mario Aguilar; Karen N. Zachery; Claudio M. Privitera; Stanley A. Klein; Thom Carney; Loren W. Nolte Decision-level fusion of EEG and pupil features for single-trial visual detection analysis Journal Article In: IEEE Transactions on Biomedical Engineering, vol. 56, no. 7, pp. 1929–1937, 2009. @article{Qian2009, Several recent studies have reported success in applying EEG-based signal analysis to achieve accurate single-trial classification of responses to visual target detection. Pupil responses are proposed as a complementary modality that can support improved accuracy of single-trial signal analysis. We develop a pupillary response feature-extraction and -selection procedure that helps to improve the classification performance of a system based only on EEG signal analysis. We apply a two-level linear classifier to obtain cognitive-task-related analysis of EEG and pupil responses. The classification results based on the two modalities are then fused at the decision level. Here, the goal is to support increased classification confidence through the inherent modality complementarities. The fusion results show significant improvement over classification performance based on a single modality. |
Clive R. Rosenthal; Emma E. Roche-Kelly; Masud Husain; Christopher Kennard Response-dependent contributions of human primary motor cortex and angular gyrus to manual and perceptual sequence learning Journal Article In: Journal of Neuroscience, vol. 29, no. 48, pp. 15115–15125, 2009. @article{Rosenthal2009, Motor sequence learning on the serial reaction time task involves the integration of response-, stimulus-, and effector-based information. Human primary motor cortex (M1) and the inferior parietal lobule (IPL) have been identified with supporting the learning of effector-dependent and -independent information, respectively. Current neurocognitive data are, however, exclusively based on learning complex sequence information via perceptual-motor responses. Here, we investigated the effects of continuous theta-burst transcranial magnetic stimulation (cTBS)-induced disruption of M1 and the angular gyrus (AG) of the IPL on learning a probabilistic sequence via sequential perceptual-motor responses (experiment 1) or covert orienting of visuospatial attention (experiment 2). Functional effects on manual sequence learning were evident during 75% of training trials in the cTBS M1 condition, whereas cTBS over the AG resulted in interference confined to a midpoint during the training phase. Posttraining direct (declarative) tests of sequence knowledge revealed that cTBS over M1 modulated the availability of newly acquired sequence knowledge, whereby sequence knowledge was implicit in the cTBS M1 condition but was available to conscious awareness in the cTBS AG and control conditions. In contrast, perceptual sequence learning was abolished in the perceptual cTBS AG condition, whereas learning was intact and available to conscious awareness in the cTBS M1 and control conditions. These results show that the right AG had a critical role in perceptual sequence learning, whereas M1 had a causal role in developing experience-dependent functional attributes relevant to conscious knowledge on manual but not perceptual sequence learning. |
Roger Kalla; Neil G. Muggleton; Alan Cowey; Vincent Walsh Human dorsolateral prefrontal cortex is involved in visual search for conjunctions but not features: A theta TMS study Journal Article In: Cortex, vol. 45, no. 9, pp. 1085–1090, 2009. @article{Kalla2009, Functional neuroimaging studies have shown that the detection of a target defined by more than one feature (for example, a conjunction of colour and orientation) amongst distractors is associated with the activation of a network of brain areas. Dorsolateral prefrontal cortex (DLPFC), along with areas such as the frontal eye fields (FEF) and posterior parietal cortex (PPC), is a component of this network. While transcranial magnetic stimulation (TMS) had shown that both FEF and PPC are necessary for, and not just correlated with, successful conjunction search, this is not the case for DLPFC. To test the hypothesis that this area is also necessary for efficient conjunction search, TMS was applied over DLPFC and the effects on conjunction and feature (in this case colour) search performance compared with those when TMS was delivered over area MT/V5 and a vertex control stimulation condition. DLPFC TMS impaired performance on the conjunction search task but was without effect on feature search, similar to findings when TMS is delivered over PPC or FEF. Vertex TMS had no effects whereas MT/V5 TMS significantly improved performance with a time course that may indicate that this was due to modulation of V4 activity. These findings illustrate that, like FEF and PPC, DLPFC is necessary for fully effective conjunction visual search performance. |
