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2022 |
Jia Liu; Jinsheng Hu; Qi Li; Xiaoning Zhao; Ying Liu; Shuqing Liu Atypical processing pattern of gaze cues in dynamic situations in autism spectrum disorders Journal Article In: Scientific Reports, vol. 12, pp. 1–11, 2022. @article{Liu2022b, Psychological studies have generally shown that individuals with Autism Spectrum Disorder (ASD) have particularity in the processing of social information by using static or abstract images. Yet, a recent study showed that there was no difference in their use of social or non-social cues in dynamic interactive situations. To establish the cause of the inconsistent results, we added gaze cues in different directions to the chase detection paradigm to explore whether they would affect the performance of participants with ASD. Meanwhile, eye-tracking methodology was used to investigate whether the processing patterns of gaze cues were different between individuals with ASD and TD. In this study, unlike typical controls, participants with ASD showed no detection advantage when the direction of gaze was consistent with the direction of movement (oriented condition). The results suggested that individuals with ASD may utilize an atypical processing pattern, which makes it difficult for them to use social information contained in oriented gaze cues in dynamic interactive situations. |
Vanessa M. Loaiza; Alessandra S. Souza The eyes don't have it: Eye movements are unlikely to reflect refreshing in working memory Journal Article In: PLoS ONE, vol. 17, no. 7, pp. 1–18, 2022. @article{Loaiza2022, There is a growing interest in specifying the mechanisms underlying refreshing, i.e., the use of attention to keep working memory (WM) contents accessible. Here, we examined whether participants' visual fixations during the retention interval of a WM task indicate the current focus of internal attention, thereby serving as an online measure of refreshing. Eye movements were recorded while participants studied and maintained an array of colored dots followed by probed recall of one (Experiments 1A and 1B) or all (Experiment 2) of the memoranda via a continuous color wheel. Experiments 1A and 2 entailed an unfilled retention interval in which refreshing is assumed to occur spontaneously, and Experiment 1B entailed a retention interval embedded with cues prompting the sequential refreshment of a subset of the memoranda. During the retention interval, fixations revisited the locations occupied by the memoranda, consistent with a looking-at-nothing phenomenon in WM, but the pattern was only evident when placeholders were onscreen in Experiment 2, indicating that most of these fixations may largely reflect random gaze. Furthermore, spontaneous fixations did not predict recall precision (Experiments 1A and 2), even when ensuring that they did not reflect random gaze (Experiment 2). In Experiment 1B, refreshing cues increased fixations to the eventually tested target and predicted better recall precision, which interacted with an overall benefit of target fixations, such that the benefit of fixations decreased as the number of refreshing cues increased. Thus, fixations under spontaneous conditions had no credible effect on recall precision, whereas the beneficial effect of fixations under instructed refreshing conditions may indicate situations in which cues were disregarded. Consequently, we conclude that eye movements do not seem suitable as an online measure of refreshing. |
Dillon Lohr; Henry Griffith; Oleg V. Komogortsev Eye know you: Metric learning for end-to-end biometric authentication using eye movements from a longitudinal dataset Journal Article In: IEEE Transactions on Biometrics, Behavior, and Identity Science, vol. 4, no. 2, pp. 276–288, 2022. @article{Lohr2022, The permanence of eye movements as a biometric modality remains largely unexplored in the literature. The present study addresses this limitation by evaluating a novel exponentially-dilated convolutional neural network for eye movement authentication using a recently proposed longitudinal dataset known as GazeBase. The network is trained using multi-similarity loss, which directly enables the enrollment and authentication of out-of-sample users. In addition, this study includes an exhaustive analysis of the effects of evaluating on various tasks and downsampling from 1000 Hz to several lower sampling rates. Our results reveal that reasonable authentication accuracy may be achieved even during both a low-cognitive-load task and at low sampling rates. Moreover, we find that eye movements are quite resilient against template aging after as long as 3 years. |
Floor C. Loonstra; Lodewijk R. J. De Ruiter; Djoeke Doesburg; Ka-Hoo Lam; Zoe Y. G. J. Van Lierop; Bastiaan Moraal; Eva M. M. Strijbis; Joep Killestein; Bernard M. J. Uitdehaag Project Y: The search for clues explaining phenotype variability in MS Journal Article In: Multiple Sclerosis and Related Disorders, vol. 57, pp. 1–8, 2022. @article{Loonstra2022, Background: To study phenotypic variability in MS patients, well-defined unbiased cohort studies are necessary. The most common and probably most important confounding factor when studying disease phenotype in MS is age. Objective: To describe study design and subject characteristics of a unique birth cohort (Project Y). The overall aim of Project Y is to identify determinants associated with phenotypic variability in MS, eliminating the possibility of confounding by age. Methods: Project Y is a population-based cross-sectional study of all people with MS born in the Netherlands in 1966. Patients and healthy controls were subjected to comprehensive examinations: functional and static imaging, physical and cognitive measurements, and lifestyle factors early and later in life. In addition body fluids were collected and stored for future biomarker research. Results: 452 eligible MS patients were identified. Between December 2017 and January 2021, 367 MS patients and 125 healthy controls participated. The total number of identified cases results in a current prevalence of at least 189/100.000 for people born in the year 1966 in The Netherlands. Conclusion: Project Y is a unique cohort designed to identify factors associated with phenotypic variability in MS patients without the confounding effects of age. This first description of the Project Y cohort indicates that the prevalence of MS in the Netherlands might be higher than previously presumed. Various studies using Project Y data are ongoing and results will be published in upcoming years. |
Kaleb A. Lowe; Wolf Zinke; Joshua D. Cosman; Jeffrey D. Schall Frontal eye fields in macaque monkeys: Prefrontal and premotor contributions to visually guided saccades Journal Article In: Cerebral Cortex, vol. 32, pp. 5083–5107, 2022. @article{Lowe2022, Neuronal spiking was sampled from the frontal eye field (FEF) and from the rostral part of area 6 that reaches to the superior limb of the arcuate sulcus, dorsal to the arcuate spur when present (F2vr) in macaque monkeys performing memory-guided saccades and visually guided saccades for visual search. Neuronal spiking modulation in F2vr resembled that in FEF in many but not all respects. A new consensus clustering algorithm of neuronal modulation patterns revealed that F2vr and FEF contain a greater variety of modulation patterns than previously reported. The areas differ in the proportions of visuomotor neuron types, the proportions of neurons discriminating a target from distractors during visual search, and the consistency of modulation patterns across tasks. However, between F2vr and FEF we found no difference in the magnitude of delay period activity, the timing of the peak discharge rate relative to saccades, or the time of search target selection. The observed similarities and differences between the 2 cortical regions contribute to other work establishing the organization of eye fields in the frontal lobe and may help explain why FEF in monkeys is identified within granular prefrontal area 8 but in humans is identified within agranular premotor area 6. |
Yun-Jhen Lu; I. -Chun Kuo; Ming-Chou Ho The effects of emotional films and subtitle types on eye movement patterns Journal Article In: Acta Psychologica, vol. 230, no. 110, pp. 1–7, 2022. @article{Lu2022, Background: In Taiwan, the use of subtitle is common in TV programs and movies. However, studies on subtitles mostly focus on foreign language learning and film subtitle translation. Few studies address how subtitle types and emotion-laden films affect the viewers' eye movement patterns. Purpose: We aim to examine how the emotion type of film (happy, sad, angry, fear, or neutral) and subtitle type (meaningful subtitle, no subtitle, or meaningless subtitle) affect the dwell times and fixation counts in the subtitle area. Methods: This study is a 5 (emotion type of film) × 3 (subtitle type) between-participants design. There were 15 participants per condition, resulting in a total of 225 participants. After watching a film, participants filled out a self-reported questionnaire regarding this film. Results: The subtitled films have more fixation counts and dwell time for the meaningful subtitle compared to meaningless subtitle and no subtitle. The dwell time was longer on the subtitle area for the sad film than the neutral and happy films. Also, the dwell time was longer on the subtitle area for the fear film than the happy film. There were more fixation counts on the subtitle area for the sad film than the angry and happy films. Conclusions: The subtitle meaning is critical in directing overt attention. Also, overt attention directed to the subtitle area is affected by the different emotion types of films. |
Malte Lüken; Šimon Kucharský; Ingmar Visser Characterising eye movement events with an unsupervised hidden markov model Journal Article In: Journal of Eye Movement Research, vol. 15, no. 1, pp. 1–29, 2022. @article{Lueken2022, Eye-tracking allows researchers to infer cognitive processes from eye movements that are classified into distinct events. Parsing the events is typically done by algorithms. Here we aim at developing an unsupervised, generative model that can be fitted to eye-movement data using maximum likelihood estimation. This approach allows hypothesis testing about fitted models, next to being a method for classification. We developed gazeHMM, an algorithm that uses a hidden Markov model as a generative model, has few critical parameters to be set by users, and does not require human coded data as input. The algorithm classifies gaze data into fixations, saccades, and optionally postsaccadic oscillations and smooth pursuits. We evaluated gazeHMM's performance in a simulation study, showing that it successfully recovered hidden Markov model parameters and hidden states. Parameters were less well recovered when we included a smooth pursuit state and/or added even small noise to simulated data. We applied generative models with different numbers of events to benchmark data. Comparing them indicated that hidden Markov models with more events than expected had most likely generated the data. We also applied the full algorithm to benchmark data and assessed its similarity to human coding and other algorithms. For static stimuli, gazeHMM showed high similarity and outperformed other algorithms in this regard. For dynamic stimuli, gazeHMM tended to rapidly switch between fixations and smooth pursuits but still displayed higher similarity than most other algorithms. Concluding that gazeHMM can be used in practice, we recommend parsing smooth pursuits only for exploratory purposes. Future hidden Markov model algorithms could use covariates to better capture eye movement processes and explicitly model event durations to classify smooth pursuits more accurately. |
Xiaoxiao Luo; Jiayan Gu; Yueyuan Zheng; Xiaolin Zhou Making a saccade enhances Stroop and Simon conflict control Journal Article In: Attention, Perception, and Psychophysics, vol. 84, no. 3, pp. 795–814, 2022. @article{Luo2022, Cognitive control is an important ability instantiated in many situations such as conflict control (e.g., Stroop/Simon task) and the control of eye movements (e.g., saccades). However, it is unclear whether eye movement control shares a common cognitive control system with the conflict control. In Experiment 1, we asked participants to make a prosaccade or antisaccade and then to identify the color of a lateralized color word (i.e., a Stroop–Simon stimulus). The stimulus onset asynchrony (SOA) between the saccadic cue and the Stroop–Simon stimulus was manipulated to be either short (200 ms) or long (600 ms). Results showed that the Stroop effect at the response level and the (negative) Simon effect were smaller when the SOA was short than long, demonstrating a decline of response control over time after making a saccade. Moreover, this temporal change of the Simon effect was more pronounced in the antisaccade session than in the prosaccade session. Furthermore, individuals who had better performance in the antisaccade task performed better in the response control of Stroop interference. When the saccade task was removed in Experiment 2, the temporal declines of the response control observed in Experiment 1 were absent. Experiment 3 replicated the key results of Experiment 1 by replacing the Stroop–Simon task with a typical Simon task and separately testing the typical Stroop and Simon tasks. Overall, our findings suggest that a common system is shared between the control of eye movements and the conflict control at the response level. |
Xinyu Lv; Suping Cheng; Zhiguo Wang; Jianrong Jia The dynamics of microsaccade amplitude reflect shifting of covert attention Journal Article In: Consciousness and Cognition, vol. 101, pp. 1–10, 2022. @article{Lv2022, Attention flexibly shifts between spatial locations to accommodate task demands. The present study examined if the dynamics of attentional shifting are seen in microsaccades whose direction has been shown to accompany the shifts of covert attention. In a spatial cueing task, the cue predicted the target location on 100%, 75%, or 50% of the trials. The results revealed that microsaccade rate and amplitude were both reduced following cue onset and then rebounded. Both microsaccade rate and amplitude were biased towards the opposite direction of the cue and then returned to the cued direction. Importantly, the cue validity modulated the temporal profile of microsaccade amplitude but had little impact on the temporal profile of microsaccade rate. In line with this, the cueing effect measured with target response accuracy was correlated with the microsaccade amplitude only. These results indicate that the temporal dynamics of microsaccade amplitude reflect shifting of covert attention. |
Wenbo Ma; Min Li; Junru Wu; Zhihao Zhang; Fangfang Jia; Mingsha Zhang; Hagai Bergman; Xuemei Li; Zhipei Ling; Xin Xu Multiple step saccades in simply reactive saccades could serve as a complementary biomarker for the early diagnosis of Parkinson's disease Journal Article In: Frontiers in Aging Neuroscience, vol. 14, pp. 1–14, 2022. @article{Ma2022a, Objective: It has been argued that the incidence of multiple step saccades (MSS) in voluntary saccades could serve as a complementary biomarker for diagnosing Parkinson's disease (PD). However, voluntary saccadic tasks are usually difficult for elderly subjects to complete. Therefore, task difficulties restrict the application of MSS measurements for the diagnosis of PD. The primary objective of the present study is to assess whether the incidence of MSS in simply reactive saccades could serve as a complementary biomarker for the early diagnosis of PD. Materials and methods: There were four groups of human subjects: PD patients, mild cognitive impairment (MCI) patients, elderly healthy controls (EHCs), and young healthy controls (YHCs). There were four monkeys with subclinical hemi-PD induced by injection of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) through the unilateral internal carotid artery and three healthy control monkeys. The behavioral task was a visually guided reactive saccade. Results: In a human study, the incidence of MSS was significantly higher in PD than in YHC, EHC, and MCI groups. In addition, receiver operating characteristic (ROC) analysis could discriminate PD from the EHC and MCI groups, with areas under the ROC curve (AUCs) of 0.76 and 0.69, respectively. In a monkey study, while typical PD symptoms were absent, subclinical hemi-PD monkeys showed a significantly higher incidence of MSS than control monkeys when the dose of MPTP was greater than 0.4 mg/kg. Conclusion: The incidence of MSS in simply reactive saccades could be a complementary biomarker for the early diagnosis of PD. |
Wenbo Ma; Mingsha Zhang The effects of age and sex on the incidence of multiple step saccades and corrective saccades Journal Article In: Frontiers in Aging Neuroscience, vol. 14, pp. 1–11, 2022. @article{Ma2022b, Objective: Although multiple step saccades (MSS) is occasionally observed in healthy subjects, it is more pronounced in patients with aging-related neurodegenerative diseases, particularly Parkinson's disease (PD). Thus, MSS has been treated as a complementary biomarker for diagnosing PD. Despite the aforementioned knowledge, several questions remain unexplored: (1) How does aging affect MSS? (2) Is there a sex difference in MSS? (3) Are there differences in MSS between vertical and horizontal saccades? (4) Are MSS and corrective saccade (CS) the same behavior? (5) How do age and sex affect CS? The objectives of the present study are to address these questions. Method: Four hundred eighty healthy participants were recruited to perform a visually guided reactive saccade task. Participants were divided into six groups according to their ages. Each group consisted of 40 male and 40 female participants. Eye movements were recorded with infrared eye trackers. Results: The incidence of MSS increased as a function of age, whereas the incidence of CS first increased with age 20–49 and then decreased with age 50–79. The incidences of both MSS and CS did not show sex differences. The incidence of MSS in vertical saccades was significantly higher than that in horizontal saccades, and their difference increased with increasing age, whereas the incidence of CS showed a reversed pattern. Conclusion: Age and saccadic direction affect the occurrences of MSS and CS differently, indicating that MSS and CS are different saccadic behaviors. In addition, measuring saccades could reliably reflect the function of human's brain which is affected by aging. |
Walker S. McKinney; Shannon E. Kelly; Kathryn E. Unruh; Robin L. Shafer; John A. Sweeney; Martin Styner; Matthew W. Mosconi Cerebellar volumes and sensorimotor behavior in autism spectrum disorder Journal Article In: Frontiers in Integrative Neuroscience, vol. 16, pp. 1–16, 2022. @article{McKinney2022, Background: Sensorimotor issues are common in autism spectrum disorder (ASD), though their neural bases are not well understood. The cerebellum is vital to sensorimotor control and reduced cerebellar volumes in ASD have been documented. Our study examined the extent to which cerebellar volumes are associated with multiple sensorimotor behaviors in ASD. Materials and Methods: Fifty-eight participants with ASD and 34 typically developing (TD) controls (8–30 years) completed a structural MRI scan and precision grip testing, oculomotor testing, or both. Force variability during precision gripping as well as absolute error and trial-to-trial error variability of visually guided saccades were examined. Volumes of cerebellar lobules, vermis, and white matter were quantified. The relationships between each cerebellar region of interest (ROI) and force variability, saccade error, and saccade error variability were examined. Results: Relative to TD controls, individuals with ASD showed increased force variability. Individuals with ASD showed a reduced volume of cerebellar vermis VI-VII relative to TD controls. Relative to TD females, females with ASD showed a reduced volume of bilateral cerebellar Crus II/lobule VIIB. Increased volume of Crus I was associated with increased force variability. Increased volume of vermal lobules VI-VII was associated with reduced saccade error for TD controls but not individuals with ASD. Increased right lobule VIII and cerebellar white matter volumes as well as reduced right lobule VI and right lobule X volumes were associated with greater ASD symptom severity. Reduced volumes of right Crus II/lobule VIIB were associated with greater ASD symptom severity in only males, while reduced volumes of right Crus I were associated with more severe restricted and repetitive behaviors only in females. Conclusion: Our finding that increased force variability in ASD is associated with greater cerebellar Crus I volumes indicates that disruption of sensory feedback processing supported by Crus I may contribute to skeletomotor differences in ASD. Results showing that volumes of vermal lobules VI-VII are associated with saccade precision in TD but not ASD implicates atypical organization of the brain systems supporting oculomotor control in ASD. Associations between volumes of cerebellar subregions and ASD symptom severity suggest cerebellar pathological processes may contribute to multiple developmental challenges in ASD. |
