Pursuit Eye Movements Research Articles

Concordant GRADE-3 Truncal Ataxia and Ocular Laterodeviation in Acute Medullary Stroke.

Background: Severe truncal ataxia associated with an inability to sit up without assistance (STA grade 3) is frequent in patients with central acute vestibular syndrome (AVS) involving the brainstem or cerebellum. When these patients have nystagmus, central HINTS excludes peripheral lesions; however, additional localization and lateralization signs are helpful, not only to resolve the peripheral versus central vestibular lesion dilemma, but to zero in on a precise lesion localization/lateralization to the lateral medulla, the most common ischemic lesion localization associated with an initially false-negative stroke MRI. Methods: This is a study of AVS patients with additional inclusion criteria: grades 2 or 3 ataxia with an eventual diagnosis of medullary stroke (MS), either involving the lateral medulla (LMS) or the medial medulla (MMS), and horizontal (h) gaze paralysis was the main exclusion criteria. All patients sat on the side of the bed or stretcher, with assistance if needed. A general neurologic examination followed in the sitting position, the testing protocol included the head impulse, spontaneous nystagmus, and skew deviation (HINTS) tests, followed by observation of the effect of brief 3-5 sec eyelid closure on ocular position, and saccade and pursuit eye movement tests. If they could sit, the protocol included the ability to stand with a wide base, then a narrow base, the Romberg test, and tandem gait. Radiographic lesion localization and horizontal gaze deviation concluded the protocol. Results: A total of 34 patients met the entry criteria, 34 MS (13 in the lateral medulla, 12 previously described, and 1 new patient), and 1 new MMS. Among them, n = 10/12 had grade 3 ataxia, and 3 (1 new patient) had grade 2 ataxia. In addition, overt ocular laterodeviation (OLD) was present in thirteen of them (35.3%). All OLD patients had gaze deviation and ipsilateral saccade and truncal lateropulsion, 1 medial medulla stroke patient had grade 3 truncal contrapulsion and contralateral hemiparesis without OLD, n = 20/21 patients with LMS without OLD had grade 3 truncal ataxia, and 1 had grade 2 truncal ataxia. Discussion: AVS patients with severe truncal ataxia (inability to sit without assistance) potentially have brainstem, cerebellum, or subcortical lesions. All patients had central HINTS; however, simultaneous direction-concordant STA 3 and OLD provided greater lateral medulla localization specificity, affecting the ipsilateral medulla. Future work to explore a practical posterior circulation stroke scale that includes HINTS, STA, and OLD will potentially select cases for thrombolysis even in the event of initially false-negative imaging.

The effect of online visual games on visual perception, oculomotor, and balance skills of children with developmental dyslexia during the COVID-19 pandemic.

To evaluate the effect of online visual games on the balance, visual perception, and oculomotor skills of children with developmental dyslexia during the COVID-19 pandemic. In this single-blind randomized clinical trial, 50 children with developmental dyslexia, aged 7 to 11years, were recruited from rehabilitation centers in Tehran, Iran, using a convenience sampling strategy. Participants were randomly divided into two groups: intervention (25) and control (25), with close matching based on sex, age, IQ, and type of disease. The interventions consisted of web-based online computer games focusing on visual perception and oculomotor skills. Outcome measures included the Test of Visual Perception Skills-Revised, the Pediatric Balance Scale, and videonystagmography. The Wechsler Intelligence Scale for Children-IV and the Reading and Dyslexia Test were used to evaluate IQ and reading skills, respectively. The intervention group exhibited significant post-intervention improvements in the Test of Visual Perception Skills-Revised, tracking gain, saccade latency, and saccade velocity scores (all P < 0.001). In contrast, the control group showed no significant differences in these tests in pre- and post-intervention (all P > 0.05). Notably, post-intervention comparisons between the groups revealed significant differences in smooth pursuit eye movements (P < 0.001), saccade latency (P = 0.027), and saccade velocity (P < 0.001). The Pediatric Balance Scale scores remained unchanged in both groups post-intervention (intervention: P = 0.317; control: P = 0.999). Game face validity was affirmed with impact scores above 1.5 for all items, suggesting that the games were straightforward, clear, and relevant. Online visual games enhanced oculomotor and visual perception skills in children with dyslexia but did not influence balance skills.

