Smooth Pursuit Tasks Research Articles

The association between eye movement characteristics and cognitive function in adolescents with major depressive disorder

ObjectiveThis study aims to explore the relationship between eye movement characteristics and cognitive function in adolescents with major depressive disorder (MDD). MethodEyeLink 1000 eye tracker was used to obtain eye movement data in free-viewing and smooth pursuit tasks. Chi-square test and Mann-Whitney test were used for inter-group comparison of demographic and clinical data. Spearman correlation was used to analyze the correlation between eye movement characteristics and cognitive function. ResultsAdolescents with MDD showed lower saccade amplitude in the free-viewing task and more fixations and saccades in the smooth pursuit task. In the free-viewing task, fixation count, saccade duration and saccade speed were found to be positively correlated with immediate memory and attention; fixation duration was negatively correlated with immediate memory. In the smooth pursuit task, saccade count was positively correlated with the faux pas test; fixation duration and saccade duration were significantly correlated with memory and attention. ConclusionAdolescents with MDD showed abnormalities in several indices of eye movement, and altered eye movement variables were also correlated with cognitive deficits. Eye-tracking technology helps illustrate the diverse cognitive strategies employed by individuals during cognitive tasks, allowing researchers to explore subtle differences in cognitive processes.

Oculomotor differences in adults with and without probable developmental coordination disorder.

Adults with Developmental Coordination Disorder (DCD), sometimes referred to as dyspraxia, experience difficulties in motor development and coordination, which impacts on all aspects of their daily lives. Surprisingly little is known about the mechanisms underlying the difficulties they experience in the motor domain. In childhood DCD, aspects of oculomotor control have been shown to be altered. The purpose of this study was to determine whether oculomotor differences are present in adults with and without probable DCD. Visual fixation stability, smooth pursuit, and pro-and anti-saccade performance were assessed in 21 adults (mean age 29 years) with probable DCD/dyspraxia (pDCD) and 21 typically-developing (TD) adults (mean age 21 years). Eye tracking technology revealed that oculomotor response preparation in the pro- and anti-saccade tasks was comparable across groups, as was pursuit gain in the slower of the two smooth pursuit tasks. However, adults with pDCD made significantly more saccades away from the fixation target than those without DCD and significantly more anti-saccade errors. Further, compared to TD adults, adults with pDCD demonstrated difficulties in maintaining engagement and had lower pursuit gain in the faster pursuit task. This suggests that adults with pDCD have problems with saccadic inhibition and maintaining attention on a visual target. Since this pattern of results has also been reported in children with DCD, oculomotor difficulties may be persistent for those with DCD across the lifespan. An awareness of the impact of atypical oculomotor control in activities of daily living across the lifespan would support clearer understanding of the causes and impacts of these difficulties for those with DCD.

Oculomotor atypicalities in motor neurone disease: a systematic review.

Cognitive dysfunction is commonplace in Motor Neurone Disease (MND). However, due to the prominent motor symptoms in MND, assessing patients' cognitive function through traditional cognitive assessments, which oftentimes require motoric responses, may become increasingly challenging as the disease progresses. Oculomotor pathways are apparently resistant to pathological degeneration in MND. As such, abnormalities in oculomotor functions, largely driven by cognitive processes such as saccades and smooth pursuit eye movement, may be reflective of frontotemporal cognitive deficits in MND. Thus, saccadic and smooth pursuit eye movements may prove to be ideal mechanistic markers of cognitive function in MND. To ascertain the utility of saccadic and smooth pursuit eye movements as markers of cognitive function in MND, this review summarizes the literature concerning saccadic and smooth pursuit eye movement task performance in people with MND. Of the 22 studies identified, noticeable patterns suggest that people with MND can be differentiated from controls based on antisaccade and smooth pursuit task performance, and thus the antisaccade task and smooth pursuit task may be potential candidates for markers of cognition in MND. However, further studies which ascertain the concordance between eye tracking measures and traditional measures of cognition are required before this assumption is extrapolated, and clinical recommendations are made. https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=376620, identifier CRD42023376620.