Miranda J. Munoz; James L. Reilly; Gian D. Pal; Leo Verhagen Metman; Yessenia M. Rivera; Quentin H. Drane; Daniel M. Corcos; Fabian J. David; Lisa C. Goelz Medication adversely impacts visually-guided eye movements in Parkinson's disease Journal Article In: Clinical Neurophysiology, vol. 143, pp. 145–153, 2022. @article{Munoz2022, Objective: We examined whether previous inconsistent findings about the effect of anti-Parkinsonian medication on visually-guided saccades (VGS) were due to the use of different paradigms, which change the timing of fixation offset and target onset, or different target eccentricities. Methods: Thirty-three participants with Parkinson's disease (PD) completed the VGS tasks OFF and ON medication, along with 13 healthy controls. Performance on 3 paradigms (gap, step, and overlap) and 2 target eccentricities was recorded. We used mixed models to determine the effect of medication, paradigm, and target eccentricity on saccade latency, gain, and peak velocity. Results: First, we confirmed known paradigm effects on latency, and target eccentricity effects on gain and peak velocity in participants with PD. Second, latency was positively associated with OFF medication Movement Disorders Society – Unified Parkinson's Disease Rating Scale (MDS-UPDRS) motor score in PD. Third, medication prolonged latency for the larger target eccentricity across the 3 paradigms, while decreasing gain and peak velocity in the step paradigm across target eccentricities. Conclusions: Medication adversely affected and was not therapeutically beneficial for VGS. Previous inconsistencies may have resulted from chosen target eccentricity. Significance: The negative medication effect on VGS may be clinically significant, as many activities in daily life require oculomotor control, inhibitory control, and visually-guided shifts of attention. |
Ryohei Nakayama; Jean Baptiste Bardin; Ai Koizumi; Isamu Motoyoshi; Kaoru Amano Building a decoder of perceptual decisions from microsaccades and pupil size Journal Article In: Frontiers in Psychology, vol. 13, pp. 1–14, 2022. @article{Nakayama2022, Many studies have reported neural correlates of visual awareness across several brain regions, including the sensory, parietal, and frontal areas. In most of these studies, participants were instructed to explicitly report their perceptual experience through a button press or verbal report. It is conceivable, however, that explicit reporting itself may trigger specific neural responses that can confound the direct examination of the neural correlates of visual awareness. This suggests the need to assess visual awareness without explicit reporting. One way to achieve this is to develop a technique to predict the visual awareness of participants based on their peripheral responses. Here, we used eye movements and pupil sizes to decode trial-by-trial changes in the awareness of a stimulus whose visibility was deteriorated due to adaptation-induced blindness (AIB). In the experiment, participants judged whether they perceived a target stimulus and rated the confidence they had in their perceptual judgment, while their eye movements and pupil sizes were recorded. We found that not only perceptual decision but also perceptual confidence can be separately decoded from the eye movement and pupil size. We discuss the potential of this technique with regard to assessing visual awareness in future neuroimaging experiments. |
Kien Trong Nguyen; Wei-Kuang Liang; Chi-Hung Juan; Chin-An Wang Time-frequency analysis of pupil size modulated by global luminance, arousal, and saccade preparation signals using Hilbert-Huang transform Journal Article In: International Journal of Psychophysiology, vol. 176, pp. 89–99, 2022. @article{Nguyen2022, Pupil size changes constantly and is mainly determined by global luminance signals. In addition, the pupil responds to various cognitive and arousal processes, with larger pupil dilation observed in higher levels of cognitive or arousal processing. Although these task-evoked pupillary responses are extensively used in the pupil research, pupil analysis focusing on the frequency domain, particularly in the context of arousal and cognitive modulations, is less established. Fourier Transform method (FFT) has been used to understand the modulation of task difficulty on pupil oscillations. However, physiological signals are often characterized as non-linear and non-stationary waves, and the conventional spectral analytical method with linearity presumption is less appropriate to reveal modulation dynamics between time and frequency. Here, we used Hilbert-Huang Transform (HHT) to examine the time-frequency modulations on pupil size regulated by arousal, cognitive, and global luminance signals. Consistent with previous research, using FFT, higher spectral densities were obtained with lower luminance background. Moreover, higher spectral densities were found in the high emotional arousal condition. With HHT, we further demonstrated temporal changes on amplitude spectrum and inter-trial phase coherence (ITPC) in each intrinsic mode function (IMF), with stronger amplitudes in higher IMFs (i.e., low frequencies). Moreover, although global luminance, arousal and saccade preparation modulated pupil oscillatory responses, the modulation pattern in different IMFs was different. Together, our results demonstrated dynamics between the time and frequency domain on pupil oscillatory responses, highlighting the importance of examining the time-frequency interactions in the context of various pupil modulations. |
James E. Niemeyer; Seth Akers-Campbell; Aaron Gregoire; Michael A. Paradiso Perceptual enhancement and suppression correlate with V1 neural activity during active sensing Journal Article In: Current Biology, vol. 32, pp. 2654–2667, 2022. @article{Niemeyer2022, Perception in multiple sensory modalities is an active process that involves exploratory behaviors. In humans and other primates, vision results from sensory sampling guided by saccadic eye movements. Saccades are known to modulate visual perception, and a corollary discharge signal associated with saccades appears to establish a sense of visual stability. Neural recordings have shown that saccades also modulate activity widely across the brain. To investigate the neural basis of saccadic effects on perception, simultaneous recordings from multiple neurons in area V1 were made as animals performed a contrast detection task. Perceptual and neural measures were compared when the animal made real saccades that brought a stimulus into V1 receptive fields and when simulated saccades were made (identical retinal stimulation but no eye movement). When real saccades were made and low spatial frequency stimuli were presented, we observed a reduction in both perceptual sensitivity and neural activity compared with simulated saccades; conversely, with higher spatial frequency stimuli, saccades increased visual sensitivity and neural activity. The performance of neural decoders, which used the activity of the population of simultaneously recorded neurons, showed saccade effects on sensitivity that mirrored the frequency-dependent perceptual changes, suggesting that the V1 population activity could support the perceptual effects. A minority of V1 neurons had significant choice probabilities, and the saccades decreased both average choice probability and pairwise noise correlations. Taken together, the findings suggest that a signal related to saccadic eye movements alters V1 spiking to increase the independence of spiking neurons and bias the system toward processing higher spatial frequencies, presumably to enhance object recognition. The effects of saccades on visual perception and noise correlations appear to parallel effects observed in other sensory modalities, suggesting a general principle of active sensory processing. |
Suhyun Park; Louis Wiliams; Rebecca Chamberlain Global saccadic eye movements characterise artists' visual ttention while drawing Journal Article In: Empirical Studies of the Arts, vol. 40, no. 2, pp. 228–244, 2022. @article{Park2022a, Previous research has shown that artists employ flexible attentional strategies during offline perceptual tasks. The current study explored visual processing online, by tracking the eye movements of artists and non-artists (n=65) while they produced representational drawings of photographic stimuli. The findings revealed that it is possible to differentiate artists from non-artists on the basis of the relative amount of global-to-local saccadic eye movements they make when looking at the target stimulus while drawing, but not in a preparatory free viewing phase. Results indicated that these differences in eye movements are not specifically related to representational drawing ability, and may be a feature of artistic ability more broadly. This eye movement analysis technique may be used in future research to characterise the dynamics of attentional shifts in eye movements while artists are carrying out a range of artistic tasks. |
Mattia Pietrelli; Jason Samaha; Bradley R. Postle Spectral distribution dynamics across different attentional priority states Journal Article In: Journal of Neuroscience, vol. 42, no. 19, pp. 4026–4041, 2022. @article{Pietrelli2022, Anticipatory covert spatial attention improves performance on tests of visual detection and discrimination, and shifts are accompanied by decreases and increases of a band power at electroencephalography (EEG) electrodes corresponding to the attended and unattended location, respectively. Although the increase at the unattended location is often interpreted as an active mechanism (e.g., inhibiting processing at the unattended location), most experiments cannot rule out the alternative possibility that it is a secondary consequence of selection elsewhere. To adjudicate between these accounts, we designed a Posner- style visual cueing task in which male and female human participants made orientation judgments of targets appearing at one of four locations: up, down, right, or left. Critically, trials were blocked such that within a block the locations along one meridian alternated in status between attended and unattended, and targets never appeared at the other two, making them irrelevant. Analyses of the concurrently measured EEG signal were conducted on “traditional” narrowband a (8–14 Hz), as well as on two components resulting from the decomposition of this signal: “periodic” a;and the slope of the aperiodic 1/f-like component. Although data from right-left blocks replicated the familiar pattern of lateralized asymmetry in narrowband a power, with neither a signal couldwe findevidence for any difference inthe time course at unattended versus irrelevant locations, an outcome consistent with the secondary-consequence interpretation of attention- related dynamics in the a band. Additionally, 1/f slope was shallower at attended and unattended locations, relative to irrelevant, suggesting a tonic adjustment of physiological state. |
Alessandro Piras; Aurelio Trofè; Andrea Meoni; Milena Raffi Influence of radial optic flow stimulation on static postural balance in Parkinson's disease: A preliminary study Journal Article In: Human Movement Science, vol. 81, pp. 1–11, 2022. @article{Piras2022, The role of optic flow in the control of balance in persons with Parkinson's disease (PD) has yet to be studied. Since basal ganglia are understood to have a role in controlling ocular fixation, we have hypothesized that persons with PD would exhibit impaired performance in fixation tasks, i.e., altered postural balance due to the possible relationships between postural disorders and visual perception. The aim of this preliminary study was to investigate how people affected by PD respond to optic flow stimuli presented with radial expanding motion, with the intention to see how the stimulation of different retinal portions may alter the static postural sway. We measured the body sway using center of pressure parameters recorded from two force platforms during the presentation of the foveal, peripheral and full field radial optic flow stimuli. Persons with PD had different visual responses in terms of fixational eye movement characteristics, with greater postural alteration in the sway area and in the medio-lateral direction than the age-matched control group. Balance impairment in the medio-lateral oscillation is often observed in persons with atypical Parkinsonism, but not in Parkinson's disease. Persons with PD are more dependent on visual feedback with respect to age-matched control subjects, and this could be due to their impaired peripheral kinesthetic feedback. Visual stimulation of standing posture would provide reliable signs in the differential diagnosis of Parkinsonism. |
Milena Raffi; Aurelio Trofè; Andrea Meoni; Luca Gallelli; Alessandro Piras Optic flow speed and retinal stimulation influence microsaccades Journal Article In: International Journal of Environmental Research and Public Health, vol. 19, pp. 1–10, 2022. @article{Raffi2022, Microsaccades are linked with extraretinal mechanisms that significantly alter spatial perception before the onset of eye movements. We sought to investigate whether microsaccadic activity is modulated by the speed of radial optic flow stimuli. Experiments were performed in the dark on 19 subjects who stood in front of a screen covering 135 × 107◦ of the visual field. Subjects were instructed to fixate on a central fixation point while optic flow stimuli were presented in full field, in the foveal, and in the peripheral visual field at different dot speeds (8, 11, 14, 17, and 20◦/s). Fixation in the dark was used as a control stimulus. For almost all tested speeds, the stimulation of the peripheral retina evoked the highest microsaccade rate. We also found combined effects of optic flow speed and the stimulated retinal region (foveal, peripheral, and full field) for microsaccade latency. These results show that optic flow speed modulates microsaccadic activity when presented in specific retinal portions, suggesting that eye movement generation is strictly dependent on the stimulated retinal regions. |
Hamidreza Ramezanpour; Shawn Blizzard; Devin Heinze Kehoe; Mazyar Fallah Oculomotor system can differentially process red and green colors during saccade programming in the presence of a competing distractor Journal Article In: Experimental Brain Research, vol. 240, no. 11, pp. 2847–2860, 2022. @article{Ramezanpour2022, Selective attention filters irrelevant information entering our brain to allow for fine-tuning of the relevant information processing. In the visual domain, shifts of attention are most often followed by a saccadic eye movement to objects and places of high relevance. Recent studies have shown that the stimulus color can affect saccade target selection and saccade trajectories. While those saccade modulations are based on perceptual color space, the level in the visual processing hierarchy at which color selection biases saccade programming remains unclear. As color has also been shown to influence manual response inhibition which is a key function of the prefrontal cortex, we hypothesized that the effects of color on executive functions would also inherently affect saccade programming. To test this hypothesis, we measured behavioral performance and saccade metrics during a modified saccadic Stroop task which reflects competition between color words (“RED” and “GREEN”) and their color at the level of the prefrontal cortex. Our results revealed that the oculomotor system can differentially process red and green colors when planning a saccade in the presence of a competing distractor. |
Lukas Recker; Rebecca M. Foerster; Werner X. Schneider; Christian H. Poth In: PLoS ONE, vol. 17, pp. 1–19, 2022. @article{Recker2022, The Trail-Making-Test (TMT) is one of the most widely used neuropsychological tests for assessing executive functions, the brain functions underlying cognitively controlled thought and action. Obtaining a number of test scores at once, the TMT allows to characterize an assortment of executive functions efficiently. Critically, however, as most test scores are derived from test completion times, the scores only provide a summary measure of various cognitive control processes. To address this problem, we extended the TMT in two ways. First, using a computerized eye-tracking version of the TMT, we added specific eye movement measures that deliver a richer set of data with a higher degree of cognitive process specificity. Second, we included an experimental manipulation of a fundamental executive function, namely participants' ability to emphasize speed or accuracy in task performance. Our study of healthy participants showed that eye movement measures differed between TMT conditions that are usually compared to assess the cognitive control process of alternating between task sets for action control. This demonstrates that eye movement measures are indeed sensitive to executive functions implicated in the TMT. Crucially, comparing performance under cognitive control sets of speed vs. accuracy emphasis revealed which test scores primarily varied due to this manipulation (e.g., trial duration, number of fixations), and which were still more sensitive to other differences between individuals (e.g., fixation duration, saccade amplitude). This provided an experimental construct validation of the test scores by distinguishing scores primarily reflecting the executive function of emphasizing speed vs. accuracy and those independent from it. In sum, both the inclusion of eye movement measures and of the experimental manipulation of executive functions in the TMT enabled a more specific interpretation of the TMT in terms of cognitive functions and mechanisms, which offers more precise diagnoses in clinical applications and basic research. |
Oded Rock; Andrea Albonico; Farnaz Javadian; Mohammad Ashkanani; Alisdair J. G. Taylor; Michael Dreyer; Jason J. S. Barton Oblique saccades in internuclear ophthalmoplegia Journal Article In: Experimental Brain Research, vol. 240, no. 3, pp. 861–869, 2022. @article{Rock2022, Purpose: Oblique saccades often display component stretching, in which the shorter vector in one cardinal direction is slowed so that its duration matches that of the longer vector in the orthogonal direction, resulting in a straighter trajectory. In internuclear ophthalmoplegia, adducting saccades are typically slowed while vertical saccades are unaffected. It is not known whether these slowed adducting movements are accompanied by adaptive component stretching of the vertical vector during oblique saccades. This was a cross-sectional study. We recorded the saccadic eye movement in 5 patients with right or bilateral internuclear ophthalmoplegia from multiple sclerosis and 17 healthy controls, using an EyeLink 1000 machine. The target stimulus was located at varying angles (0–360) and amplitudes (4, 8, 12 degrees). For each saccade we have calculated the curvature index as the main outcome measure, which is the area between the actual and ideal straight trajectory for oblique saccadic eye movements, divided by the square of the length of the straight trajectory, to give a unit-less metric for curvature. In the 17 control subjects, curvature showed a strong positive correlation between adducting saccades and the yoked abducting saccades of the other eye. In internuclear ophthalmoplegia, adducting saccades showed a strong curvature concave to the horizontal meridian, indicating inadequate component stretching, while abducting saccades did not differ from controls. This new sign of oblique saccadic curvature in internuclear ophthalmoplegia indicates a limitation of the range of central adaptive changes in response to distal lesions affecting transmission of the saccadic command. |
Shannon Ross-Sheehy; Bret Eschman; Esther E. Reynolds Seeing and looking: Evidence for developmental and stimulus-dependent changes in infant scanning efficiency Journal Article In: PLoS ONE, vol. 17, no. 9, pp. 1–24, 2022. @article{RossSheehy2022, Though previous work has examined infant attention across a variety of tasks, less is known about the individual saccades and fixations that make up each bout of attention, and how individual differences in saccade and fixation patterns (i.e., scanning efficiency) change with development, scene content and perceptual load. To address this, infants between the ages of 5 and 11 months were assessed longitudinally (Experiment 1) and cross-sectionally (Experiment 2). Scanning efficiency (fixation duration, saccade rate, saccade amplitude, and saccade velocity) was assessed while infants viewed six quasi-naturalistic scenes that varied in content (social or non-social) and scene complexity (3, 6 or 9 people/objects). Results from Experiment 1 revealed moderate to strong stability of individual differences in saccade rate, mean fixation duration, and saccade amplitude, and both experiments revealed 5-month-old infants to make larger, faster, and more frequent saccades than older infants. Scanning efficiency was assessed as the relation between fixation duration and saccade amplitude, and results revealed 11-month-olds to have high scanning efficiency across all scenes. However, scanning efficiency also varied with scene content, such that all infants showing higher scanning efficiency when viewing social scenes, and more complex scenes. These results suggest both developmental and stimulus-dependent changes in scanning efficiency, and further highlight the use of saccade and fixation metrics as a sensitive indicator of cognitive processing. |
