EyeLink Reading and Language Eye-Tracking Publications
All EyeLink reading and language research publications up until 2023 (with some early 2024s) are listed below by year. You can search the publications using keywords such as Visual World, Comprehension, Speech Production, etc. You can also search for individual author names. If we missed any EyeLink reading or language articles, please email us!
2021 |
Martin R. Vasilev; Victoria I. Adedeji; Calvin Laursen; Marcin Budka; Timothy J. Slattery Do readers use character information when programming return-sweep saccades? Journal Article In: Vision Research, vol. 183, pp. 30–40, 2021. @article{Vasilev2021, Reading saccades that occur within a single line of text are guided by the size of letters. However, readers occasionally need to make longer saccades (known as return-sweeps) that take their eyes from the end of one line of text to the beginning of the next. In this study, we tested whether return-sweep saccades are also guided by font size information and whether this guidance depends on visual acuity of the return-sweep target area. To do this, we manipulated the font size of letters (0.29 vs 0.39° per character) and the length of the first line of text (16 vs 26°). The larger font resulted in return-sweeps that landed further to the right of the line start and in a reduction of under-sweeps compared to the smaller font. This suggests that font size information is used when programming return-sweeps. Return-sweeps in the longer line condition landed further to the right of the line start and the proportion of under-sweeps increased compared to the short line condition. This likely reflects an increase in saccadic undershoot error with the increase in intended saccade size. Critically, there was no interaction between font size and line length. This suggests that when programming return-sweeps, the use of font size information does not depend on visual acuity at the saccade target. Instead, it appears that readers rely on global typographic properties of the text in order to maintain an optimal number of characters to the left of their first fixation on a new line. |
Martin R. Vasilev; Fabrice B. R. Parmentier; Julie A. Kirkby Distraction by auditory novelty during reading: Evidence for disruption in saccade planning, but not saccade execution Journal Article In: Quarterly Journal of Experimental Psychology, vol. 74, no. 5, pp. 826–842, 2021. @article{Vasilev2021a, Novel or unexpected sounds that deviate from an otherwise repetitive sequence of the same sound cause behavioural distraction. Recent work has suggested that distraction also occurs during reading as fixation durations increased when a deviant sound was presented at the fixation onset of words. The present study tested the hypothesis that this increase in fixation durations occurs due to saccadic inhibition. This was done by manipulating the temporal onset of sounds relative to the fixation onset of words in the text. If novel sounds cause saccadic inhibition, they should be more distracting when presented during the second half of fixations when saccade programming usually takes place. Participants read single sentences and heard a 120 ms sound when they fixated five target words in the sentence. On most occasions (p =.9), the same sine wave tone was presented (“standard”), while on the remaining occasions (p =.1) a new sound was presented (“novel”). Critically, sounds were played, on average, either during the first half of the fixation (0 ms delay) or during the second half of the fixation (120 ms delay). Consistent with the saccadic inhibition hypothesis (SIH), novel sounds led to longer fixation durations in the 120 ms compared to the 0 ms delay condition. However, novel sounds did not generally influence the execution of the subsequent saccade. These results suggest that unexpected sounds have a rapid influence on saccade planning, but not saccade execution. |
Lucy Vivash; Kelly L. Bertram; Charles B. Malpas; Cassandra Marotta; Ian H. Harding; Scott Kolbe; Joanne Fielding; Meaghan Clough; Simon J. G. Lewis; Stephen Tisch; Andrew H. Evans; John D. O'Sullivan; Thomas Kimber; David Darby; Leonid Churilov; Meng Law; Christopher M. Hovens; Dennis Velakoulis; Terence J. O'Brien In: BMJ Open, vol. 11, no. 12, pp. 1–9, 2021. @article{Vivash2021, Introduction: Progressive supranuclear palsy (PSP) is a neurodegenerative disorder for which there are currently no disease-modifying therapies. The neuropathology of PSP is associated with the accumulation of hyperphosphorylated tau in the brain. We have previously shown that protein phosphatase 2 activity in the brain is upregulated by sodium selenate, which enhances dephosphorylation. Therefore, the objective of this study is to evaluate the efficacy and safety of sodium selenate as a disease-modifying therapy for PSP. Methods and analysis This will be a multi-site, phase 2b, double-blind, placebo-controlled trial of sodium selenate. 70 patients will be recruited at six Australian academic hospitals and research institutes. Following the confirmation of eligibility at screening, participants will be randomised (1:1) to receive 52 weeks of active treatment (sodium selenate; 15 mg three times a day) or matching placebo. Regular safety and efficacy visits will be completed throughout the study period. The primary study outcome is change in an MRI volume composite (frontal lobe+midbrain–3rd ventricle) over the treatment period. Analysis will be with a general linear model (GLM) with the MRI composite at 52 weeks as the dependent variable, treatment group as an independent variable and baseline MRI composite as a covariate. Secondary outcomes are change in PSP rating scale, clinical global impression of change (clinician) and change in midbrain mean diffusivity. These outcomes will also be analysed with a GLM as above, with the corresponding baseline measure entered as a covariate. Secondary safety and tolerability outcomes are frequency of serious adverse events, frequency of down- titration occurrences and frequency of study discontinuation. Additional, as yet unplanned, exploratory outcomes will include analyses of other imaging, cognitive and biospecimen measures. Ethics and dissemination The study was approved by the Alfred Health Ethics Committee (594/20). Each participant their study partner will provide written informed consent at trial commencement. The results of the study will be presented at national and international conferences and published in peer- reviewed journals. |
Kerri Walter; Peter Bex Cognitive load influences oculomotor behavior in natural scenes Journal Article In: Scientific Reports, vol. 11, pp. 12405, 2021. @article{Walter2021, Cognitive neuroscience researchers have identified relationships between cognitive load and eye movement behavior that are consistent with oculomotor biomarkers for neurological disorders. We develop an adaptive visual search paradigm that manipulates task difficulty and examine the effect of cognitive load on oculomotor behavior in healthy young adults. Participants (N = 30) free-viewed a sequence of 100 natural scenes for 10 s each, while their eye movements were recorded. After each image, participants completed a 4 alternative forced choice task in which they selected a target object from one of the previously viewed scenes, among 3 distracters of the same object type but from alternate scenes. Following two correct responses, the target object was selected from an image increasingly farther back (N-back) in the image stream; following an incorrect response, N decreased by 1. N-back thus quantifies and individualizes cognitive load. The results show that response latencies increased as N-back increased, and pupil diameter increased with N-back, before decreasing at very high N-back. These findings are consistent with previous studies and confirm that this paradigm was successful in actively engaging working memory, and successfully adapts task difficulty to individual subject's skill levels. We hypothesized that oculomotor behavior would covary with cognitive load. We found that as cognitive load increased, there was a significant decrease in the number of fixations and saccades. Furthermore, the total duration of saccades decreased with the number of events, while the total duration of fixations remained constant, suggesting that as cognitive load increased, subjects made fewer, longer fixations. These results suggest that cognitive load can be tracked with an adaptive visual search task, and that oculomotor strategies are affected as a result of greater cognitive demand in healthy adults. |
Chin-An Wang; Douglas P. Munoz Coordination of pupil and saccade responses by the superior colliculus Journal Article In: Journal of Cognitive Neuroscience, vol. 33, no. 5, pp. 1–35, 2021. @article{Wang2021a, The appearance of a salient stimulus evokes saccadic eye movements and pupil dilation as part of the orienting response. Although the role of the superior colliculus (SC) in saccade and pupil dilation has been established separately, whether and how these responses are coordinated remains unknown. The SC also receives global luminance signals from the retina, but whether global luminance modulates saccade and pupil responses coordinated by the SC remains unknown. Here, we used microstimulation to causally determine how the SC coordinates saccade and pupil responses and whether global luminance modulates these responses by varying stimulation frequency and global luminance in male monkeys. Stimulation frequency modulated saccade and pupil responses, with trial-by-trial correlations between the two responses. Global luminance only modulated pupil, but not saccade, responses. Our results demonstrate an integrated role of the SC on coordinating saccade and pupil responses, characterizing luminance independent modulation in the SC, together elucidating the differentiated pathways underlying this behavior. |
Chin-An Wang; Douglas P. Munoz Differentiating global luminance, arousal and cognitive signals on pupil size and microsaccades Journal Article In: European Journal of Neuroscience, vol. 54, no. 10, pp. 7560–7574, 2021. @article{Wang2021, Pupil size reflects a proxy for neural activity associated with global luminance, arousal and cognitive processing. Microsaccades are also modulated by arousal and cognitive processing. Are these effects of arousal and cognitive signals on pupil size and microsaccades coordinated? If so, via what neural mechanisms? We hypothesized that if pupil size and microsaccades are coordinately modulated by these processes, pupil size immediately before microsaccade onset, as an index for ongoing cognitive and arousal processing, should correlate with microsaccade responses during tasks alternating these signals. Here, we examined the relationship between pupil size and microsaccade responses in tasks that included variations in global luminance, arousal and inhibitory control. Higher microsaccade peak velocities correlated with larger pre-microsaccade pupil response related to arousal and inhibitory control signals. In contrast, pupil responses evoked by global luminance signals did not correlate with microsaccade responses. Given the central role of the superior colliculus in microsaccade generation, these results suggest the critical involvement of the superior colliculus to coordinate pupil and microsaccade responses for arousal and inhibitory control modulations, but not for the pupil luminance modulation. |
Chin-An Wang; Kien Trong Nguyen; Chi-Hung Juan Linking pupil size modulated by global luminance and motor preparation to saccade behavior Journal Article In: Neuroscience, vol. 476, pp. 90–101, 2021. @article{Wang2021b, Saccades are rapid eye movements that are used to move the high acuity fovea in a serial manner in the exploration of the visual scene. Stimulus contrast is known to modulate saccade latency and metrics possibly via changing visual activity in the superior colliculus (SC), a midbrain structure causally involved in saccade generation. However, the quality of visual signals should also be modulated by the amount of lights projected onto the retina, which is gated by the size of the pupil. Although absolute pupil size should modulate visual signals and in turn affect saccade responses, research examining this relationship is very limited. Besides, pupil size is associated with motor preparation. However, the role of pupil dilation in saccade metrics remains unexplored. Through varying peripheral background luminance level and target visual contrast in the saccade task, we investigated the role of absolute pupil size and baseline-corrected pupil dilation in saccade latency and metrics. Higher target detection accuracy was obtained with lower background luminance level, and larger absolute pupil diameter correlated with smaller saccade amplitude and higher saccade peak velocities. More interestingly, the comparable modulation between pupil dilation and stimulus contrast was obtained, showing larger pupil dilation (or higher contrast stimuli) correlating with faster saccade latencies, larger amplitude, higher peak velocities, and smaller endpoint deviation. Together, our results demonstrated the influence of absolute pupil size induced by global luminance level and baseline-corrected pupil dilation associated with motor preparation on saccade latency and metrics, implicating the role of the SC in this behavior. |
James R. Williamson; Doug Sturim; Trina Vian; Joseph Lacirignola; Trey E. Shenk; Sophia Yuditskaya; Hrishikesh M. Rao; Thomas M. Talavage; Kristin J. Heaton; Thomas F. Quatieri Using dynamics of eye movements, speech articulation and brain activity to predict and track mTBI screening outcomes Journal Article In: Frontiers in Neurology, vol. 12, pp. 665338, 2021. @article{Williamson2021, Repeated subconcussive blows to the head during sports or other contact activities may have a cumulative and long lasting effect on cognitive functioning. Unobtrusive measurement and tracking of cognitive functioning is needed to enable preventative interventions for people at elevated risk of concussive injury. The focus of the present study is to investigate the potential for using passive measurements of fine motor movements (smooth pursuit eye tracking and read speech) and resting state brain activity (measured using fMRI) to complement existing diagnostic tools, such as the Immediate Post-concussion Assessment and Cognitive Testing (ImPACT), that are used for this purpose. Thirty-one high school American football and soccer athletes were tracked through the course of a sports season. Hypotheses were that (1) measures of complexity of fine motor coordination and of resting state brain activity are predictive of cognitive functioning measured by the ImPACT test, and (2) within-subject changes in these measures over the course of a sports season are predictive of changes in ImPACT scores. The first principal component of the six ImPACT composite scores was used as a latent factor that represents cognitive functioning. This latent factor was positively correlated with four of the ImPACT composites: verbal memory, visual memory, visual motor speed and reaction speed. Strong correlations, ranging between r = 0.26 and r = 0.49, were found between this latent factor and complexity features derived from each sensor modality. Based on a regression model, the complexity features were combined across sensor modalities and used to predict the latent factor on out-of-sample subjects. The predictions correlated with the true latent factor with r = 0.71. Within-subject changes over time were predicted with r = 0.34. These results indicate the potential to predict cognitive performance from passive monitoring of fine motor movements and brain activity, offering initial support for future application in detection of performance deficits associated with subconcussive events. |
Clara Mestre; Harold E. Bedell; Fernando Díaz-Doutón; Jaume Pujol; Josselin Gautier Characteristics of saccades during the near point of convergence test Journal Article In: Vision Research, vol. 187, pp. 27–40, 2021. @article{Mestre2021, The near point of convergence test is widely used to evaluate binocular vision. It assesses the ability of the eyes to converge at short distances. Although the test consists of a pure symmetrical vergence task, small involuntary saccades occur concurrently. The main goal of this study was to analyze saccadic characteristics as a function of vergence demand when testing the near point of convergence. To this purpose, the eye movements of 11 participants were registered with an eye-tracker while they performed the near point of convergence test by following a target that traveled forward and backward on a motorized bench. Saccade amplitude increased and, on average, saccade rate decreased with vergence demand. In general, the direction of the concurrent vergence movement had no significant effect on saccade characteristics. However, each individual subject showed idiosyncratic behavior. Most saccades tended to be corrective in terms of both binocular disparity and individual fixation position errors. In particular, most participants tended to correct the fixation position error of the dominant eye. |
Rakesh Nanjappa; Robert M. McPeek Microsaccades and attention in a high-acuity visual alignment task Journal Article In: Journal of Vision, vol. 21, no. 2, pp. 1–15, 2021. @article{Nanjappa2021, While aiming and shooting, we make tiny eye movements called microsaccades that shift gaze between task-relevant objects within a small region of the visual field. However, in the brief period before pressing the trigger, microsaccades are suppressed. This might be due to the lack of a requirement to shift gaze as the retinal images of the two objects begin to overlap on the fovea. Alternatively, we might actively suppress microsaccades to prevent any disturbances in visual perception caused by microsaccades around the time of their occurrence and their subsequent effect on shooting performance. In this study we looked at microsaccade rates while participants performed a simulated shooting task under two conditions: a normal condition in which they moved their eyes freely, and an eccentric condition in which they maintained gaze on a fixed target while performing the shooting task at 5° eccentricity. As expected, microsaccade rate dropped near the end of the task in the normal viewing condition. However, we also found the same decrease for the eccentric condition in which microsaccades did not shift gaze between the task objects. Microsaccades are also produced in response to shifts in covert attention. To test whether disengagement of covert attention from the eccentric shooting location caused the drop in microsaccade rate, we monitored the location of participants' spatial attention by using a Rapid Serial Visual Presentation (RSVP) task simultaneously at a location opposite to the shooting task. Target letter detection at the RSVP location did not improve during the drop in microsaccade rate, suggesting that covert attention was maintained at the shooting task location.We conclude that in addition to their usual gaze-shifting function, microsaccades during fine-acuity tasks might be modulated by cognitive processes other than spatial attention. |
Jenny A. Nij Bijvank; Esther Sánchez Aliaga; Lisanne J. Balk; Danko Coric; Indran Davagnanam; H. Stevie Tan; Bernard M. J. Uitdehaag; Laurentius J. Rijn; Axel Petzold A model for interrogating the clinico-radiological paradox in multiple sclerosis: Internuclear ophthalmoplegia Journal Article In: European Journal of Neurology, vol. 28, no. 5, pp. 1617–1626, 2021. @article{NijBijvank2021a, Background and purpose: The clinico-radiological paradox in multiple sclerosis (MS) is well recognized, relevant and yet poorly understood. The suitability of an in vivo model for the clinico-radiological paradox was tested, using internuclear ophthalmoplegia (INO) and the medial longitudinal fasciculus (MLF). Methods: In this cross-sectional study lesions of the MLF were rated by an experienced MS neuroradiologist blinded to all other information. The presence of an INO was objectively determined by a validated infrared oculography protocol (DEMoNS). Clinical information, including the National Eye Institute Visual Function Questionnaire, was obtained. Results: This study included 202 patients with MS. The clinico-radiological paradox occurred in 50 patients (25%). This consisted of 45 patients having an INO without an MLF lesion and five patients with an MLF lesion but without an INO. The visual function overall score was related to the presence of an INO (p = 0.016), but not to MLF lesions seen on magnetic resonance imaging (MRI) (p = 0.207). A consensus list of potential causes for the clinico-radiological paradox was compiled and the MRI images were deposited in a repository. Conclusion: This study provides an objective and quantitative model to investigate the clinico-radiological paradox. Our data suggest that pathology of the MLF is more frequently detected and more clinically relevant by infrared oculography than by MLF lesion rating on MRI. |
Marcus Nyström; Diederick C. Niehorster; Richard Andersson; Ignace Hooge The Tobii Pro Spectrum: A useful tool for studying microsaccades? Journal Article In: Behavior Research Methods, vol. 53, no. 1, pp. 335–353, 2021. @article{Nystroem2021, Due to its reported high sampling frequency and precision, the Tobii Pro Spectrum is of potential interest to researchers who want to study small eye movements during fixation. We test how suitable the Tobii Pro Spectrum is for research on microsaccades by computing data-quality measures and common properties of microsaccades and comparing these to the currently most used system in this field: the EyeLink 1000 Plus. Results show that the EyeLink data provide higher RMS precision and microsaccade rates compared with data acquired with the Tobii Pro Spectrum. However, both systems provide microsaccades with similar directions and shapes, as well as rates consistent with previous literature. Data acquired at 1200 Hz with the Tobii Pro Spectrum provide results that are more similar to the EyeLink, compared to data acquired at 600 Hz. We conclude that the Tobii Pro Spectrum is a useful tool for researchers investigating microsaccades. |