Eye Movement Characteristics for Predicting a Transition to Psychosis: Longitudinal Changes and Implications.

Substantive inquiry into the predictive power of eye movement (EM) features for clinical high-risk (CHR) conversion and their longitudinal trajectories is currently sparse. This study aimed to investigate the efficiency of machine learning predictive models relying on EM indices and examine the longitudinal alterations of these indices across the temporal continuum. EM assessments (fixation stability, free-viewing, and smooth pursuit tasks) were performed on 140 CHR and 98 healthy control participants at baseline, followed by a 1-year longitudinal observational study. We adopted Cox regression analysis and constructed random forest prediction models. We also employed linear mixed-effects models (LMMs) to analyze longitudinal changes of indices while stratifying by group and time. Of the 123 CHR participants who underwent a 1-year clinical follow-up, 25 progressed to full-blown psychosis, while 98 remained non-converters. Compared with the non-converters, the converters exhibited prolonged fixation durations, decreased saccade amplitudes during the free-viewing task; larger saccades, and reduced velocity gain during the smooth pursuit task. Furthermore, based on 4 baseline EM measures, a random forest model classified converters and non-converters with an accuracy of 0.776 (95% CI: 0.633, 0.882). Finally, LMMs demonstrated no significant longitudinal alterations in the aforementioned indices among converters after 1 year. Aberrant EMs may precede psychosis onset and remain stable after 1 year, and applying eye-tracking technology combined with a modeling approach could potentially aid in predicting CHRs evolution into overt psychosis.

Multi‐task analysis of oculographic biomarkers to evaluate motoric and cognitive patterns in Alzheimer’s Disease

AbstractBackgroundAlzheimer’s disease (AD) is characterized by progressive loss or damage to the nervous system which can cause impairment in movement, coordination, and cognition. Due to the complexity of clinical features at different stages of the disease, it may require months for an accurate diagnosis. Oculomotor researchers have demonstrated the utility of examining eye movements for differentiating various neurodegenerative disorders including AD, Parkinson’s disease (PD), and other PD mimics (PDM). In this study, we propose an automatic pipeline to identify saccade, fixation, and blinks and extract response‐to‐stimuli‐derived interpretable biomarkers that could inform clinicians in making accurate assessment.MethodEye tracking data in smooth pursuit, pro‐saccade, and anti‐saccade tasks were recorded from 146 participants ‐ 14 with AD or Mild Cognitive Impairment (MCI), 46 with PD, 16 with PDM, and 70 age‐matched normal controls (CTL). Biomarkers based on the identified eye movement and interaction with the stimuli were extracted with our algorithms. Then, pairwise Kruskal‐Wallis H tests were conducted to determine if there were statistically significant differences between groups. The Benjamini‐Hochberg correction was performed to control the false discovery rate.ResultThe results show that, in the smooth pursuit task, the AD/MCI group had a significantly higher (p < 0.05) saccade count than CTL and PD groups. The AD/MCI group also exhibited significantly longer (p < 0.05) average saccade duration than CTL and PDM groups. The mean and standard deviation for the number of saccadic adjustments to reach and stay on the target significantly differed (p < 0.05) between AD/MCI and CTL and between PD and CTL in trials of the pro‐saccade task. The magnitude of overshoot or undershoot was significantly greater (p < 0.05) for AD/MCI, PD, and PDM compared to CTL. Moreover, the number of saccades in the wrong direction was significantly higher (p < 0.05) for AD/MCI and PD compared to CTL in the anti‐saccade task.ConclusionOculographic biomarkers can be leveraged within a machine learning framework and may be useful in distinguishing different types of neurodegenerative diseases in their early stages yielding more objective and precise protocols to monitor disease progression than current methods.