Webcam eye tracking close to laboratory standards: Comparing a new webcam-based system and the EyeLink 1000

This paper aims to compare a new webcam-based eye-tracking system, integrated into the Labvanced platform for online experiments, to a “gold standard” lab-based eye tracker (EyeLink 1000 - SR Research). Specifically, we simultaneously recorded data with both eye trackers in five different tasks, analyzing their real-time performance. These tasks were a subset of a standardized test battery for eye trackers, including a Large Grid task, Smooth Pursuit eye movements, viewing natural images, and two Head Movements tasks (roll, yaw). The results show that the webcam-based system achieved an overall accuracy of 1.4°, and a precision of 1.1° (standard deviation (SD) across subjects), an error of about 0.5° larger than the EyeLink system. Interestingly, both accuracy (1.3°) and precision (0.9°) were slightly better for centrally presented targets, the region of interest in many psychophysical experiments. Remarkably, the correlation of raw gaze samples between the EyeLink and webcam-based was at about 90% for the Large Grid task and about 80% for Free View and Smooth Pursuit. Overall, these results put the performance of the webcam-based system roughly on par with mobile eye-tracking devices (Ehinger et al. PeerJ, 7, e7086, 2019; Tonsen et al., 2020) and demonstrate substantial improvement compared to existing webcam eye-tracking solutions (Papoutsaki et al., 2017).

Clinical Application of Eye Tracker in Pursuit Eye Movements

Clinical Application of Eye Tracker in Pursuit Eye Movements

A review of pursuit and saccadic eye movements and their utility in stroke

The head impulse-nystagmus-test of skew (+ hearing) or HINTS+ exam is a well-established clinical bedside test used in evaluating whether patients with the acute vestibular syndrome have features concerning for a central etiology (e.g., stroke). There are other components of the ocular motor exam that are helpful in the acute setting, including smooth pursuit and saccades. We discuss the anatomy and physiology of the saccade and smooth pursuit pathways from the cortex to the infratentorial region in the context of anterior and posterior circulation strokes in general but with a particular emphasis on distinct vestibular stroke syndromes. For each stroke localization, we review the vascular supply and the expected findings on the HINTS+ exam and correlate this with the expected findings on the smooth pursuit and saccade exams to aid in bedside diagnosis.

Investigation of Camera-Free Eye-Tracking Glasses Compared to a Video-Based System.

Technological advances in eye-tracking have resulted in lightweight, portable solutions that are capable of capturing eye movements beyond laboratory settings. Eye-tracking devices have typically relied on heavier, video-based systems to detect pupil and corneal reflections. Advances in mobile eye-tracking technology could facilitate research and its application in ecological settings; more traditional laboratory research methods are able to be modified and transferred to real-world scenarios. One recent technology, the AdHawk MindLink, introduced a novel camera-free system embedded in typical eyeglass frames. This paper evaluates the AdHawk MindLink by comparing the eye-tracking recordings with a research "gold standard", the EyeLink II. By concurrently capturing data from both eyes, we compare the capability of each eye tracker to quantify metrics from fixation, saccade, and smooth pursuit tasks-typical elements in eye movement research-across a sample of 13 adults. The MindLink system was capable of capturing fixation stability within a radius of less than 0.5∘, estimating horizontal saccade amplitudes with an accuracy of 0.04∘± 2.3∘, vertical saccade amplitudes with an accuracy of 0.32∘± 2.3∘, and smooth pursuit speeds with an accuracy of 0.5 to 3∘s, depending on the pursuit speed. While the performance of the MindLink system in measuring fixation stability, saccade amplitude, and smooth pursuit eye movements were slightly inferior to the video-based system, MindLink provides sufficient gaze-tracking capabilities for dynamic settings and experiments.

Gaze behaviour during multiple object tracking is dependent on binocular vision integrity.