Franziska Kretzschmar; Ina Bornkessel-Schlesewsky; Matthias Schlesewsky Parafoveal versus foveal N400s dissociate spreading activation from contextual fit Journal Article In: NeuroReport, vol. 20, no. 18, pp. 1613–1618, 2009. @article{Kretzschmar2009, Using concurrent electroencephalogram and eye movement measures to track natural reading, this study shows that N400 effects reflecting predictability are dissociable from those owing to spreading activation. In comparing predicted sentence endings with related and unrelated unpredicted endings in antonym constructions ('the opposite of black is white/yellow/nice'), fixation-related potentials at the critical word revealed a predictability-based N400 effect (unpredicted vs. predicted words). By contrast, event-related potentials time locked to the last fixation before the critical word showed an N400 only for the nonrelated unpredicted condition (nice). This effect is attributed to a parafoveal mismatch between the critical word and preactivated lexical features (i.e. features of the predicted word and its associates). In addition to providing the first demonstration of a parafoveally induced N400 effect, our results support the view that the N400 is best viewed as a component family. |
2008 |
Roger Kalla; Neil G. Muggleton; Chi-Hung Juan; Alan Cowey; Vincent Walsh The timing of the involvement of the frontal eye fields and posterior parietal cortex in visual search Journal Article In: NeuroReport, vol. 19, no. 10, pp. 1069–1073, 2008. @article{Kalla2008, The frontal eye fields (FEFs) and posterior parietal cortex (PPC) are important for target detection in conjunction visual search but the relative timings of their contribution have not been compared directly. We addressed this using temporally specific double pulse transcranial magnetic stimulation delivered at different times over FEFs and PPC during performance of a visual search task. Disruption of performance was earlier (0/40 ms) with FEF stimulation than with PPC stimulation (120/160 ms), revealing a clear and substantial temporal dissociation of the involvement of these two areas in conjunction visual search. We discuss these timings with reference to the respective roles of FEF and PPC in the modulation of extrastriate visual areas and selection of responses. |
Marine Vernet; Qing Yang; Gintautas Daunys; Christophe Orssaud; Thomas Eggert; Zoï Kapoula How the brain obeys Hering's law: A TMS study of the posterior parietal cortex Journal Article In: Investigative Ophthalmology & Visual Science, vol. 49, no. 1, pp. 230–237, 2008. @article{Vernet2008, PURPOSE: Human ocular saccades are not perfectly yoked; the origin of this disconjugacy (muscular versus central) remains controversial. The purpose of this study was to test a cortical influence on the binocular coordination of saccades. METHODS: The authors used a gap paradigm to elicit vertical or horizontal saccades of 10 degrees , randomly interleaved; transcranial magnetic stimulation (TMS) was applied on the posterior parietal cortex (PPC) 100 ms after the target onset. RESULTS: TMS of the left or right PPC increased (i) the misalignment of the eyes during the presaccadic fixation period; (ii) the size difference between the saccades of the eyes, called disconjugacy; the increase of disconjugacy was significant for rightward and downward saccades after TMS of the right PPC and for downward saccades after TMS of the left PPC. CONCLUSIONS: The authors conclude that the PPC is actively involved in maintaining eye alignment during fixation and in the control of binocular coordination of saccades. |
Marine Vernet; Qing Yang; Gintautas Daunys; Christophe Orssaud; Zoï Kapoula TMS of the posterior parietal cortex delays the latency of unpredictable saccades but not when they are combined with predictable divergence Journal Article In: Brain Research Bulletin, vol. 76, no. 1-2, pp. 50–56, 2008. @article{Vernet2008a, This study tests the influence of transcranial magnetic stimulation (TMS) of the posterior parietal cortex (PPC) on the initiation of horizontal and vertical saccades, alone or combined with a predictable divergence. A gap paradigm was used; TMS was applied 100 ms after target onset. TMS of the left PPC increased the latency of unpredictable rightward saccades, while TMS of the right PPC increased the latency of unpredictable downward saccades. Yet, when unpredictable saccades were combined with predictable divergence, neither component was affected. We suggest that in the latter case, the initiation of both components was taken in charge by another area, e.g. frontal. Thus, even when one component was predictable, a common mechanism controls the initiation of both components. The results confirm that TMS only modifies the latency when the cortical area stimulated is involved in the triggering of the eye movement. |