Multi‐task analysis of oculographic biomarkers to evaluate motoric and cognitive patterns in Alzheimer’s Disease

AbstractBackgroundAlzheimer’s disease (AD) is characterized by progressive loss or damage to the nervous system which can cause impairment in movement, coordination, and cognition. Due to the complexity of clinical features at different stages of the disease, it may require months for an accurate diagnosis. Oculomotor researchers have demonstrated the utility of examining eye movements for differentiating various neurodegenerative disorders including AD, Parkinson’s disease (PD), and other PD mimics (PDM). In this study, we propose an automatic pipeline to identify saccade, fixation, and blinks and extract response‐to‐stimuli‐derived interpretable biomarkers that could inform clinicians in making accurate assessment.MethodEye tracking data in smooth pursuit, pro‐saccade, and anti‐saccade tasks were recorded from 146 participants ‐ 14 with AD or Mild Cognitive Impairment (MCI), 46 with PD, 16 with PDM, and 70 age‐matched normal controls (CTL). Biomarkers based on the identified eye movement and interaction with the stimuli were extracted with our algorithms. Then, pairwise Kruskal‐Wallis H tests were conducted to determine if there were statistically significant differences between groups. The Benjamini‐Hochberg correction was performed to control the false discovery rate.ResultThe results show that, in the smooth pursuit task, the AD/MCI group had a significantly higher (p < 0.05) saccade count than CTL and PD groups. The AD/MCI group also exhibited significantly longer (p < 0.05) average saccade duration than CTL and PDM groups. The mean and standard deviation for the number of saccadic adjustments to reach and stay on the target significantly differed (p < 0.05) between AD/MCI and CTL and between PD and CTL in trials of the pro‐saccade task. The magnitude of overshoot or undershoot was significantly greater (p < 0.05) for AD/MCI, PD, and PDM compared to CTL. Moreover, the number of saccades in the wrong direction was significantly higher (p < 0.05) for AD/MCI and PD compared to CTL in the anti‐saccade task.ConclusionOculographic biomarkers can be leveraged within a machine learning framework and may be useful in distinguishing different types of neurodegenerative diseases in their early stages yielding more objective and precise protocols to monitor disease progression than current methods.

Eye movement dysfunction for screening mild cognitive impairment

AbstractBackgroundEarly screening of cognitive impairment is crucial to delay cognitive deterioration and daily living disability in the elderly. However, the complexity and high cost of existing strategies appear to be great limits to the early screening on a large scale. Eye movement test shows a huge advantage in the early identification of mild cognitive impairment (MCI) because of quick, non‐invasive and cost‐effective features.MethodThe study involved a total of 151 participants: 90 MCI patients and 50 cognitive normal controls (CN) . All participants underwent eye movement signals under four visual tasks, including direct gaze towards target, smooth pursuit tasks, saccading toward a jumping target and looking away a jumping target. Five features were extracted from eye movement signals by linear and nonlinear analysis, including saccade number in resting state, saccade number in smooth persuit tasks, saccade lantency, antisaccade lantency, antisaccade error rate. Discriminant features selection was performed using the logistic regression (LR) analysis. Receiver operator characteristic (ROC) analyses and the area under the curve (AUC) were employed to investigate classification ability.ResultAfter the penalization of LR analysis, there were two top features that exhibited significant differences between MCI and CN, which included saccade number in smooth pursuit tasks and antisaccade error rate (p<0.05). ROC curves showed a favorable diagnostic accuracy of the two features in the discrimination between controls and MCI (AUC: 0.823, P<0.01).ConclusionThese results suggest that eye movement test has the potential to screen patients with MCI from the elderly with cognitive normality. Therefore, eye movement test is a powerful tool for broad screening in community‐dwelling older adults.

GazeBaseVR, a large-scale, longitudinal, binocular eye-tracking dataset collected in virtual reality

We present GazeBaseVR, a large-scale, longitudinal, binocular eye-tracking (ET) dataset collected at 250 Hz with an ET-enabled virtual-reality (VR) headset. GazeBaseVR comprises 5,020 binocular recordings from a diverse population of 407 college-aged participants. Participants were recorded up to six times each over a 26-month period, each time performing a series of five different ET tasks: (1) a vergence task, (2) a horizontal smooth pursuit task, (3) a video-viewing task, (4) a self-paced reading task, and (5) a random oblique saccade task. Many of these participants have also been recorded for two previously published datasets with different ET devices, and 11 participants were recorded before and after COVID-19 infection and recovery. GazeBaseVR is suitable for a wide range of research on ET data in VR devices, especially eye movement biometrics due to its large population and longitudinal nature. In addition to ET data, additional participant details are provided to enable further research on topics such as fairness.