Uzma Samadani; Robert J. Spinner; Gerard Dynkowski; Susan Kirelik; Tory Schaaf; Stephen P. Wall; Paul Huang Eye tracking for classification of concussion in adults and pediatrics Journal Article In: Frontiers in Neurology, vol. 13, no. 2, pp. 1–6, 2022. @article{Samadani2022, INTRODUCTION In order to obtain FDA Marketing Authorization for aid in the diagnosis of concussion, an eye tracking study in an intended use population was conducted. METHODS Potentially concussed subjects recruited in emergency department and concussion clinic settings prospectively underwent eye tracking and a subset of the Sport Concussion Assessment Tool 3 at 6 sites. The results of an eye tracking-based classifier model were then validated against a pre-specified algorithm with a cutoff for concussed vs. non-concussed. The sensitivity and specificity of eye tracking were calculated after plotting of the receiver operating characteristic curve and calculation of the AUC (area under curve). RESULTS When concussion is defined by SCAT3 subsets, the sensitivity and specificity of an eye tracking algorithm was 80.4 and 66.1%, The AUC was 0.718. The misclassification rate (n = 282) was 31.6%. CONCLUSION A pre-specified algorithm and cutoff for diagnosis of concussion vs. non-concussion has a sensitivity and specificity that is useful as a baseline-free aid in diagnosis of concussion. Eye tracking has potential to serve as an objective "gold-standard" for detection of neurophysiologic disruption due to brain injury. |
Amy Chow; Rajkumar Nallour Raveendran; Ian Erkelens; Raiju Babu; Benjamin Thompson Increased saccadic latency in Amblyopia: Oculomotor and attentional factors Journal Article In: Vision Research, vol. 197, pp. 1–11, 2022. @article{Chow2022, Amblyopia is a neurodevelopmental disorder of vision that arises from disrupted binocular vision during early childhood. Delayed initiation of saccadic eye movements is an established feature of amblyopia. The present study investigated whether oculomotor and/or attentional factors contribute to increased amblyopic eye saccadic latencies. Participants with normal vision (n = 10) and amblyopia (n = 10; 4 anisometropia, 6 strabismic/mixed) performed visually-guided saccades to targets presented via a mirror haploscope. Eye movements were recorded for both eyes even under monocular viewing conditions. In Experiment 1, we measured the latency, amplitude gain and peak velocity of saccades as targets were presented binocularly, or monocularly. Saccadic latencies were significantly longer for both eyes when targets were presented to only the amblyopic eye compared to all other conditions. Saccade gain and main sequence rate constants were similar across groups for all viewing conditions. In Experiment 2, we tested the hypothesis that shifts of overt attention may be deficient when viewing with the amblyopic eye. We presented the fixation target to one eye and the subsequent peripheral target (saccadic error signal) to the other eye. Shifting saccadic targets between the eyes expedited saccadic latencies irrespective of which eye viewed the target in the amblyopia group. These findings indicate that oculomotor factors related to saccade generation are unlikely to be responsible for amblyopic eye saccadic latency delays. We propose that an impairment in the ability to disengage attention from a fixation target and orient to a peripheral target when both targets are seen by the amblyopic eye may contribute to increased saccadic latency. |
Alessio D'Aquino; Cornelia Frank; John Elvis Hagan; Thomas Schack Imagining interceptions: Eye movements as an online indicator of covert motor processes during motor imagery Journal Article In: Frontiers in Neuroscience, vol. 16, pp. 1–15, 2022. @article{DAquino2022, The analysis of eye movements during motor imagery has been used to understand the influence of covert motor processes on visual-perceptual activity. There is evidence showing that gaze metrics seem to be affected by motor planning often dependent on the spatial and temporal characteristics of a task. However, previous research has focused on simulated actions toward static targets with limited empirical evidence of how eye movements change in more dynamic environments. The study examined the characteristics of eye movements during motor imagery for an interception task. Twenty-four participants were asked to track a moving target over a computer display and either mentally simulate an interception or rest. The results showed that smooth pursuit variables, such as duration and gain, were lower during motor imagery when compared to passive observation. These findings indicate that motor plans integrate visual-perceptual information based on task demands and that eye movements during imagery reflect such constraint. |
Bertrand Degos; Pierre Pouget; Marcus Missal From anticipation to impulsivity in Parkinson's disease Journal Article In: npj Parkinson's Disease, vol. 8, pp. 1–12, 2022. @article{Degos2022, Anticipatory actions require to keep track of elapsed time and inhibitory control. These cognitive functions could be impacted in Parkinson's disease (iPD). To test this hypothesis, a saccadic reaction time task was used where a visual warning stimulus (WS) predicted the occurrence of an imperative one (IS) appearing after a short delay. In the implicit condition, subjects were not informed about the duration of the delay, disfavoring anticipatory behavior but leaving inhibitory control unaltered. In the explicit condition, delay duration was cued. This should favor anticipatory behavior and perhaps alter inhibitory control. This hypothesis was tested in controls (N = 18) and age-matched iPD patients (N = 20; ON and OFF L-DOPA). We found that the latency distribution of saccades before the IS was bimodal. The 1st mode weakly depended on temporal information and was more prominent in iPD. Saccades in this mode were premature and could result of a lack of inhibition. The 2nd mode covaried with cued duration suggesting that these movements were genuine anticipatory saccades. The explicit condition increased the probability of anticipatory saccades before the IS in controls and iPDON but not iPDOFF patients. Furthermore, in iPD patients the probability of sequences of 1st mode premature responses increased. In conclusion, the triggering of a premature saccade or the initiation of a controlled anticipatory one could be conceptualized as the output of two independent stochastic processes. Altered time perception and increased motor impulsivity could alter the balance between these two processes in favor of the latter in iPD, particularly OFF L-Dopa. |
Dominika Drcażyk; Marcus Missal The oculomotor signature of expected surprise Journal Article In: Scientific Reports, vol. 12, no. 1, pp. 1–14, 2022. @article{Dra̧zyk2022, Expected surprise, defined as the anticipation of uncertainty associated with the occurrence of a future event, plays a major role in gaze shifting and spatial attention. In the present study, we analyzed its impact on oculomotor behavior. We hypothesized that the occurrence of anticipatory saccades could decrease with increasing expected surprise and that its influence on visually-guided responses could be different given the presence of sensory information and perhaps competitive attentional effects. This hypothesis was tested in humans using a saccadic reaction time task in which a cue indicated the future stimulus position. In the ‘no expected surprise' condition, the visual target could appear only at one previously cued location. In other conditions, more likely future positions were cued with increasing expected surprise. Anticipation was more frequent and pupil size was larger in the ‘no expected surprise' condition compared with all other conditions, probably due to increased arousal. The latency of visually-guided saccades increased linearly with the logarithm of surprise (following Hick's law) but their maximum velocity repeated the arousal-related pattern. Therefore, expected surprise affects anticipatory and visually-guided responses differently. Moreover, these observations suggest a causal chain linking surprise, attention and saccades that could be disrupted in attentional or impulse control disorders. |
Matt J. Dunn; J. Margaret Woodhouse Voluntary flutter presenting during ophthalmoscopy: A case report Journal Article In: Case Reports in Ophthalmology, pp. 286–291, 2022. @article{Dunn2022a, Voluntary flutter (sometimes known as “voluntary nystagmus”) is a conjugate saccadic oscillation of the eyes that occurs in some healthy individuals. It has no relation to pathological nystagmus, which can manifest in infancy or become acquired later in life. This report presents an unusual case of voluntary flutter that presented in a 20-year-old male with autism spectrum disorder during ocular examination via direct ophthalmoscopy. Refraction and ocular motor balance were normal, and visual acuity was good in each eye (−0.10 logMAR). During direct ophthalmoscopy, a fine intermittent tremor was initiated. The patient was referred for further assessment, and eye movements were recorded at 1,000 Hz with an EyeLink 1000 eye tracker. Upon request, the patient could manifest voluntary flutter again and sustain the eye movements with effort during convergence. The voluntary flutter consisted of back-to-back saccadic oscillations in a predominantly horizontal direction, with an average frequency of 13 Hz and an amplitude of ∼8°, both reducing over time. We speculate that the discomfort induced by the proximity of the clinician during direct ophthalmoscopy examination may have triggered the eye oscillations. Although the oscillations typically manifest during convergence, atypical forms of voluntary flutter can also occur during divergence. Voluntary flutter can be a useful differential diagnosis in patients with a recently onset apparent “nystagmus,” and no other neurological signs and symptoms. |
Dan Zhang; Qian Guo; Lihua Xu; Xu Liu; Tian Hong Zhang; Xiaohua Liu; Haiying Chen; Guanjun Li; Jijun Wang The impact of COVID-19 pandemic on individuals at clinical high-risk for psychosis: Evidence from eye-tracking measures Journal Article In: Progress in Neuro-Psychopharmacology and Biological Psychiatry, vol. 118, pp. 1–8, 2022. @article{Zhang2022b, Emerging evidence suggested that people with severe mental disorders were more vulnerable to the negative effects of the COVID-19 pandemic. However, few researches investigated the influence of global pandemics on people at clinical high risk (CHR) for psychosis. This study aimed to investigate the impact of the COVID-19 pandemic on clinical symptoms, psychological distress, and eye-tracking characteristics in CHR individuals and healthy participants. Forty-nine CHR individuals and 50 healthy controls (HC) were assessed by PTSD Checklist for DSM-5 (PCL-5), Perceived Stress Scale, 10-item version (PSS-10), and Coronavirus Impact Scale (CIS). Eye movement performances were measured by the tests of fixation stability, free-viewing, and anti-saccade. According to the mean score of CIS, participants were stratified into high-impact (n = 35) and low-impact (n = 64) subgroups. Compared with the HC group, CHR participants reported significantly higher levels of post-traumatic symptoms caused by the COVID-19 pandemic and showed abnormalities in most of the eye movement indexes. Among the altered indexes, the saccade amplitude of fixation stability test (far distractor), the scan path length of free-viewing test, and the accuracy of anti-saccade test were negatively affected by the severity of impact level in the CHR group. Moreover, the altered eye movement indexes were significantly associated with the total scores of CIS, PCL-5, and subscales of the Scale of Prodromal Syndromes (SOPS) among CHR individuals. Overall, our findings suggested the negative impact of the COVID-19 pandemic on the eye movement characteristics of CHR individuals. The present study provides valuable information on physiological distress related to the COVID-19 pandemic and sensitive neuropsychological biomarkers that interacted with social and environment stress in the CHR population. |
Xiuyun Wu; Miriam Spering Tracking and perceiving diverse motion signals: Directional biases in human smooth pursuit and perception Journal Article In: PLoS ONE, vol. 17, no. 9, pp. 1–22, 2022. @article{Wu2022a, Human smooth pursuit eye movements and motion perception behave similarly when observers track and judge the motion of simple objects, such as dots. But moving objects in our natural environment are complex and contain internal motion. We ask how pursuit and perception integrate the motion of objects with motion that is internal to the object. Observers (n = 20) tracked a moving random-dot kinematogram with their eyes and reported the object's perceived direction. Objects moved horizontally with vertical shifts of 0, ±3, ±6, or ±9° and contained internal dots that were static or moved ±90° up/down. Results show that whereas pursuit direction was consistently biased in the direction of the internal dot motion, perceptual biases differed between observers. Interestingly, the perceptual bias was related to the magnitude of the pursuit bias (r = 0.75): perceptual and pursuit biases were directionally aligned in observers that showed a large pursuit bias, but went in opposite directions in observers with a smaller pursuit bias. Dissociations between perception and pursuit might reflect different functional demands of the two systems. Pursuit integrates all available motion signals in order to maximize the ability to monitor and collect information from the whole scene. Perception needs to recognize and classify visual information, thus segregating the target from its context. Ambiguity in whether internal motion is part of the scene or contributes to object motion might have resulted in individual differences in perception. The perception-pursuit correlation suggests shared early-stage motion processing or perception- pursuit interactions. |
Jin Xie; Ting Yan; Jie Zhang; Zhengyu Ma; Huihui Zhou Modulation of neuronal activity and saccades at theta rhythm during visual search in non-human primates Journal Article In: Neuroscience Bulletin, vol. 38, no. 10, pp. 1183–1198, 2022. @article{Xie2022, Active exploratory behaviors have often been associated with theta oscillations in rodents, while theta oscillations during active exploration in non-human primates are still not well understood. We recorded neural activities in the frontal eye field (FEF) and V4 simultaneously when monkeys performed a free-gaze visual search task. Saccades were strongly phase-locked to theta oscillations of V4 and FEF local field potentials, and the phase-locking was dependent on saccade direction. The spiking probability of V4 and FEF units was significantly modulated by the theta phase in addition to the time-locked modulation associated with the evoked response. V4 and FEF units showed significantly stronger responses following saccades initiated at their preferred phases. Granger causality and ridge regression analysis showed modulatory effects of theta oscillations on saccade timing. Together, our study suggests phase-locking of saccades to the theta modulation of neural activity in visual and oculomotor cortical areas, in addition to the theta phase locking caused by saccade-triggered responses. |
Mengmi Zhang; Marcelo Armendariz; Will Xiao; Olivia Rose; Katarina Bendtz; Margaret Livingstone; Carlos Ponce; Gabriel Kreiman Look twice: A generalist computational model predicts return fixations across tasks and species Journal Article In: PLoS Computational Biology, vol. 18, no. 11, pp. 1–38, 2022. @article{Zhang2022i, Primates constantly explore their surroundings via saccadic eye movements that bring different parts of an image into high resolution. In addition to exploring new regions in the visual field, primates also make frequent return fixations, revisiting previously foveated locations. We systematically studied a total of 44,328 return fixations out of 217,440 fixations. Return fixations were ubiquitous across different behavioral tasks, in monkeys and humans, both when subjects viewed static images and when subjects performed natural behaviors. Return fixations locations were consistent across subjects, tended to occur within short temporal offsets, and typically followed a 180-degree turn in saccadic direction. To understand the origin of return fixations, we propose a proof-of-principle, biologically-inspired and image-computable neural network model. The model combines five key modules: an image feature extractor, bottom-up saliency cues, task-relevant visual features, finite inhibition-of-return, and saccade size constraints. Even though there are no free parameters that are fine-tuned for each specific task, species, or condition, the model produces fixation sequences resembling the universal properties of return fixations. These results provide initial steps towards a mechanistic understanding of the trade-off between rapid foveal recognition and the need to scrutinize previous fixation locations. |
Jinghui Yin; Jiande Sun; Jing Li; Ke Liu An effective gaze-based authentication method with the spatiotemporal feature of eye movement Journal Article In: Sensors, vol. 22, no. 3002, pp. 1–18, 2022. @article{Yin2022, Eye movement has become a new behavioral feature for biometric authentication. In the eye movement-based authentication methods that use temporal features and artificial design features, the required duration of eye movement recordings are too long to be applied. Therefore, this study aims at using eye movement recordings with shorter duration to realize authentication. And we give out a reasonable eye movement recording duration that should be less than 12 s, referring to the changing pattern of the deviation degree between the gaze point and the stimulus point on the screen. In this study, the temporal motion features of the gaze points and the spatial distribution features of the saccade are using to represent the personal identity. Two datasets are constructed for the experiments, including 5 s and 12 s of eye movement recordings. On the datasets constructed in this paper, the open-set authentication results show that the Equal Error Rate of our proposed methods can reach 10.62% when recording duration is 12 s and 12.48% when recording duration is 5 s. The closed-set authentication results show that the Equal Error Rate of our proposed methods can reach 5.25% when recording duration is 12 s and 7.82% when recording duration is 5 s. It demonstrates that the proposed method provides a reference for the eye movements data-based identity authentication. |
Eckart Zimmermann Mislocalization in saccadic suppression of displacement Journal Article In: Vision Research, vol. 196, pp. 1–6, 2022. @article{Zimmermann2022, Visual stability across saccades requires us to discriminate self-generated motion by eye movements from motion occurring in the external world. In the laboratory visual stability is often studied by asking observers to discriminate the direction of trans-saccadic target displacements. It is a well established finding that in this paradigm performance is usually very poor. If observers are insensitive to the intra-saccadic motion and see the pre- and the post-saccadic target in one location, one of both targets should be reported as shifted when observers would localize them. Here, I asked participants to perform a saccade to a target. During saccade execution the target was displaced either in backward or forward direction. After finishing the saccade, subjects had to report the position of either the pre-or the post-saccadic target. I found that subjects mislocalized the pre-saccadic target to the physical position of the post-saccadic target. This mislocalization occurred only after backward but not after forward displacements. |
Gongchen Yu; James P. Herman; Leor N. Katz; Richard J. Krauzlis Microsaccades as a marker not a cause for attention-related modulation Journal Article In: eLife, vol. 11, pp. 1–14, 2022. @article{Yu2022, Recent evidence suggests that microsaccades are causally linked to the attentionrelated modulation of neurons—specifically, that microsaccades toward the attended location are required for the subsequent changes in firing rate. These findings have raised questions about whether attention-related modulation is due to different states of attention as traditionally assumed or might instead be a secondary effect of microsaccades. Here, in two rhesus macaques, we tested the relationship between microsaccades and attention-related modulation in the superior colliculus (SC), a brain structure crucial for allocating attention. We found that attention-related modulation emerged even in the absence of microsaccades, was already present prior to microsaccades toward the cued stimulus, and persisted through the suppression of activity that accompanied all microsaccades. Nonetheless, consistent with previous findings, we also found significant attention-related modulation when microsaccades were directed toward, rather than away from, the cued location. Thus, despite the clear links between microsaccades and attention, microsaccades are not necessary for attention-related modulation, at least not in the SC. They do, however, provide an additional marker for the state of attention, especially at times when attention is shifting from one location to another. |