Jessie R. Oldham; William P. Meehan; David R. Howell Impaired eye tracking is associated with symptom severity but not dynamic postural control in adolescents following concussion Journal Article In: Journal of Sport and Health Science, vol. 10, no. 2, pp. 138–144, 2021. @article{Oldham2021a, Purpose: The purpose of the study was to (1) examine the relationship between self-reported symptoms and concussion-related eye tracking impairments, and (2) compare gait performance between (a) adolescents with a concussion who have normal eye tracking, (b) adolescents with a concussion who have abnormal eye tracking, and (c) healthy controls. Methods: A total of 30 concussed participants (age: 14.4 ± 2.2 years, mean ± SD, 50% female) and 30 controls (age: 14.2 ± 2.2 years, 47% female) completed eye tracking and gait assessments. The BOX score is a metric of pupillary disconjugacy, with scores <10 classified as normal and ≥10 abnormal. Symptoms were collected using the Post-Concussion Symptom Scale (PCSS), and gait speed was measured with triaxial inertial measurement units. We conducted a linear regression to examine the relationship between PCSS and BOX scores and a two-way mixed effects analysis of variance to examine the effect of group (abnormal BOX, normal BOX, and healthy control) on single- and dual-task gait speed. Results: There was a significant association between total PCSS score and BOX score in the concussion group (β = 0.16 |
Yumie Ono; Takahiro Niida; Yuma Shinomiya; Kenji Suzuki; Naoto Hara; Yasuhiko Azegami; Taeko Sato; Chigusa Mimori; Hideo Shimoizumi Eye-tracker-based evaluation of saccadic deficits in young children with developmental disorders Journal Article In: Advanced Biomedical Engineering, vol. 10, pp. 70–79, 2021. @article{Ono2021, Visually guided saccadic eye movement has been considered a promising screening tool for cognitive function because of its simple and objective nature. However, its application to young children, especially those with developmental disorders, is limited due to the lack of sustained attention required to complete the measurement using the traditional electrophysiological protocol. We have previously reported that saccades can be reliably evaluated in typically developing young children using an eye tracker, which allows non-contact measurement of eye movement with a sufficiently short preparation time. Using the eye tracker system combined with an in-house developed analysis software, we investigated the changes in saccadic behavior between typically developing children (n = 30) and children with developmental disorders (attention-deficit/hyperactivity disorder [ADHD] and autism spectrum disorder [ASD] |
Simon P. Orozco; Scott T. Albert; Reza Shadmehr Adaptive control of movement deceleration during saccades Journal Article In: PLoS Computational Biology, vol. 17, no. 7, pp. e1009176, 2021. @article{Orozco2021, As you read this text, your eyes make saccades that guide your fovea from one word to the next. Accuracy of these movements require the brain to monitor and learn from visual errors. A current model suggests that learning is supported by two different adaptive processes, one fast (high error sensitivity, low retention), and the other slow (low error sensitivity, high retention). Here, we searched for signatures of these hypothesized processes and found that following experience of a visual error, there was an adaptive change in the motor commands of the subsequent saccade. Surprisingly, this adaptation was not uniformly expressed throughout the movement. Rather, after experience of a single error, the adaptive response in the subsequent trial was limited to the deceleration period. After repeated exposure to the same error, the acceleration period commands also adapted, and exhibited resistance to forgetting during set-breaks. In contrast, the deceleration period commands adapted more rapidly, but suffered from poor retention during these same breaks. Statespace models suggested that acceleration and deceleration periods were supported by a shared adaptive state which re-aimed the saccade, as well as two separate processes which resembled a two-state model: one that learned slowly and contributed primarily via acceleration period commands, and another that learned rapidly but contributed primarily via deceleration period commands. |
Abdullah Aamir; Helen J. Kuht; Rebecca J. McLean; Gail D. E. Maconachie; Viral Sheth; Basu Dawar; Ravi Purohit; Nicolas Sylvius; Michael Hisaund; Alina Zubcov-Iwantscheff; Frank A. Proudlock; Irene Gottlob; Mervyn G. Thomas Discordant phenotypes in twins with infantile nystagmus Journal Article In: Scientific Reports, vol. 11, pp. 2826, 2021. @article{Aamir2021, Infantile nystagmus (IN) may result from aetiologies including albinism and FRMD7 mutations. IN has low prevalence, and twins with IN are rare. Whilst discordant presentation has been previously reported for IN, we present for the first time the comprehensive assessment of diagnostically discordant monozygotic twins. From a cohort of over 2000 patients, we identified twins and triplets discordant for nystagmus. Using next-generation sequencing, high-resolution infra-red pupil tracking and optical coherence tomography, we characterised differences in genotype and phenotype. Monozygotic twins (n = 1), dizygotic twins (n = 3) and triplets (n = 1) were included. The monozygotic twins had concordant TYR variants. No causative variants were identified in the triplets. Dizygotic twins had discordant variants in TYR, OCA2 and FRMD7. One unaffected co-twin demonstrated sub-clinical nystagmus. Foveal hypoplasia (FH) was noted in four of five probands. Both co-twins of the monozygotic pair and triplets displayed FH. In three families, at least one parent had FH without nystagmus. FH alone may be insufficient to develop nystagmus. Whilst arrested optokinetic reflex pathway development is implicated in IN, discordant twins raise questions regarding where differences in development have arisen. In unaffected monozygotes therefore, genetic variants may predispose to oculomotor instability, with variable expressivity possibly responsible for the discordance observed. |
Francesca Ales; Luciano Giromini; Lara Warmelink; Megan Polden; Thomas Wilcockson; Claire Kelly; Christina Winters; Alessandro Zennaro; Trevor Crawford An eye tracking study on feigned schizophrenia Journal Article In: Psychological Injury and Law, vol. 14, no. 3, pp. 213–226, 2021. @article{Ales2021, Research on malingering detection has not yet taken full advantage of eye tracking technology. In particular, while several studies indicate that patients with schizophrenia behave notably differently from controls on specific oculomotor tasks, no study has yet investigated whether experimental participants instructed to feign could reproduce those behaviors, if coached to do so. Due to the automatic nature of eye movements, we anticipated that eye tracking analyses would help detect feigned schizophrenic problems. To test this hypothesis, we recorded the eye movements of 83 adult UK volunteers, and tested whether eye movements of healthy volunteers instructed to feign schizophrenia (n = 43) would differ from those of honest controls (n = 40), while engaging in smooth pursuit and pro- and anti-saccade tasks. Additionally, results from our investigation were also compared against previously published data observed in patients with schizophrenia performing similar oculomotor tasks. Data analysis showed that eye movements of experimental participants instructed to feign (a) only partially differed from those of controls and (b) did not closely resemble those from patients with schizophrenia reported in previously published papers. Taken together, these results suggest that examination of eye movements does have the potential to help detecting feigned schizophrenia. |
Robert G. Alexander; Ashwin Venkatakrishnan; Jordi Chanovas; Stephen L. Macknik; Susana Martinez-Conde Microsaccades mediate perceptual alternations in Monet's “Impression, sunrise” Journal Article In: Scientific Reports, vol. 11, pp. 3612, 2021. @article{Alexander2021a, Troxler fading, the perceptual disappearance of stationary images upon sustained fixation, is common for objects with equivalent luminance to that of the background. Previous work showed that variations in microsaccadic rates underlie the perceptual vanishing and intensification of simple stimuli, such as Gabor patches. Here, we demonstrate that microsaccade dynamics also contribute to Troxler fading and intensification during the viewing of representational art. Participants fixated a small spot while viewing either a Gabor patch on a blank background, or Monet's painting “Impression, Sunrise.” They continuously reported, via button press/release, whether the Gabor patch, or the sun in Monet's painting, was fading versus intensifying, while their eye movements were recorded with high precision. Microsaccade rates peaked before reports of increased visibility, and dropped before reports of decreased visibility or fading, both when viewing Gabor patches and Monet's sun. These results reveal that the relationship between microsaccade production and the reversal and prevention of Troxler fading applies not only to the viewing of contrived stimuli, but also to the observation of “Impression, Sunrise.” Whether or not perceptual fading was consciously intended by Monet, our findings indicate that observers' oculomotor dynamics are a contributor to the cornerstone of Impressionism. |
Tara L. Alvarez; Mitchell Scheiman; Cristian Morales; Suril Gohel; Ayushi Sangoi; Elio M. Santos; Chang Yaramothu; John Vito D'Antonio-Bertagnolli; Xiaobo Li; Bharat B. Biswal Underlying neurological mechanisms associated with symptomatic convergence insufficiency Journal Article In: Scientific Reports, vol. 11, pp. 6545, 2021. @article{Alvarez2021, Convergence insufficiency (CI) is the most common binocular vision problem, associated with blurred/double vision, headaches, and sore eyes that are exacerbated when doing prolonged near work, such as reading. The Convergence Insufficiency Neuro-mechanism Adult Population Study (NCT03593031) investigates the mechanistic neural differences between 50 binocularly normal controls (BNC) and 50 symptomatic CI participants by examining the fast and slow fusional disparity vergence systems. The fast fusional system is preprogrammed and is assessed with convergence peak velocity. The slow fusional system optimizes vergence effort and is assessed by measuring the phoria adaptation magnitude and rate. For the fast fusional system, significant differences are observed between the BNC and CI groups for convergence peak velocity, final position amplitude, and functional imaging activity within the secondary visual cortex, right cuneus, and oculomotor vermis. For the slow fusional system, the phoria adaptation magnitude and rate, and the medial cuneus functional activity, are significantly different between the groups. Significant correlations are observed between vergence peak velocity and right cuneus functional activity (p = 0.002) and the rate of phoria adaptation and medial cuneus functional activity (p = 0.02). These results map the brain-behavior of vergence. Future therapeutic interventions may consider implementing procedures that increase cuneus activity for this debilitating disorder. |
Inbar Avni; Gal Meiri; Analya Michaelovski; Idan Menashe; Lior Shmuelof; Ilan Dinstein Basic oculomotor function is similar in young children with ASD and typically developing controls Journal Article In: Autism Research, vol. 14, no. 12, pp. 2580–2591, 2021. @article{Avni2021, A variety of eye tracking studies have demonstrated that young children with ASD gaze at images and movies of social interactions differently than typically developing children. These findings have supported the hypothesis that gaze behavior differences are generated by a weaker preference for social stimuli in ASD children. The hypothesis assumes that gaze differences are not caused by abnormalities in oculomotor function including saccade frequency and kinematics. Previous studies of oculomotor function have mostly been performed with school-age children, adolescents, and adults using visual search, anti-saccade, and gap saccade tasks that are less suitable for young pre-school children. Here, we examined oculomotor function in 144 children (90 with ASD and 54 controls), 1–10-years-old, as they watched two animated movies interleaved with the presentation of multiple salient stimuli that elicited saccades-to-targets. The results revealed that the number of fixations, fixation duration, number of saccades, saccade duration, saccade accuracy, and saccade latency did not differ significantly across groups. Minor initial differences in saccade peak velocity were not supported by analysis with a linear mixed model. These findings suggest that most children with ASD exhibit similar oculomotor function to that of controls, when performing saccades-to-targets or freely viewing child-friendly movies. This suggests that previously reported gaze abnormalities in children with ASD are not due to underlying oculomotor deficiencies. Lay Summary: This study demonstrates that children with ASD perform similar eye movements to those of controls when freely observing movies or making eye movements to targets. Similar results were apparent across groups in the number of eye movements, their accuracy, duration, and other measures that assess eye movement control. These findings are important for interpreting previously reported differences in gaze behavior of children with ASD, which are likely due to atypical social preferences rather than impaired control of eye movements. |
Naila Ayala; Ewa Niechwiej-Szwedo Effects of blocked vs. interleaved administration mode on saccade preparatory set revealed using pupillometry Journal Article In: Experimental Brain Research, vol. 239, no. 1, pp. 245–255, 2021. @article{Ayala2021a, Eye movements have been used extensively to assess information processing and cognitive function. However, significant variability in saccade performance has been observed, which could arise from methodological variations across different studies. For example, prosaccades and antisaccades have been studied using either a blocked or interleaved design, which has a significant influence on error rates and latency. This is problematic as it makes it difficult to compare saccade performance across studies and may limit the ability to use saccades as a behavioural assay to assess neurocognitive function. Thus, the current study examined how administration mode influences saccade related preparatory activity by employing pupil size as a non-invasive proxy for neural activity related to saccade planning and execution. Saccade performance and pupil dynamics were examined in eleven participants as they completed pro- and antisaccades in blocked and interleaved paradigms. Results showed that administration mode significantly modulated saccade performance and preparatory activity. Reaction times were longer for both pro- and antisaccades in the interleaved condition, compared to the blocked condition (p < 0.05). Prosaccade pupil dilations were larger in the interleaved condition (p < 0.05), while antisaccade pupil dilations did not significantly differ between administration modes. Additionally, ROC analysis provided preliminary evidence that pupil size can effectively predict saccade directional errors prior to saccade onset. We propose that task-evoked pupil dilations reflect an increase in preparatory activity for prosaccades and the corresponding cognitive demands associated with interleaved administration mode. Overall, the results highlight the importance that administration mode plays in the design of neurocognitive tasks. |
Reza Azadi; Elizabeth Y. Zhu; Robert M. McPeek Modulation of saccade trajectories during sequential saccades Journal Article In: Journal of Neurophysiology, vol. 125, no. 3, pp. 796–804, 2021. @article{Azadi2021, The planning and execution of sequential saccades can overlap in time, and abrupt changes in neural activity in the oculomotor system can alter the normal trajectory of saccades. In this study, we analyzed saccade trajectories to assess the combined programming of sequential saccades. In two separate psychophysical experiments, subjects were instructed to make a sequence of two saccades. The results showed modulation of saccade curvature by the direction and amplitude of both the preceding and following saccade: saccade curvature is modulated in the direction of preceding saccades and away from the direction of following saccades. Moreover, larger preceding and following saccades have stronger effects on curvature. These results support the idea that sequential saccades are programmed concurrently. Finally, the amount of saccade curvature is correlated with the deviation of saccade start and end points, and the time of maximum deviation of saccade trajectories is highly consistent in both experiments. Based on this, we propose a novel benefit for the modulation of saccade trajectories by the oculomotor system: minimizing the saccadic error in sequential saccades.NEW & NOTEWORTHY We show that in saccade sequences, saccade trajectory is modulated in the direction of the preceding saccade and away from the following saccade. The magnitude of this effect is correlated with preceding and following saccade amplitude. This confirms that programming of sequential saccades overlaps. Curvature is also correlated with the deviation of saccade start and end points. Thus, we propose a novel benefit for the modulation of saccade trajectories: minimizing end point error in sequential saccades. |
Shonraj Ballae Ganeshrao; Amina Jaleel; Srija Madicharla; Vanga Kavya Sri; Juwariah Zakir; Chandra S. Garudadri; Sirisha Senthil Comparison of saccadic eye movements among the high-tension glaucoma, primary angle-closure glaucoma, and normal-tension glaucoma Journal Article In: Journal of Glaucoma, vol. 30, no. 3, pp. e76–e82, 2021. @article{BallaeGaneshrao2021, Précis:Saccadic eye movements were compared between high-tension glaucoma (HTG), normal-tension glaucoma (NTG), and primary angle-closure glaucoma (PACG). Saccades were differently affected between the subtypes of primary glaucoma.Aim:The aim of the study was to compare saccadic eye movements in eyes with HTG, PACG, and NTG.Methods:Saccadic eye movements were recorded using the eye tracker Eyelink-1000 in 52 participants: 15 HTG, 14 PACG, 8 NTG, and 15 normal controls. All participants underwent a complete ophthalmic and visual field examination. Prosaccades were measured using the gap paradigm. Prosaccades were measured at 3 target eccentricities (5-, 7-, and 10-degree eccentricity). All prosaccade targets were projected outside the area of visual field defect. Saccade latency, average and peak velocity, and amplitude difference of the saccades were compared between glaucoma subtypes.Results:The mean±SD age was lesser in controls compared with glaucoma (P=0.02). The mean age in all the glaucoma subtypes was comparable (P=0.92). The average mean deviation in PACG (-16.66±6.69 dB) was worse (P=0.01) than in HTG (-11.56±6.08 dB) and NTG (-9.55±3.96 dB). The latencies were delayed, average and peak velocities were reduced, and saccades were hypometric in glaucoma compared with controls (P<0.01). Between subtypes, the differences in latency (P<0.01), peak velocity (P=0.02), and amplitude (P=0.02) were significant. Saccadic eye movements were significantly different in NTG compared with other glaucoma subtypes (post hoc analysis; latency (HTG vs. NTG; P<0.01, HTG vs. PACG; P=0.01), peak velocity (HTG vs. NTG; P=0.02) and amplitude difference (HTG vs. NTG; P=0.02).Conclusions:Saccadic eye movement parameters were differently affected among the glaucoma subtypes. Saccadic parameters were more affected in NTG. |
Sonia Bansal; Wilsaan M. Joiner Transsaccadic visual perception of foveal compared to peripheral environmental changes Journal Article In: Journal of Vision, vol. 21, no. 6, pp. 1–21, 2021. @article{Bansal2021, The maintenance of stable visual perception across eye movements is hypothesized to be aided by extraretinal information (e.g., corollary discharge [CD]). Previous studies have focused on the benefits of this information for perception at the fovea. However, there is little information on the extent that CD benefits peripheral visual perception. Here we systematically examined the extent that CD supports the ability to perceive transsaccadic changes at the fovea compared to peripheral changes. Human subjects made saccades to targets positioned at different amplitudes (4° or 8°) and directions (rightward or upward). On each trial there was a reference point located either at (fovea) or 4° away (periphery) from the target. During the saccade the target and reference disappeared and, after a blank period, the reference reappeared at a shifted location. Subjects reported the perceived shift direction, and we determined the perceptual threshold for detection and estimate of the reference location. We also simulated the detection and location if subjects solely relied on the visual error of the shifted reference experienced after the saccade. The comparison of the reference location under these two conditions showed that overall the perceptual estimate was approximately 53% more accurate and 30% less variable than estimates based solely on visual information at the fovea. These values for peripheral shifts were consistently lower than that at the fovea: 34% more accurate and 9% less variable. Overall, the results suggest that CD information does support stable visual perception in the periphery, but is consistently less beneficial compared to the fovea. |
Chama Belkhiria; Vsevolod Peysakhovich EOG metrics for cognitive workload detection Journal Article In: Procedia Computer Science, vol. 192, pp. 1875–1884, 2021. @article{Belkhiria2021, Increasing workload is a central notion in human factors research that can decrease the performance and yield accidents. Thus, it is crucial to understand the impact of different internal operator's factors including eye movements, memory and audio-visual integration. Here, we explored the relationship between cognitive workload (low vs. high) and eye movements (saccades, fixations and smooth pursuit). The task difficulty was induced by auditory noise, arithmetical count and working memory load. We estimated cognitive workload using EOG and EEG-based mental state monitoring. One novelty consists in recording the EOG around the ears (alternative EOG) and around the eyes (conventional EOG). The number of blinks and saccades amplitude increased along with the difficulty increase (p ≤ 0.05). We found significant correlations between EOG and EEG (theta/alpha ratio) and between conventional and alternative EOG signal. The increase in cognitive load may disturb the coding and maintenance of related visual information. Alternative EOG metrics could be a valuable tool for detecting workload. |