Eye tracking as a tool for assessing social cognition: A case-control study comparing patients with psychosis and healthy controls

Background: Eye movement dysfunction is a common abnormality in Schizophrenia and other psychotic disorders. Various eye movement paradigms can be used to measure predefined parameters using eye trackers. The current study intends to understand the eye movement characteristics in individuals suffering from psychosis using newer eye-tracking instruments with better precision. Methodology: In this study, we included 29 individuals meeting the diagnostic criteria for schizophrenia spectrum and other psychotic disorders based on the clinical assessment as per Diagnostic and Statistical Manual of Mental Disorders, 5th Edition along with 29 age- and gender-matched healthy controls and measured various eye tracking parameters using a Tobii Pro Spectrum. We compared the eye-tracking parameters between both groups. Results: There were significant differences between the groups in the free-viewing task. The average duration of fixations was higher, whereas the number of fixations and total amplitude of saccades was found to be reduced in the patient group. The peak velocity of the first saccade was also seen to be reduced in the patient group. However, there were no abnormalities in the anti-saccade, predictive saccade, memory saccade, and smooth pursuit tasks. Eye movement parameters were also found to be significantly correlated with the cognitive task measurements. Conclusion: These findings confirm the presence of eye movement abnormalities in psychosis spectrum disorders and their role in cognitive deficits in psychosis. Altered free viewing may be linked to deficits in social cognition found in patients with schizophrenia.

Keeping balance during head-free smooth pursuit: The role of aging

Standing balance is often more unstable when visually pursuing a moving target than when fixating on a stationary one. These effects are common in both young and older adults when the head is restrained during visual task performance. The present study focused on the role of head motion on standing balance during smooth pursuit as a function of age. Three predictions were tested: a) standing balance is compromised to a greater extent in older than young adults by gaze target pursuit compared to fixation, b) older adults pursue a moving target with greater and more variable head rotation than young adults, and c) greater and more variable head rotation during the smooth pursuit task is associated with greater Center of Pressure (CoP) sway. Twenty-two (22) older (age: 71.7 ± 8.1, 12 M / 10 F) and twenty-three (23) young adults (age: 23.6 ± 2.5, 12 M / 11 F) stood on a force plate while either fixating a stationary or smoothly pursuing a horizontally moving target (31.9° peak-to-peak visual angle). CoP (Bertec Balance Plate), head kinematics (Vicon Motion Analysis) and head-unconstrained gaze (Pupil Labs Invisible) were synchronously recorded. The root means square (RMS) of CoP velocity increased during smooth pursuit compared to fixation regardless of age (p < .05), while the interquartile CoP range increased only in older and not in young participants (p < .05). We also calculated the head rotation range (peak to peak cycle amplitude) of motion and variability (SD of range of motion) across the cycles of the smooth pursuit task. Older adults pursued the moving target employing more variable (p = .022) head yaw rotation than young participants although the mean range of head rotation was similar between groups (p =. 077). The amplitude and variability of head yaw rotation did not correlate with CoP sway measures. Results suggest that head-free pursuing of a moving target decreased balance to a greater extent in old than young individuals when compared to fixation. Nevertheless, postural sway during head-free smooth pursuit was not associated with the extent or variability of head rotation.