Steffen Gais; Sabine Köster; Andreas Sprenger; Judith Bethke; Wolfgang Heide; Hubert Kimmig Sleep is required for improving reaction times after training on a procedural visuo-motor task Journal Article In: Neurobiology of Learning and Memory, vol. 90, no. 4, pp. 610–615, 2008. @article{Gais2008, Sleep has been found to enhance consolidation of many different forms of memory. However in most procedural tasks, a sleep-independent, fast learning component interacts with slow, sleep-dependent improvements. Here, we show that in humans a visuo-motor saccade learning task shows no improvements during training, but only during a delayed recall testing after a period of sleep. Subjects were trained in a prosaccade task (saccade to a visual target). Performance was tested in the prosaccade and the antisaccade task (saccade to opposite direction of the target) before training, after a night of sleep or sleep deprivation, after a night of recovery sleep, and finally in a follow-up test 4 weeks later. We found no immediate improvement in saccadic reaction time (SRT) during training, but a delayed reduction in SRT, indicating a slow-learning process. This reduction occurred only after a period of sleep, i.e. after the first night in the sleep group and after recovery sleep in the sleep deprivation group. This improvement was stable during the 4-week follow-up. Saccadic training can thus induce covert changes in the saccade generation pathway. During the following sleep period, these changes in turn bring about overt performance improvements, presuming a learning effect based on synaptic tagging. |
Shlomit Yuval-Greenberg; Orr Tomer; Alon S. Keren; Israel Nelken; Leon Y. Deouell Transient induced gamma-band response in EEG as a manifestation of miniature saccades Journal Article In: Neuron, vol. 58, no. 3, pp. 429–441, 2008. @article{YuvalGreenberg2008, The induced gamma-band EEG response (iGBR) recorded on the scalp is widely assumed to reflect synchronous neural oscillation associated with object representation, attention, memory, and consciousness. The most commonly reported EEG iGBR is a broadband transient increase in power at the gamma range ∼200-300 ms following stimulus onset. A conspicuous feature of this iGBR is the trial-to-trial poststimulus latency variability, which has been insufficiently addressed. Here, we show, using single-trial analysis of concomitant EEG and eye tracking, that this iGBR is tightly time locked to the onset of involuntary miniature eye movements and reflects a saccadic "spike potential." The time course of the iGBR is related to an increase in the rate of saccades following a period of poststimulus saccadic inhibition. Thus, whereas neuronal gamma-band oscillations were shown conclusively with other methods, the broadband transient iGBR recorded by scalp EEG reflects properties of miniature saccade dynamics rather than neuronal oscillations. |
Thomas Nyffeler; Dario Cazzoli; Pascal Wurtz; Mathias Lüthi; Roman Von Wartburg; Silvia Chaves; Anouk Déruaz; Christian W. Hess; René M. Müri Neglect-like visual exploration behaviour after theta burst transcranial magnetic stimulation of the right posterior parietal cortex Journal Article In: European Journal of Neuroscience, vol. 27, no. 7, pp. 1809–1813, 2008. @article{Nyffeler2008, The right posterior parietal cortex (PPC) is critically involved in visual exploration behaviour, and damage to this area may lead to neglect of the left hemispace. We investigated whether neglect-like visual exploration behaviour could be induced in healthy subjects using theta burst repetitive transcranial magnetic stimulation (rTMS). To this end, one continuous train of theta burst rTMS was applied over the right PPC in 12 healthy subjects prior to a visual exploration task where colour photographs of real-life scenes were presented on a computer screen. In a control experiment, stimulation was also applied over the vertex. Eye movements were measured, and the distribution of visual fixations in the left and right halves of the screen was analysed. In comparison to the performance of 28 control subjects without stimulation, theta burst rTMS over the right PPC, but not the vertex, significantly decreased cumulative fixation duration in the left screen-half and significantly increased cumulative fixation duration in the right screen-half for a time period of 30 min. These results suggest that theta burst rTMS is a reliable method of inducing transient neglect-like visual exploration behaviour. |
2007 |