Haojue Yu; Foroogh Shamsi; MiYoung Kwon Altered eye movements during reading under degraded viewing conditions: Background luminance, text blur, and text contrast Journal Article In: Journal of Vision, vol. 22, no. 10, pp. 1–20, 2022. @article{Yu2022a, Degraded viewing conditions caused by either natural environments or visual disorders lead to slow reading. Here, we systematically investigated how eye movement patterns during reading are affected by degraded viewing conditions in terms of spatial resolution, contrast, and background luminance. Using a high-speed eye tracker, binocular eye movements were obtained from 14 young normally sighted adults. Images of text passages were manipulated with varying degrees of background luminance (1.3–265 cd/m2), text blur (severe blur to no blur), or text contrast (2.6%–100%). We analyzed changes in key eye movement features, such as saccades, microsaccades, regressive saccades, fixations, and return-sweeps across different viewing conditions. No significant changes were observed for the range of tested background luminance values. However, with increasing text blur and decreasing text contrast, we observed a significant decrease in saccade amplitude and velocity, as well as a significant increase in fixation duration, number of fixations, proportion of regressive saccades, microsaccade rate, and duration of return-sweeps. Among all, saccade amplitude, fixation duration, and proportion of regressive saccades turned out to be the most significant contributors to reading speed, together accounting for 90% of variance in reading speed. Our results together showed that, when presented with degraded viewing conditions, the patterns of eye movements during reading were altered accordingly. These findings may suggest that the seemingly deviated eye movements observed in individuals with visual impairments may be in part resulting from active and optimal information acquisition strategies operated when visual sensory input becomes substantially deprived. |
Dan Zhang; Xu Liu; Lihua Xu; Yu Li; Yangyang Xu; Mengqing Xia; Zhenying Qian; Yingying Tang; Zhi Liu; Tao Chen; HaiChun Liu; TianHong Zhang; Jijun Wang Effective differentiation between depressed patients and controls using discriminative eye movement features Journal Article In: Journal of Affective Disorders, vol. 307, pp. 237–243, 2022. @article{Zhang2022c, Background: Depression is a common debilitating mental disorder caused by various factors. Identifying and diagnosing depression are challenging because the clinical evaluation of depression is mainly subjective, lacking objective and quantitative indicators. The present study investigated the value and significance of eye movement measurements in distinguishing depressed patients from controls. Methods: Ninety-five depressed patients and sixty-nine healthy controls performed three eye movement tests, including fixation stability, free-viewing, and anti-saccade tests, and eleven eye movement indexes were obtained from these tests. The independent t-test was adopted for group comparisons, and multiple logistic regression analysis was employed to identify diagnostic biomarkers. Support vector machine (SVM), quadratic discriminant analysis (QDA), and Bayesian (BYS) algorithms were applied to build the classification models. Results: Depressed patients exhibited eye movement anomalies, characterized by increased saccade amplitude in the fixation stability test; diminished saccade velocity in the anti-saccade test; and reduced saccade amplitude, shorter scan path length, lower saccade velocity, decreased dynamic range of pupil size, and lower pupil size ratio in the free-viewing test. Four features mentioned above entered the logistic regression equation. The classification accuracies of SVM, QDA, and BYS models reached 86.0%, 81.1%, and 83.5%, respectively. Conclusions: Depressed patients exhibited abnormalities across multiple tests of eye movements, assisting in differentiating depressed patients from healthy controls in a cost-effective and non-invasive manner. |
Christian Wolf; Artem V. Belopolsky; Markus Lappe Current foveal inspection and previous peripheral preview influence subsequent eye movement decisions Journal Article In: iScience, vol. 25, no. 9, pp. 1–16, 2022. @article{Wolf2022, Humans visually inspect the world with their fovea and select new parts of the scene using saccadic eye movements. Foveal inspection and the decision of where and when to look next proceed simultaneously, but there is mixed evidence concerning their independence. Here, we tested their interdependence using drift-diffusion modeling. Participants first made a saccade to a predetermined inspection target and subsequently decided between two selection targets. We found that the inspected target's meaningfulness and the opportunity to preview it peripherally affects fixation durations and the upcoming saccadic selection. Drift-diffusion modeling showed that meaningfulness and the absence of peripheral preview can both delay the subsequent saccadic decision process and affect the rate at which peripheral information is accumulated. Our results thus show that foveal inspection and peripheral selection are dependent on each other and that peripheral information can be maintained across the saccade to influence subsequent eye movement decisions. |
Ómar I. Jóhannesson; Árni Kristjánsson; Jérôme Tagu Contrasting attentional biases in a saccadic choice task Journal Article In: Experimental Brain Research, vol. 240, no. 1, pp. 173–187, 2022. @article{Johannesson2022, To gain insight into how human observers select items in the visual field we pitted two attentional biases against one another in a single free choice design. The first bias is the nasal-temporal asymmetry during free choice tasks, where observers tend to choose targets that appear in their temporal hemifield over targets appearing in their nasal hemifield. The second is the choice bias found in studies of attentional priming. When observers have to select between a stimulus that shares features with a preceding target and a stimulus sharing features with previous distractors, they have a strong tendency to choose the preceding search target and this bias increases the more often the same search is repeated. Our results show that both biases affect saccadic choice, but they also show that the nasal-temporal bias can modulate the strength of the priming effects, but not vice versa. The priming effect was stronger for stimuli appearing in the temporal than in the nasal hemifield, but the nasal-temporal bias was similar for primed and unprimed targets. Additionally, our findings are the first to show how search repetition leads to faster saccades. The observed difference between the effects of the NTA and priming biases may reflect the difference in neural mechanisms thought to be behind these biases and that biases at lower levels may outrank higher-level biases, at least in their effect on visual attention. |
Richard Johnston; Adam C. Snyder; Sanjeev B. Khanna; Deepa Issar; Matthew A. Smith The eyes reflect an internal cognitive state hidden in the activity of the neurons Journal Article In: Cerebral Cortex, vol. 32, pp. 3331–3346, 2022. @article{Johnston2022, Decades of research have shown that global brain states such as arousal can be indexed by measuring the properties of the eyes. The spiking responses of neurons throughout the brain have been associated with the pupil, small fixational saccades, and vigor in eye movements, but it has been difficult to isolate how internal states affect the eyes, and vice versa. While recording from populations of neurons in the visual and prefrontal cortex (PFC), we recently identified a latent dimension of neural activity called “slow drift,” which appears to reflect a shift in a global brain state. Here, we asked if slow drift is correlated with the action of the eyes in distinct behavioral tasks. We recorded from visual cortex (V4) while monkeys performed a change detection task, and PFC, while they performed a memory-guided saccade task. In both tasks, slow drift was associated with the size of the pupil and the microsaccade rate, two external indicators of the internal state of the animal. These results show that metrics related to the action of the eyes are associated with a dominant and task-independent mode of neural activity that can be accessed in the population activity of neurons across the cortex. |
Oren Kadosh; Yoram Bonneh Face familiarity revealed by fixational eye movements and fixation-related potentials in free viewing Journal Article In: Scientific Reports, vol. 12, no. 1, pp. 1–13, 2022. @article{Kadosh2022a, Event-related potentials (ERPs) and the oculomotor inhibition (OMI) in response to visual transients are known to be sensitive to stimulus properties, attention, and expectation. We have recently found that the OMI is also sensitive to face familiarity. In natural vision, stimulation of the visual cortex is generated primarily by saccades, and it has been recently suggested that fixation-related potentials (FRPs) share similar components with the ERPs. Here, we investigated whether FRPs and microsaccade inhibition (OMI) in free viewing are sensitive to face familiarity. Observers freely watched a slideshow of seven unfamiliar and one familiar facial images presented randomly for 4-s periods, with multiple images per identity. We measured the occipital fixation-related N1 relative to the P1 magnitude as well as the associated fixation-triggered OMI. We found that the average N1-P1 was significantly smaller and the OMI was shorter for the familiar face, compared with any of the seven unfamiliar faces. Moreover, the P1 was suppressed across saccades for the familiar but not for the unfamiliar faces. Our results highlight the sensitivity of the occipital FRPs to stimulus properties such as face familiarity and advance our understanding of the integration process across successive saccades in natural vision. |
Oren Kadosh; Yoram S. Bonneh Fixation-related saccadic inhibition in free viewing in response to stimulus saliency Journal Article In: Scientific Reports, vol. 12, pp. 1–12, 2022. @article{Kadosh2022b, Microsaccades that occur during fixation were studied extensively in response to transient stimuli, showing a typical inhibition (Oculomotor Inhibition, OMI), and a later release with a latency that depends on stimulus saliency, attention, and expectations. Here, we investigated the hypothesis that in free viewing every saccade provides a new transient stimulation that should result in a stimulus-dependent OMI like a flashed presentation during fixation. Participants (N = 16) freely inspected static displays of randomly oriented Gabor texture images, with varied contrast and spatial frequency (SF) for periods of 10 s each. Eye tracking recordings were divided into epochs triggered by saccade landing (> 1 dva), and microsaccade latency relative to fixation onset was computed (msRT). We found that the msRT in free viewing was shorter for more salient stimuli (higher contrast or lower SF), as previously found for flashed stimuli. It increased with saccade size and decreased across successive saccades, but only for higher contrast, suggesting contrast-dependent repetition enhancement in free viewing. Our results indicate that visual stimulus-dependent inhibition of microsaccades also applies to free viewing. These findings are in agreement with the similarity found between event-related and fixation-related potentials and open the way for studies combining both approaches to study natural vision. |
Oren Kadosh; Yoram S. Bonneh Involuntary oculomotor inhibition markers of saliency and deviance in response to auditory sequences Journal Article In: Journal of Vision, vol. 22, no. 5, pp. 1–19, 2022. @article{Kadosh2022, Our eyes move constantly but are often inhibited momentarily in response to external stimuli (oculomotor inhibition [OMI]), depending on the stimulus saliency, anticipation, and attention. Previous studies have shown prolonged OMI for auditory oddballs; however, they required counting the oddballs, possibly reflecting voluntary attention. Here, we investigated whether the “passive” OMI response to auditory deviants can provide a quantitative measure of deviance strength (pitch difference) and studied its dependence on the inter-trial interval (ITI). Participants fixated centrally and passively listened to repeated short sequences of pure tones that contained a deviant tone either regularly or with 20% probability (oddballs). In an “active” control experiment, participants counted the deviant or the standard. As in previous studies, the results showed prolonged microsaccade inhibition and increased pupil dilation following the rare deviant tone. Earlier inhibition onset was found in proportion to the pitch deviance (the saliency effect), and a later release was found for oddballs, but only for ITI <2.5 seconds. The active control experiment showed similar results when counting the deviant but longer OMI for the standard when counting it. Taken together, these results suggest that OMI provides involuntary markers of saliency and deviance, which can be obtained without the participant's response. |
Tatiana Karpouzian-Rogers; Rob Hurley; Mustafa Seckin; Stacey Moeller; Nathan Gill; Hui Zhang; Christina Coventry; Matthew Nelson; Sandra Weintraub; Emily Rogalski; M. Marsel Mesulam Eye movements as a measure of word comprehension deficits in primary progressive aphasia Journal Article In: Brain and Language, vol. 232, pp. 1–5, 2022. @article{KarpouzianRogers2022, Introduction: Eye movement studies can uncover subtle aspects of language processing impairment in individuals with primary progressive aphasia (PPA), who may have difficulty understanding words. This study examined eye movement patterns on a word-object matching task in response to varying levels of word-knowledge in PPA. Methods: Participants with semantic and non-semantic PPA completed an object-matching task, where a word was presented and participants then selected the corresponding pictured object from an array. Afterwards, participants defined words for trials to which they incorrectly pointed. Linear mixed-effects analyses examined fixation differences on targets and related and unrelated foils. Results: On incorrectly-pointed trials, participants demonstrated greater fixation duration on related foils, demonstrating intra-category blurring. For words that could not be defined, there was similar fixation duration on related and unrelated foils, demonstrating inter-category semantic blurring. Discussion: This study demonstrated that fixation patterns reflect varying levels of word knowledge in PPA. |
Chaim N. Katz; Andrea G. P. Schjetnan; Kramay Patel; Victoria Barkley; Kari L. Hoffman; Suneil K. Kalia; Katherine D. Duncan; Taufik A. Valiante A corollary discharge mediates saccade-related inhibition of single units in mnemonic structures of the human brain Journal Article In: Current Biology, vol. 32, no. 14, pp. 3082–3094, 2022. @article{Katz2022, Despite the critical link between visual exploration and memory, little is known about how neuronal activity in the human mesial temporal lobe (MTL) is modulated by saccades. Here, we characterize saccade-associated neuronal modulations, unit-by-unit, and contrast them to image onset and to occipital lobe neurons. We reveal evidence for a corollary discharge (CD)-like modulatory signal that accompanies saccades, inhibiting/exciting a unique population of broad-/narrow-spiking units, respectively, before and during saccades and with directional selectivity. These findings comport well with the timing, directional nature, and inhibitory circuit implementation of a CD. Additionally, by linking neuronal activity to event-related potentials (ERPs), which are directionally modulated following saccades, we recontextualize the ERP associated with saccades as a proxy for both the strength of inhibition and saccade direction, providing a mechanistic underpinning for the more commonly recorded saccade-related ERP in the human brain. |
Johannes Kirchner; Tamara Watson; Niko A. Busch; Markus Lappe Timing and kinematics of horizontal within-blink saccades measured by EOG Journal Article In: Journal of Neurophysiology, vol. 127, no. 6, pp. 1655–1668, 2022. @article{Kirchner2022, Eyeblinks are the brief closures of the lid. They are accompanied by a cocontraction of the eye muscles that temporarily pulls the whole eyeball back into its socket. When blinks occur together with execution of saccadic gaze shifts, they interfere with the saccadic premotor circuit, causing these within-blink saccades to be slower than normal and also time-locked to blinks. To analyze the trajectory of within-blink saccades, subtraction of the entangled blink-related eye movement is required. Here we propose a combination of principal component analysis (PCA) and a regression model to subtract the blink-related component of the eye movement based on the respective blink metrics. We used electrooculography (EOG) to measure eye and lid movements of 12 participants who performed saccades with and without blinks. We found that within-blink saccades are slower than without-blink saccades and are tightly coupled in time to blink onset. Surprisingly, in some participants we observed large dynamic overshoots of up to 15° for saccades of only 5° amplitude. The finding of dynamic overshoots was independently confirmed by dynamic MRI for two of the participants and challenges the current view that within-blink saccades are programmed as slow, but straight, saccades. We hypothesize that the dynamic overshoots could be attributed to inhibition of omnipause neurons during blinks, the simultaneous cocontraction of extraocular muscles, or a combination of both. |
Colin C. Korbisch; Daniel R. Apuan; Reza Shadmehr; Alaa A. Ahmed Saccade vigor reflects the rise of decision variables during deliberation Journal Article In: Current Biology, vol. 32, pp. 5374–5381, 2022. @article{Korbisch2022, During deliberation, as we quietly consider our options, the neural activities representing the decision variables that reflect the goodness of each option rise in various regions of the cerebral cortex.1,2,3,4,5,6,7 If the options are depicted visually, we make saccades, focusing gaze on each option. Do the kinematics of these saccades reflect the state of the decision variables? To test this idea, we engaged human participants in a decision-making task in which they considered two effortful options that required walking across various distances and inclines. As they deliberated, they made saccades between the symbolic representations of their options. These deliberation period saccades had no bearing on the effort they would later expend, yet saccade velocities increased gradually and differentially: the rate of rise was faster for saccades toward the option that they later indicated as their choice. Indeed, the rate of rise encoded the difference in the subjective value of the two options. Importantly, the participants did not reveal their choice at the conclusion of deliberation, but rather waited during a delay period, and finally expressed their choice by making another saccade. Remarkably, vigor for this saccade dropped to baseline and no longer encoded subjective value. Thus, saccade vigor appeared to provide a real-time window to the otherwise hidden process of option evaluation during deliberation. |
Lisa M. Kroell; Martin Rolfs Foveal vision anticipates defining features of eye movement targets Journal Article In: eLife, vol. 11, pp. 1–38, 2022. @article{Kroell2022, High-acuity foveal processing is vital for human vision. Nonetheless, little is known about how the preparation of large-scale rapid eye movements (saccades) affects visual sensitivity in the center of gaze. Based on findings from passive fixation tasks, we hypothesized that during saccade preparation, foveal processing anticipates soon-to-be fixated visual features. Using a dynamic large-field noise paradigm, we indeed demonstrate that defining features of an eye movement target are enhanced in the pre-saccadic center of gaze. Enhancement manifested as higher Hit Rates for foveal probes with target-congruent orientation and a sensitization to incidental, target-like orientation information in foveally presented noise. Enhancement was spatially confined to the center of gaze and its immediate vicinity, even after parafoveal task performance had been raised to a foveal level. Moreover, foveal enhancement during saccade preparation was more pronounced and developed faster than enhancement during passive fixation. Based on these findings, we suggest a crucial contribution of foveal processing to trans-saccadic visual continuity: Foveal processing of saccade targets commences before the movement is executed and thereby enables a seamless transition once the center of gaze reaches the target. |
Sunwoo Kwon; Berkeley K. Fahrenthold; Matthew R. Cavanaugh; Krystel R. Huxlin; Jude F. Mitchell Perceptual restoration fails to recover unconscious processing for smooth eye movements after occipital stroke Journal Article In: eLife, vol. 11, pp. 1–23, 2022. @article{Kwon2022, The visual pathways that guide actions do not necessarily mediate conscious perception. Patients with primary visual cortex (V1) damage lose conscious perception but often retain unconscious abilities (e.g. blindsight). Here, we asked if saccade accuracy and post-saccadic following responses (PFRs) that automatically track target motion upon saccade landing are retained when conscious perception is lost. We contrasted these behaviors in the blind and intact fields of 11 chronic V1-stroke patients, and in 8 visually intact controls. Saccade accuracy was relatively normal in all cases. Stroke patients also had normal PFR in their intact fields, but no PFR in their blind fields. Thus, V1 damage did not spare the unconscious visual processing necessary for automatic, postsaccadic smooth eye movements. Importantly, visual training that recovered motion perception in the blind field did not restore the PFR, suggesting a clear dissociation between pathways mediating perceptual restoration and automatic actions in the V1-damaged visual system. |