Blink duration is increased in concussed youth athletes: a validity study using eye tracking in male youth and adult athletes of selected contact sports

Objective. Diagnosing a sports-related concussion (SRC) remains challenging, and research into diagnostic tools is limited. This study investigated whether selected eye tracking variables would be a valid tool to diagnose and monitor SRC in adult and youth participants in selected contact sports, such as Rugby Union (rugby) and football (soccer). Methods. This prospective cohort study, with 70 concussed and 92 non-concussed adult and youth athletes, assessed the validity of five previously selected eye tracking variables for SRC diagnostics and management. The performance between concussed and age-matched control (non-concussed) athletes, as well as between three successive testing sessions in the concussed athletes were compared. Self-paced saccade count in adult group; blink duration in the memory-guided saccade and sinusoidal smooth pursuit tasks, proportion of antisaccade errors, and gain of diagonal smooth pursuit in the youth group were assessed. Results. The youth concussed group had higher blink duration in the fast memory-guided saccades task (p = 0.001, η 2 = 0.17) and a tendency for higher blink duration in the sinusoidal smooth pursuit task (p = 0.016, η 2 = 0.06) compared to the youth control group. In both tasks the blink duration in the concussed youth group decreased from session 1 to session 2 by 24% and 18%, accordingly, although statistical significance was not reached. The concussed adult group demonstrated a lower number of self-paced saccades compared to controls (p = 0.05, η 2 = 0.09), which gradually increased, with the largest difference between session 1 and session 3 (p = 0.02). Conclusions. Blink duration in youth athletes holds promise as a valid metric for concussion diagnostics and monitoring. It is recommended to focus future studies on comparing eye tracking performance within the same concussed athletes over time rather than comparing them to healthy controls.

The similar eye movement dysfunction between major depressive disorder, bipolar depression and bipolar mania

Objective To find eye movement characteristics in patients with affective disorders. Method The demographic and clinical evaluation data of patients with major depressive disorder (MDD), bipolar disorder (BPD), and healthy control (HC) were collected. EyeLink 1000 eye tracker was used to collect eye movement data. Chi-squared test and independent sample t-test were used for demographics and clinical characteristics. The Mann–Whitney U-test was used to compare the eye movement variables among four groups, and the FDR method was used for multiple comparison correction. Pearson correlation analysis was used to analyse the relationship between clinical symptoms and eye movement variables. Results Patients with affective disorders showed smaller saccade amplitude under free-viewing task, more fixations and saccades, shorter fixation duration, longer saccade duration under fixation stability and smooth pursuit tasks (all, p < 0.05) when compared to HC, but there was no significant difference in all eye movement variables among patients in the three groups. Also, all eye movement variables under the three paradigms had no significant correlation with clinical scale scores. Conclusion Patients with major depression, bipolar depression and bipolar mania share similar eye movement dysfunction under free-viewing, fixation stability and smooth pursuit tasks.

Eye Movement Patterns Can Distinguish Schizophrenia From the Major Affective Disorders and Healthy Control Subjects.

Background and hypothesisNo objective tests are currently available to help diagnosis of major psychiatric disorders. This study evaluates the potential of eye movement behavior patterns to predict schizophrenia subjects compared to those with major affective disorders and control groups.Study designEye movements were recorded from a training set of UK subjects with schizophrenia (SCZ; n = 120), bipolar affective disorder (BPAD; n = 141), major depressive disorder (MDD; n = 136), and healthy controls (CON; n = 142), and from a hold-out set of 133 individuals with proportional group sizes. A German cohort of SCZ (n = 60) and a Scottish cohort of CON subjects (n = 184) acted as a second semi-independent test set. All patients met DSMIV and ICD10 criteria for SCZ, BPAD, and MDD. Data from 98 eye movement features were extracted. We employed a gradient boosted (GB) decision tree multiclass classifier to develop a predictive model. We calculated the area under the curve (AUC) as the primary performance metric.Study resultsEstimates of AUC in one-versus-all comparisons were: SCZ (0.85), BPAD (0.78), MDD (0.76), and CON (0.85). Estimates on part-external validation were SCZ (0.89) and CON (0.65). In all cases, there was good specificity but only moderate sensitivity. The best individual discriminators included free viewing, fixation duration, and smooth pursuit tasks. The findings appear robust to potential confounders such as age, sex, medication, or mental state at the time of testing.ConclusionsEye movement patterns can discriminate schizophrenia from major mood disorders and control subjects with around 80% predictive accuracy.