Katharina Bey; Julia V. Lippold; Behrem Aslan; René Hurlemann; Ulrich Ettinger Effects of lorazepam on prosaccades and saccadic adaptation Journal Article In: Journal of Psychopharmacology, vol. 35, no. 1, pp. 91–99, 2021. @article{Bey2021, Background: Benzodiazepines have reliable adverse effects on saccadic eye movements, but the impact of sex as a potential modulator of these effects is less clear. A recent study reported stronger adverse effects on the spatial consistency of saccades in females, which may reflect sex differences in cerebellar mechanisms. Aims: We aimed to further examine the role of sex as a potential modulator of benzodiazepine effects by employing the saccadic adaptation paradigm, which is known to be sensitive to cerebellar functioning. Methods: A total of n=50 healthy adults performed a horizontal step prosaccade task and a saccadic adaptation task under 0.5 mg lorazepam, 1 mg lorazepam and placebo in a double-blind, within-subjects design. Results: In the prosaccade task, lorazepam had adverse effects on measures of peak velocity, latency and spatial consistency. The administration of 0.5 mg lorazepam led to significant reductions in gain-decrease adaptation, while a dose of 1 mg did not impair adaptation learning. Gain-increase adaptation was generally less pronounced, and unaffected by the drug. There were no significant drug×sex interactions in either task. Conclusions: We conclude that a low dose of lorazepam impairs gain-decrease adaptation independent of sex. At higher doses, however, increasing fatigue may facilitate adaptation and thus counteract the adverse effects observed at lower doses. With regards to prosaccades, our findings confirm peak velocity as well as latency and spatial measures as sensitive biomarkers of GABAergic effects. |
Sinem Balta Beylergil; Jordan Murray; Angela M. Noecker; Palak Gupta; Camilla Kilbane; Cameron C. McIntyre; Aasef G. Shaikh; Fatema F. Ghasia Effects of subthalamic deep brain stimulation on fixational eye movements in Parkinson's disease Journal Article In: Journal of Computational Neuroscience, vol. 49, no. 3, pp. 345–356, 2021. @article{Beylergil2021, Miniature yoked eye movements, fixational saccades, are critical to counteract visual fading. Fixational saccades are followed by a return saccades forming squarewaves. Present in healthy states, squarewaves, if too many or too big, affect visual stability. Parkinson's disease (PD), where visual deficits are not uncommon, is associated with the squarewaves that are excessive in number or size. Our working hypothesis is that the basal ganglia are at the epicenter of the abnormal fixational saccades and squarewaves in PD; the effects are manifested through their connections to the superior colliculus (affecting saccade frequency and amplitude) and the cerebellum (affecting velocity and amplitude). We predict that the subthalamic deep brain stimulation (DBS) variably affects the amplitude, frequency, and velocity of fixational saccade and that the effect depends on the electrode's proximity or the volume of activated tissue in the subthalamic nucleus' connections with the superior colliculus or the cerebellum. We found that DBS modulated saccade amplitude, frequency, and velocity in 11 PD patients. Although all three parameters were affected, the extent of the effects varied amongst subjects. The modulation was dependent upon the location and size of the electrically activated volume of the subthalamic region. |
Stephan G. Bodkin; Jay Hertel; Joseph M. Hart Gaze accuracy differences during single-leg balance following anterior cruciate ligament reconstruction Journal Article In: Journal of Sport Rehabilitation, vol. 30, no. 5, pp. 1–7, 2021. @article{Bodkin2021, Context: Individuals following anterior cruciate ligament reconstruction (ACLR) demonstrate altered postural stability and functional movement patterns. It is hypothesized that individuals following ACLR may compensate with sensory adaptations with greater reliance on visual mechanisms during activities. It is unknown if visual compensatory strategies are implemented to maintain postural stability during functional tasks. Objective: To examine visual gaze accuracy during a single-leg balance task in individuals following ACLR compared with healthy, active controls. Design: Case control. Setting: Controlled laboratory. Participants: A total of 20 individuals (10 ACLR and 10 healthy controls) participated in the study. Data Collection and Analysis: Visual gaze patterns were obtained during 20-second single-leg balance trials while participants were instructed to look at presented targets. During the Stationary Target Task, the visual target was presented in a central location for the duration of the trial. The Moving Target Task included a visual target that randomly moved to 1 of 9 target locations for a period of 2 seconds. Targets were stratified into superior, middle, and inferior levels for the Moving Target Task. Results: The Stationary Target Task demonstrated no differences in visual error between groups (P = .89). The Moving Target Task demonstrated a significant interaction between group and target level (F2 |
Claudia Bonmassar; Francesco Pavani; Alessio Di Renzo; Maria Cristina Caselli; Wieske Zoest Eye-movement patterns to social and non-social cues in early deaf adults Journal Article In: Quarterly Journal of Experimental Psychology, vol. 74, no. 6, pp. 1021–1036, 2021. @article{Bonmassar2021, Previous research on covert orienting to the periphery suggested that early profound deaf adults were less susceptible to uninformative gaze-cues, though were equally or more affected by non-social arrow-cues. The aim of this work was to investigate whether spontaneous eye movement behaviour helps explain the reduced impact of the social cue in deaf adults. We tracked the gaze of 25 early profound deaf and 25 age-matched hearing observers performing a peripheral discrimination task with uninformative central cues (gaze vs arrow), stimulus-onset asynchrony (250 vs 750 ms), and cue validity (valid vs invalid) as within-subject factors. In both groups, the cue effect on reaction time (RT) was comparable for the two cues, although deaf observers responded significantly slower than hearing controls. While deaf and hearing observers' eye movement pattern looked similar when the cue was presented in isolation, deaf participants made significantly more eye movements than hearing controls once the discrimination target appeared. Notably, further analysis of eye movements in the deaf group revealed that independent of the cue type, cue validity affected saccade landing position, while latency was not modulated by these factors. Saccade landing position was also strongly related to the magnitude of the validity effect on RT, such that the greater the difference in saccade landing position between invalid and valid trials, the greater the difference in manual RT between invalid and valid trials. This work suggests that the contribution of overt selection in central cueing of attention is more prominent in deaf adults and helps determine the manual performance, irrespective of the cue type. |
Mareike Brych; Supriya Murali; Barbara Händel The role of blinks, microsaccades and their retinal consequences in bistable motion perception Journal Article In: Frontiers in Psychology, vol. 12, pp. 647256, 2021. @article{Brych2021, Eye-related movements such as blinks and microsaccades are modulated during bistable perceptual tasks. However, if they play an active role during internal perceptual switches is not known. We conducted two experiments involving an ambiguous plaid stimulus, wherein participants were asked to continuously report their percept, which could consist of either unidirectional coherent or bidirectional component movement. Our main results show that blinks and microsaccades did not facilitate perceptual switches. On the contrary, a reduction in eye movements preceded the perceptual switch. Blanks, on the other hand, thought to mimic the retinal consequences of a blink, consistently led to a switch. Through the timing of the blank-introduced perceptual change, we were able to estimate the delay between the internal switch and the response. This delay further allowed us to evaluate that the reduction in blink probability co-occurred with the internal perceptual switch. Additionally, our results indicate that distinct internal processes underlie the switch to coherent vs. component percept. Blanks exclusively facilitated a switch to the coherent percept, and only the switch to coherent percept was followed by an increase in blink rate. In a second study, we largely replicated the findings and included a microsaccade analysis. Microsaccades only showed a weak relation with perceptual switches, but their direction was correlated with the perceived motion direction. Nevertheless, our data suggests an interaction between microsaccades and blinks by showing that microsaccades were differently modulated around blinks compared with blanks. This study shows that a reduction in eye movements precedes internal perceptual switches indicating that the rate of blinks can set the stage for a reinterpretation of sensory input. While a perceptual switch based on changed sensory input usually leads to an increase in blink rate, such an increase was only present after the perceptual switch to coherent motion but absent after the switch to component percept. This provides evidence of different underlying mechanism or internal consequence of the two perceptual switches and suggests that blinks can uncover differences in internal percept-related processes that are not evident from the percept itself. |
Xiaoxiao Cai; Zidong Chen; Yanping Liu; Daming Deng; Minbin Yu A dichoptic optokinetic nystagmus paradigm for interocular suppression quantification in intermittent exotropia Journal Article In: Frontiers in Neuroscience, vol. 15, pp. 772341, 2021. @article{Cai2021, Purposes: To investigate the effectiveness of a dichoptic optokinetic nystagmus (dOKN) test to objectively quantify interocular suppression in intermittent exotropia (IXT) patients during the states of orthotropia and exodeviation. Methods: The OKN motion in subjects (15 controls and 59 IXT subjects) who viewed dichoptic oppositely moving gratings with different contrast ratios was monitored and recorded by an eye tracker. Interocular suppression in control subjects was induced using neutral density (ND) filters. The OKN direction ratios were fitted to examine the changes of interocular suppression in subjects under different viewing states. Two established interocular suppression tests (phase and motion) were conducted for a comparative study. Results: The dOKN test, which requires a minimal response from subjects, could accurately quantify the interocular suppression in both IXT and control subjects, which is in line with the established interocular suppression tests. Overall, although comparative, the strength of interocular suppression detected by the dOKN test (0.171 ± 0.088) was stronger than those of the phase (0.293 ± 0.081) and the motion tests (0.212 ± 0.068) in the control subjects with 1.5 ND filters. In IXT patients, when their eyes kept aligned, the dOKN test (0.58 ± 0.09) measured deeper visual suppression compared with the phase (0.73 ± 0.17) or the motion test (0.65 ± 0.14). Interestingly, strong interocular suppression (dOKN: 0.15 ± 0.12) was observed in IXT subjects during the periods of exodeviation, irrespective of their binocular visual function as measured by synoptophore. Conclusion: The dOKN test provides efficient and objective quantification of interocular suppression in IXT, and demonstrates how it fluctuates under different eye positions. |
Matan Cain; Yehudit Botschko; Mati Joshua Passive motor learning: Oculomotor adaptation in the absence of behavioral errors Journal Article In: eNeuro, vol. 8, no. 2, pp. 1–12, 2021. @article{Cain2021, Motor adaptation is commonly thought to be a trial-and-error process in which the accuracy of movement improves with repetition of behavior. We challenged this view by testing whether erroneous movements are necessary for motor adaptation. In the eye movement system, the association between movements and errors can be disentangled, since errors in the predicted stimulus trajectory can be perceived even without movements. We modified a smooth pursuit eye movement adaptation paradigm in which monkeys learn to make an eye movement that predicts an upcoming change in target direction. We trained the monkeys to fixate on a target while covertly, an additional target initially moved in one direction and then changed direction after 250 ms. The monkeys showed a learned response to infre-quent probe trials in which they were instructed to follow the moving target. Additional experiments confirmed that probing learning or residual eye movements during fixation did not drive learning. These results show that motor adaptation can be elicited in the absence of movement and provide an animal model for studying the implementation of passive motor learning. Current models assume that the interaction between movement and error signals underlies adaptive motor learning. Our results point to other mechanisms that may drive learning in the absence of movement. |
Valeria C. Caruso; Daniel S. Pages; Marc A. Sommer; Jennifer M. Groh In: Journal of Neurophysiology, vol. 126, pp. 82–94, 2021. @article{Caruso2021, Stimulus locations are detected differently by different sensory systems, but ultimately they yield similar percepts and behavioral responses. How the brain transcends initial differences to compute similar codes is unclear. We quantitatively compared the reference frames of two sensory modalities, vision and audition, across three interconnected brain areas involved in generating saccades, namely the frontal eye fields (FEF), lateral and medial parietal cortex (LIP/MIP), and superior colliculus (SC). We recorded from single neurons in head-restrained monkeys performing auditory- and visually-guided saccades from variable initial fixation locations, and evaluated whether their receptive fields were better described as eye-centered, head-centered, or hybrid (i.e. not anchored uniquely to head- or eye-orientation). We found a progression of reference frames across areas and across time, with considerable hybrid-ness and persistent differences between modalities during most epochs/brain regions. For both modalities, the SC was more eye-centered than the FEF, which in turn was more eye-centered than the predominantly hybrid LIP/MIP. In all three areas and temporal epochs from stimulus onset to movement, visual signals were more eye-centered than auditory signals. In the SC and FEF, auditory signals became more eye-centered at the time of the saccade than they were initially after stimulus onset, but only in the SC at the time of the saccade did the auditory signals become predominantly eye-centered. The results indicate that visual and auditory signals both undergo transformations, ultimately reaching the same final reference frame but via different dynamics across brain regions and time. SIGNIFICANCE STATEMENT Models for visual-auditory integration posit that visual signals are eye-centered throughout the brain, while auditory signals are converted from head-centered to eye-centered coordinates. We show instead that both modalities largely employ hybrid reference frames: neither fully head-nor eye-centered. In three multimodal regions involved in orienting behaviors (Intraparietal Cortex, Frontal Eye Field and Superior Colliculus) these mixed codes persist in various proportions, shifting towards eye-centeredness both across time and across brain areas. Throughout, visual signals are more eye-centered than auditory signals, until a common predominantly eye-centered code for sound finally emerges during the saccade burst in the Superior Colliculus. In summary, visual and auditory signals reach the same final reference frame but via different dynamics across brain regions and time. |
Chih-Yang Chen; Denis Matrov; Richard Veale; Hirotaka Onoe; Masatoshi Yoshida; Kenichiro Miura; Tadashi Isa Properties of visually guided saccadic behavior and bottom-up attention in marmoset, macaque, and human Journal Article In: Journal of Neurophysiology, vol. 125, no. 2, pp. 437–457, 2021. @article{Chen2021, Saccades are stereotypic behaviors whose investigation improves our understanding of how primate brains implement precise motor control. Furthermore, saccades offer an important window into the cognitive and attentional state of the brain. Historically, saccade studies have largely relied on macaques. However, the cortical network giving rise to the saccadic command is difficult to study in macaques because relevant cortical areas lie in deep sulci and are difficult to access. Recently, a New World monkey. the marmoset, has garnered attention as an alternative to macaques because of advantages including its smooth cortical surface. However, adoption of the marmoset for oculomotor research has been limited due to a lack of in-depth descriptions of marmoset saccade kinematics and their ability to perform psychophysical tasks. Here, we directly compare free-viewing and visually guided behavior of marmoset, macaque, and human engaged in identical tasks under similar conditions. In the video free-viewing task, all species exhibited qualitatively similar saccade kinematics up to 25o in amplitude although with different parameters. Furthermore, the conventional bottom-up saliency model predicted gaze targets at similar rates for all species. We further verified their visually guided behavior by training them with step and gap saccade tasks. In the step paradigm, marmosets did not show shorter saccade reaction time for upward saccades whereas macaques and humans did. In the gap paradigm, all species showed similar gap effect and express saccades. Our results suggest that the marmoset can serve as a model for oculomotor, attentional, and cognitive research while we need to be aware of their difference from macaque or human. NEW & NOTEWORTHY We directly compared the results of a video free-viewing task and visually guided saccade tasks (step and gap) among three different species: marmoset, macaque, and human. We found that all species exhibit qualitatively similar saccadic kinematics and saliency-driven saccadic behavior albeit with different parameters. Our results suggest that the marmoset possesses similar neural mechanisms to macaque and human for saccadic control, and it is an appropriate model to study neural mechanisms for active vision and attention. |
Min Li; Junru Wu; Wenbo Ma; Zhihao Zhang; Mingsha Zhang; Xuemei Li; Zhipei Ling; Xin Xu Spatiotemporal characteristics of postsaccadic dynamic overshoot in young and elderly subjects Journal Article In: iScience, vol. 24, no. 7, pp. 102764, 2021. @article{Li2021e, Saccadic eye movements may not stop steadily but fluctuate briefly, known as saccadic dynamic overshoot (SDO). The reported relationships between SDO and saccadic parameters of main saccade and the effect of aging on SDO are controversial. In addition, it is not clear whether aging-related disease, such as mild cognitive impairment (MCI) and Parkinson disease (PD), causes the specific change of SDO. To address these questions, we analyzed the spatiotemporal features of SDO in young healthy subjects, elderly healthy subjects, and subjects with PD and MCI in three oculomotor tasks. We found two types of SDOs—simple and complex SDO. We confirmed that the frequency and amplitude of SDO were positively correlated with the peak velocity and deceleration of main saccades and increased in elderly subjects; however, they were not significantly different among the three elderly groups. Our results support the previous argument that the oculomotor structure in brainstem and cerebellum directly develop SDO. |
Raúl Luna; Ignacio Serrano-Pedraza; Karl R. Gegenfurtner; Alexander C. Schütz; David Souto Achieving visual stability during smooth pursuit eye movements: Directional and confidence judgements favor a recalibration model Journal Article In: Vision Research, vol. 184, pp. 58–73, 2021. @article{Luna2021, During smooth pursuit eye movements, the visual system is faced with the task of telling apart reafferent retinal motion from motion in the world. While an efference copy signal can be used to predict the amount of reafference to subtract from the image, an image-based adaptive mechanism can ensure the continued accuracy of this computation. Indeed, repeatedly exposing observers to background motion with a fixed direction relative to that of the target that is pursued leads to a shift in their point of subjective stationarity (PSS). We asked whether the effect of exposure reflects adaptation to motion contingent on pursuit direction, recalibration of a reference signal or both. A recalibration account predicts a shift in reference signal (i.e. predicted reafference), resulting in a shift of PSS, but no change in sensitivity. Results show that both directional judgements and confidence judgements about them favor a recalibration account, whereby there is an adaptive shift in the reference signal caused by the prevailing retinal motion during pursuit. We also found that the recalibration effect is specific to the exposed visual hemifield. |