Natalia Ladyka-Wojcik; Zhong-Xu Liu; Jennifer D. Ryan Unrestricted eye movements strengthen effective connectivity from hippocampal to oculomotor regions during scene construction Journal Article In: NeuroImage, vol. 260, pp. 1–15, 2022. @article{LadykaWojcik2022, Scene construction is a key component of memory recall, navigation, and future imagining, and relies on the medial temporal lobes (MTL). A parallel body of work suggests that eye movements may enable the imagination and construction of scenes, even in the absence of external visual input. There are vast structural and functional connections between regions of the MTL and those of the oculomotor system. However, the directionality of connections between the MTL and oculomotor control regions, and how it relates to scene construction, has not been studied directly in human neuroimaging. In the current study, we used dynamic causal modeling (DCM) to interrogate effective connectivity between the MTL and oculomotor regions using a scene construction task in which participants' eye movements were either restricted (fixed-viewing) or unrestricted (free-viewing). By omitting external visual input, and by contrasting free- versus fixed- viewing, the directionality of neural connectivity during scene construction could be determined. As opposed to when eye movements were restricted, allowing free-viewing during construction of scenes strengthened top-down connections from the MTL to the frontal eye fields, and to lower-level cortical visual processing regions, suppressed bottom-up connections along the visual stream, and enhanced vividness of the constructed scenes. Taken together, these findings provide novel, non-invasive evidence for the underlying, directional, connectivity between the MTL memory system and oculomotor system associated with constructing vivid mental representations of scenes. |
2021 |
Delia A. Gheorghe; Muriel T. N. Panouillères; Nicholas D. Walsh Investigating the effects of cerebellar transcranial direct current stimulation on saccadic adaptation and cortisol response Journal Article In: Cerebellum and Ataxias, vol. 8, no. 1, pp. 1–11, 2021. @article{Gheorghe2021, Background: Transcranial Direct Current Stimulation (tDCS) over the prefrontal cortex has been shown to modulate subjective, neuronal and neuroendocrine responses, particularly in the context of stress processing. However, it is currently unknown whether tDCS stimulation over other brain regions, such as the cerebellum, can similarly affect the stress response. Despite increasing evidence linking the cerebellum to stress-related processing, no studies have investigated the hormonal and behavioural effects of cerebellar tDCS. Methods: This study tested the hypothesis of a cerebellar tDCS effect on mood, behaviour and cortisol. To do this we employed a single-blind, sham-controlled design to measure performance on a cerebellar-dependent saccadic adaptation task, together with changes in cortisol output and mood, during online anodal and cathodal stimulation. Forty-five participants were included in the analysis. Stimulation groups were matched on demographic variables, potential confounding factors known to affect cortisol levels, mood and a number of personality characteristics. Results: Results showed that tDCS polarity did not affect cortisol levels or subjective mood, but did affect behaviour. Participants receiving anodal stimulation showed an 8.4% increase in saccadic adaptation, which was significantly larger compared to the cathodal group (1.6%). Conclusion: The stimulation effect on saccadic adaptation contributes to the current body of literature examining the mechanisms of cerebellar stimulation on associated function. We conclude that further studies are needed to understand whether and how cerebellar tDCS may module stress reactivity under challenge conditions. |
Léa Entzmann; Nathalie Guyader; Louise Kauffmann; Juliette Lenouvel; Clémence Charles; Carole Peyrin; Roman Vuillaume; Martial Mermillod The role of emotional content and perceptual saliency during the programming of saccades toward faces Journal Article In: Cognitive Science, vol. 45, no. 10, pp. e13042, 2021. @article{Entzmann2021, Previous studies have shown that the human visual system can detect a face and elicit a saccadic eye movement toward it very efficiently compared to other categories of visual stimuli. In the first experiment, we tested the influence of facial expressions on fast face detection using a saccadic choice task. Face-vehicle pairs were simultaneously presented and participants were asked to saccade toward the target (the face or the vehicle). We observed that saccades toward faces were initiated faster, and more often in the correct direction, than saccades toward vehicles, regardless of the facial expressions (happy, fearful, or neutral). We also observed that saccade endpoints on face images were lower when the face was happy and higher when it was neutral. In the second experiment, we explicitly tested the detection of facial expressions. We used a saccadic choice task with emotional-neutral pairs of faces and participants were asked to saccade toward the emotional (happy or fearful) or the neutral face. Participants were faster when they were asked to saccade toward the emotional face. They also made fewer errors, especially when the emotional face was happy. Using computational modeling, we showed that this happy face advantage can, at least partly, be explained by perceptual factors. Also, saccade endpoints were lower when the target was happy than when it was fearful. Overall, we suggest that there is no automatic prioritization of emotional faces, at least for saccades with short latencies, but that salient local face features can automatically attract attention. |
Peter Essig; Yannick Sauer; Siegfried Wahl Contrast sensitivity testing in healthy and blurred vision conditions using a novel optokinetic nystagmus live-detection method Journal Article In: Translational Vision Science & Technology, vol. 10, no. 12, pp. 12, 2021. @article{Essig2021, Purpose: The aim of the current study was to develop and validate an automated contrast sensitivity (CS) test using a live-detection of optokinetic nystagmus (OKN) and an adaptive psychometric procedure. In addition, the study sought to replicate the known effect of defocus on CS for the OKN-based measurements in emmetropic partic-ipants. Methods: Fifteen participants viewed a horizontally moving grating while their eyes were tracked with an infra-red (IR) eye-tracker. To simulate the clinical conditions of the CS measurements, the participants were stimulated monocularly as the left eye was occluded by an IR filter. The horizontal eye position was continuously analyzed for OKN responses, and the stimulus contrast was changed by an adaptive psychometric method depending on the outcome. Furthermore, the newly proposed OKN live-detection was verified against an offline analysis and an expert-observer judgement. The OKN-based CS was measured for six spatial frequencies at normal vision and three levels of defocus using spherical convex lenses. Results: The newly proposed OKN live-detection method showed a sufficient detection performance for implementation of adaptive procedures, and the detection rate is similar or better compared to offline detection methods. Spatial frequency and defocus had a significant effect on the OKN-based CS (P < 0.0001 for both). Conclusions: The current study presents a novel method to measure motion CS in an automated way, combining the real-time detection of OKN and an adaptive psychometric procedure. Furthermore, the known effect of defocus on CS was successfully repli-cated with the newly developed tool. Translational Relevance: OKN-based CS is a novel approach to assess spatial vision, which is sensitive to subtle effects of defocus, allowing use with nonverbal patients and infants. Furthermore, the newly developed tool may improve the performance of such measurements. |
Barbara Feulner; Danilo Postin; Caspar M. Schwiedrzik; Arezoo Pooresmaeili Previous motor actions outweigh sensory information in sensorimotor statistical learning Journal Article In: eNeuro, vol. 8, no. 5, pp. 1–17, 2021. @article{Feulner2021, Humans can use their previous experience in form of statistical priors to improve decisions. It is, however, unclear how such priors are learned and represented. Importantly, it has remained elusive whether prior learning is independent of the sensorimotor system involved in the learning process or not, as both modality-specific and modality-general learning have been reported in the past. Here, we used a saccadic eye movement task to probe the learning and representation of a spatial prior across a few trials. In this task, learning occurs in an unsupervised manner and through encountering trial-by-trial visual hints drawn from a distribution centered on the target location. Using a model-comparison approach, we found that participants' prior knowledge is largely represented in the form of their previous motor actions, with minimal influence from the previously seen visual hints. By using two different motor contexts for response (looking either at the estimated target lo-cation, or exactly opposite to it), we could further compare whether prior experience obtained in one motor context can be transferred to the other. Although learning curves were highly similar, and participants seemed to use the same strategy for both response types, they could not fully transfer their knowledge between con-texts, as performance and confidence ratings dropped after a switch of the required response. Together, our results suggest that humans preferably use the internal representations of their previous motor actions, rather than past incoming sensory information, to form statistical sensorimotor priors on the timescale of a few trials. |
Jolande Fooken; Pooja Patel; Christina B. Jones; Martin J. McKeown; Miriam Spering Preservation of eye movements in Parkinson's disease is stimulus and task specific Journal Article In: Journal of Neuroscience, vol. 42, no. 3, pp. 487–499, 2021. @article{Fooken2021, Parkinson's disease (PD) is a neurodegenerative disease that includes motor impairments, such as tremor, bradykinesia, and postural instability. Although eye movement deficits are commonly found in saccade and pursuit tasks, preservation of oculo- motor function has also been reported. Here we investigate specific task and stimulus conditions under which oculomotor function in PD is preserved. Sixteen PD patients and 18 healthy, age-matched controls completed a battery of movement tasks that included stationary or moving targets eliciting reactive or deliberate eye movements: pro-saccades, anti-saccades, visually guided pursuit, and rapid go/no-go manual interception. Compared with controls, patients demonstrated systematic impairments in tasks with stationary targets: pro-saccades were hypometric and anti-saccades were incorrectly initiated to- ward the cued target in ;35% of trials compared with 14% errors in controls. In patients, task errors were linked to short la- tency saccades, indicating abnormalities in inhibitory control. However, patients' eye movements in response to dynamic targets were relatively preserved. PD patients were able to track and predict a disappearing moving target and make quick go/no-go decisions as accurately as controls. Patients' interceptive hand movements were slower on average but initiated ear- lier, indicating adaptive processes to compensate for motor slowing. We conclude that PD patients demonstrate stimulus and task dependency of oculomotor impairments, and we propose that preservation of eye and hand movement function in PD is linked to a separate functional pathway through the superior colliculus-brainstem loop that bypasses the fronto-basal ganglia network. Our results demonstrate that studying oculomotor and hand movement function in PD can support disease diagno- sis and further our understanding of disease progression and dynamics. |
Markus Frey; Matthias Nau; Christian F. Doeller Magnetic resonance-based eye tracking using deep neural networks Journal Article In: Nature Neuroscience, vol. 24, no. 12, pp. 1772–1779, 2021. @article{Frey2021, Viewing behavior provides a window into many central aspects of human cognition and health, and it is an important variable of interest or confound in many functional magnetic resonance imaging (fMRI) studies. To make eye tracking freely and widely available for MRI research, we developed DeepMReye, a convolutional neural network (CNN) that decodes gaze position from the magnetic resonance signal of the eyeballs. It performs cameraless eye tracking at subimaging temporal resolution in held-out participants with little training data and across a broad range of scanning protocols. Critically, it works even in existing datasets and when the eyes are closed. Decoded eye movements explain network-wide brain activity also in regions not associated with oculomotor function. This work emphasizes the importance of eye tracking for the interpretation of fMRI results and provides an open source software solution that is widely applicable in research and clinical settings. |
Lee Friedman; Timothy Hanson; Dillon Lohr; Oleg V. Komogortsev Angular offset distributions during fixation are, more often than not, multimodal Journal Article In: Journal of Eye Movement Research, vol. 14, no. 3, pp. 2, 2021. @article{Friedman2021, Typically, the position error of an eye-tracking device is measured as the distance of the eye-position from the target position in two-dimensional space (angular offset). Accuracy is the mean angular offset. The mean is a highly interpretable measure of central tendency if the underlying error distribution is unimodal and normal. However, in the context of an underlying multimodal distribution, the mean is less interpretable. We will present evidence that the majority of such distributions are multimodal. Only 14.7% of fixation angular offset distributions were unimodal, and of these, only 11.5% were normally distributed. (Of the entire dataset, 1.7% were unimodal and normal.) This multimodality is true even if there is only a single, continuous tracking fixation segment per trial. We present several ap-proaches to measure accuracy in the face of multimodality. We also address the role of fixation drift in partially explaining multimodality. |
Lee Friedman; Oleg V. Komogortsev In: Journal of Eye Movement Research, vol. 14, no. 3, pp. 4, 2021. @article{Friedman2021a, This paper is a follow-on to our earlier paper (Friedman, Lohr, Hanson, & Komogortsev, 2021), which focused on the multimodality of angular offsets. This paper applies the same analysis to the measurement of spatial precision. Following the literature, we refer these measurements as estimates of device precision, but, in fact, subject characteristics clearly affect the measurements. One typical measure of the spatial precision of an eye-tracking device is the standard deviation (SD) of the position signals (horizontal and vertical) during a fixation. The SD is a highly interpretable measure of spread if the underlying error distri- bution is unimodal and normal. However, in the context of an underlying multimodal dis- tribution, the SD is less interpretable. We will present evidence that the majority of such distributions are multimodal (68-70% strongly multimodal). Only 21-23% of position dis- tributions were unimodal. We present an alternative method for measuring precision that is appropriate for both unimodal and multimodal distributions. This alternative method pro- duces precision estimates that are substantially smaller than classic measures. We present illustrations of both unimodality and multimodality with either drift or a microsaccade pre- sent during fixation. At present, these observations apply only to the EyeLink 1000, and the subjects evaluated herein. |
Virginia T. Gallagher; Prianka Murthy; Jane Stocks; Brian Vesci; Jeffrey Mjaanes; Yufen Chen; Hans C. Breiter; Cynthia LaBella; Amy A. Herrold; James L. Reilly Eye movements detect differential change after participation in male collegiate collision versus non-collision sports Journal Article In: Neurotrauma Reports, vol. 2, no. 1, pp. 440–452, 2021. @article{Gallagher2021, Although neuroimaging studies of collision (COLL) sport athletes demonstrate alterations in brain structure and function from pre-to post-season, reliable tools to detect behavioral/cognitive change relevant to functional networks associated with participation in collision sports are lacking. This study evaluated the use of eye-movement testing to detect change in cognitive and sensorimotor processing among male club collegiate athletes after one season of participation in collision sports of variable exposure. We predicted that COLL (High Dose [hockey] |
Agostino Gibaldi; Noah C. Benson; Martin S. Banks Crossed–uncrossed projections from primate retina are adapted to disparities of natural scenes Journal Article In: Proceedings of the National Academy of Sciences, vol. 118, no. 7, pp. e2015651118, 2021. @article{Gibaldi2021a, In mammals with frontal eyes, optic-nerve fibers from nasal retina project to the contralateral hemisphere of the brain, and fibers from temporal retina project ipsilaterally. The division between crossed and uncrossed projections occurs at or near the vertical meridian. If the division was precise, a problem would arise. Small objects near midline, but nearer or farther than current fixation, would produce signals that travel to opposite hemispheres, making the binocular disparity of those objects difficult to compute. However, in species that have been studied, the division is not precise. Rather, there are overlapping crossed and uncrossed projections such that some fibers from nasal retina project ipsilaterally as well as contralaterally and some from temporal retina project contralaterally as well as ipsilaterally. This increases the probability that signals from an object near vertical midline travel to the same hemisphere, thereby aiding disparity estimation. We investigated whether there is a deficit in binocular vision near the vertical meridian in humans and found no evidence for one. We also investigated the effectiveness of the observed decussation pattern, quantified from anatomical data in monkeys and humans. We used measurements of naturally occurring disparities in humans to determine disparity distributions across the visual field. We then used those distributions to calculate the probability of natural disparities transmitting to the same hemisphere, thereby aiding disparity computation. We found that the pattern of overlapping projections is quite effective. Thus, crossed and uncrossed projections from the retinas are well designed for aiding disparity estimation and stereopsis. |
Agostino Gibaldi; Silvio P. Sabatini The saccade main sequence revised: A fast and repeatable tool for oculomotor analysis Journal Article In: Behavior Research Methods, vol. 53, no. 1, pp. 167–187, 2021. @article{Gibaldi2021, Saccades are rapid ballistic eye movements that humans make to direct the fovea to an object of interest. Their kinematics is well defined, showing regular relationships between amplitude, duration, and velocity: the saccadic 'main sequence'. Deviations of eye movements from the main sequence can be used as markers of specific neurological disorders. Despite its significance, there is no general methodological consensus for reliable and repeatable measurements of the main sequence. In this work, we propose a novel approach for standard indicators of oculomotor performance. The obtained measurements are characterized by high repeatability, allowing for fine assessments of inter- and intra-subject variability, and inter-ocular differences. The designed experimental procedure is natural and non-fatiguing, thus it is well suited for fragile or non-collaborative subjects like neurological patients and infants. The method has been released as a software toolbox for public use. This framework lays the foundation for a normative dataset of healthy oculomotor performance for the assessment of oculomotor dysfunctions. |
Alexander Goettker Retinal error signals and fluctuations in eye velocity influence oculomotor behavior in subsequent trials Journal Article In: Journal of Vision, vol. 21, no. 1, pp. 1–19, 2021. @article{Goettker2021, The oculomotor system makes use of an integration of previous stimulus velocities (the prior) and current sensory inputs to adjust initial eye speeds. The present study extended this research by investigating the roles of different retinal or extra-retinal signals for this process. To test for this, participants viewed movement sequences that all ended with the same test trial. Earlier in the sequence, the prior was manipulated by presenting targets that either had different velocities, different starting positions, or target movements designed to elicit differential oculomotor behavior (tracked with or without additional corrective saccades). Additionally, these prior targets could vary in terms of contrast to manipulate reliability. When the velocity of prior trials differed from test trials, the reliability-weighted integration of prior information was replicated. When the prior trials differed in starting position, significant effects on subsequent oculomotor behavior were only observed for the reliable target. Although there were also differences in eye velocity across the different manipulations, they could not explain the observed reliability-weighted integration. When comparing the same physical prior trials but tracked with additional corrective saccades, the eye velocity in the test trial also differed systematically (slower for forward saccades, and faster for backward saccades). The direction of the observed effect contradicts the expectations based on perceived speed and eye velocity, but can be predicted by a combination of retinal velocity and position error signals. Together, these results suggest that general fluctuations in eye velocity as well as retinal error signals are related to oculomotor behavior in subsequent trials. |