The role of the SLC6A3 3\u2019 UTR VNTR in nicotine effects on cognitive, affective, and motor function

RationaleNicotine has been widely studied for its pro-dopaminergic effects. However, at the behavioural level, past investigations have yielded heterogeneous results concerning effects on cognitive, affective, and motor outcomes, possibly linked to individual differences at the level of genetics. A candidate polymorphism is the 40-base-pair variable number of tandem repeats polymorphism (rs28363170) in the SLC6A3 gene coding for the dopamine transporter (DAT). The polymorphism has been associated with striatal DAT availability (9R-carriers > 10R-homozygotes), and 9R-carriers have been shown to react more strongly to dopamine agonistic pharmacological challenges than 10R-homozygotes.ObjectivesIn this preregistered study, we hypothesized that 9R-carriers would be more responsive to nicotine due to genotype-related differences in DAT availability and resulting dopamine activity.MethodsN=194 non-smokers were grouped according to their genotype (9R-carriers, 10R-homozygotes) and received either 2-mg nicotine or placebo gum in a between-subject design. Spontaneous blink rate (SBR) was obtained as an indirect measure of striatal dopamine activity and smooth pursuit, stop signal, simple choice and affective processing tasks were carried out in randomized order.ResultsReaction times were decreased under nicotine compared to placebo in the simple choice and stop signal tasks, but nicotine and genotype had no effects on any of the other task outcomes. Conditional process analyses testing the mediating effect of SBR on performance and how this is affected by genotype yielded no significant results.ConclusionsOverall, we could not confirm our main hypothesis. Individual differences in nicotine response could not be explained by rs28363170 genotype.

Eye Movement Patterns Can Distinguish Schizophrenia from the Major Affective Disorders and Healthy Control Subjects

Background: At present there are no objective tests or biomarkers in routine use that can help with the diagnosis of major mental disorders. This study aimed to determine the potential value of eye movement behaviour patterns for distinguishing individuals with schizophrenia compared to those with major affective disorders and control groups. Methods: Using a boosted decision tree multiclass classifier in a machine learning framework, we compared eye movement viewing patterns in a training set of UK subjects with Schizophrenia (SCZ) n=120, Bipolar affective disorder (BPAD) n=141, Major depressive disorder (MDD) n=136 and control (CON) n=142 group. A total of 133 individuals with group ratios similar to the training set acted as a hold-out test set for internal validation and a German cohort of SCZ (n=60) and a Scottish cohort of CON subjects (n=184) were used as a semi-independent test set for external validation. Findings: Based on internal validation, estimates of the area under the curve (AUC) for the one-versus-all comparisons for SCZ (0.85), BPAD (0.78), MDD (0.76) and CON (0.85) (with an overall estimate of 0.81) suggested high levels of discriminability between groups. The estimates of AUCs for the one-versus-one comparisons were also reasonably high; SCZ v CON 0.84, SCZ v BPAD 0.82, SCZ v MDD 0.76. The classifier showed good discrimination of BPAD and MDD from CON with AUCs 0.85 and 0.82, respectively; however, the performance was relatively lower between BPAD versus MDD with AUC 0.69. The estimates of AUC based on external validation were comparable: 0.89 for German SCZ and 0.65 for Scottish CON. The best individual discriminators included free viewing, fixation duration and smooth pursuit tasks. Our findings appear robust in the presence of potential confounders such as age, sex, medication or mental state at the time of testing. Interpretation: Eye movement behaviour patterns have good power to discriminate schizophrenia from both the major mood disorders and control subjects. The performance characteristics are within the range required of diagnostic biomarkers. Our findings are consistent with the Kraepelinian dichotomy of the functional psychoses. Funding: Royal Society of London, Chief Scientist Office Scotland (CZB/4/734), NHS Grampian,Tenovus Scotland (G12/31), Miller MacKenzie Trust, EU-FP6 (SGENE) and Health Innovation Challenge Fund, Wellcome Trust and Department of Health (WT-103911/Z/14/Z Declaration of Interest: Philip Benson and David St Clair are co-founders of SACCADE Diagnostics Ltd a spin out company tasked to develop eye movement technology to assist diagnosis of major mental health disorders. The University of Aberdeen has patents pending in Europe (PCT/GB2013/050016) and USA (14/370,611). The data reported in this paper arose solely from the acknowledged UK research bodies and charities none of whom have vested interests in the company. There are otherwise no competing interests. Ethical Approval: The Scottish and German studies obtained full multiregional ethics committee (MREC) and institutional review board (IRB) approvals respectively and were conducted in accordance with the Declaration of Helsinki.