Marvin R. Maechler; Nathan H. Heller; Matteo Lisi; Patrick Cavanagh; Peter U. Tse Smooth pursuit operates over perceived not physical positions of the double-drift stimulus Journal Article In: Journal of Vision, vol. 21, no. 11, pp. 1–11, 2021. @article{Maechler2021a, The double-drift illusion produces a large deviation in perceived direction that strongly dissociates physical position from perceived position. Surprisingly, saccades do not seem to be affected by the illusion (Lisi & Cavanagh, 2015). When targeting a double-drift stimulus, the saccade system is driven by retinal rather than perceived position. Here, using paired double-drift targets, we test whether the smooth pursuit system is driven by perceived or physical position. Participants (n = 7) smoothly pursued the inferred midpoint (Steinbach, 1976) between two horizontally aligned Gabor patches that were separated by 20° and moving on parallel, oblique paths. On the first half of each trial, the Gabors' internal textures were static while both drifted obliquely downward. On the second half of each trial, while the envelope moved obliquely upward, the internal texture drifted orthogonally to the envelope's motion, producing a large perceived deviation from the downward path even though the upward and downward trajectories always followed the same physical path but in opposite directions.We find that smooth pursuit eye movements accurately followed the nonillusory downward path of the midpoint between the two Gabors, but then followed the illusory rather than the physical trajectory on the upward return. Thus, virtual targets for smooth pursuit are derived from perceived rather than retinal coordinates. |
Tatiana Malevich; Antimo Buonocore; Ziad M. Hafed Dependence of the stimulus-driven microsaccade rate signature in rhesus macaque monkeys on visual stimulus size and polarity Journal Article In: Journal of Neurophysiology, vol. 125, no. 1, pp. 282–295, 2021. @article{Malevich2021, Microsaccades have a steady rate of occurrence during maintained gaze fixation, which gets transiently modulated by abrupt sensory stimuli. Such modulation, characterized by a rapid reduction in microsaccade frequency followed by a stronger rebound phase of high microsaccade rate, is often described as the microsaccadic rate signature, owing to its stereotyped nature. Here, we investigated the impacts of stimulus polarity (luminance increments or luminance decrements relative to background luminance) and size on the microsaccadic rate signature. We presented brief, behaviorally irrelevant visual flashes consisting of large or small, white or black stimuli over an otherwise gray image background. Both large and small stimuli caused robust early microsaccadic inhibition, but postinhibition microsaccade rate rebound was significantly delayed and weakened for large stimuli when compared with small ones. Critically, small black stimuli were associated with stronger modulations in the microsaccade rate signature than small white stimuli, particularly in the postinhibition rebound phase, and black stimuli also amplified the incidence of early stimulus-directed microsaccades. Our results demonstrate that the microsaccadic rate signature is sensitive to stimulus size and polarity, and they point to dissociable neural mechanisms underlying early microsaccadic inhibition after stimulus onset and later microsaccadic rate rebound at longer times thereafter. These results also demonstrate early access of oculomotor control circuitry to diverse sensory representations, particularly for momentarily inhibiting saccade generation with short latencies. NEW & NOTEWORTHY Microsaccade rate is transiently reduced after sudden stimulus onsets, and then strongly rebounds before returning to baseline. We explored the influence of stimulus polarity (black vs. white) and size on this “rate signature.” Large stimuli caused more muted microsaccadic rebound than small ones, and microsaccadic rebound was also differentially affected by black versus white stimuli, particularly with small stimuli. These results suggest dissociated neural mechanisms for microsaccadic inhibition and rebound in the microsaccadic rate signature. |
Talora L. Martin; Jordan Murray; Kiran Garg; Charles Gallagher; Aasef G. Shaikh; Fatema F. Ghasia Fixation eye movement abnormalities and stereopsis recovery following strabismus repair Journal Article In: Scientific Reports, vol. 11, pp. 14417, 2021. @article{Martin2021, We evaluated the effects of strabismus repair on fixational eye movements (FEMs) and stereopsis recovery in patients with fusion maldevelopment nystagmus (FMN) and patients without nystagmus. Twenty-one patients with strabismus, twelve with FMN and nine without nystagmus, were tested before and after strabismus repair. Eye-movements were recorded during a gaze-holding task under monocular viewing conditions. Fast (fixational saccades and quick phases of nystagmus) and slow (inter-saccadic drifts and slow phases of nystagmus) FEMs and bivariate contour ellipse area (BCEA) were analyzed in the viewing and non-viewing eye. Strabismus repair improved the angle of strabismus in subjects with and without FMN, however patients without nystagmus were more likely to have improvement in stereoacuity. The fixational saccade amplitudes and intersaccadic drift velocities in both eyes decreased after strabismus repair in subjects without nystagmus. The slow phase velocities were higher in patients with FMN compared to inter-saccadic drifts in patients without nystagmus. There was no change in the BCEA after surgery in either group. In patients without nystagmus, the improvement of the binocular function (stereopsis), as well as decreased fixational saccade amplitude and intersaccadic drift velocity, could be due, at least partially, to central adaptive mechanisms rendered possible by surgical realignment of the eyes. The absence of improvement in patients with FMN post strabismus repair likely suggests the lack of such adaptive mechanisms in patients with early onset infantile strabismus. Assessment of fixation eye movement characteristics can be a useful tool to predict functional improvement post strabismus repair. |
Eugene McSorley; Alice G. Cruickshank; Rachel McCloy In: Journal of Vision, vol. 21, no. 3, pp. 17, 2021. @article{McSorley2021, When a distractor appears close to the target location, saccades are less accurate. However, the presence of a further distractor, remote from those stimuli, increases the saccade response latency and improves accuracy. Explanations for this are either that the second, remote distractor impacts directly on target selection processes or that the remote distractor merely impairs the ability to initiate a saccade and changes the time at which unaffected target selection processes are accessed. In order to tease these two explanations apart, here we examine the relationship between latency and accuracy of saccades to a target and close distractor pair while a remote distractor appears at variable distance. Accuracy improvements are found to follow a similar pattern, regardless of the presence of the remote distractor, which suggests that the effect of the remote distractor is not the result of a direct impact on the target selection process. Our findings support the proposal that a remote distractor impairs the ability to initiate a saccade, meaning the competition between target and close distractor is accessed at a later time, thus resulting in more accurate saccades. |
Kimberly Meier; Deanna L. Lundell; Eric S. Seemiller; Deborah Giaschi; Laurie M. Wilcox; T. Rowan Candy The relationship between reflex eye realignment and the percept of single vision in young children Journal Article In: Scientific Reports, vol. 11, pp. 375, 2021. @article{Meier2021, Effective binocular vision is dependent on both motor and perceptual function. Young children undergo development of both components while interacting with their dynamic three-dimensional environment. When this development fails, eye misalignment and double vision may result. We compared the range of image disparities over which young children display reflex motor realignment of their eyes with the range over which they report a single versus double percept. In response to step changes in the disparity of a 2.2° wide stimulus, 5-year-olds generated an adult-like reflex vergence velocity tuning function peaking at 2° of disparity, with a mean latency of 210 ms. On average, they reported double vision for stimulus disparities of 3° and larger, compared to 1° in adult reports. Three-year-olds also generated reflex vergence tuning functions peaking at approximately 2° of disparity, but their percepts could not be assessed. These data suggest that, by age 5, reflex eye realignment responses and percepts driven by these brief stimuli are tightly coordinated in space and time to permit robust binocular function around the point of fixation. Importantly, the plastic neural processes maintaining this tight coordination during growth control the stability of visual information driving learning during childhood. |
Seng Bum Michael Yoo; Jiaxin Cindy Tu; Benjamin Yost Hayden Multicentric tracking of multiple agents by anterior cingulate cortex during pursuit and evasion Journal Article In: Nature Communications, vol. 12, pp. 1–14, 2021. @article{Yoo2021a, Successful pursuit and evasion require rapid and precise coordination of navigation with adaptive motor control. We hypothesize that the dorsal anterior cingulate cortex (dACC), which communicates bidirectionally with both the hippocampal complex and premotor/motor areas, would serve a mapping role in this process. We recorded responses of dACC ensembles in two macaques performing a joystick-controlled continuous pursuit/evasion task. We find that dACC carries two sets of signals, (1) world-centric variables that together form a representation of the position and velocity of all relevant agents (self, prey, and predator) in the virtual world, and (2) avatar-centric variables, i.e. self-prey distance and angle. Both sets of variables are multiplexed within an overlapping set of neurons. Our results suggest that dACC may contribute to pursuit and evasion by computing and continuously updating a multicentric representation of the unfolding task state, and support the hypothesis that it plays a high-level abstract role in the control of behavior. |
Hong Zhou; Xia Wang; Di Ma; Yanyan Jiang; Fan Li; Yunchuang Sun; Jing Chen; Wei Sun; Elmar H. Pinkhardt; Bernhard Landwehrmeyer; Albert Ludolph; Lin Zhang; Guiping Zhao; Zhaoxia Wang The differential diagnostic value of a battery of oculomotor evaluation in Parkinson's Disease and Multiple System Atrophy Journal Article In: Brain and Behavior, vol. 11, no. 7, pp. 1–10, 2021. @article{Zhou2021a, Introduction: Clinical diagnosis of Parkinsonism is still challenging, and the diagnostic biomarkers of Multiple System Atrophy (MSA) are scarce. This study aimed to investigate the diagnostic value of the combined eye movement tests in patients with Parkinson's disease (PD) and those with MSA. Methods: We enrolled 96 PD patients, 33 MSA patients (18 with MSA-P and 15 with MSA-C), and 40 healthy controls who had their horizontal ocular movements measured. The multiple-step pattern of memory-guided saccade (MGS), the hypometria/hypermetria of the reflexive saccade, the abnormal saccade in smooth pursuit movement (SPM), gaze-evoked nystagmus, and square-wave jerks in gaze-holding test were qualitatively analyzed. The reflexive saccadic parameters and gain of SPM were also quantitatively analyzed. Results: The MGS test showed that patients with either diagnosis had a significantly higher incidence of multiple-step pattern compared with controls (68.6%, 65.2%, and versus. 2.5%, p <.05, in PD, MSA, versus. controls, respectively). The reflexive saccade test showed that MSA patients showing a prominent higher incidence of the abnormal saccade (63.6%, both hypometria and hypermetria) than that of PD patients and controls (33.3%, 7.5%, respectively, hypometria) (p <.05). The SPM test showed PD patients had mildly decreased gain among whom 28.1% presenting “saccade intrusions”; and that MSA patients had the significant decreased gain with 51.5% presenting “catch-up saccades”(p <.05). Only MSA patients showed gaze-evoked nystagmus (24.2%), square-wave jerks (6.1%) in gaze-holding test (p <.05). Conclusions: A panel of eye movements tests may help to differentiate PD from MSA. The combined presence of hypometria and hypermetria in saccadic eye movement, the impaired gain of smooth pursuit movement with “catch-up saccades,” gaze-evoked nystagmus, square-wave jerks in gaze-holding test, and multiple-step pattern in MGS may provide clues to the diagnosis of MSA. |
Xiuyun Wu; Austin C. Rothwell; Miriam Spering; Anna Montagnini Expectations about motion direction affect perception and anticipatory smooth pursuit differently Journal Article In: Journal of Neurophysiology, vol. 125, no. 3, pp. 1–41, 2021. @article{Wu2021c, Smooth pursuit eye movements and visual motion perception rely on the integration of current sensory signals with past experience. Experience shapes our expectation of current visual events and can drive eye movement responses made in anticipation of a target, such as anticipatory pursuit. Previous research revealed consistent effects of expectation on anticipatory pursuit—eye movements follow the expected target direction or speed—and contrasting effects on motion perception, but most studies considered either eye movement or perceptual responses. The current study directly compared effects of direction expectation on perception and anticipatory pursuit within the same direction discrimination task to investigate whether both types of responses are affected similarly or differently. Observers (n = 10) viewed high-coherence random-dot kinematograms (RDKs) moving rightward and leftward with a probability of 50%, 70%, or 90% in a given block of trials to build up an expectation of motion direction. They were asked to judge motion direction of interleaved low-coherence RDKs (0%–15%). Perceptual judgements were compared with changes in anticipatory pursuit eye movements as a function of probability. Results show that anticipatory pursuit velocity scaled with probability and followed direction expectation (attraction bias), whereas perceptual judgments were biased opposite to direction expectation (repulsion bias). Control experiments suggest that the repulsion bias in perception was not caused by retinal slip induced by anticipatory pursuit, or by motion adaptation. We conclude that direction expectation can be processed differently for perception and anticipatory pursuit. NEW & NOTEWORTHY We show that expectations about motion direction that are based on long-term trial history affect perception and anticipatory pursuit differently. Whereas anticipatory pursuit direction was coherent with the expected motion direction (attraction bias), perception was biased opposite to the expected direction (repulsion bias). These opposite biases potentially reveal different ways in which perception and action utilize prior information and support the idea of different information processing for perception and pursuit. |
Jessica Wunderlich; Anna Behler; Jens Dreyhaupt; Albert C. Ludolph; Elmar H. Pinkhardt; Jan Kassubek Diagnostic value of video-oculography in progressive supranuclear palsy: a controlled study in 100 patients Journal Article In: Journal of Neurology, vol. 268, no. 9, pp. 3467–3475, 2021. @article{Wunderlich2021, Background: The eponymous feature of progressive supranuclear palsy (PSP) is oculomotor impairment which is one of the relevant domains in the Movement Disorder Society diagnostic criteria. Objective: We aimed to investigate the value of specific video-oculographic parameters for the use as diagnostic markers in PSP. Methods: An analysis of video-oculography recordings of 100 PSP patients and 49 age-matched healthy control subjects was performed. Gain of smooth pursuit eye movement and latency, gain, peak eye velocity, asymmetry of downward and upward velocities of saccades as well as rate of saccadic intrusions were analyzed. Results: Vertical saccade velocity and saccadic intrusions allowed for the classification of about 70% and 56% of the patients, respectively. By combining both parameters, almost 80% of the PSP patients were covered, while vertical velocity asymmetry was observed in approximately 34%. All parameters had a specificity of above 95%. The sensitivities were lower with around 50–60% for the velocity and saccadic intrusions and only 27% for vertical asymmetry. Conclusions: In accordance with oculomotor features in the current PSP diagnostic criteria, video-oculographic assessment of vertical saccade velocity and saccadic intrusions resulted in very high specificity. Asymmetry of vertical saccade velocities, in the opposite, did not prove to be useful for diagnostic purposes. |
Inbal Ziv; Yoram S. Bonneh Oculomotor inhibition during smooth pursuit and its dependence on contrast sensitivity Journal Article In: Journal of Vision, vol. 21, no. 2, pp. 1–20, 2021. @article{Ziv2021, Our eyes are never still, but tend to "freeze" in response to stimulus onset. This effect is termed "oculomotor inhibition" (OMI); its magnitude and time course depend on the stimulus parameters, attention, and expectation. We previously showed that the time course and duration of microsaccade and spontaneous eye-blink inhibition provide an involuntary measure of low-level visual properties such as contrast sensitivity during fixation. We investigated whether this stimulus-dependent inhibition also occurs during smooth pursuit, for both the catch-up saccades and the pursuit itself. Observers followed a target with continuous back-and-forth horizontal motion while a Gabor patch was briefly flashed centrally with varied spatial frequency and contrast. Catch-up saccades of the size of microsaccades had a similar pattern of inhibition as microsaccades during fixation, with stronger inhibition onset and faster inhibition release for more salient stimuli. Moreover, a similar stimulus dependency of inhibition was shown for pursuit latencies and peak velocity. Additionally, microsaccade latencies at inhibition release, peak pursuit velocities, and latencies at minimum pursuit velocity were correlated with contrast sensitivity.We demonstrated the generality of OMI to smooth pursuit for both microsaccades and the pursuit itself and its close relation to the low-level processes that define saliency, such as contrast sensitivity. |
Junyi Zhou Differences on prosaccade task in skilled and less skilled female adolescent soccer players Journal Article In: Frontiers in Psychology, vol. 12, pp. 711420, 2021. @article{Zhou2021b, Although the relationship between cognitive processes and saccadic eye movements has been outlined, the relationship between specific cognitive processes underlying saccadic eye movements and skill level of soccer players remains unclear. Present study used the prosaccade task as a tool to investigate the difference in saccadic eye movements in skilled and less skilled Chinese female adolescent soccer players. Fifty-six healthy female adolescent soccer players (range: 14–18years, mean age: 16.5years) from Fujian Youth Football Training Base (Fujian Province, China) took part in the experiment. In the prosaccade task, participants were instructed to fixate at the cross at the center of the screen as long as the target appeared peripherally. They were told to saccade to the target as quickly and accurately as possible once it appeared. The results indicated that skilled soccer players exhibited shorter saccade latency (p=0.031), decreased variability of saccade latency (p=0.013), and higher spatial accuracy of saccade (p=0.032) than their less skilled counterparts. The shorter saccade latency and decreased variability of saccade latency may imply that the attentional system of skilled soccer player is superior which leads to smaller attention fluctuation and less attentional lapse. Additionally, higher spatial accuracy of saccade may imply potential structural differences in brain underlying saccadic eye movement between skilled and less skilled soccer players. More importantly, the results of the present study demonstrated that soccer players' cognitive capacities vary as a function of their skill levels. The limitations of the present study and future directions of research were discussed. |
Kevin Parisot; Steeve Zozor; Anne Guérin-Dugué; Ronald Phlypo; Alan Chauvin Micro-pursuit: A class of fixational eye movements correlating with smooth, predictable, small-scale target trajectories Journal Article In: Journal of Vision, vol. 21, no. 1, pp. 1–30, 2021. @article{Parisot2021, Humans generate ocular pursuit movements when a moving target is tracked throughout the visual field. In this article, we show that pursuit can be generated and measured at small amplitudes, at the scale of fixational eye movements, and tag these eye movements as micro-pursuits. During micro-pursuits, gaze direction correlates with a target's smooth, predictable target trajectory. We measure similarity between gaze and target trajectories using a so-called maximally projected correlation and provide results in three experimental data sets. A first observation of micro-pursuit is provided in an implicit pursuit task, where observers were tasked to maintain their gaze fixed on a static cross at the center of screen, while reporting changes in perception of an ambiguous, moving (Necker) cube. We then provide two experimental paradigms and their corresponding data sets: a first replicating micro-pursuits in an explicit pursuit task, where observers had to follow a moving fixation cross (Cross), and a second with an unambiguous square (Square). Individual and group analyses provide evidence that micro-pursuits exist in both the Necker and Cross experiments but not in the Square experiment. The interexperiment analysis results suggest that the manipulation of stimulus target motion, task, and/or the nature of the stimulus may play a role in the generation of micro-pursuits. |