Doria M. Gold; John-Ross Rizzo; Yuen Shan Christine Lee; Amanda Childs; Todd E. Hudson; John Martone; Yuka K. Matsuzawa; Felicia Fraser; Joseph H. Ricker; Weiwei Dai; Ivan Selesnick; Laura J. Balcer; Steven L. Galetta; Janet C. Rucker King-Devick test performance and cognitive dysfunction after concussion: A pilot eye movement study Journal Article In: Brain Sciences, vol. 11, pp. 1571, 2021. @article{Gold2021, (1) Background: The King-Devick (KD) rapid number naming test is sensitive for concussion diagnosis, with increased test time from baseline as the outcome measure. Eye tracking during KD performance in concussed individuals shows an association between inter-saccadic interval (ISI) (the time between saccades) prolongation and prolonged testing time. This pilot study retrospectively assesses the relation between ISI prolongation during KD testing and cognitive performance in persistently-symptomatic individuals post-concussion. (2) Results: Fourteen participants (median age 34 years; 6 women) with prior neuropsychological assessment and KD testing with eye tracking were included. KD test times (72.6 ± 20.7 s) and median ISI (379.1 ± 199.1 msec) were prolonged compared to published normative values. Greater ISI prolongation was associated with lower scores for processing speed (WAIS-IV Coding |
Henry Griffith; Dillon Lohr; Evgeny Abdulin; Oleg Komogortsev GazeBase, a large-scale, multi-stimulus, longitudinal eye movement dataset Journal Article In: Scientific Data, vol. 8, no. 1, pp. 1–9, 2021. @article{Griffith2021, This manuscript presents GazeBase, a large-scale longitudinal dataset containing 12,334 monocular eye-movement recordings captured from 322 college-aged participants. Participants completed a battery of seven tasks in two contiguous sessions during each round of recording, including a – (1) fixation task, (2) horizontal saccade task, (3) random oblique saccade task, (4) reading task, (5/6) free viewing of cinematic video task, and (7) gaze-driven gaming task. Nine rounds of recording were conducted over a 37 month period, with participants in each subsequent round recruited exclusively from prior rounds. All data was collected using an EyeLink 1000 eye tracker at a 1,000 Hz sampling rate, with a calibration and validation protocol performed before each task to ensure data quality. Due to its large number of participants and longitudinal nature, GazeBase is well suited for exploring research hypotheses in eye movement biometrics, along with other applications applying machine learning to eye movement signal analysis. Classification labels produced by the instrument's real-time parser are provided for a subset of GazeBase, along with pupil area. |
Zhenlan Jin; Ruie Gou; Junjun Zhang; Ling Li The role of frontal pursuit area in interaction between smooth pursuit eye movements and attention: A TMS study Journal Article In: Journal of Vision, vol. 21, no. 3, pp. 1–10, 2021. @article{Jin2021, Close coupling between attention and smooth pursuit eye movements has been widely established and frontal eye field (FEF) is a “hub” region for attention and eye movements. Frontal pursuit area (FPA), a subregion of the FEF, is part of neural circuit for the pursuit, here, we directly checked the role of the FPA in the interaction between the pursuit and attention. To do it, we applied a dual-task paradigm where an attention demanding task was integrated into the pursuit target and interrupted the FPA using transcranial magnetic stimulation (TMS). In the study, participants were required to pursue a moving circle with a letter inside, which changed to another one every 100 ms and report whether “H” (low attentional load) or one of “H,” “S,” or “L” (high attentional load) appeared during the trial. As expected, increasing the attentional load decreased accuracy of the letter detection. Importantly, the FPA TMS had no effect on both the pursuit and letter detection tasks in the low load condition, whereas it reduced 200 to 320 ms gain, but tended to increase the letter detection accuracy in the high load condition. Moreover, individual's FPA TMS effect on pursuit gain |
Kei Kanari; Hirohiko Kaneko Pupil response is modulated with optokinetic nystagmus in transparent motion Journal Article In: Journal of the Optical Society of America A, vol. 38, no. 2, pp. 149–156, 2021. @article{Kanari2021, When two visual patterns moving in opposite directions are superimposed on the same depth plane, they appear to have two transparent surfaces moving independently (transparent motion). Additionally, the direction of the slowphase ofoptokinetic nystagmus (OKN) corresponds to the direction ofmotion that dominates the perceptual appearance. This study examines whether pupil changes correspond to the luminance of the dominated objects related to the transition of the slow-phase direction in OKN following objects. Stimuli consisted oftwo random dot patterns ofdifferent luminance that moved in opposite directions. The results showed that pupil size changed in accordance with the luminance ofthe pattern in the slowphase ofOKNimmediately after OKN transition. This suggests that pupil size is modulated withOKNin transparent motion. |
Kei Kanari; Moe Kikuchi-Ito Estimation of the degree of autism spectrum disorder by the slow phase of optokinetic nystagmus in typical adults Journal Article In: Heliyon, vol. 7, no. 8, pp. e07751, 2021. @article{Kanari2021a, Atypical eye movement patterns demonstrated by individuals with autism spectrum disorder (ASD) have the potential to serve as biomarkers for ASD diagnosis. However, instead of estimating individual differences in the degree of ASD from those patterns, many researchers have compared ASD groups with typical development groups. This study investigates the relationship between the Autism-spectrum Quotient (AQ) scores in typical adults, which can evaluate the degree of the traits associated with ASD, as well as the properties of optokinetic nystagmus (OKN), including the gain of the slow phase, the peak velocity and duration of the fast phase, the frequency, and the mean eye position of OKN. A random dot pattern that moved in one direction was presented on the display, and the participants' eye movements were measured. The results showed a negative correlation between subjects' AQ scores and the gain of slow-phase OKN. In addition, the correlations between subjects' AQ scores and the properties of OKN fast phase were not significant. These results indicate that the gain of slow-phase OKN could be a biomarker that estimates individual differences in the degree of ASD, reflected in our findings which considered AQ scores in typical adults. |
Louise Kauffmann; Sarah Khazaz; Carole Peyrin; Nathalie Guyader Isolated face features are sufficient to elicit ultra-rapid and involuntary orienting responses toward faces Journal Article In: Journal of Vision, vol. 21, no. 2, pp. 1–24, 2021. @article{Kauffmann2021, Previous studies have shown that face stimuli influence the programming of eye movements by eliciting involuntary and extremely fast saccades toward them. The present study examined whether holistic processing of faces mediates these effects.We used a saccadic choice task in which participants were presented simultaneously with two images and had to perform a saccade toward the one containing a target stimulus (e.g., a face). Across three experiments, stimuli were altered via upside-down inversion (Experiment 1) or scrambling of thumbnails within the images (Experiments 2 and 3) in order to disrupt holistic processing.We found that disruption of holistic processing only had a limited impact on the latency of saccades toward face targets, which remained extremely short (minimum saccadic reaction times of only ∼120–130 ms), and did not affect the proportion of error saccades toward face distractors that captured attention more than other distractor categories. It, however, resulted in increasing error rate of saccades toward face targets. These results suggest that the processing of isolated face features is sufficient to elicit extremely fast and involuntary saccadic responses toward them. Holistic representations of faces may, however, be used as a search template to accurately detect faces. |
Brandon Keehn; Girija Kadlaskar; Sophia Bergmann; Rebecca McNally Keehn; Alexander Francis Attentional disengagement and the locus coeruleus – norepinephrine system in children With autism spectrum disorder Journal Article In: Frontiers in Integrative Neuroscience, vol. 15, pp. 716447, 2021. @article{Keehn2021, Background: Differences in non-social attentional functions have been identified as among the earliest features that distinguish infants later diagnosed with autism spectrum disorder (ASD), and may contribute to the emergence of core ASD symptoms. Specifically, slowed attentional disengagement and difficulty reorienting attention have been found across the lifespan in those at risk for, or diagnosed with, ASD. Additionally, the locus coeruleus-norepinephrine (LC-NE) system, which plays a critical role in arousal regulation and selective attention, has been shown to function atypically in ASD. While activity of the LC-NE system is associated with attentional disengagement and reorienting in typically developing (TD) individuals, it has not been determined whether atypical LC-NE activity relates to attentional disengagement impairments observed in ASD. Objective: To examine the relationship between resting pupil diameter (an indirect measure of tonic LC-NE activation) and attentional disengagement in children with ASD. Methods: Participants were 21 school-aged children with ASD and 20 age- and IQ-matched TD children. The study consisted of three separate experiments: a resting eye-tracking task and visual and auditory gap-overlap paradigms. For the resting eye-tracking task, pupil diameter was monitored while participants fixated a central crosshair. In the gap-overlap paradigms, participants were instructed to fixate on a central stimulus and then move their eyes to peripherally presented visual or auditory targets. Saccadic reaction times (SRT), percentage of no-shift trials, and disengagement efficiency were measured. Results: Children with ASD had significantly larger resting pupil size compared to their TD peers. The groups did not differ for overall SRT, nor were there differences in SRT for overlap and gap conditions between groups. However, the ASD group did evidence impairments in disengagement (larger step/gap effects, higher percentage of no-shift trials, and reduced disengagement efficiency) compared to their TD peers. Correlational analyses showed that slower, less efficient disengagement was associated with increased pupil diameter. Conclusion: Consistent with prior reports, children with ASD show significantly larger resting pupil diameter, indicative of atypically elevated tonic LC-NE activity. Associations between pupil size and measures of attentional disengagement suggest that atypically increased tonic activation of the LC-NE system may be associated with poorer attentional disengagement in children with ASD. |
Devin H. Kehoe; Jennifer Lewis; Mazyar Fallah Oculomotor target selection is mediated by complex objects Journal Article In: Journal of Neurophysiology, vol. 126, no. 3, pp. 845–863, 2021. @article{Kehoe2021, Oculomotor target selection often requires discriminating visual features, but it remains unclear how oculomotor substrates encoding saccade vectors functionally contribute to this process. One possibility is that oculomotor vector representations (observed directly as physiological activation or inferred from behavioral interference) of potential targets are continuously reweighted by task relevance computed elsewhere in specialized visual modules, whereas an alternative possibility is that oculomotor modules use local featural analyses to actively discriminate potential targets. Strengthening the former account, oculomotor vector representations have longer onset latencies for ventral- (i.e., color) than dorsal-stream features (i.e., luminance), suggesting that oculomotor vector representations originate from featurally relevant specialized visual modules. Here, we extended this reasoning by behaviorally examining whether the onset latency of saccadic interference elicited by visually complex stimuli is greater than is commonly observed for simple stimuli. We measured human saccade metrics (saccade curvature, endpoint deviations, saccade frequency, and error proportion) as a function of time after abrupt distractor onset. Distractors were novel, visually complex, and had to be discriminated from targets to guide saccades. The earliest saccadic interference latency was ~110 ms, considerably longer than previous experiments, suggesting that sensory representations projected into the oculomotor system are gated to allow for sufficient featural processing to satisfy task demands. Surprisingly, initial oculomotor vector representations encoded features, as we manipulated the visual similarity between targets and distractors and observed increased vector modulation response magnitude and duration when the distractor was highly similar to the target. Oculomotor vector modulation was gradually extinguished over the time course of the experiment. NEW & NOTEWORTHY We challenge the role of the oculomotor system in discriminating features during saccadic target selection. Our data suggest that the onset latency of oculomotor vector representations is scaled by task difficulty and featural complexity, suggesting that featural computations are performed outside of the oculomotor system, which receives the output of these computations only after sufficient visual and cognitive processing. We also challenge the convention that initial oculomotor vector representations are feature invariant, as they encoded task relevance. |
Makoto Kobayashi; Satoshi Kuwabara The association of visually guided saccades and DAT-SPECT findings in Parkinson's disease Journal Article In: European Neurology, vol. 84, no. 2, pp. 110–118, 2021. @article{Kobayashi2021, Background: In individuals with Parkinson's disease (PD), visually guided saccades (VGSs) reportedly reflect general motor dysfunction and cognitive impairments. However, it has not been fully elucidated whether the VGS abnormalities result from nigrostriatal degeneration or other PD-related neural changes. Methods: We measured VGS latency and gain in 50 PD participants and 56 age-matched normal controls (NCs), and PD participants underwent dopamine transporter (DAT) single-photon emission computed tomography (SPECT) within 2 months of the measurement. VGSs were evoked by a white dot on a monitor, which was presented at the center and pseudo-randomly jumped off horizontally (10° or 20° eccentricity) or vertically (10° or 15°). First, we compared the parameters between PD participants and NCs for each target location. Second, in the participants who exhibited striatal DAT asymmetry on SPECT, VGSs contralaterally directed to the more severely affected striatum were compared with those ipsilaterally directed. Third, effects of the DAT-SPECT specific binding ratio (SBR) on VGSs were analyzed. Results: PD participants demonstrated prolonged latencies when the target was presented at the upward 15° eccentricity and decreased gains at all target locations. Contralateral VGSs relative to the side of the more severely affected striatum were more delayed and hypometric than ipsilateral. The SBR had a significant positive effect on VGS gain. Conclusions: In participants with PD, saccadic abnormalities were emphasized when VGSs were directed contralaterally to the more severely affected striatum. Moreover, the dopaminergic nigrostriatal degeneration on DAT-SPECT was mainly associated with VGS gain. |
Helen J. Kuht; Rebecca J. McLean; Abdullah Aamir; Gail D. E. Maconachie; Irene Gottlob; Mervyn G. Thomas Albinism associated with torsional nystagmus masquerading as spasmus nutans Journal Article In: Journal of Neuro-Ophthalmology, pp. 1–3, 2021. @article{Kuht2021, Oculocutaneous albinism (OCA) is a genetically heterogenous disorder caused by disruption to the melanin biosynthesis pathway, affecting approximately 1 in 20,000 individuals worldwide (1). OCA has an autosomal recessive inheritance characterized by reduced pigmentation of the hair, skin, and eyes. Nonsyndromic OCA can be subdivided into 7 main types (OCA1-7), based on the genetic mutation. Ocular characteristics of OCA demonstrate significant phenotypic variability and can include iris transillumination defects (TIDs), fundus hypopigmentation, foveal hypoplasia, and optic nerve decussation defects (1,2). Nystagmus is often associated with OCA; however, it typically demon- strates a conjugate, horizontal, jerk waveform with increasing slow-phase velocities. We describe a rare presentation of intermittent torsional nystagmus in an individual with genetically confirmed OCA, initially masquerading as spasmus. |
Sze Ying Lam; Alexandre Zénon Information rate in humans during visuomotor tracking Journal Article In: Entropy, vol. 23, no. 2, pp. 1–13, 2021. @article{Lam2021, Previous investigations concluded that the human brain's information processing rate remains fundamentally constant, irrespective of task demands. However, their conclusion rested in analyses of simple discrete-choice tasks. The present contribution recasts the question of human information rate within the context of visuomotor tasks, which provides a more ecologically relevant arena, albeit a more complex one. We argue that, while predictable aspects of inputs can be encoded virtually free of charge, real-time information transfer should be identified with the processing of surprises. We formalise this intuition by deriving from first principles a decomposition of the total information shared by inputs and outputs into a feedforward, predictive component and a feedback, error-correcting component. We find that the information measured by the feedback component, a proxy for the brain's information processing rate, scales with the difficulty of the task at hand, in agreement with cost-benefit models of cognitive effort. |
Hsing-Hao Lee; Su-Ling Yeh Blue-light effects on saccadic eye movements and attentional disengagement Journal Article In: Attention, Perception, and Psychophysics, vol. 83, no. 4, pp. 1713–1728, 2021. @article{Lee2021a, People are constantly exposed to high-energy blue light as they spend considerable amounts of time reading and browsing materials on electronic products like computers and cellphones. Recent studies suggest that the stimulation of intrinsically photosensitive retinal ganglion cells (ipRGCs)—a newly discovered type of photoreceptor shown to be particularly sensitive to blue light—activates brain regions related to eye movements and attentional orienting (e.g., frontal eye fields). It remains unclear, however, whether and how blue light affects eye movements and attention behaviorally. We examined this by adopting the gap paradigm in which participants made saccades to a peripheral target as quickly and accurately as possible while the fixation sign vanished (i.e., the gap condition) or remained visible. Participants were exposed to blue and orange light on two separate days. Faster saccade latency under blue light was found across two experiments, and the results indicate that blue light shortened saccade latency when attention and eye movements operate simultaneously. Our findings provide evidence for the blue-light facilitatory effect on eye movements and attentional disengagement, and suggest that blue light can enhance the speed of saccadic eye movements. |