Eye tracker outcomes in a randomized trial of 40 sessions of hyperbaric oxygen or sham in participants with persistent post concussive symptoms

Eye movements may offer a sensitive method to measure response to intervention in mild traumatic brain injury (mTBI). The Brain Injury and Mechanisms of Action of Hyperbaric Oxygen for Persistent Post-Concussive Symptoms after Mild Traumatic Brain Injury Study (BIMA) randomized 71 participants to 40 sessions of hyperbaric oxygen or sham. A companion normative study (Normal) enrolled 75 participants. An eye tracking system measured left and right eye movements for saccadic and smooth pursuit. At baseline two smooth pursuit tasks, circular and horizontal ramp, and four saccadic tasks, horizontal and vertical step, reading, and memory guided-on tasks differentiated BIMA from Normal participants. The change from baseline in these tasks were measured and compared between interventions and against Normal participants at 13 weeks and six-month follow-up using the two-sample t-test. The Holm-Bonferroni procedure was used to adjust for multiple testing. Change from baseline in eyetracker measures for participants assigned to the hyperbaric oxygen arm did not significantly differ from those assigned to the sham arm at post-randomization time points 13 weeks and six months. Consistent shifts of BIMA participant values toward Normal values at 13 weeks and six months were observed for overall fixation duration, forward saccadic duration, and number of lines read for the reading task, number of misses on the memory guided-on task, and absolute intersaccadic interval velocity and absolute saccadic amplitude on the circular task. The distributions between Normal and BIMA participants were no longer statistically significantly different at 13 weeks and six months post enrollment for these measures. The baseline differences between BIMA and Normal suggest potential vulnerability of the smooth pursuit system and the saccadic system. During the six-month follow-up period, improvement toward Normal was seen on some measures in both the hyperbaric oxygen and sham intervention arms without difference between intervention groups. clinicaltrials.gov Identifiers NCT01611194 and NCT01925963.

Visuo-oculomotor Function and Reaction Times in Athletes with and without Concussion.

Oculomotor tests in concussion commonly show impairment in smooth pursuit and saccadic function. Honing in on the systems likely to be affected by concussion will streamline use of oculomotor function as a supplemental diagnostic and prognostic tool, as well as improve our understanding of the pathophysiology of concussion. This study investigates oculomotor function between concussed and healthy collegiate athletes and determines measurement test-retest reliability of those tools. Eighty-seven healthy athletes were recruited from a U.S. Division 1 sports university and completed a 30-minute vestibular ocular testing battery in an enclosed rotary chair system equipped with 100-Hz eye-tracking goggles. Forty-three individuals completed the battery twice. Twenty-eight individuals with a current diagnosis of concussion also completed the battery. All participants were aged 18 to 24 years. Bivariate statistical tests examined differences in scores across groups, and intraclass coefficients were computed to test reliability. Concussed individuals had significantly longer saccadic, visual, and dual-task reaction times and reduced saccadic accuracy. There was no difference in optokinetic reflex gain, but few concussed individuals tolerated the task. Reaction time latencies and optokinetic gain show moderate test-retest reliability. Smooth pursuit tasks and saccadic accuracies showed poor test-retest reliability. Saccadic latency was the most sensitive oculomotor function to change after concussion and was reliable over time. Saccadic accuracy was significantly lower in the concussed group but had poor retest reliability. Optokinetic gain may warrant more investigation because of its high test-retest reliability and symptom provocation in concussion, despite not showing a significant difference between groups.