Tyler R. Peel; Suryadeep Dash; Stephen G. Lomber; Brian D. Corneil Frontal eye field inactivation alters the readout of superior colliculus activity for saccade generation in a task-dependent manner Journal Article In: Journal of Computational Neuroscience, vol. 49, no. 3, pp. 229–249, 2021. @article{Peel2021, Saccades require a spatiotemporal transformation of activity between the intermediate layers of the superior colliculus (iSC) and downstream brainstem burst generator. The dynamic linear ensemble-coding model (Goossens and Van Opstal 2006) proposes that each iSC spike contributes a fixed mini-vector to saccade displacement. Although biologically-plausible, this model assumes cortical areas like the frontal eye fields (FEF) simply provide the saccadic goal to be executed by the iSC and brainstem burst generator. However, the FEF and iSC operate in unison during saccades, and a pathway from the FEF to the brainstem burst generator that bypasses the iSC exists. Here, we investigate the impact of large yet reversible inactivation of the FEF on iSC activity in the context of the model across four saccade tasks. We exploit the overlap of saccade vectors generated when the FEF is inactivated or not, comparing the number of iSC spikes for metrically-matched saccades. We found that the iSC emits fewer spikes for metrically-matched saccades during FEF inactivation. The decrease in spike count is task-dependent, with a greater decrease accompanying more cognitively-demanding saccades. Our results show that FEF integrity influences the readout of iSC activity in a task-dependent manner. We propose that the dynamic linear ensemble-coding model be modified so that FEF inactivation increases the gain of a readout parameter, effectively increasing the influence of a single iSC spike. We speculate that this modification could be instantiated by FEF and iSC pathways to the cerebellum that could modulate the excitability of the brainstem burst generator. |
Jairo Perez-Osorio; Abdulaziz Abubshait; Agnieszka Wykowska In: Journal of Cognitive Neuroscience, vol. 34, no. 1, pp. 108–126, 2021. @article{PerezOsorio2021, Understanding others' nonverbal behavior is essential for social interaction, as it allows, among others, to infer mental states. While gaze communication, a well-established nonverbal social behavior, has shown its importance in inferring others' mental states, not much is known about the effects of irrelevant gaze signals on cognitive conflict markers during collaborative settings. Here, participants completed a categorization task where they categorized objects based on their color while observing images of a robot. On each trial, participants observed the robot iCub grasping an object from a table and offering it to them to simulate a handover. Once the robot “moved” the object forward, participants were asked to categorize the object according to its color. Before participants were allowed to respond, the robot made a lateral head/gaze shift. The gaze shifts were either congruent or incongruent with the object's color. We expected that incongruent head-cues would induce more errors (Study 1), would be associated with more curvature in eye-tracking trajectories (Study 2), and induce larger amplitude in electrophysiological markers of cognitive conflict (Study 3). Results of the three studies show more oculomotor interference as measured in error rates (Study 1), larger curvatures eye-tracking trajectories (Study 2), and higher amplitudes of the N2 event-related potential (ERP) of the EEG signals as well as higher Event-Related Spectral Perturbation (ERSP) amplitudes (Study 3) for incongruent trials compared to congruent trials. Our findings reveal that behavioral, ocular and electrophysiological markers can index the influence of irrelevant signals during goal-oriented tasks. |
Andrea Phillipou; Susan L. Rossell; Caroline Gurvich; David J. Castle; Denny Meyer; Larry A. Abel A biomarker and endophenotype for anorexia nervosa? Journal Article In: Australian and New Zealand Journal of Psychiatry, pp. 1–9, 2021. @article{Phillipou2021, Objective: Recent research has suggested that a type of atypical eye movement, called square wave jerks, together with anxiety, may distinguish individuals with anorexia nervosa from those without anorexia nervosa and may represent a biomarker and endophenotype for the illness. The aim of this study was to identify the presence of this proposed marker in individuals currently with anorexia nervosa relative to healthy controls, and to identify the state independence and heritability of this putative marker by exploring whether it also exists in individuals who are weight-restored from anorexia nervosa and first-degree relatives (i.e. sisters of people with anorexia nervosa). Methods: Data from 80 female participants (20/group: current anorexia nervosa, weight-restored from anorexia nervosa, sisters of people with anorexia nervosa and healthy controls) were analysed. Square wave jerk rate was acquired during a fixation task, and anxiety was measured with the State Trait Anxiety Inventory. Results: Current anorexia nervosa, weight-restored from anorexia nervosa and sisters of people with anorexia nervosa groups made significantly more square wave jerks than healthy controls, but did not differ from one another. Square wave jerk rate and anxiety were found to discriminate groups with exceptionally high accuracy (current anorexia nervosa vs healthy control = 92.5%; weight-restored from anorexia nervosa vs healthy control = 77.5%; sisters of people with anorexia nervosa vs healthy control = 77.5%; p <.001). Conclusion: The combination of square wave jerk rate and anxiety was found to be a promising two-element marker for anorexia nervosa, and has the potential to be used as a biomarker or endophenotype to identify people at risk of anorexia nervosa and inform future treatments. |
Alessandro Piras; Matthew A. Timmis; Aurelio Trofè; Milena Raffi Visual strategies underpinning the spatiotemporal demands during visuomotor tasks in predicting ball direction Journal Article In: Journal of Sport and Exercise Psychology, vol. 43, no. 6, pp. 514–523, 2021. @article{Piras2021, We investigated gaze behavior of expert goalkeepers during the prediction of penalty kicks in different spatiotemporal constraints: penalties taken from 11 and 6 m. From 11 m, goalkeepers were more successful in predicting ball direction, with longer movement time initiation and a visual strategy with more fixations and greater saccade rates than penalties from 6 m, where they exhibited fewer fixations with higher microsaccade rates. As long as the opponent's distance is large and time pressure low, gaze can be frequently shifted between the kicker's body and the ball, due to the low cost of saccades. Conversely, when the objects are close, there is increased reliance on foveal and parafoveal information. In conclusion, when the spatiotemporal constraint is less severe, goalkeepers adopt a visual strategy with more fixations and small saccades. When the spatiotemporal constraint is more severe, they rely on peripheral vision to monitor kickers' movements through the use of microsaccades. |
Milena Raffi; Andrea Meoni; Alessandro Piras Analysis of microsaccades during extended practice of a visual discrimination task in the macaque monkey Journal Article In: Neuroscience Letters, vol. 743, pp. 135581, 2021. @article{Raffi2021, The spatial location indicated by a visual cue can bias microsaccades directions towards or away from the cue. Aim of this work was to evaluate the microsaccades characteristics during the monkey's training, investigating the relationship between a shift of attention and practice. The monkey was trained to press a lever at a target onset, then an expanding optic flow stimulus appeared to the right of the target. After a variable time delay, a visual cue appeared within the optic flow stimulus and the monkey had to release the lever in a maximum reaction time (RT) of 700 ms. In the control task no visual cue appeared and the monkey had to attend a change in the target color. Data were recorded in 9 months. Results revealed that the RTs at the control task changed significantly across time. The microsaccades directions were significantly clustered toward the visual cue, suggesting that the animal developed an attentional bias toward the visual space where the cue appeared. The microsaccades amplitude differed significantly across time. The microsaccades peak velocity differed significantly both across time and within the time delays, indicating that the monkey made faster microsaccades when it expected the cue to appear. The microsaccades number was significantly higher in the control task with respect to discrimination. The lack of change in microsaccades rate, duration, number and direction across time indicates that the experience acquired during practicing the task did not influence microsaccades generation. |
Milena Raffi; Aurelio Trofè; Monica Perazzolo; Andrea Meoni; Alessandro Piras Sensory input modulates microsaccades during heading perception Journal Article In: International Journal of Environmental Research and Public Health, vol. 18, no. 6, pp. 1–17, 2021. @article{Raffi2021a, Microsaccades are small eye movements produced during attempted fixation. During locomotion, the eyes scan the environment; the gaze is not always directed to the focus of expansion of the optic flow field. We sought to investigate whether the microsaccadic activity was modulated by eye position during the view of radial optic flow stimuli, and if the presence or lack of a proprioceptive input signal may influence the microsaccade characteristics during self-motion perception. We recorded the oculomotor activity when subjects were either standing or sitting in front of a screen during the view of optic flow stimuli that simulated specific heading directions with different gaze positions. We recorded five trials of each stimulus. Results showed that microsaccade duration, peak velocity, and rate were significantly modulated by optic flow stimuli and trial sequence. We found that the microsaccade rate increased in each condition from trial 1 to trial 5. Microsaccade peak velocity and duration were significantly different across trials. The analysis of the microsaccade directions showed that the different combinations of optic flow and eye position evoked non-uniform directions of microsaccades in standing condition with mean vectors in the upper-left quadrant of the visual field, uncorrelated with optic flow directions and eye positions. In sitting conditions, all stimuli evoked uniform directions of microsaccades. Present results indicate that the proprioceptive signals when the subjects stand up creates a different input that could alter the eye-movement characteristics during heading perceptions. |
Hrishikesh M. Rao; Sophia Yuditskaya; James R. Williamson; Trina R. Vian; Joseph J. Lacirignola; Trey E. Shenk; Thomas M. Talavage; Kristin J. Heaton; Thomas F. Quatieri Using oculomotor features to predict changes in optic nerve sheath diameter and ImPACT scores from contact-sport athletes Journal Article In: Frontiers in Neurology, vol. 12, pp. 584684, 2021. @article{Rao2021, There is mounting evidence linking the cumulative effects of repetitive head impacts to neuro-degenerative conditions. Robust clinical assessment tools to identify mild traumatic brain injuries are needed to assist with timely diagnosis for return-to-field decisions and appropriately guide rehabilitation. The focus of the present study is to investigate the potential for oculomotor features to complement existing diagnostic tools, such as measurements of Optic Nerve Sheath Diameter (ONSD) and Immediate Post-concussion Assessment and Cognitive Testing (ImPACT). Thirty-one high school American football and soccer athletes were tracked through the course of a sports season. Given the high risk of repetitive head impacts associated with both soccer and football, our hypotheses were that (1) ONSD and ImPACT scores would worsen through the season and (2) oculomotor features would effectively capture both neurophysiological changes reflected by ONSD and neuro-functional status assessed via ImPACT. Oculomotor features were used as input to Linear Mixed-Effects Regression models to predict ONSD and ImPACT scores as outcomes. Prediction accuracy was evaluated to identify explicit relationships between eye movements, ONSD, and ImPACT scores. Significant Pearson correlations were observed between predicted and actual outcomes for ONSD (Raw = 0.70; Normalized = 0.45) and for ImPACT (Raw = 0.86; Normalized = 0.71), demonstrating the capability of oculomotor features to capture neurological changes detected by both ONSD and ImPACT. The most predictive features were found to relate to motor control and visual-motor processing. In future work, oculomotor models, linking neural structures to oculomotor function, can be built to gain extended mechanistic insights into neurophysiological changes observed through seasons of participation in contact sports. |
Giulietta M. Riboldi; John Martone; John-Ross Rizzo; Todd E. Hudson; Janet C. Rucker; Steven J. Frucht Looking “cherry red spot myoclonus” in the eyes: clinical phenotype, treatment response, and eye movements in sialidosis type 1 Journal Article In: Tremor and Other Hyperkinetic Movements, vol. 11, no. 1, pp. 53, 2021. @article{Riboldi2021, Sialidosis type 1 is a rare lysosomal storage disorder caused by mutations of the neura-minidase gene. Specific features suggesting this condition include myoclonus, ataxia and macular cherry-red spots. However, phenotypic variability exists. Here, we present detailed clinical and video description of three patients with this rare condition. We also provide an in?depth characterization of eye movement abnormalities, as an additional tool to investigate pathophysiological mechanisms and to facilitate diagnosis. In our patients, despite phenotypic differences, eye movement deficits largely localized to the cerebellum. |
Samy Rima; Michael C. Schmid Reading specific small saccades predict individual phonemic awareness and reading speed Journal Article In: Frontiers in Neuroscience, vol. 15, pp. 663242, 2021. @article{Rima2021, Small fixational eye-movements are a fundamental aspect of vision and thought to reflect fine shifts in covert attention during active viewing. While the perceptual benefits of these small eye movements have been demonstrated during a wide range of experimental tasks including during free viewing, their function during reading remains surprisingly unclear. Previous research demonstrated that readers with increased microsaccade rates displayed longer reading speeds. To what extent increased fixational eye movements are, however, specific to reading and might be indicative of reading skill deficits remains, however, unknown. To address this topic, we compared the eye movement scan paths of 13 neurotypical individuals and 13 subjects diagnosed with developmental dyslexia during short story reading and free viewing of natural scenes. We found that during reading only, dyslexics tended to display small eye movements more frequently compared to neurotypicals, though this effect was not significant at the population level, as it could also occur in slow readers not diagnosed as dyslexics. In line with previous research, neurotypical readers had twice as many regressive compared to progressive microsaccades, which did not occur during free viewing. In contrast, dyslexics showed similar amounts of regressive and progressive small fixational eye movements during both reading and free viewing. We also found that participants with smaller fixational saccades from both neurotypical and dyslexic samples displayed reduced reading speeds and lower scores during independent tests of reading skill. Slower readers also displayed greater variability in the landing points and temporal occurrence of their fixational saccades. Both the rate and spatio-temporal variability of fixational saccades were associated with lower phonemic awareness scores. As none of the observed differences between dyslexics and neurotypical readers occurred during control experiments with free viewing, the reported effects appear to be directly related to reading. In summary, our results highlight the predictive value of small saccades for reading skill, but not necessarily for developmental dyslexia. |
William Rosengren; Marcus Nyström; Björn Hammar; Martin Stridh Waveform characterisation and comparison of nystagmus eye-tracking signals Journal Article In: Physiological Measurement, vol. 42, pp. 015004, 2021. @article{Rosengren2021, Objective: Pathological nystagmus is a symptom of oculomotor disease where the eyes oscillate involuntarily. The underlying cause of the nystagmus and the characteristics of the oscillatory eye movements are patient specific. An important part of clinical assessment in nystagmus patients is therefore to characterise different recorded eye-tracking signals, i.e., waveforms. Approach: A method for characterisation of the nystagmus waveform morphology is proposed. The method extracts local morphologic characteristics based on a sinusoidal model, and clusters these into a description of the complete signal. The clusters are used to characterise and compare recordings within and between patients and tasks. New metrics are proposed that can measure waveform similarity at different scales; from short signal segments up to entire signals, both within and between patients. Main results: The results show that the proposed method robustly can find the most prominent nystagmus waveforms in a recording. The method accurately identifies different eye movement patterns within and between patients and across different tasks. Significance: In conclusion, by allowing characterisation and comparison of nystagmus waveform patterns, the proposed method opens up for investigation and identification of the underlying condition in the individual patient, and for quantifying eye movements during tasks. |
Lucy L. Russell; Caroline V. Greaves; Rhian S. Convery; Martina Bocchetta; Jason D. Warren; Diego Kaski; Jonathan D. Rohrer Eye movements in frontotemporal dementia: Abnormalities of fixation, saccades and anti‐saccades Journal Article In: Alzheimer's & Dementia: Translational Research & Clinical Interventions, vol. 7, no. 1, pp. e12218, 2021. @article{Russell2021, Introduction: Oculomotor function has not been systematically studied in frontotemporal dementia (FTD) and yet may offer a simple target to monitor disease activity. Methods: We assessed fixation stability, smooth pursuit, pro-saccades, and anti- saccades using the Eyelink 1000-plus eye-tracker in 19 individuals with behavioral variantFTD (bvFTD) and22 controls.Neuroanatomical correlates were assessed using a region of interest magnetic resonance imaging (MRI) analysis. Results: Measures of fixation stability were impaired in the bvFTD group compared with controls. However, performance did not differ from controls in the pro-saccade tasks except in the vertical overlap condition. The bvFTD group performed worse in the anti-saccade task,which correlated strongly with executive function. Neural corre- lates included the orbitofrontal and ventromedial prefrontal cortices and striatum for fixation stability, and the dorsolateral prefrontal and parietal cortices and striatum for anti-saccades. Discussion: Overall, oculomotor function is abnormal in bvFTD, with performance likely related to impairment of inhibitory control and executive dysfunction. |
Musa Basseer Sami; Luciano Annibale; Aisling O'Neill; Tracy Collier; Chidimma Onyejiaka; Savitha Eranti; Debasis Das; Marlene Kelbrick; Philip McGuire; Steve C. R. Williams; Anas Rana; Ulrich Ettinger; Sagnik Bhattacharyya Eye movements in patients in early psychosis with and without a history of cannabis use Journal Article In: npj Schizophrenia, vol. 7, pp. 24, 2021. @article{Sami2021, It is unclear whether early psychosis in the context of cannabis use is different from psychosis without cannabis. We investigated this issue by examining whether abnormalities in oculomotor control differ between patients with psychosis with and without a history of cannabis use. We studied four groups: patients in the early phase of psychosis with a history of cannabis use (EPC; n = 28); patients in the early phase of psychosis without (EPNC; n = 25); controls with a history of cannabis use (HCC; n = 16); and controls without (HCNC; n = 22). We studied smooth pursuit eye movements using a stimulus with sinusoidal waveform at three target frequencies (0.2, 0.4 and 0.6 Hz). Participants also performed 40 antisaccade trials. There were no differences between the EPC and EPNC groups in diagnosis, symptom severity or level of functioning. We found evidence for a cannabis effect (χ2 = 23.14, p < 0.001), patient effect (χ2 = 4.84 |
Praveen Sanmugananthan; Nam Nguyen; Bernadette Murphy; Ali Hosseini Design and development of a rotating chair to measure the cervico-ocular reflex Journal Article In: Cureus, vol. 13, no. 10, pp. 1–6, 2021. @article{Sanmugananthan2021, Eye reflexes that stabilize gaze are essential in navigating daily life. One such reflex is the cervico-ocular reflex (COR). An important neural structure involved in the COR is the cerebellum, which facilitates proper gaze stability through sensorimotor integration to adjust eye movements accordingly. This reflex is tested by fixating the head in space and rotating the body around the neck. Thus, a rotating chair is needed to elicit proper cervical rotation while keeping the head fixed. The chair that was developed for this project was able to rotate to the specified amplitude (±0.5º of accuracy) and frequency. The parameters of the rotation amount, frequency, and amplitude can be adjusted as desired by the project guidelines. Our project aimed to improve upon existing chair models and develop a chair that can be used to assess the COR in neck pain populations. |
Matteo Scaramuzzi; Jordan Murray; Paolo Nucci; Aasef G. Shaikh; Fatema F. Ghasia Fixational eye movements abnormalities and rate of visual acuity and stereoacuity improvement with part time patching Journal Article In: Scientific Reports, vol. 11, pp. 1217, 2021. @article{Scaramuzzi2021, Residual amblyopia is seen in 40% of amblyopic patients treated with part-time patching. Amblyopic patients with infantile onset strabismus or anisometropia can develop fusion maldevelopment nystagmus syndrome (FMNS). The purpose of this study was to understand the effects of presence of FMNS and clinical subtype of amblyopia on visual acuity and stereo-acuity improvement in children treated with part-time patching. Forty amblyopic children who had fixation eye movement recordings and at least 12 months of follow-up after initiating part-time patching were included. We classified amblyopic subjects per the fixational eye movements characteristics into those without any nystagmus, those with FMNS and patients with nystagmus without any structural anomalies that do not meet the criteria of FMNS or idiopathic infantile nystagmus. We also classified the patients per the clinical type of amblyopia. Patching was continued until amblyopia was resolved or no visual acuity improvement was noted at two consecutive visits. Children with anisometropic amblyopia and without FMNS have a faster improvement and plateaued sooner. Regression was only seen in patients with strabismic/mixed amblyopia particularly those with FMNS. Patients with FMNS had improvement in visual acuity but poor stereopsis with part-time patching and required longer duration of treatment. |