Rebekka Schröder; Philine Margarete Baumert; Ulrich Ettinger Replicability and reliability of the background and target velocity effects in smooth pursuit eye movements Journal Article In: Acta psychologica, vol. 219, pp. 103364, 2021. @article{Schroeder2021, When we follow a slowly moving target with our eyes, we perform smooth pursuit eye movements (SPEM). Previous investigations point to significantly and robustly reduced SPEM performance in the presence of a stationary background and at higher compared to lower target velocities. However, the reliability of these background and target velocity effects has not yet been investigated systematically. To address this issue, 45 healthy participants (17 m, 28 f) took part in two experimental sessions 7 days apart. In each session, participants were instructed to follow a horizontal SPEM target moving sinusoidally between ±7.89° at three different target velocities, corresponding to frequencies of 0.2, 0.4 and 0.6 Hz. Each target velocity was presented once with and once without a stationary background, resulting in six blocks. The blocks were presented twice per session in order to additionally explore potential task length effects. To assess SPEM performance, velocity gain was calculated as the ratio of eye to target velocity. In line with previous research, detrimental background and target velocity effects were replicated robustly in both sessions with large effect sizes. Good to excellent test-retest reliabilities were obtained at higher target velocities and in the presence of a stationary background, whereas lower reliabilities occurred with slower targets and in the absence of background stimuli. Target velocity and background effects resulted in largely good to excellent reliabilities. These findings not only replicated robust experimental effects of background and target velocity at group level, but also revealed that these effects can be translated into reliable individual difference measures. |
Ehsan Sedaghat-Nejad; Reza Shadmehr The cost of correcting for error during sensorimotor adaptation Journal Article In: Proceedings of the National Academy of Sciences, vol. 118, no. 40, pp. e2101717118, 2021. @article{SedaghatNejad2021, Learning from error is often a slow process. In machine learning, the learning rate depends on a loss function that specifies a cost for error. Here, we hypothesized that during motor learning, error carries an implicit cost for the brain because the act of correcting for error consumes time and energy. Thus, if this implicit cost could be increased, it may robustly alter how the brain learns from error. To vary the implicit cost of error, we designed a task that combined saccade adaptation with motion discrimination: movement errors resulted in corrective saccades, but those corrections took time away from acquiring information in the discrimination task. We then modulated error cost using coherence of the discrimination task and found that when error cost was large, pupil diameter increased and the brain learned more from error. However, when error cost was small, the pupil constricted and the brain learned less from the same error. Thus, during sensorimotor adaptation, the act of correcting for error carries an implicit cost for the brain. Modulating this cost affects how much the brain learns from error. |
Janahan Selvanayagam; Kevin D. Johnston; Raymond K. Wong; David Schaeffer; Stefan Everling Ketamine disrupts gaze patterns during face viewing in the common marmoset Journal Article In: Journal of Neurophysiology, vol. 126, no. 1, pp. 330–339, 2021. @article{Selvanayagam2021, Faces are stimuli of critical importance for primates. The common marmoset (Callithrix jacchus) is a promising model for investigations of face processing, as this species possesses oculomotor and face-processing networks resembling those of macaques and humans. Face processing is often disrupted in neuropsychiatric conditions such as schizophrenia (SZ), and thus, it is important to recapitulate underlying circuitry dysfunction preclinically. The N-methyl-D-aspartate (NMDA) noncompetitive antagonist ketamine has been used extensively to model the cognitive symptoms of SZ. Here, we investigated the effects of a subanesthetic dose of ketamine on oculomotor behavior in marmosets during face viewing. Four marmosets received systemic ketamine or saline injections while viewing phase-scrambled or intact videos of conspecifics' faces. To evaluate effects of ketamine on scan paths during face viewing, we identified regions of interest in each face video and classified locations of saccade onsets and landing positions within these areas. A preference for the snout over eye regions was observed following ketamine administration. In addition, regions in which saccades landed could be significantly predicted by saccade onset region in the saline but not the ketamine condition. Effects on saccade control were limited to an increase in saccade peak velocity in all conditions and a reduction in saccade amplitudes during viewing of scrambled videos. Thus, ketamine induced a significant disruption of scan paths during viewing of conspecific faces but limited effects on saccade motor control. These findings support the use of ketamine in marmosets for investigating changes in neural circuits underlying social cognition in neuropsychiatric disorders. NEW & NOTEWORTHY Face processing, an important social cognitive ability, is impaired in neuropsychiatric conditions such as schizophrenia. The highly social common marmoset model presents an opportunity to investigate these impairments. We administered subanesthetic doses of ketamine to marmosets to model the cognitive symptoms of schizophrenia. We observed a disruption of scan paths during viewing of conspecifics' faces. These findings support the use of ketamine in marmosets as a model for investigating social cognition in neuropsychiatric disorders. |
Maria Solé Puig; August Romeo; Hans Supèr Vergence eye movements during figure-ground perception Journal Article In: Consciousness and Cognition, vol. 92, pp. 103138, 2021. @article{SolePuig2021, Figure-ground, that is the segmentation of visual information into objects and their surrounding backgrounds, provides structure for visual attention. Recent evidence shows a novel role of vergence eye movements in visual attention. In the present work, vergence responses during figure-ground segregation tasks are psychophysically investigated. We show that during a figure-ground detection task, subjects convergence their eyes. Vergence eye movements are larger in figure trials than in ground trials. In detected figures trials, vergence are stronger than in trials where the figure went unnoticed. Moreover in figure trials, vergence responses are stronger to low-contrast figures than to high-contrast figures. We argue that these discriminative vergence responses have a role in figure-ground. |
Youngmin Song; Lydia Ouchene; Aarlenne Zein Khan Saccadic adaptation in the presence of artificial central scotomas Journal Article In: Journal of Vision, vol. 21, no. 1, pp. 1–15, 2021. @article{Song2021a, Saccadic adaptation can occur over a short period of time through a constant adjustment of the saccade target during the saccade, resulting in saccadic re-referencing, which directs the saccade to a location different from the target that elicited the saccade. Saccade re-referencing could be used to help patients with age-related macular degeneration to optimally use their residual visual function. However, it remains unknown whether saccade adaptation can take place in the presence of central scotomas (i.e., without central vision).We tested participants in two experiments in a conventional double-step paradigm with a central gaze-contingent artificial scotoma. Experiment 1 (N = 12) comprised a backward adaptation paradigm with no scotoma control, visible, and invisible 3 diameter scotoma conditions. Experiment 2 (N = 13) comprised a forward adaptation paradigm with no scotoma control, invisible 2 , and 4 diameter scotoma conditions. In Experiment 1, we observed significant adaptation in both the visible and invisible scotoma conditions comparable to the control condition with no scotoma. This was the case even when the saccade landed such that the target was occluded by the scotoma.We observed that adaptation occurred based on peripheral viewing of the stepped target during the deceleration period. In Experiment 2, we found that both scotoma conditions showed adaptation again comparable to the control condition with no scotoma. We conclude that saccadic adaptation can occur with central scotomas, showing that it does not require central vision and can be driven primarily by peripheral retinal error. |
Emma Sumner; Samuel B. Hutton; Elisabeth L. Hill Subtle oculomotor difficulties and their relation to motor skill in children with autism spectrum disorder Journal Article In: Advances in Neurodevelopmental Disorders, vol. 5, no. 2, pp. 144–155, 2021. @article{Sumner2021, Objectives: Sensorimotor difficulties are often reported in autism spectrum disorders (ASD). Visual and motor skills are linked in that the processing ofvisual information can help in guiding motor movements. The present study investigated oculomotor skill and its relation to general motor skill in ASD by providing a comprehensive assessment of oculomotor control. Methods: Fifty children (25 ASD; 25 typically developing [TD]), aged 7–10 years, completed a motor assessment (comprising fine and gross motor tasks) and oculomotor battery (comprising fixation, smooth pursuit, prosaccade and antisaccade tasks). Results: No group differences were found for antisaccade errors, nor saccade latencies in prosaccade and antisaccade tasks, but increased saccade amplitude variability was observed in children with ASD, suggesting a reduced consistency in saccade accuracy. Children with ASD also demonstrated poorer fixation stability than their peers and spent less time in pursuit of a moving target. Motor skill was not correlated with saccade amplitude variability. However, regression analyses revealed that motor skill (and not diagnosis) accounted for variance in fixation performance and fast smooth pursuit. Conclusions: The findings highlight the importance of considering oculomotor paradigms to inform the functional impact of neuropathologies in ASD and also assessing the presentation of co-occurring difficulties to further our understanding ofASD. Avenues for future research are suggested. |
Georgia F. Symons; Meaghan Clough; Steven Mutimer; Brendan P. Major; William T. O'Brien; Daniel Costello; Stuart J. McDonald; Zhibin Chen; Owen White; Richelle Mychasiuk; Meng Law; David K. Wright; Terence J. O'Brien; Joanne Fielding; Scott C. Kolbe; Sandy R. Shultz Cognitive ocular motor deficits and white matter damage chronically after sports-related concussion Journal Article In: Brain Communications, vol. 3, no. 3, pp. 1–12, 2021. @article{Symons2021, A history of concussion has been linked to long-term cognitive deficits; however, the neural underpinnings of these abnormalities are poorly understood. This study recruited 26 asymptomatic male Australian footballers with a remote history of concussion (i.e. at least six months since last concussion), and 23 non-collision sport athlete controls with no history of concussion. Participants completed three ocular motor tasks (prosaccade, antisaccade and a cognitively complex switch task) to assess processing speed, inhibitory control and cognitive flexibility, respectively. Diffusion tensor imaging data were acquired using a 3 T MRI scanner, and analysed using tract-based spatial statistics, to investigate white matter abnormalities and how they relate to ocular motor performance. Australian footballers had significantly slower adjusted antisaccade latencies compared to controls (P = 0.035). A significant switch cost (i.e. switch trial error > repeat trial error) was also found on the switch task, with Australian footballers performing increased magnitude of errors on prosaccade switch trials relative to prosaccade repeat trials (P = 0.023). Diffusion tensor imaging analysis found decreased fractional anisotropy, a marker of white matter damage, in major white matter tracts (i.e. corpus callosum, corticospinal tract) in Australian footballers relative to controls. Notably, a larger prosaccade switch cost was significantly related to reduced fractional anisotropy in anterior white matter regions found to connect to the prefrontal cortex (i.e. a key cortical ocular motor centre involved in executive functioning and task switching). Taken together, Australian footballers with a history of concussion have ocular motor deficits indicative of poorer cognitive processing speed and cognitive flexibility, which are related to reduce white matter integrity in regions projecting to important cognitive ocular motor structures. These findings provide novel insights into the neural mechanisms that may underly chronic cognitive impairments in individuals with a history of concussion. |
Junichi Takahashi; Yoji Hirano; Kenichiro Miura; Kentaro Morita; Michiko Fujimoto; Hidenaga Yamamori; Yuka Yasuda; Noriko Kudo; Emiko Shishido; Kosuke Okazaki; Tomoko Shiino; Tomohiro Nakao; Kiyoto Kasai; Ryota Hashimoto; Toshiaki Onitsuka Eye movement abnormalities in major depressive disorder Journal Article In: Frontiers in Psychiatry, vol. 12, pp. 673443, 2021. @article{Takahashi2021, Background: Despite their high lifetime prevalence, major depressive disorder (MDD) is often difficult to diagnose, and there is a need for useful biomarkers for the diagnosis of MDD. Eye movements are considered a non-invasive potential biomarker for the diagnosis of psychiatric disorders such as schizophrenia. However, eye movement deficits in MDD remain unclear. Thus, we evaluated detailed eye movement measurements to validate its usefulness as a biomarker in MDD. Methods: Eye movements were recorded from 37 patients with MDD and 400 healthy controls (HCs) using the same system at five University hospitals. We administered free-viewing, fixation stability, and smooth pursuit tests, and obtained 35 eye movement measurements. We performed analyses of covariance with group as an independent variable and age as a covariate. In 4 out of 35 measurements with significant group-by-age interactions, we evaluated aging effects. Discriminant analysis and receiver operating characteristic (ROC) analysis were conducted. Results: In the free-viewing test, scanpath length was significantly shorter in MDD (p = 4.2 × 10−3). In the smooth pursuit test, duration of saccades was significantly shorter and peak saccade velocity was significantly lower in MDD (p = 3.7 × 10−3 |
Junichi Takahashi; Kenichiro Miura; Kentaro Morita; Michiko Fujimoto; Seiko Miyata; Kosuke Okazaki; Junya Matsumoto; Naomi Hasegawa; Yoji Hirano; Hidenaga Yamamori; Yuka Yasuda; Manabu Makinodan; Kiyoto Kasai; Norio Ozaki; Toshiaki Onitsuka; Ryota Hashimoto Effects of age and sex on eye movement characteristics Journal Article In: Neuropsychopharmacology Reports, vol. 41, no. 2, pp. 152–158, 2021. @article{Takahashi2021a, Abnormal eye movements are often associated with psychiatric disorders. Eye movements are sensorimotor functions of the brain, and aging and sex would affect their characteristics. A precise understanding of normal eye movements is required to distinguish disease-related abnormalities from natural differences associated with aging or sex. To date, there is no multicohort study examining age-related dependency and sex effects of eye movements in healthy, normal individuals using large samples to ensure the robustness and reproducibility of the results. In this study, we aimed to provide findings showing the impact of age and sex on eye movement measures. The present study used eye movement measures of more than seven hundred healthy individuals from three large independent cohorts. We herein evaluated eye movement measures quantified by using a set of standard eye movement tests that have been utilized for the examination of patients with schizophrenia. We assessed the statistical significance of the effects of age and sex and its reproducibility across cohorts. We found that 4-18 out of 35 eye movement measures were significantly correlated with age, depending on the cohort, and that 10 of those, which are related to the fixation and motor control of smooth pursuit and saccades, showed high reproducibility. On the other hand, the effects of sex, if any, were less reproducible. The present results suggest that we should take age into account when we evaluate abnormalities in eye movements. |
Norihiro Takakuwa; Kaoru Isa; Hirotaka Onoe; Jun Takahashi; Tadashi Isa Contribution of the pulvinar and lateral geniculate nucleus to the control of visually guided saccades in blindsight monkeys Journal Article In: Journal of Neuroscience, vol. 41, no. 8, pp. 1755–1768, 2021. @article{Takakuwa2021, After damage to the primary visual cortex (V1), conscious vision is impaired. However, some patients can respond to visual stimuli presented in their lesion-affected visual field using residual visual pathways bypassing V1. This phenomenon is called “blindsight.” Many studies have tried to identify the brain regions responsible for blindsight, and the pulvinar and/or lateral geniculate nucleus (LGN) are suggested to play key roles as the thalamic relay of visual signals. However, there are critical problems regarding these preceding studies in that subjects with different sized lesions and periods of time after lesioning were investigated; furthermore, the ability of blindsight was assessed with different measures. In this study, we used double dissociation to clarify the roles of the pulvinar and LGN by pharmacological inactivation of each region and investigated the effects in a simple task with visually guided saccades (VGSs) using monkeys with a unilateral V1 lesion, by which nearly all of the contralesional visual field was affected. Inactivating either the ipsilesional pulvinar or LGN impaired VGS toward a visual stimulus in the affected field. In contrast, inactivation of the contralesional pulvinar had no clear effect, but inactivation of the contralesional LGN impaired VGS to the intact visual field. These results suggest that the pulvinar and LGN play key roles in performing the simple VGS task after V1 lesioning, and that the visuomotor functions of blindsight monkeys were supported by plastic changes in the visual pathway involving the pulvinar, which emerged after V1 lesioning. |
Ken W. S. Tan; Chris Scholes; Neil W. Roach; Elizabeth M. Haris; Paul V. McGraw Impact of microsaccades on visual shape processing Journal Article In: Journal of neurophysiology, vol. 125, no. 2, pp. 609–619, 2021. @article{Tan2021, Sensitivity to subtle changes in the shape of visual objects has been attributed to the existence of global pooling mechanisms that integrate local form information across space. Although global pooling is typically demonstrated under steady fixation, other work suggests prolonged fixation can lead to a collapse of global structure. Here, we ask whether small ballistic eye movements that naturally occur during periods of fixation affect the global processing of radial frequency (RF) patterns-closed contours created by sinusoidally modulating the radius of a circle. Observers were asked to discriminate the shapes of circular patterns and RF-modulated patterns while fixational eye movements were recorded binocularly at 500 Hz. Microsaccades were detected using a velocity-based algorithm, allowing trials to be sorted according to the relative timing of stimulus and microsaccade onset. Results revealed clear perisaccadic changes in shape discrimination thresholds. Performance was impaired when microsaccades occurred close to stimulus onset, but facilitated when they occurred shortly afterward. In contrast, global integration of shape was unaffected by the timing of microsaccades. These findings suggest that microsaccades alter the discrimination sensitivity to briefly presented shapes but do not disrupt the spatial pooling of local form signals.NEW & NOTEWORTHY Microsaccades cause rapid displacement of visual images during fixation and dramatically alter the perception of basic image features. However, their effect on more complex aspects of visual processing is not well understood. Here, we demonstrate a dissociation in the impact of microsaccades on shape perception. Although overall shape discrimination performance is modulated around the time of microsaccades, the pooling efficiency of global mechanisms that combine local form information across space remains unaffected. |
Benjamin Tari; Mustafa Shirzad; Nicholas A. Badcock; Glen R. Belfry; Matthew Heath ‘Delaying' a saccade: Preparatory phase cortical hemodynamics evince the neural cost of response inhibition Journal Article In: Brain and Cognition, vol. 154, pp. 1–7, 2021. @article{Tari2021, Minimally delayed (MD) saccades require inhibition of a prepotent response until a target is extinguished, and unlike the more extensively studied antisaccade task, do not require the additional cognitive component of vector inversion (i.e., 180° target spatial transposition). Here, participants completed separate blocks of MD and prepotent stimulus-driven saccades (i.e., respond at target onset) while cortical hemodynamics were measured via functional transcranial Doppler ultrasound. MD saccades produced longer and more variable reaction times (RT). In turn, MD and stimulus-driven saccade preparatory phase cortical hemodynamics increased and decreased, respectively, relative to baseline and the two conditions differed from one another throughout the preparatory phase. The longer RTs and increased cortical hemodynamics of MD saccades is taken to evince response complexity and the increased neural activity to accommodate response inhibition. To our knowledge, such findings provide the first work to examine the neural foundations of MD saccades. |