Sebastiaan F. W. Neggers; W. Huijbers; C. M. Vrijlandt; Björn N. S. Vlaskamp; D. J. L. G. Schutter; J. Leon Kenemans TMS pulses on the frontal eye fields break coupling between visuospatial attention and eye movements Journal Article In: Journal of Neurophysiology, vol. 98, no. 5, pp. 2765–2778, 2007. @article{Neggers2007, While preparing a saccadic eye movement, visual processing of the saccade goal is prioritized. Here, we provide evidence that the frontal eye fields (FEFs) are responsible for this coupling between eye movements and shifts of visuospatial attention. Functional magnetic resonance imaging (fMRI)-guided transcranial magnetic stimulation (TMS) was applied to the FEFs 30 ms before a discrimination target was presented at or next to the target of a saccade in preparation. Results showed that the well-known enhancement of discrimination performance on locations to which eye movements are being prepared was diminished by TMS contralateral to eye movement direction. Based on the present and other reports, we propose that saccade preparatory processes in the FEF affect selective visual processing within the visual cortex through feedback projections, in that way coupling saccade preparation and visuospatial attention. |
Michael Dambacher; Reinhold Kliegl Synchronizing timelines: Relations between fixation durations and N400 amplitudes during sentence reading Journal Article In: Brain Research, vol. 1155, no. 1, pp. 147–162, 2007. @article{Dambacher2007, We examined relations between eye movements (single-fixation durations) and RSVP-based event-related potentials (ERPs; N400s) recorded during reading the same sentences in two independent experiments. Longer fixation durations correlated with larger N400 amplitudes. Word frequency and predictability of the fixated word as well as the predictability of the upcoming word accounted for this covariance in a path-analytic model. Moreover, larger N400 amplitudes entailed longer fixation durations on the next word, a relation accounted for by word frequency. This pattern offers a neurophysiological correlate for the lag-word frequency effect on fixation durations: word processing is reliably expressed not only in fixation durations on currently fixated words, but also in those on subsequently fixated words. |
Sven-Thomas Graupner; Boris M. Velichkovsky; Sebastian Pannasch; Johannes Marx Surprise, surprise: Two distinct components in the visually evoked distractor effect Journal Article In: Psychophysiology, vol. 44, no. 2, pp. 251–261, 2007. @article{Graupner2007, The distractor effect is an inhibition of saccades shortly after a sudden visual event. It has been explained both as an oculomotor reflex and as a manifestation of the orienting response. To clarify which explanation is more appropriate, we investigated a possible habituation of this effect. Visual and auditory distractors were presented at gaze-contingent intervals during the perception of meaningful pictures. Both reflexlike and modifiable components were present in the visual distractor effect, with latencies of about 110 and 180 ms, respectively. The influence of visual and auditory distractors on saccades preceded the earliest changes in cortical ERPs. Only for long-term habituation in the visual modality was a correlation with ERPs (N1) found. |
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. |
Naoyuki Sato; Yoko Yamaguchi Theta synchronization networks emerge during human object-place memory encoding Journal Article In: NeuroReport, vol. 18, no. 5, pp. 419–424, 2007. @article{Sato2007, Recent rodent hippocampus studies have suggested that theta rhythm-dependent neural dynamics ('theta phase precession') is essential for an on-line memory formation. A computational study indicated that the phase precession enables a human object-place association memory with voluntary eye movements, although it is still an open question whether the human brain uses the dynamics. Here we elucidated subsequent memory-correlated activities in human scalp electroencephalography in an object-place association memory designed according the former computational study. Our results successfully demonstrated that subsequent memory recall is characterized by an increase in theta power and coherence, and further, that multiple theta synchronization networks emerge. These findings suggest the human theta dynamics in common with rodents in episodic memory formation. |
Glenn F. Wilson; John A. Caldwell; Christopher A. Russell Performance and psychophysiological measures of fatigue effects on aviation related tasks of varying difficulty Journal Article In: International Journal of Aviation Psychology, vol. 17, no. 2, pp. 219–247, 2007. @article{Wilson2007, Fatigue is a well known stressor in aviation operations and its interaction with mental workload needs to be understood. Performance, psychophysiological, and subjective measures were collected during performance of three tasks of increasing complexity. A psychomotor vigilance task, multi-attribute task battery and an uninhabited air vehicle task were performed five times during one night's sleep loss. EEG, ECG and pupil area were recorded during task performance. Performance decrements were found at the next to last and/or last testing session. The EEG showed concomitant changes. The degree of impairment was at least partially dependent on the task being performed and the performance variable assessed. |