Chris Scholes; Paul V. McGraw; Neil W. Roach Learning to silence saccadic suppression Journal Article In: Proceedings of the National Academy of Sciences, vol. 118, no. 6, pp. e2012937118, 2021. @article{Scholes2021, Perceptual stability is facilitated by a decrease in visual sensitivity during rapid eye movements, called saccadic suppression. While a large body of evidence demonstrates that saccadic programming is plastic, little is known about whether the perceptual consequences of saccades can be modified. Here, we demonstrate that saccadic suppression is attenuated during learning on a standard visual detection-in-noise task, to the point that it is effectively silenced. Across a period of 7 days, 44 participants were trained to detect brief, low-contrast stimuli embedded within dynamic noise, while eye position was tracked. Although instructed to fixate, participants regularly made small fixational saccades. Data were accumulated over a large number of trials, allowing us to assess changes in performance as a function of the temporal proximity of stimuli and saccades. This analysis revealed that improvements in sensitivity over the training period were accompanied by a systematic change in the impact of saccades on performance-robust saccadic suppression on day 1 declined gradually over subsequent days until its magnitude became indistinguishable from zero. This silencing of suppression was not explained by learning-related changes in saccade characteristics and generalized to an untrained retinal location and stimulus orientation. Suppression was restored when learned stimulus timing was perturbed, consistent with the operation of a mechanism that temporarily reduces or eliminates saccadic suppression, but only when it is behaviorally advantageous to do so. Our results indicate that learning can circumvent saccadic suppression to improve performance, without compromising its functional benefits in other viewing contexts. |
Jui-Tai Chen; Rachel Yep; Yu-Fan Hsu; Yih-Giun Cherng; Chin-An Wang Investigating arousal, saccade preparation, and global luminance effects on microsaccade behavior Journal Article In: Frontiers in Human Neuroscience, vol. 15, pp. 602835, 2021. @article{Chen2021c, Microsaccades, small saccadic eye movements occurring during fixation, have been suggested to be modulated by various sensory, cognitive, and affective processes relating to arousal. Although the modulation of fatigue-related arousal on microsaccade behavior has previously been characterized, the influence of other aspects of arousal, such as emotional arousal, is less understood. Moreover, microsaccades are modulated by cognitive processes (e.g., voluntary saccade preparation) that could also be linked to arousal. To investigate the influence of emotional arousal, saccade preparation, and global luminance levels on microsaccade behavior, emotional auditory stimuli were presented prior to the onset of a fixation cue whose color indicated to look either at the peripheral stimulus (pro-saccade) or in the opposite direction of the stimulus (anti-saccade). Microsaccade behavior was found to be significantly modulated by saccade preparation and global luminance level, but not emotional arousal. In the pro- and anti-saccade task, microsaccade rate was lower during anti-saccade preparation as compared to pro-saccade preparation, though microsaccade dynamics were comparable during both trial types. Our results reveal a differential role of arousal linked to emotion, fatigue, saccade preparation, and global luminance level on microsaccade behavior. |
Rongrong Chen; Leland S. Stone; Li Li Visuomotor predictors of batting performance in baseball players Journal Article In: Journal of Vision, vol. 21, no. 3, pp. 1–16, 2021. @article{Chen2021e, Hitting a baseball, one of the most difficult skills in all of sports, requires complex hand-eye coordination, but its link with basic visuomotor capabilities remains largely unknown. Here we examined basic visuomotor skills of baseball players and demographically matched nonathletes by measuring their ocular-tracking and manual-control performance. We further investigated how these two capabilities relate to batting performance in baseball players. Compared to nonathletes, baseball players showed better ocular-tracking and manual-control capabilities, which remain unchanged with increasing baseball experience. Both, however, become more correlated with batting accuracy with increasing experience. Ocular-tracking performance is predictive of batting skill, accounting for > 70% of the variance in batting performance across players with > 10 years of experience. A simple linear additive-noise cascade model with shared front-end visual noise that limits batting performance can explain manyofourresults. Ourfindings show that fundamental visuomotor capabilities can predictthe complex, learned skill of baseball batting. |
Hiu Mei Chow; Jonas Knöll; Matthew Madsen; Miriam Spering Look where you go: Characterizing eye movements toward optic flow Journal Article In: Journal of Vision, vol. 21, no. 3, pp. 1–15, 2021. @article{Chow2021a, When we move through our environment, objects in the visual scene create optic flow patterns on the retina. Even though optic flow is ubiquitous in everyday life, it is not well understood how our eyes naturally respond to it. In small groups of human and non-human primates, optic flow triggers intuitive, uninstructed eye movements to the focus of expansion of the pattern (Knöll, Pillow, & Huk, 2018). Here, we investigate whether such intuitive oculomotor responses to optic flow are generalizable to a larger group of human observers and how eye movements are affected by motion signal strength and task instructions. Observers (N = 43) viewed expanding or contracting optic flow constructed by a cloud of moving dots radiating from or converging toward a focus of expansion that could randomly shift. Results show that 84% of observers tracked the focus of expansion with their eyes without being explicitly instructed to track. Intuitive tracking was tuned to motion signal strength: Saccades landed closer to the focus of expansion, and smooth tracking was more accurate when dot contrast, motion coherence, and translational speed were high. Under explicit tracking instruction, the eyes aligned with the focus of expansion more closely than without instruction. Our results highlight the sensitivity of intuitive eye movements as indicators of visual motion processing in dynamic contexts. |
Jan Churan; Andre Kaminiarz; Jakob C. B. Schwenk; Frank Bremmer Coding of interceptive saccades in parietal cortex of macaque monkeys Journal Article In: Brain Structure and Function, vol. 226, no. 8, pp. 2707–2723, 2021. @article{Churan2021a, The oculomotor system can initiate remarkably accurate saccades towards moving targets (interceptive saccades) the processing of which is still under debate. The generation of these saccades requires the oculomotor centers to have information about the motion parameters of the target that then must be extrapolated to bridge the inherent processing delays. We investigated to what degree the information about motion of a saccade target is available in the lateral intra-parietal area (area LIP) of macaque monkeys for generation of accurate interceptive saccades. When a multi-layer neural network was trained based on neural discharges from area LIP around the time of saccades towards stationary targets, it was also able to predict the end points of saccades directed towards moving targets. This prediction, however, lagged behind the actual post-saccadic position of the moving target by ~ 80 ms when the whole neuronal sample of 105 neurons was used. We further found that single neurons differentially code for the motion of the target. Selecting neurons with the strongest representation of target motion reduced this lag to ~ 30 ms which represents the position of the moving target approximately at the onset of the interceptive saccade. We conclude that—similarly to recent findings from the Superior Colliculus (Goffart et al. J Neurophysiol 118(5):2890–2901)—there is a continuum of contributions of individual LIP neurons to the accuracy of interceptive saccades. A contribution of other gaze control centers (like the cerebellum or the frontal eye field) that further increase the saccadic accuracy is, however, likely. |
Celine Cont; Eckart Zimmermann The motor representation of sensory experience Journal Article In: Current Biology, vol. 31, no. 5, pp. 1029–1036, 2021. @article{Cont2021, How do we estimate the position of an object in the world around us? Naturally, we would direct our gaze to that object. Accordingly, neural motor coordinates entail the distance of external objects and thus might be used to derive perceptual estimates. Several general frameworks in the history of perceptual science have offered such a view.1–4 However, a mechanism showing how motor and visual processes communicate remains elusive. Here, we report that every post-saccadic error biases visual localization in a serially dependent manner. In order to simulate a realignment of visual space through motor coordinates, we induced an artificial de-alignment between visual and motor space. We found that when performing saccades under this distortion, post-saccadic error information clearly realigned visual and motor space, again in a serially dependent manner. These results demonstrate that the consequences of every saccade directly influence where we see objects in the world. On a neural basis, this requires that motor signals, which generate close to the saccade production machinery, are reported to cortical areas and arrange visual space. This view is consistent with recent electrophysiological findings of post-saccadic error processing in posterior parietal cortex. |
Annabell Coors; Natascha Merten; David D. Ward; Matthias Schmid; Monique M. B. Breteler; Ulrich Ettinger Strong age but weak sex effects in eye movement performance in the general adult population: Evidence from the Rhineland Study Journal Article In: Vision Research, vol. 178, pp. 124–133, 2021. @article{Coors2021, Assessing physiological changes that occur with healthy ageing is prerequisite for understanding pathophysiological age-related changes. Eye movements are studied as biomarkers for pathological changes because they are altered in patients with neurodegenerative disorders. However, there is a lack of data from large samples assessing age-related physiological changes and sex differences in oculomotor performance. Thus, we assessed and quantified cross-sectional relations of age and sex with oculomotor performance in the general population. We report results from the first 4,000 participants (aged 30–95 years) of the Rhineland Study, a community-based prospective cohort study in Bonn, Germany. Participants completed fixation, smooth pursuit, prosaccade and antisaccade tasks. We quantified associations of age and sex with oculomotor outcomes using multivariable linear regression models. Performance in 12 out of 18 oculomotor measures declined with increasing age. No differences between age groups were observed in five antisaccade outcomes (amplitude-adjusted and unadjusted peak velocity, amplitude gain, spatial error and percentage of corrected errors) and for blink rate during fixation. Small sex differences occurred in smooth pursuit velocity gain (men have higher gain) and blink rate during fixation (men blink less). We conclude that performance declines with age in two thirds of oculomotor outcomes but that there was no evidence of sex differences in eye movement performance except for two outcomes. Since the percentage of corrected antisaccade errors was not associated with age but is known to be affected by pathological cognitive decline, it represents a promising candidate preclinical biomarker of neurodegeneration. |
2020 |
Mohsen Rakhshan; Vivian Lee; Emily Chu; Lauren Julius Harris; Lillian Laiks; Peyman Khorsand; Alireza Soltani Influence of expected reward on temporal order judgment Journal Article In: Journal of Cognitive Neuroscience, vol. 32, no. 4, pp. 674–690, 2020. @article{Rakhshan2020a, Perceptual decision-making has been shown to be influenced by reward expected from alternative options or actions, but the underlying neural mechanisms are currently unknown. More specifically, it is debated whether reward effects are mediated through changes in sensory processing, later stages of decision-making, or both. To address this question, we conducted two experiments in which human participants made saccades to what they perceived to be either the first or second of two visually identical but asynchronously presented targets while we manipulated expected reward from correct and incorrect responses on each trial. By comparing reward-induced bias in target selection (i.e., reward bias) during the two experiments, we determined whether reward caused changes in sensory or decision-making processes. We found similar reward biases in the two experiments indicating that reward information mainly influenced later stages of decision-making [R1.1]. Moreover, the observed reward biases were independent of the individual's sensitivity to sensory signals. This suggests that reward effects were determined heuristically via modulation of decision-making processes instead of sensory processing. To further explain our findings and uncover plausible neural mechanisms, we simulated our experiments with a cortical network model and tested alternative mechanisms for how reward could exert its influence. We found that our experimental observations are more compatible with reward-dependent input to the output layer of the decision circuit. Together, our results suggest that, during a temporal judgment task, reward exerts its influence via changing later stages of decision-making (i.e., response bias) rather than early sensory processing (i.e., perceptual bias). |
Guillaume Doucet; Roberto A. Gulli; Benjamin W. Corrigan; Lyndon R. Duong; Julio C. Martinez-Trujillo Modulation of local field potentials and neuronal activity in primate hippocampus during saccades Journal Article In: Hippocampus, vol. 30, no. 3, pp. 192–209, 2020. @article{Doucet2020, Primates use saccades to gather information about objects and their relative spatial arrangement, a process essential for visual perception and memory. It has been proposed that signals linked to saccades reset the phase of local field potential (LFP) oscillations in the hippocampus, providing a temporal window for visual signals to activate neurons in this region and influence memory formation. We investigated this issue by measuring hippocampal LFPs and spikes in two macaques performing different tasks with unconstrained eye movements. We found that LFP phase clustering (PC) in the alpha/beta (8–16 Hz) frequencies followed foveation onsets, while PC in frequencies lower than 8 Hz followed spontaneous saccades, even on a homogeneous background. Saccades to a solid grey background were not followed by increases in local neuronal firing, whereas saccades toward appearing visual stimuli were. Finally, saccade parameters correlated with LFPs phase and amplitude: saccade direction correlated with delta (≤4 Hz) phase, and saccade amplitude with theta (4–8 Hz) power. Our results suggest that signals linked to saccades reach the hippocampus, producing synchronization of delta/theta LFPs without a general activation of local neurons. Moreover, some visual inputs co-occurring with saccades produce LFP synchronization in the alpha/beta bands and elevated neuronal firing. Our findings support the hypothesis that saccade-related signals enact sensory input-dependent plasticity and therefore memory formation in the primate hippocampus. |
Ming-Ray Liao; Brian A. Anderson Reward learning biases the direction of saccades Journal Article In: Cognition, vol. 196, pp. 1–9, 2020. @article{Liao2020a, The role of associative reward learning in guiding feature-based attention and spatial attention is well established. However, no studies have looked at the extent to which reward learning can modulate the direction of saccades during visual search. Here, we introduced a novel reward learning paradigm to examine whether reward-associated directions of eye movements can modulate performance in different visual search tasks. Participants had to fixate a peripheral target before fixating one of four disks that subsequently appeared in each cardinal position. This was followed by reward feedback contingent upon the direction chosen, where one direction consistently yielded a high reward. Thus, reward was tied to the direction of saccades rather than the absolute location of the stimulus fixated. Participants selected the target in the high-value direction on the majority of trials, demonstrating robust learning of the task contingencies. In an untimed visual foraging task that followed, which was performed in extinction, initial saccades were reliably biased in the previously rewarded-associated direction. In a second experiment, following the same training procedure, eye movements in the previously high-value direction were facilitated in a saccade-to-target task. Our findings suggest that rewarding directional eye movements biases oculomotor search patterns in a manner that is robust to extinction and generalizes across stimuli and task. |
Kaleb A. Lowe; Wolf Zinke; Anthony M. Phipps; Josh Cosman; Micala Maddox; Jeffrey D. Schall; Charles F. Caskey Visuomotor transformations are modulated by focused ultrasound over frontal eye field Journal Article In: Ultrasound in Medicine & Biology, pp. 1–14, 2020. @article{Lowe2020, Neuromodulation with focused ultrasound (FUS) is being widely explored as a non-invasive tool to stimulate focal brain regions because of its superior spatial resolution and coverage compared with other neuro- modulation methods. The precise effects of FUS stimulation on specific regions of the brain are not yet fully understood. Here, we characterized the behavioral effects of FUS stimulation directly applied through a craniot- omy over the macaque frontal eye field (FEF). In macaque monkeys making directed eye movements to perform visual search tasks with direct or arbitrary responses, focused ultrasound was applied through a craniotomy over the FEF. Saccade response times (RTs) and error rates were determined for trials without or with FUS stim- ulation with pulses at a peak negative pressure of either 250 or 425 kPa. Both RTs and error rates were affected by FUS. Responses toward a target located contralateral to the FUS stimulation were approximately 3 ms slower in the presence of FUS in both monkeys studied, while only one exhibited a slowing of responses for ipsilateral targets. Error rates were lower in one monkey in this study. In another search task requiring making eye move- ments toward a target (pro-saccades) or in the opposite direction (anti-saccades), the RT for pro-saccades increased in the presence of FUS stimulation. Our results indicate the effectiveness of FUS to modulate saccadic responses when stimulating FEF in awake, behaving non-human primates. (E-mail: |
Liya Ma; Janahan Selvanayagam; Maryam Ghahremani; Lauren K. Hayrynen; Kevin D. Johnston; Stefan Everling Single-unit activity in marmoset posterior parietal cortex in a gap saccade task Journal Article In: Journal of Neurophysiology, vol. 123, no. 3, pp. 896–911, 2020. @article{Ma2020, Abnormal saccadic eye movements can serve as biomarkers for patients with several neuropsychiatric disorders. The common marmoset (Callithrix jacchus) is becoming increasingly popular as a nonhuman primate model to investigate the cortical mechanisms of saccadic control. Recently, our group demonstrated that microstimulation in the posterior parietal cortex (PPC) of marmosets elicits contralateral saccades. Here we recorded single-unit activity in the PPC of the same two marmosets using chronic microelectrode arrays while the monkeys performed a saccadic task with gap trials (target onset lagged fixation point offset by 200 ms) interleaved with step trials (fixation point disappeared when the peripheral target appeared). Both marmosets showed a gap effect, shorter saccadic reaction times (SRTs) in gap vs. step trials. On average, stronger gap-period responses across the entire neuronal population preceded shorter SRTs on trials with contralateral targets although this correlation was stronger among the 15% “gap neurons,” which responded significantly during the gap. We also found 39% “target neurons” with significant saccadic target-related responses, which were stronger in gap trials and correlated with the SRTs better than the remaining neurons. Compared with saccades with relatively long SRTs, short-SRT saccades were preceded by both stronger gap-related and target-related responses in all PPC neurons, regardless of whether such response reached significance. Our findings suggest that the PPC in the marmoset contains an area that is involved in the modulation of saccadic preparation. NEW & NOTEWORTHY As a primate model in systems neuroscience, the marmoset is a great complement to the macaque monkey because of its unique advantages. To identify oculomotor networks in the marmoset, we recorded from the marmoset posterior parietal cortex during a saccadic task and found single-unit activities consistent with a role in saccadic modulation. This finding supports the marmoset as a valuable model for studying oculomotor control. |