Benjamin Tari; Luc Tremblay; Matthew Heath Visually guided saccades and acoustic distractors: No evidence for the remote distractor effect or global effect Journal Article In: Experimental Brain Research, vol. 239, no. 1, pp. 1–8, 2021. @article{Tari2021b, A remote visual distractor increases saccade reaction time (RT) to a visual target and may reflect the time required to resolve conflict between target- and distractor-related information within a common retinotopic representation in the superior colliculus (SC) (i.e., the remote distractor effect: RDE). Notably, because the SC serves as a sensorimotor interface it is possible that the RDE may be associated with the pairing of an acoustic distractor with a visual target; that is, the conflict related to saccade generation signals may be sensory-independent. To address that issue, we employed a traditional RDE experiment involving a visual target and visual proximal and remote distractors (Experiment 1) and an experiment wherein a visual target was presented with acoustic proximal and remote distractors (Experiment 2). As well, Experiments 1 and 2 employed no-distractor trials. Experiment 1 RTs elicited a reliable RDE, whereas Experiment 2 RTs for proximal and remote distractors were shorter than their no distractor counterparts. Accordingly, findings demonstrate that the RDE is sensory specific and arises from conflicting visual signals within a common retinotopic map. As well, Experiment 2 findings indicate that an acoustic distractor supports an intersensory facilitation that optimizes oculomotor planning. |
Palak Gupta; Sinem Beylergil; Jordan Murray; Jonathan Jacobs; Camilla Kilbane; Aasef G. Shaikh; Fatema F. Ghasia Effects of Parkinson disease on blur-driven and disparity-driven vergence eye movements Journal Article In: Journal of Neuro-Ophthalmology, vol. 41, no. 4, pp. 442–451, 2021. @article{Gupta2021, Synchronous movements of the 2 eyes in the opposite direction, disconjugate movements such as vergence, facilitate depth perception. The vergence eye movements are affected in Parkinson disease (PD). Visual blur (accommodation) and fusion (retinal disparity) are important triggers for the vergence. The neural circuit responsible for blur-driven and disparity-driven vergence is tightly coupled. We investigated the effect of PD on these 2 vergence paradigms. In the experiment involving 14 patients with PD and 6 healthy controls, substantial differences between blur-driven and disparity-driven vergence were found. The gain (ratio of actual vs desired eye movements) was reduced in patients with PD in case of disparity-driven vergence but not in blur-driven vergence. The latency of disparity-driven vergence onset was significantly longer for patients with PD compared with healthy controls. Four strategies were used to drive disparity-driven vergence: a) pure disconjugate vergence, b) conjugate saccadic movements, c) disconjugate vergence followed by saccadic movements, and d) conjugate saccades followed by disconjugate vergence movements. Blur-driven vergence had only 2 strategies: a) conjugate saccades followed by disconjugate vergence and b) conjugate saccadic movements only. The results are consistent with the prediction that PD primarily affects disparity-driven vergence, but there are some effects on the strategies to execute blur-driven vergence. We speculate that the deep cerebellar nuclei and the supraoculomotor area of the midbrain that carry the disparity-driven and blur-driven vergence are affected in PD. It is possible to modulate their function through projections to the subthalamic nuclei. |
Palak Gupta; Sinem Beylergil; Jordan Murray; Camilla Kilbane; Fatema F. Ghasia; Aasef G. Shaikh Computational models to delineate 3D gaze-shift strategies in Parkinson's disease Journal Article In: Journal of Neural Engineering, vol. 18, no. 4, pp. 0460a5, 2021. @article{Gupta2021a, Objective: Parkinson's disease (PD) frequently affects vergence eye movements interfering with the perception of depth and dimensionality critical for mitigating falls. We examined neural strategies that compensate for abnormal vergence and their mechanistic underpinning in PD. Approach: The a priori hypothesis was that impaired vergence is compensated by incorporating rapid eye movements (saccades) to accomplish gaze shifts at different depths. Our experiments examined the hypothesis by simulating biologically plausible computational models of saccade-vergence interactions in PD and validating predictions in the actual patient data. Main results: We found four strategies to accomplish 3D gaze shift; pure vergence eye movements, pure saccadic eye movements, combinations of vergence followed by a saccade, and combination of saccade followed by vergence. The gaze shifting strategy of the two eyes was incongruent in PD. The latency of vergence was prolonged, and it was more so when the saccades preceded the vergence or when the saccades only made 3D gaze shift. Computational models predicted at least two possible mechanisms triggering saccades along with vergence. One is based on the lack of foveal accuracy when the vergence gain is suboptimal. The second mechanism reflects the noise in the gating mechanism, the omnipause neurons, for vergence and saccades. None of the two model predictions alone were completely supported by the patient data. However, a combined model incorporating both abnormal vergence velocity gain and impaired gating accurately simulated the results from PD patients. Significance: The combined strategy is biologically plausible for two reasons: (a) The basal ganglia that is prominently affected in PD projects to the vergence velocity neurons in the midbrain via the cerebellum. The projection directly affects the vergence velocity gain. (b) The basal ganglia, via superior colliculus, influences the pattern of omnipause neuronal activity. Abnormal basal ganglia activity may introduce noise in the omnipause neurons. |
Coralie Hemptinne; Nicolas Deravet; Jean-Jacques Orban de Xivry; Philippe Lefèvre; Demet Yüksel Influence of prior and visual information on eye movements in amblyopic children Journal Article In: Journal of Computational Neuroscience, vol. 49, pp. 333–343, 2021. @article{Hemptinne2021, This study analyzed the characteristics of pursuit and assessed the influence of prior and visual information on eye velocity and saccades in amblyopic and control children, in comparison to adults. Eye movements of 41 children (21 amblyopes and 20 controls) were compared to eye movements of 55 adults (18 amblyopes and 37 controls). Participants were asked to pursue a target moving at a constant velocity. The target was either a ‘standard' target, with a uniform color intensity, or a ‘noisy' target, with blurry edges, to mimic the blurriness of an amblyopic eye. Analysis of pursuit patterns showed that the onset was delayed, and the gain was decreased in control children with a noisy target in comparison to amblyopic or control children with a standard target. Furthermore, a significant effect of prior and visual information on pursuit velocity and saccades was found across all participants. Moreover, the modulation of the effect of visual information on the pursuit velocity by group, that is amblyopes or controls with a standard target, and controls with a noisy target, was more limited in children. In other words, the effect of visual information was higher in control adults with a standard target compared to control children with the same target. However, in the case of a blurry target, either in control participants with a noisy target or in amblyopic participants with a standard target, the effect of visual information was larger in children. |
Peter J. Hills; Martin R. Vasilev; Panarai Ford; Lucy Snell; Emma Whitworth; Tessa Parsons; Rebecca Morisson; Abigail Silveira; Bernhard Angele Sensory gating is related to positive and disorganised schizotypy in contrast to smooth pursuit eye movements and latent inhibition Journal Article In: Neuropsychologia, vol. 161, pp. 107989, 2021. @article{Hills2021a, Since the characteristics and symptoms of both schizophrenia and schizotypy are manifested heterogeneously, it is possible that different endophenotypes and neurophysiological measures (sensory gating and smooth pursuit eye movement errors) represent different clusters of symptoms. Participants (N = 205) underwent a standard conditioned-pairing paradigm to establish their sensory gating ratio, a smooth-pursuit eye-movement task, a latent inhibition task, and completed the Schizotypal Personality Questionnaire. A Multidimensional Scaling analysis revealed that sensory gating was related to positive and disorganised dimensions of schizotypy. Latent inhibition and prepulse inhibition were not related to any dimension of schizotypy. Smooth pursuit eye movement error was unrelated to sensory gating and latent inhibition, but was related to negative dimensions of schizotypy. Our findings suggest that the symptom clusters associated with two main endophenotypes are largely independent. To fully understand symptomology and outcomes of schizotypal traits, the different subtypes of schizotypy (and potentially, schizophrenia) ought to be considered separately rather than together. |
Tzu-Yu Hsu; Jui-Tai Chen; Philip Tseng; Chin-An Wang Role of the frontal eye field in human microsaccade responses: A TMS study Journal Article In: Biological Psychology, vol. 165, pp. 108202, 2021. @article{Hsu2021, Microsaccade is a type of fixational eye movements that is modulated by various sensory and cognitive processes, and impact our visual perception. Although studies in monkeys have demonstrated a functional role for the superior colliculus and frontal eye field (FEF) in controlling microsaccades, our understanding of the neural mechanisms underlying the generation of microsaccades is still limited. By applying continuous theta-burst stimulation (cTBS) over the right FEF and the vertex, we investigated the role of the FEF in generating human microsaccade responses evoked by salient stimuli or by changes in background luminance. We observed higher microsaccade rates prior to target appearance, and larger rebound in microsaccade occurrence following salient stimuli, when disruptive cTBS was applied over FEF compared to vertex stimulation. Moreover, the microsaccade direction modulation after changes in background luminance was disrupted with FEF stimulation. Together, our results constitute the first evidence of FEF modulation in human microsaccade responses. |
Tzu-Yu Hsu; Yu-Fan Hsu; Hsin-Yi Wang; Chin-An Wang Role of the frontal eye field in human pupil and saccade orienting responses Journal Article In: European Journal of Neuroscience, vol. 54, no. 1, pp. 4283–4294, 2021. @article{Hsu2021a, The appearance of a salient stimulus evokes a series of orienting responses including saccades and pupil size to prepare the body for appropriate action. The midbrain superior colliculus (SC) that receives critical control signals from the frontal eye field (FEF) is hypothesized to coordinate all components of orienting. It has shown recently that the FEF, together with the SC, is also importantly involved in the control of pupil size, in addition to its well-documented role in eye movements. Although the role of the FEF in pupil size is demonstrated in monkeys, its role in human pupil responses and the coordination between pupil size and saccades remains to be established. Through applying continuous theta-burst stimulation over the right FEF and vertex, we investigated the role of the FEF in human pupil and saccade responses evoked by a salient stimulus, and the coordination between pupil size and saccades. Our results showed that neither saccade reaction times (SRT) nor pupil responses evoked by salient stimuli were modulated by FEF stimulation. In contrast, the correlation between pupil size and SRTs in the contralateral stimulus condition was diminished with FEF stimulation, but intact with vertex stimulation. Moreover, FEF stimulation effects between saccade and pupil responses associated with salient stimuli correlated across participants. This is the first transcranial magnetic stimulation (TMS) study on the pupil orienting response, and our findings suggest that human FEF was involved in coordinating pupil size and saccades, but not involved in the control of pupil orienting responses. |
Linjing Jiang; Hoi-Chung Leung Errors in visuospatial working memory across space and time Journal Article In: Scientific Reports, vol. 11, pp. 14449, 2021. @article{Jiang2021, Visuospatial working memory (VSWM) involves cortical regions along the dorsal visual pathway, which are topographically organized with respect to the visual space. However, it remains unclear how such functional organization may constrain VSWM behavior across space and time. Here, we systematically mapped VSWM performance across the 2-dimensional (2D) space in various retention intervals in human subjects using the memory-guided and visually guided saccade tasks in two experiments. Relative to visually guided saccades, memory-guided saccades showed significant increases in unsystematic errors, or response variability, with increasing target eccentricity (3°–13° of visual angle). Unsystematic errors also increased with increasing delay (1.5–3 s, Experiment 1; 0.5–5 s, Experiment 2), while there was little or no interaction between delay and eccentricity. Continuous bump attractor modeling suggested neurophysiological and functional organization factors in the increasing unsystematic errors in VSWM across space and time. These findings indicate that: (1) VSWM representation may be limited by the functional topology of the visual pathway for the 2D space; (2) Unsystematic errors may reflect accumulated noise from memory maintenance while systematic errors may originate from non-mnemonic processes such as noisy sensorimotor transformation; (3) There may be independent mechanisms supporting the spatial and temporal processing of VSWM. |
Shin-ichi Tokushige; Shunichi Matsuda; Satomi Inomata-Terada; Masashi Hamada; Yoshikazu Ugawa; Shoji Tsuji; Yasuo Terao Premature saccades: A detailed physiological analysis Journal Article In: Clinical Neurophysiology, vol. 132, no. 1, pp. 63–76, 2021. @article{Tokushige2021, Objective: Premature saccades (PSs) are those made with latencies too short for the direction and amplitude to be specifically programmed. We sought to determine the minimum latency needed to establish accurate direction and amplitude, and observed what occurs when saccades are launched before this minimum latency. Methods: In Experiment 1, 249 normal subjects performed the gap saccade task with horizontal targets. In Experiment 2, 28 normal subjects performed the gap saccade task with the targets placed in eight directions. In Experiment 3, 38 normal subjects, 49 patients with Parkinson's disease (PD), and 10 patients with spinocerebellar degeneration (SCD) performed the gap saccade task with horizontal targets. Results: In Experiment 1, it took 100 ms to accurately establish saccade amplitudes and directions. In Experiment 2, however, the latencies needed for accurate amplitude and direction establishment were both approximately 150 ms. In Experiment 3, the frequencies of PSs in patients with PD and SCD were lower than those of normal subjects. Conclusions: The saccade amplitudes and directions are determined simultaneously, 100–150 ms after target presentation. PSs may result from prediction of the oncoming target direction or latent saccade activities in the superior colliculus. Significance: Saccade direction and amplitude are determined simultaneously. |
Kathryn E. Unruh; Walker S. McKinney; Erin K. Bojanek; Kandace K. Fleming; John A. Sweeney; Matthew W. Mosconi Initial action output and feedback-guided motor behaviors in autism spectrum disorder Journal Article In: Molecular Autism, vol. 12, no. 1, pp. 1–25, 2021. @article{Unruh2021, Background: Sensorimotor issues are common in autism spectrum disorder (ASD), related to core symptoms, and predictive of worse functional outcomes. Deficits in rapid behaviors supported primarily by feedforward mechanisms, and continuous, feedback-guided motor behaviors each have been reported, but the degrees to which they are distinct or co-segregate within individuals and across development are not well understood. Methods: We characterized behaviors that varied in their involvement of feedforward control relative to feedback control across skeletomotor (precision grip force) and oculomotor (saccades) control systems in 109 individuals with ASD and 101 age-matched typically developing controls (range: 5–29 years) including 58 individuals with ASD and 57 controls who completed both grip and saccade tests. Grip force was examined across multiple force (15, 45, and 85% MVC) and visual gain levels (low, medium, high). Maximum grip force also was examined. During grip force tests, reaction time, initial force output accuracy, variability, and entropy were examined. For the saccade test, latency, accuracy, and trial-wise variability of latency and accuracy were examined. Results: Relative to controls, individuals with ASD showed similar accuracy of initial grip force but reduced accuracy of saccadic eye movements specific to older ages of our sample. Force variability was greater in ASD relative to controls, but saccade gain variability (across trials) was not different between groups. Force entropy was reduced in ASD, especially at older ages. We also find reduced grip strength in ASD that was more severe in dominant compared to non-dominant hands. Limitations: Our age-related findings rely on cross-sectional data. Longitudinal studies of sensorimotor behaviors and their associations with ASD symptoms are needed. Conclusions: We identify reduced accuracy of initial motor output in ASD that was specific to the oculomotor system implicating deficient feedforward control that may be mitigated during slower occurring behaviors executed in the periphery. Individuals with ASD showed increased continuous force variability but similar levels of trial-to-trial saccade accuracy variability suggesting that feedback-guided refinement of motor commands is deficient specifically when adjustments occur rapidly during continuous behavior. We also document reduced lateralization of grip strength in ASD implicating atypical hemispheric specialization. |
Jonathan Leeuwen; Artem V. Belopolsky Rapid spatial oculomotor updating across saccades is malleable Journal Article In: Vision Research, vol. 178, pp. 60–69, 2021. @article{Leeuwen2021, The oculomotor system uses a sophisticated updating mechanism to adjust for large retinal displacements which occur with every saccade. Previous studies have shown that updating operates rapidly and starts before saccade is initiated. Here we used saccade adaptation to alter life-long expectations about how a saccade changes the location of an object on the retina. Participants made a sequence of one horizontal and one vertical saccade and ignored an irrelevant distractor. The time-course of oculomotor updating was estimated using saccade curvature of the vertical saccade, relative to the distractor. During the first saccade both saccade targets were shifted on 80% of trials, which induced saccade adaptation (Experiment 1). Critically, since the distractor was left stationary, successful saccade adaptation (e.g., saccade becoming shorter) meant that after the first saccade the distractor appeared in a different hemifield than without adaptation. After adaptation, second saccades curved away only from the newly learned distractor location starting at 80 ms after the first saccade. When on the minority of trials (20%) the targets were not shifted, saccades again first curved away from the newly learned (now empty) location, but then quickly switched to curving away from the life-long learned, visible location. When on some trials the distractor was removed during the first saccade, saccades curved away only from the newly learned (but empty) location (Experiment 2). The results show that updating of locations across saccades is not only fast, but is highly malleable, relying on recently learned sensorimotor contingencies. |
Wieske Zoest; Christoph Huber-Huber; Matthew D. Weaver; Clayton Hickey Strategic distractor suppression improves selective control in human vision Journal Article In: Journal of Neuroscience, vol. 41, no. 33, pp. 7120–7135, 2021. @article{Zoest2021, Our visual environment is complicated, and our cognitive capacity is limited. As a result, we must strategically ignore some stimuli to prioritize others. Common sense suggests that foreknowledge of distractor characteristics, like location or color, might help us ignore these objects. But empirical studies have provided mixed evidence, often showing that knowing about a distractor before it appears counterintuitively leads to its attentional selection. What has looked like strategic distractor suppression in the past is now commonly explained as a product of prior experience and implicit statistical learning, and the long-standing notion the distractor suppression is reflected in a band oscillatory brain activity has been challenged by results appearing to link a to target resolution. Can we strategically, proactively suppress distractors? And, if so, does this involve a? Here, we use the concurrent recording of human EEG and eye movements in optimized experimental designs to identify behavior and brain activity associated with proactive distractor suppression. Results from three experiments show that knowing about distractors before they appear causes a reduction in electrophysiological indices of covert attentional selection of these objects and a reduction in the overt deployment of the eyes to the location of the objects. This control is established before the distractor appears and is predicted by the power of cue-elicited a activity over the visual cortex. Foreknowledge of distractor characteristics therefore leads to improved selective control, and a oscillations in visual cortex reflect the implementation of this strategic, proactive mechanism. |