A. J. Wills; Aureliu Lavric; G. S. Croft; Timothy L. Hodgson Predictive learning, prediction errors, and attention: evidence from event-related potentials and eye tracking Journal Article In: Journal of Cognitive Neuroscience, vol. 19, no. 5, pp. 843–854, 2007. @article{Wills2007, Prediction error ("surprise") affects the rate of learning: We learn more rapidly about cues for which we initially make incorrect predictions than cues for which our initial predictions are correct. The current studies employ electrophysiological measures to reveal early attentional differentiation of events that differ in their previous involvement in errors of predictive judgment. Error-related events attract more attention, as evidenced by features of event-related scalp potentials previously implicated in selective visual attention (selection negativity, augmented anterior N1). The earliest differences detected occurred around 120 msec after stimulus onset, and distributed source localization (LORETA) indicated that the inferior temporal regions were one source of the earliest differences. In addition, stimuli associated with the production of prediction errors show higher dwell times in an eye-tracking procedure. Our data support the view that early attentional processes play a role in human associative learning. |
2006 |
Danny Gagnon Transcranial magnetic stimulation of frontal oculomotor regions during smooth pursuit Journal Article In: Journal of Neuroscience, vol. 26, no. 2, pp. 458–466, 2006. @article{Gagnon2006, Both the frontal eye fields (FEFs) and supplementary eye fields (SEFs) are known to be involved in smooth pursuit eye movements. It has been shown recently that stimulation of the smooth-pursuit area of the FEF [frontal pursuit area (FPA)] in monkey increases the pursuit response to unexpected changes in target motion during pursuit. In the current study, we applied transcranial magnetic stimulation (TMS) to the FPA and SEF in humans during sinusoidal pursuit to assess its effects on the pursuit response to predictable, rather than unexpected, changes in target motion. For the FPA, we found that TMS applied immediately before the target reversed direction increased eye velocity in the new direction, whereas TMS applied in mid-cycle, immediately before the target began to slow, decreased eye velocity. For the SEF, TMS applied at target reversal increased eye velocity in the new direction but had no effect on eye velocity when applied at mid-cycle. TMS of the control region (leg region of the somatosensory cortex) did not affect eye velocity at either point. Previous stimulation studies of FPA during pursuit have suggested that this region is involved in controlling the gain of the transformation of visual signals into pursuit motor commands. The current results suggest that the gain of the transformation of predictive signals into motor commands is also controlled by the FPA. The effect of stimulation of the SEF is distinct from that of the FPA and suggests that its role in sinusoidal pursuit is primarily at the target direction reversal. |
2005 |
Christian Bellebaum; Klaus-Peter Hoffmann; Irene Daum Post-saccadic updating of visual space in the posterior parietal cortex in humans Journal Article In: Behavioural Brain Research, vol. 163, no. 2, pp. 194–203, 2005. @article{Bellebaum2005a, Updating of visual space takes place in the posterior parietal cortex to guarantee spatial constancy across eye movements. However, the timing of updating with respect to saccadic eye movements remains a matter of debate. In the present study, event-related potentials (ERPs) were recorded in 15 volunteers during a saccadic double-step task to elucidate the time course of the updating process. In the experimental condition updating of visual space was required, because both saccade targets had already disappeared before the first saccade was executed. A similar task without updating requirements served as control condition. ERP analysis revealed a significantly larger slow positive wave in the retino-spatial dissonance condition compared to the control condition, starting between 150 and 200 ms after first saccade onset. Source analysis showed an asymmetry with respect to the direction of the first saccade. Whereas the source was restricted to the right PPC in trials with leftward first saccades, left and right PPC were involved in rightward trials. The results of the present study suggest that updating of visual space in a saccadic double-step task occurs not earlier than 150 ms after the onset of the first saccade. We conclude that extraretinal information about the first saccade is integrated with motor information about the second saccade in the inter-saccade interval. |