Abhimanyu Mahajan; Palak Gupta; Jonathan Jacobs; Luca Marsili; Andrea Sturchio; H. A. Jinnah; Alberto J. Espay; Aasef G. Shaikh Impaired saccade adaptation in tremor-dominant cervical dystonia - Evidence for maladaptive cerebellum Journal Article In: Cerebellum, pp. 1–9, 2020. @article{Mahajan2020, We examined the role of the cerebellum in patients with tremor-dominant cervical dystonia by measuring the adaptive capacity of rapid reflexive eye movements (saccades). We chose the saccade adaptation paradigm because, unlike other motor learning paradigms, the real-time modification of saccades cannot “wait” for the sensory (visual) feedback. Instead, saccades rely primarily on the internal reafference modulated by the cerebellum. The saccade adaptation happens over fast and slow timescales. The fast timescale has poor retention of learned response, while the slow timescale has strong retention. Cerebellar defects resulting in loss of function affect the fast timescale but the slow timescale of saccade adaptation is retained. In contrast, maladaptive cerebellar disorders feature the absence of both fast and slow timescales. We were able to measure both timescales using noninvasive oculography in 6 normal individuals. In contrast, both timescales were absent in 12 patients with tremor-dominant cervical dystonia. These findings are consistent with maladaptive cerebellar outflow as a putative pathophysiological basis for tremor-dominant cervical dystonia. |
Tatiana Malevich; Antimo Buonocore; Ziad M. Hafed Rapid stimulus-driven modulation of slow ocular position drifts Journal Article In: eLife, vol. 9, pp. 1–22, 2020. @article{Malevich2020, The eyes are never still during maintained gaze fixation. When microsaccades are not occurring, ocular position exhibits continuous slow changes, often referred to as drifts. Unlike microsaccades, drifts remain to be viewed as largely random eye movements. Here we found that ocular position drifts can, instead, be very systematically stimulus-driven, and with very short latencies. We used highly precise eye tracking in three well trained macaque monkeys and found that even fleeting (~8 ms duration) stimulus presentations can robustly trigger transient and stimulus-specific modulations of ocular position drifts, and with only approximately 60 ms latency. Such drift responses are binocular, and they are most effectively elicited with large stimuli of low spatial frequency. Intriguingly, the drift responses exhibit some image pattern selectivity, and they are not explained by convergence responses, pupil constrictions, head movements, or starting eye positions. Ocular position drifts have very rapid access to exogenous visual information. |
Diako Mardanbegi; Thomas D. W. Wilcockson; Rebecca Killick; Baiqiang Xia; Hans Gellersen; Peter Sawyer; Trevor J. Crawford A comparison of post-saccadic oscillations in European-born and China-born British university undergraduates Journal Article In: PLoS ONE, vol. 15, no. 2, pp. e0229177, 2020. @article{Mardanbegi2020, Previous research has revealed that people from different genetic, racial, biological, and/or cultural backgrounds may display fundamental differences in eye-tracking behavior. These differences may have a cognitive origin or they may be at a lower level within the neurophysiology of the oculomotor network, or they may be related to environment factors. In this paper we investigated one of the physiological aspects of eye movements known as post-saccadic oscillations and we show that this type of eye movement is very different between two different populations. We compared the post-saccadic oscillations recorded by a video-based eye tracker between two groups of participants: European-born and Chinese-born British students. We recorded eye movements from a group of 42 Caucasians defined as White British or White Europeans and 52 Chinese-born participants all with ages ranging from 18 to 36 during a prosaccade task. The post-saccadic oscillations were extracted from the gaze data which was compared between the two groups in terms of their first overshoot and undershoot. The results revealed that the shape of the post-saccadic oscillations varied significantly between the two groups which may indicate a difference in a multitude of genetic, cultural, physiologic, anatomical or environmental factors. We further show that the differences in the post-saccadic oscillations could influence the oculomotor characteristics such as saccade duration. We conclude that genetic, racial, biological, and/or cultural differences can affect the morphology of the eye movement data recorded and should be considered when studying eye movements and oculomotor fixation and saccadic behaviors. |
Lee McIlreavy; Tom C. A. Freeman; Jonathan T. Erichsen Two-dimensional analysis of horizontal and vertical pursuit in infantile nystagmus reveals quantitative deficits in accuracy and precision Journal Article In: Investigative Ophthalmology & Visual Science, vol. 61, no. 6, pp. 1–12, 2020. @article{McIlreavy2020, PURPOSE. Infantile nystagmus (IN) presents with continuous, predominantly horizontal eye oscillations. It remains controversial whether those with IN have normal horizontal pursuit, while vertical pursuit has rarely been studied. We examined whether there are pursuit deficits associated with IN by investigating the effect of target direction, velocity, and amplitude. METHODS. Twelve adults with idiopathic IN performed a pursuit task, a 0.4° dot moved either horizontally or vertically at 8 or 16°/s, through amplitudes of 8°, 16°, or 32°. Accuracy and precision errors were computed as bivariate probability density functions of target-relative eye velocities. RESULTS. Eye velocity was less precise along the horizontal axis during both horizontal and vertical pursuit, reflecting the primary axis of the eye oscillation. Mean accuracy error along the target trajectory during vertical pursuit was just as impaired as during horizontal pursuit. There was a greater error in accuracy along the target trajectory for 16°/s targets than 8°/s. Finally, targets that oscillated at 2.0 Hz had a greater error in accuracy along the target trajectory than frequencies of 1.0 Hz or 0.5 Hz. When studied using the same experimental protocol, pursuit performance for typical observers was always better. CONCLUSIONS. These findings strongly support our hypothesis of severe deficits in pursuit accuracy in observers with IN for horizontally and vertically moving targets, as well as for targets that move at higher speeds or oscillate more quickly. Overall, IN pursuit impairment appears to have previously been underestimated, highlighting a need for further quantitative studies of dynamic visual function in those with IN. |
Eugene McSorley; Iain D. Gilchrist; Rachel McCloy The parallel programming of landing position in saccadic eye movement sequences Journal Article In: Journal of Vision, vol. 20, no. 1, pp. 1–14, 2020. @article{McSorley2020, Saccadic eye movements occur in sequences, gathering new information about the visual environment to support successful task completion. Here, we examine the control of these saccadic sequences and specifically the extent to which the spatial aspects of the saccadic responses are programmed in parallel. We asked participants to saccade to a series of visual targets and, while they shifted their gaze around the display, we displaced select targets. We found that saccade landing position was deviated toward the previous location of the target suggesting that partial parallel programming of target location information was occurring. The saccade landing position was also affected by the new target location, which demonstrates that the saccade landing position was also partially updated following the shift. This pattern was present even for targets that were the subject of the next fixation. Having a greater preview about the sequence path influenced saccade accuracy with saccades being less affected by relocations when there is less preview information. The results demonstrate that landing positions from a saccade sequence are programmed in parallel and combined with more immediate visual signals. |
Radha Nila Meghanathan; Cees Leeuwen; Marcello Giannini; Andrey R. Nikolaev Neural correlates of task-related refixation behavior Journal Article In: Vision Research, vol. 175, pp. 90–101, 2020. @article{Meghanathan2020, Eye movement research has shown that attention shifts from the currently fixated location to the next before a saccade is executed. We investigated whether the cost of the attention shift depends on higher-order processing at the time of fixation, in particular on visual working memory load differences between fixations and refixations on task-relevant items. The attention shift is reflected in EEG activity in the saccade-related potential (SRP). In a free viewing task involving visual search and memorization of multiple targets amongst distractors, we compared the SRP in first fixations versus refixations on targets and distractors. The task-relevance of targets implies that more information will be loaded in memory (e.g. both identity and location) than for distractors (e.g. location only). First fixations will involve greater memory load than refixations, since first fixations involve loading of new items, while refixations involve rehearsal of previously visited items. The SRP in the interval preceding the saccade away from a target or distractor revealed that saccade preparation is affected by task-relevance and refixation behavior. For task-relevant items only, we found longer fixation duration and higher SRP amplitudes for first fixations than for refixations over the occipital region and the opposite effect over the frontal region. Our findings provide first neurophysiological evidence that working memory loading of task-relevant information at fixation affects saccade planning. |
David Melcher; Devpriya Kumar; Narayanan Srinivasan The role of action intentionality and effector in the subjective expansion of temporal duration after saccadic eye movements Journal Article In: Scientific Reports, vol. 10, pp. 16922, 2020. @article{Melcher2020, Visual perception is based on periods of stable fixation separated by saccadic eye movements. Although naive perception seems stable (in space) and continuous (in time), laboratory studies have demonstrated that events presented around the time of saccades are misperceived spatially and temporally. Saccadic chronostasis, the “stopped clock illusion”, represents one such temporal distortion in which the movement of the clock hand after the saccade is perceived as lasting longer than usual. Multiple explanations for chronostasis have been proposed including action-backdating, temporal binding of the action towards the moment of its effect (“intentional binding”) and post-saccadic temporal dilation. The current study aimed to resolve this debate by using different types of action (keypress vs saccade) and varying the intentionality of the action. We measured both perceived onset of the motor action and perceived onset of an auditory tone presented at different delays after the keypress/saccade. The results showed intentional binding for the keypress action, with perceived motor onset shifted forwards in time and the time of the tone shifted backwards. Saccades resulted in the opposite pattern, showing temporal expansion rather than compression, especially with cued saccades. The temporal illusion was modulated by intentionality of the movement. Our findings suggest that saccadic chronostasis is not solely dependent on a backward shift in perceived saccade onset, but instead reflects a temporal dilation. This percept of an effectively “longer” period at the beginning of a new fixation may reflect the pattern of suppressed, and then enhanced, visual processing around the time of saccades. |
Brendan T. Barrett; Alice G. Cruickshank; Jonathan C. Flavell; Simon J. Bennett; John G. Buckley; Julie M. Harris; Andrew J. Scally Faster visual reaction times in elite athletes are not linked to better gaze stability Journal Article In: Scientific Reports, vol. 10, pp. 13216, 2020. @article{Barrett2020, The issue of whether visually-mediated, simple reaction time (VRT) is faster in elite athletes is contentious. Here, we examined if and how VRT is affected by gaze stability in groups of international cricketers (16 females, 28 males), professional rugby-league players (21 males), and non-sporting controls (20 females, 30 males). VRT was recorded via a button-press response to the sudden appearance of a stimulus (circular target—diameter 0.8°), that was presented centrally, or 7.5° to the left or right of fixation. The incidence and timing of saccades and blinks occurring from 450 ms before stimulus onset to 225 ms after onset were measured to quantify gaze stability. Our results show that (1) cricketers have faster VRT than controls; (2) blinks and, in particular, saccades are associated with slower VRT regardless of the level of sporting ability; (3) elite female cricketers had steadier gaze (fewer saccades and blinks) compared to female controls; (4) when we accounted for the presence of blinks and saccades, our group comparisons of VRT were virtually unchanged. The stability of gaze is not a factor that explains the difference between elite and control groups in VRT. Thus we conclude that better gaze stability cannot explain faster VRT in elite sports players. |
Denise Baumeler; Josef G. Schönhammer; Sabine Born Microsaccade dynamics in the attentional repulsion effect Journal Article In: Vision Research, vol. 170, pp. 46–52, 2020. @article{Baumeler2020b, A briefly flashed peripheral cue has been shown to repulse the perceived position of a subsequently presented foveal probe - a bias called the Attentional Repulsion Effect (ARE). While this bias has originally been assumed to reflect attentional capturing by the cue, its attentional nature has recently been questioned. To investigate the ARE's attentional properties, we recorded microsaccades as an attentional marker in the ARE paradigm. Microsaccades, small fixational eye movements performed during fixation, have previously been described to reflect the dynamics of spatial attention deployment. Our results favor an attentional explanation for the ARE: In trials in which an ARE was found, microsaccades were directed more often toward the cue, presumably reflecting the covert shift of attention. In contrast, more cue-incongruent microsaccades were observed in trials in which no ARE was found. Therefore, both repulsion as well as measured microsaccade modulations, are most likely an outcome of the preceding shifts of covert attention. |
Valerie M. Beck; Timothy J. Vickery Oculomotor capture reveals trial-by-trial neural correlates of attentional guidance by contents of visual working memory Journal Article In: Cortex, vol. 122, pp. 159–169, 2020. @article{Beck2020, Evidence from attentional and oculomotor capture, contingent capture, and other paradigms suggests that mechanisms supporting human visual working memory (VWM) and visual attention are intertwined. Features held in VWM bias guidance toward matching items even when those features are task irrelevant. However, the neural basis of this interaction is underspecified. Prior examinations using fMRI have primarily relied on coarse comparisons across experimental conditions that produce varying amounts of capture. To examine the neural dynamics of attentional capture on a trial-by-trial basis, we applied an oculomotor paradigm that produced discrete measures of capture. On each trial, subjects were shown a memory item, followed by a blank retention interval, then a saccade target that appeared to the left or right. On some trials, an irrelevant distractor appeared above or below fixation. Once the saccade target was fixated, subjects completed a forced-choice memory test. Critically, either the target or distractor could match the feature held in VWM. Although task irrelevant, this manipulation produced differences in behavior: participants were more likely to saccade first to an irrelevant VWM-matching distractor compared with a non-matching distractor – providing a discrete measure of capture. We replicated this finding while recording eye movements and scanning participants' brains using fMRI. To examine the neural basis of oculomotor capture, we separately modeled the retention interval for capture and non-capture trials within the distractor-match condition. We found that frontal activity, including anterior cingulate cortex and superior frontal gyrus regions, differentially predicted subsequent oculomotor capture by a memory-matching distractor. Other regions previously implicated as involved in attentional capture by VWM-matching items showed no differential activity across capture and non-capture trials, even at a liberal threshold. Our findings demonstrate the power of trial-by-trial analyses of oculomotor capture as a means to examine the underlying relationship between VWM and attentional guidance systems. |
Sonya Bells; Silvia L. Isabella; Donald C. Brien; Brian C. Coe; Douglas P. Munoz; Donald J. Mabbott; Douglas O. Cheyne Mapping neural dynamics underlying saccade preparation and execution and their relation to reaction time and direction errors Journal Article In: Human Brain Mapping, vol. 41, no. 7, pp. 1934–1949, 2020. @article{Bells2020, Our ability to control and inhibit automatic behaviors is crucial for negotiating complex environments, all of which require rapid communication between sensory, motor, and cognitive networks. Here, we measured neuromagnetic brain activity to investigate the neural timing of cortical areas needed for inhibitory control, while 14 healthy young adults performed an interleaved prosaccade (look at a peripheral visual stimulus) and antisaccade (look away from stimulus) task. Analysis of how neural activity relates to saccade reaction time (SRT) and occurrence of direction errors (look at stimulus on antisaccade trials) provides insight into inhibitory control. Neuromagnetic source activity was used to extract stimulus-aligned and saccade-aligned activity to examine temporal differences between prosaccade and antisaccade trials in brain regions associated with saccade control. For stimulus-aligned antisaccade trials, a longer SRT was associated with delayed onset of neural activity within the ipsilateral parietal eye field (PEF) and bilateral frontal eye field (FEF). Saccade-aligned activity demonstrated peak activation 10ms before saccade-onset within the contralateral PEF for prosaccade trials and within the bilateral FEF for antisaccade trials. In addition, failure to inhibit prosaccades on anti-saccade trials was associated with increased activity prior to saccade onset within the FEF contralateral to the peripheral stimulus. This work on dynamic activity adds to our knowledge that direction errors were due, at least in part, to a failure to inhibit automatic prosaccades. These findings provide novel evidence in humans regarding the temporal dynamics within oculomotor areas needed for saccade programming and the role frontal brain regions have on top-down inhibitory control. |
Klinton Bicknell; Roger Levy; Keith Rayner Ongoing cognitive processing influences precise eye-movement targets in reading Journal Article In: Psychological Science, vol. 31, no. 4, pp. 351–362, 2020. @article{Bicknell2020, Reading is a highly complex learned skill in which humans move their eyes three to four times every second in response to visual and cognitive processing. The consensus view is that the details of these rapid eye-movement decisions—which part of a word to target with a saccade—are determined solely by low-level oculomotor heuristics. But maximally efficient saccade targeting would be sensitive to ongoing word identification, sending the eyes farther into a word the farther its identification has already progressed. Here, using a covert text-shifting paradigm, we showed just such a statistical relationship between saccade targeting in reading and trial-to-trial variability in cognitive processing. This result suggests that, rather than relying purely on heuristics, the human brain has learned to optimize eye movements in reading even at the fine-grained level of character-position targeting, reflecting efficiency-based sensitivity to ongoing cognitive processing. |
Francesca Bonetti; Matteo Valsecchi; Massimo Turatto In: Cortex, vol. 131, pp. 251–264, 2020. @article{Bonetti2020, The oculomotor capture triggered by a peripheral onset is subject to habituation, a basic form of learning consisting in a response decrement toward a repeatedly presented stimulus. However, it is unclear whether habituation of reflexive saccades takes place at the saccadic programming or execution stage (or both). To address this issue, we exploited the fact that during fixation the programming of a reflexive saccade exerts a robust but short-lasting phasic inhibition in the absolute microsaccadic frequency. Hence, if habituation of reflexive saccades occurs at the programming stage, then this should also affect the microsaccadic frequency, with a progressive reduction of the inhibitory phase. Conversely, if habituation occurs only at the later stage of saccade execution, the no change in the microsaccadic pattern is expected. Participants were repeatedly exposed to a peripheral onset distractor, and when eye movements were allowed, we replicated the oculomotor capture habituation. Crucially, however, when fixation was maintained the microsaccadic response did not change as exposure to the onset progressed, suggesting that habituation of reflexive saccades does not take place at the programming stage in the superior colliculus (SC), but at the later stage of saccade execution in the brainstem, where the competition between different saccades might be resolved. This scenario challenges one of the main assumptions of the competitive integration model for oculomotor control, which assumes that competition between exogenous and endogenous saccade programs occurs in the (SC). Our results and interpretation are instead in agreement with neurophysiological studies in non-human primates showing that saccadic adaption, another form of oculomotor plasticity, takes place downstream from the SC. |