Neural Plasticity Following Surgical Correction of Strabismus in Monkeys.

PurposeAlthough widely practiced, surgical treatment of strabismus has varying levels of success and permanence. In this study we investigated adaptive responses within the brain and the extraocular muscles (EOM) that occur following surgery and therefore determine long-term success of the treatment.MethodsSingle cell responses were collected from cells in the oculomotor and abducens nuclei before and after two monkeys (M1, M2) with exotropia (divergent strabismus) underwent a strabismus correction surgery that involved weakening of the lateral rectus (LR) and strengthening of the medial rectus (MR) muscle of one eye. Eye movement and neuronal data were collected for up to 10 months after surgery during a monocular viewing smooth-pursuit task. These data were fit with a first-order equation and resulting coefficients were used to estimate the population neuronal drive (ND) to each EOM of both eyes.ResultsSurgery resulted in a ∼70% reduction in strabismus angle in both animals that reverted toward presurgical misalignment by approximately 6 months after treatment. In the first month after surgery, the ND to the treated MR reduced in one animal and ND to the LR increased in the other animal, both indicating active neural plasticity that reduced the effectiveness of the treatment. Adaptive changes in ND to the untreated eye were also identified.ConclusionsActive neural and muscle plasticity corresponding to both the treated and the untreated eye determines longitudinal success following surgical correction of strabismus. Outcome of surgical treatment could be improved by identifying ways to enhance “positive” adaptation and limit “negative” adaptation.

Shared variance of oculomotor phenotypes in a large sample of healthy young men

This study used canonical correlation analysis to investigate patterns of shared variance between parameters measured in seven different occulomotor function tasks, namely the visually guided saccade task, the antisaccade task, the closed-loop smooth-pursuit task, the open-loop smooth-pursuit task, and three active visual fixation tasks. These tasks were performed by 2130 young army recruits. Only a small percentage (1-10%) of shared variance existed between sets of parameters for all oculomotor function tasks measured. The most correlated tasks were the visually guided saccade and the antisaccade. The first common factor correlated with speed of performance between these tasks (latency), while the second and third correlated with accuracy of performance. Better performance in active visual fixation tasks correlated with better performance accuracy (lower error rate) and increased speed (lower latency) in the antisaccade and saccade tasks as well as better performance in the closed-loop smooth-pursuit task (increase in gain and decrease in the rate of unwanted saccades during pursuit). Better performance in the closed-loop smooth-pursuit task (increased gain and decreased number of unwanted saccades) also correlated with increased accuracy and increased speed of performing saccades and antisaccades. Finally, the open-loop fixation task had no correlation with all other oculomotor tasks except for a very weak negative correlation with the closed-loop pursuit task where better performance (increased gain) in one correlated with worse performance (decreased gain) in the other. The results of this analysis showed that a small percentage of variance is shared among different oculomotor function tasks. The structure of this shared variance could be used to derive common oculomotor function indices to study their relation to genetic and other sources of inter-subject variation.

Weighted integration of short-term memory and sensory signals in the oculomotor system.

Oculomotor behaviors integrate sensory and prior information to overcome sensory-motor delays and noise. After much debate about this process, reliability-based integration has recently been proposed and several models of smooth pursuit now include recurrent Bayesian integration or Kalman filtering. However, there is a lack of behavioral evidence in humans supporting these theoretical predictions. Here, we independently manipulated the reliability of visual and prior information in a smooth pursuit task. Our results show that both smooth pursuit eye velocity and catch-up saccade amplitude were modulated by visual and prior information reliability. We interpret these findings as the continuous reliability-based integration of a short-term memory of target motion with visual information, which support modeling work. Furthermore, we suggest that saccadic and pursuit systems share this short-term memory. We propose that this short-term memory of target motion is quickly built and continuously updated, and constitutes a general building block present in all sensorimotor systems.