Annalisa Bosco; Katharina Rifai; Siegfried Wahl; Patrizia Fattori; Markus Lappe Trans-saccadic adaptation of perceived size independent of saccadic adaptation Journal Article In: Journal of Vision, vol. 20, no. 7, pp. 1–11, 2020. @article{Bosco2020, Systematic shortening or lengthening of target objects during saccades modifies saccade amplitudes and perceived size of the objects. These two events are concomitant when size change during the saccade occurs asymmetrically, thereby shifting the center of mass of the object. In the present study, we asked whether or not the two are necessarily linked. We tested human participants in symmetrical systematic shortening and lengthening of a vertical bar during a horizontal saccade, aiming to not modify the saccade amplitude. Before and after a phase of trans-saccadic changes of the target bar, participants manually indicated the sizes of various vertically oriented bars by open-loop grip aperture. We evaluated the effect of trans-saccadic changes of bar length on manual perceptual reports and whether this change depended on saccade amplitude. As expected, we did not induce any change in horizontal or vertical components of saccade amplitude, but we found a significant difference in perceived size after the lengthening experiment compared to after the shortening experiment. Moreover, after the lengthening experiment, perceived size differed significantly from pre-lengthening baseline. These findings suggest that a change of size perception can be induced trans-saccadically, and its mechanism does not depend on saccadic amplitude change. |
Antimo Buonocore; Olaf Dimigen; David Melcher Post-saccadic face processing is modulated by pre-saccadic preview: Evidence from fixation-related potentials Journal Article In: Journal of Neuroscience, vol. 40, no. 11, pp. 2305–2313, 2020. @article{Buonocore2020, Humans actively sample their environment with saccadic eye movements to bring relevant information into high-acuity foveal vision. Despite being lower in resolution, peripheral information is also available before each saccade. How the pre-saccadic extrafoveal preview of a visual object influences its post-saccadic processing is still an unanswered question. The current study investigated this question by simultaneously recording behavior and fixation-related brain potentials while human subjects made saccades to face stimuli. We manipulated the relationship between pre-saccadic "previews" and post-saccadic images to explicitly isolate the influences of the former. Subjects performed a gender discrimination task on a newly foveated face under three preview conditions: scrambled face, incongruent face (different identity from the foveated face), and congruent face (same identity). As expected, reaction times were faster after a congruent-face preview compared with a scrambled-face preview. Importantly, intact face previews (either incongruent or congruent) resulted in a massive reduction of post-saccadic neural responses. Specifically, we analyzed the classic face-selective N170 component at occipitotemporal electroencephalogram electrodes, which was still present in our experiments with active looking. However, the post-saccadic N170 was strongly attenuated following intact-face previews compared with the scrambled condition. This large and long-lasting decrease in evoked activity is consistent with a trans-saccadic mechanism of prediction that influences category-specific neural processing at the start of a new fixation. These findings constrain theories of visual stability and show that the extrafoveal preview methodology can be a useful tool to investigate its underlying mechanisms. |
Elisa Castaldi; David Burr; Marco Turi; Paola Binda Fast saccadic eye-movements in humans suggest that numerosity perception is automatic and direct: Numerosity drives fast saccades Journal Article In: Proceedings of the Royal Society B: Biological Sciences, vol. 287, pp. 1–9, 2020. @article{Castaldi2020, Fast saccades are rapid automatic oculomotor responses to salient and ecologically important visual stimuli such as animals and faces. Discriminating the number of friends, foe, or prey may also have an evolutionary advantage. In this study, participants were asked to saccade rapidly towards the more numerous of two arrays. Participants could discriminate numerosities with high accuracy and great speed, as fast as 190 ms. Intermediate numerosities were more likely to elicit fast saccades than very low or very high numerosities. Reaction-times for vocal responses (collected in a separate experiment) were slower, did not depend on numerical range, and correlated only with the slow not the fast saccades, pointing to different systems. The short saccadic reaction-times we observe are surprising given that discrimination using numerosity estimation is thought to require a relatively complex neural circuit, with several relays of information through the parietal and prefrontal cortex. Our results suggest that fast numerosity-driven saccades may be generated on a single feed-forward pass of information recruiting a primitive system that cuts through the cortical hierarchy and rapidly transforms the numerosity information into a saccade command. |
Soazig Casteau; Daniel T. Smith On the link between attentional search and the oculomotor system: Is preattentive search restricted to the range of eye movements? Journal Article In: Attention, Perception, and Psychophysics, vol. 82, no. 2, pp. 518–532, 2020. @article{Casteau2020, It has been proposed that covert visual search can be fast, efficient, and stimulus driven, particularly when the target is defined by a salient single feature, or slow, inefficient, and effortful when the target is defined by a nonsalient conjunction of features. This distinction between fast, stimulus-driven orienting and slow, effortful orienting can be related to the distinction between exogenous spatial attention and endogenous spatial attention. Several studies have shown that exogenous, covert orienting is limited to the range of saccadic eye movements, whereas covert endogenous orienting is independent of the range of saccadic eye movements. The current study examined whether covert visual search is affected in a similar way. Experiment 1 showed that covert visual search for feature singletons was impaired when stimuli were presented beyond the range of saccadic eye movements, whereas conjunction search was unaffected by array position. Experiment 2 replicated and extended this effect by measuring search times at 6 eccentricities. The impairment in covert feature search emerged only when stimuli crossed the effective oculomotor range and remained stable for locations further into the periphery, ruling out the possibility that the results of Experiment 1 were due to a failure to fully compensate for the effects of cortical magnification. The findings are interpreted in terms of biased competition and oculomotor theories of spatial attention. It is concluded that, as with covert exogenous orienting, biological constraints on overt orienting in the oculomotor system constrain covert, preattentive search. |
Johan Chandra; André Krügel; Ralf Engbert Experimental test of Bayesian saccade targeting under reversed reading direction Journal Article In: Attention, Perception, and Psychophysics, vol. 82, no. 3, pp. 1230–1240, 2020. @article{Chandra2020a, During reading, rapid eye movements (saccades) shift the reader's line of sight from one word to another for high-acuity visual information processing. While experimental data and theoretical models show that readers aim at word centers, the eye-movement (oculomotor) accuracy is low compared to other tasks. As a consequence, distributions of saccadic landing positions indicate large (i) random errors and (ii) systematic over- and undershoot of word centers, which additionally depend on saccade lengths (McConkie et al. Visual Research, 28(10), 1107–1118, 1988). Here we show that both error components can be simultaneously reduced by reading texts from right to left in German language (N = 32). We used our experimental data to test a Bayesian model of saccade planning. First, experimental data are consistent with the model. Second, the model makes specific predictions of the effects of the precision of prior and (sensory) likelihood. Our results suggest that it is a more precise sensory likelihood that can explain the reduction of both random and systematic error components. |
Chih-Yang Chen; Denis Matrov; Richard Veale; Hirotaka Onoe; Masatoshi Yoshida; Kenichiro Miura; Tadashi Isa Properties of visually-guided saccadic behavior and bottom-up attention in marmoset, macaque, and human Journal Article In: Journal of Neurophysiology, 2020. @article{Chen2020a, The saccade is a stereotypic behavior whose investigation improves our understanding of how primate brains implement precise motor control. Furthermore, saccades offer an important window into the cognitive and attentional state of the brain. Historically, saccade studies have largely relied on macaque. However, the cortical network giving rise to the saccadic command is difficult to study in macaque because relevant cortical areas lie in sulci and are difficult to access. Recently, a New World monkey – the marmoset – has garnered attention as an attractive alternative to macaque because of its smooth cortical surface, its smaller body, and its amenability to transgenic technology. However, adoption of marmoset for oculomotor research has been limited due to a lack of in-depth descriptions of marmoset saccade kinematics and their ability to perform psychophysical and cognitive tasks. Here, we directly compare free-viewing and visually-guided behavior of marmoset, macaque, and human engaged in identical tasks under similar conditions. In video free-viewing task, all species exhibited qualitatively similar saccade kinematics including saccade main sequence up to 25° in amplitude. Furthermore, the conventional bottom-up saliency model predicted gaze targets at similar rates for all species. We further verified their visually-guided behavior by training them with step and gap saccade tasks. All species showed similar gap effect and express saccades in the gap paradigm. Our results suggest that the three species have similar natural and task-guided visuomotor behavior. The marmoset can be trained on saccadic tasks and thus can serve as a model for oculomotor, attention, and cognitive research. |
Rebekka Schröder; Anna-Maria Kasparbauer; Inga Meyhöfer; Maria Steffens; Peter Trautner; Ulrich Ettinger Functional connectivity during smooth pursuit eye movements Journal Article In: Journal of Neurophysiology, vol. 124, pp. 1839–1856, 2020. @article{Schroeder2020, Smooth pursuit eye movements (SPEM) hold the image of a slowly moving stimulus on the fovea. The neural system underlying SPEM primarily includes visual, parietal and frontal areas. In the present study, we investigated how these areas are functionally coupled and how these couplings are influenced by target motion frequency. To this end, healthy participants (N=57) were instructed to follow a sinusoidal target stimulus moving horizontally at two different frequencies (0.2 Hz, 0.4 Hz). Eye movements and BOLD activity were recorded simultaneously. Functional connectivity of the key areas of the SPEM network was investigated using a Psychophysiological Interaction (PPI) approach. It was analyzed how activity in five eye movement related seed regions (lateral geniculate nucleus, V1, V5, posterior parietal cortex, frontal eye fields) relates to activity in other parts of the brain during SPEM. The behavioral results showed clear deterioration of SPEM performance at higher target frequency. BOLD activity during SPEM vs. fixation occurred in a geniculo-occipito-parieto-frontal network, replicating previous findings. PPI analysis yielded wide-spread, partially overlapping networks. Especially frontal eye fields and posterior parietal cortex showed task-dependent connectivity to large parts of the entire cortex, while other seed regions demonstrated more regionally focused connectivity. Higher target frequency was associated with stronger activations in visual areas but had no effect on functional connectivity. In summary, the results confirm and extend previous knowledge regarding the neural mechanisms underlying SPEM and provide a valuable basis for further investigations such as in patients with SPEM impairments and known alterations in brain connectivity. |
Huiru Shao; Jing Li; Wenbo Wan; Huaxiang Zhang; Jiande Sun Saccadic trajectory-based identity authentication Journal Article In: Multimedia Tools and Applications, vol. 79, no. 7-8, pp. 4891–4905, 2020. @article{Shao2020, The saccadic trajectory is generated by extra-ocular muscles in the eyes, which is a complex mechanism related to brain-driven neural signal. The saccadic trajectory has the characteristics of non-reproducibility and non-contact. In this paper, we propose a saccadic trajectory-based identity authentication method considering that saccadic trajectory can be used as a behavior-based biometric. In this method, we adopt Velocity-Threshold (I-VT) algorithm to extract saccadic trajectories from the whole eye movement data, extract features via wavelet packet transform and authenticate the identity via classifying these features by SVM. In this paper, we verify the proposed method on EMDBv1.0 dataset for horizontal eye movements. We select one subject to be the host and randomly choose another 50 subjects from the remaining 58 subjects as the attackers. We achieve the best performance via optimizing feature selection and the parameter of SVM. The experiment results show that the average accuracy for accepting the host can reach 98.09%, and the average accuracy for rejecting the attackers can reach 99.55%. It demonstrates that the saccadic trajectory-based identity authentication is promising in information security. |
Andréanne Sharp; Christine Turgeon; Aaron Paul Johnson; Sebastian Pannasch; François Champoux; Dave Ellemberg Congenital deafness leads to altered overt oculomotor behaviors Journal Article In: Frontiers in Neuroscience, vol. 14, pp. 273, 2020. @article{Sharp2020, The human brain is highly cross-modal, and sensory information may affect a wide range of behaviors. In particular, there is evidence that auditory functions are implicated in oculomotor behaviors. Considering this apparent auditory-oculomotor link, one might wonder how the loss of auditory input from birth might have an influence on these motor behaviors. Eye movement tracking enables to extract several components, including saccades and smooth pursuit. One study suggested that deafness can alter saccades processing. Oculomotor behaviors have not been examined further in the deaf. The main goal of this study was to examine smooth pursuit following deafness. A pursuit task paradigm was used in this experiment. Participants were instructed to move their eyes to follow a target as it moved. The target movements have a possibility of four different trajectories (horizontal, vertical, elliptic clockwise, and elliptic counter-clockwise). Results indicate a significant reduction in the ability to track a target in both elliptical conditions showing that more complex motion processing differs in deaf individuals. The data also revealed significantly more saccades per trial in the vertical, anti-clockwise, and, to a lesser extent, the clockwise elliptic condition. This suggests that auditory deprivation from birth leads to altered overt oculomotor behaviors. |
Emma E. M. Stewart; Carolin Hubner; Alexander C. Schutz Stronger saccadic suppression of displacement and blanking effect in children Journal Article In: Journal of Vision, vol. 20, no. 10, pp. 1–25, 2020. @article{Stewart2020, Humans do not notice small displacements to objects that occur during saccades, termed saccadic suppression of displacement (SSD), and this effect is reduced when a blank is introduced between the pre- and postsaccadic stimulus (Bridgeman, Hendry, & Stark, 1975; Deubel, Schneider, & Bridgeman, 1996). While these effects have been studied extensively in adults, it is unclear how these phenomena are characterized in children. A potentially related mechanism, saccadic suppression of contrast sensitivity—a prerequisite to achieve a stable percept—is stronger for children (Bruno, Brambati, Perani, & Morrone, 2006). However, the evidence for how transsaccadic stimulus displacements may be suppressed or integrated is mixed. While they can integrate basic visual feature information from an early age, they cannot integrate multisensory information (Gori, Viva, Sandini, & Burr, 2008; Nardini, Jones, Bedford, & Braddick, 2008), suggesting a failure in the ability to integrate more complex sensory information. We tested children 7 to 12 years old and adults 19 to 23 years old on their ability to perceive intrasaccadic stimulus displacements, with and without a postsaccadic blank. Results showed that children had stronger SSD than adults and a larger blanking effect. Children also had larger undershoots and more variability in their initial saccade endpoints, indicating greater intrinsic uncertainty, and they were faster in executing corrective saccades to account for these errors. Together, these results suggest that children may have a greater internal expectation or prediction of saccade error than adults; thus, the stronger SSD in children may be due to higher intrinsic uncertainty in target localization or saccade execution. |
Georgia F. Symons; Meaghan Clough; William T. O'Brien; Joel Ernest; Sabrina Salberg; Daniel Costello; Mujun Sun; Rhys D. Brady; Stuart J. McDonald; David K. Wright; Owen White; Larry Abel; Terence J. O'Brien; Jesse Mccullough; Roxanne Aniceto; I-Hsuan Lin; Denes V. Agoston; Joanne Fielding; Richelle Mychasiuk; Sandy R. Shultz Shortened telomeres and serum protein biomarker abnormalities in collision sport athletes regardless of concussion history and sex Journal Article In: Journal of Concussion, vol. 4, pp. 1–11, 2020. @article{Symons2020, Mild brain injuries are frequent in athletes engaging in collision sports and have been linked to a range of long-term neurological abnormalities. There is a need to identify how these potential abnormalities manifest using objective measures; determine whether changes are due to concussive and/or sub-concussive injuries; and examine how biological sex affects outcomes. This study investigated cognitive, cellular, and molecular biomarkers in male and female amateur Australian footballers (i.e. Australia's most participated collision sport). 95 Australian footballers (69 males, 26 females), both with and without a history of concussion, as well as 49 control athletes (28 males, 21 females) with no history of brain trauma or participation in collision sports were recruited to the study. Ocular motor assessment was used to examine cognitive function. Telomere length, a biomarker of cellular senescence and neurological health, was examined in saliva. Serum levels of tau, phosphorylated tau, neurofilament light chain, and 4-hydroxynonenal were used as markers to assess axonal injury and oxidative stress. Australian footballers had reduced telomere length (p = 0.031) and increased serum protein levels of 4-hydroxynonenal (p = 0.001), tau (p = 0.007), and phosphorylated tau (p = 0.036). These findings were independent of concussion history and sex. No significant ocular motor differences were found. Taken together, these findings suggest that engagement in collision sports, regardless of sex or a history of concussion, is associated with shortened telomeres, axonal injury, and oxidative stress. These saliva- and serum-based biomarkers may be useful to monitor neurological injury in collision sport athletes. |
Martin Szinte; David Aagten-Murphy; Donatas Jonikaitis; Luca Wollenberg; Heiner Deubel Sounds are remapped across saccades Journal Article In: Scientific Reports, vol. 10, pp. 21332, 2020. @article{Szinte2020, To achieve visual space constancy, our brain remaps eye-centered projections of visual objects across saccades. Here, we measured saccade trajectory curvature following the presentation of visual, auditory, and audiovisual distractors in a double-step saccade task to investigate if this stability mechanism also accounts for localized sounds. We found that saccade trajectories systematically curved away from the position at which either a light or a sound was presented, suggesting that both modalities are represented in eye-centered oculomotor centers. Importantly, the same effect was observed when the distractor preceded the execution of the first saccade. These results suggest that oculomotor centers keep track of visual, auditory and audiovisual objects by remapping their eye-centered representations across saccades. Furthermore, they argue for the existence of a supra-modal map which keeps track of multi-sensory object locations across our movements to create an impression of space constancy. |
Jérôme Tagu; Karine Doré-Mazars; Dorine Vergilino-Perez Saccade accuracy as an indicator of the competition between functional asymmetries in vision Journal Article In: Experimental Brain Research, vol. 238, no. 2, pp. 411–425, 2020. @article{Tagu2020, Hemispheric specialization refers to the fact that cerebral hemispheres are not equivalent and that cognitive processes are lateralized in the brain. Although the potential links between handedness and the left hemisphere specialization for language have been widely studied, little attention has been paid to other motor preferences, such as eye dominance, that also are lateralized in the brain. For example, saccadic accuracy is higher in the hemifield contralateral to the dominant eye compared to the ipsilateral hemifield. Saccade accuracy is, however, also known to be sensitive to other functional asymmetries, such as the lateralization of visuo-spatial attention in the right hemisphere of the brain. Using a global effect paradigm in three different saccade latency ranges, we here propose to use saccade accuracy as an indicator of visual functional asymmetries. We show that for the shortest latencies, saccade accuracy is higher in the left than in the right visual hemifield, which could be due to the lateralization of visuo-spatial attention in the right hemisphere. For the longest latencies, however, saccade accuracy is higher toward the right than the left hemifield, probably due to the lateralization of local and global processing in the left and right hemispheres, respectively. These results could have a major impact on studies designed to measure the degree of lateralization of individuals. We here discuss both the theoretical and clinical contributions of these results. |