Despite the critical importance of binocular vision integrity in daily activities, there exists limited understanding of how alterations in binocular vision integrity impact gaze behaviour during dynamic, complex psychomotor skills. This study aimed to measure how alterations in binocular vision integrity, created by Bangerter filters (BF), affect gaze behaviour during multiple object tracking (MOT). During the experiment, 22 volunteers completed the MOT task under three different visual conditions. The first condition involved natural binocular viewing, while the second and third conditions used 0.4 and 0.2 neutral density BF, respectively, resulting in monocular blur in the sensorially dominant eye. During the MOT task, participants were instructed to track three of eight balls for 10 s, and the speed was adjusted using a staircase procedure. Throughout the task, the following gaze parameters were recorded: fixation duration, saccade duration, amplitude and frequency as well as blink rate. During MOT execution, participants employed three gaze strategies regardless of viewing conditions: saccadic movements were predominant, followed by maintaining fixation on a central location throughout the trial and to a lesser extent, smooth pursuit eye movements. There was a significant effect of manipulating viewing conditions on the MOT scores (p = 0.046, η2 = 0.09). As the viewing conditions became more difficult, we observed a decrease in fixation duration (p = 0.004, η2 = 0.16) and blink rate (p < 0.001, η2 = 0.20) and an increase in saccadic amplitude (p < 0.001, η2 = 0.29). The results support the notion that perceptual-cognitive skills depend on the integrity of binocular vision, underscoring the sensitivity of gaze behaviours to any impairment of binocular function.

A sensory-motor decoder that transforms neural responses in extrastriate area MT into smooth pursuit eye movements.

Visual motion drives smooth pursuit eye movements through a sensory-motor decoder that uses multiple parallel neural pathways to transform the population response in extrastriate area MT into movement. We evaluated the decoder by challenging pursuit in monkeys with reduced motion reliability created by reducing coherence of motion in patches of dots. Our strategy was to determine how reduced dot coherence changes the population response in MT. We then predicted the properties of a decoder that transforms the MT population response into dot coherence-induced deficits in the initiation of pursuit and steady-state tracking. During pursuit initiation, decreased dot coherence reduces MT population response amplitude without changing the preferred speed at its peak. The successful decoder reproduces the measured eye movements by multiplication of 1) the estimate of target speed from the peak of the population response with 2) visual-motor gain based on the amplitude of the population response. During steady-state tracking, the decoder that worked for pursuit initiation failed to reproduce the paradox that steady-state eye speeds do not accelerate to the target speed despite persistent image motion. It predicted eye acceleration to target speed even when monkeys' eye speeds were steady at well below the target speed. To account for the effect of dot coherence on steady-state eye speed, we postulate that the decoder uses sensory-motor gain to modulate the eye velocity positive feedback that normally sustains perfect steady-state tracking. Then, poor steady-state tracking persists because of balance between eye deceleration caused by low positive feedback gain and acceleration driven by MT.NEW & NOTEWORTHY By challenging a sensory-motor system with degraded sensory stimuli, we reveal how the sensory-motor decoder transforms the population response in extrastriate area MT into commands for the initiation and steady-state behavior of smooth pursuit eye movements. Conclusions are based on measuring population responses in MT for multiple target speeds and different levels of motion reliability and evaluating a decoder with a biologically motivated architecture to determine the decoder properties that create the measured eye movements.

Rate versus synchrony codes for cerebellar control of motor behavior

Information transmission between neural populations could occur through either coordinated changes in firing rates or the precise transmission of spike timing. We investigate the code for information transmission from a part of the cerebellar cortex that is crucial for the accurate execution of a quantifiable motor behavior. Simultaneous recordings from Purkinje cell pairs in the cerebellum of rhesus macaques reveal how these cells coordinate their activity to drive smooth pursuit eye movements. Purkinje cells show millisecond-scale coordination of spikes (synchrony), but the level of synchrony is small and insufficient to impact the firing of downstream vestibular nucleus neurons. Analysis of previous metrics that purported to reveal Purkinje cell synchrony demonstrates that these metrics conflate changes in firing rate and neuron-neuron covariance. We conclude that the output of the cerebellar cortex uses primarily a rate rather than a synchrony code to drive the activity of downstream neurons and thus control motor behavior.

Smooth pursuit eye movements incorporate the knowledge of Newtonian mechanics and other cues for motion prediction

Smooth pursuit eye movements incorporate the knowledge of Newtonian mechanics and other cues for motion prediction

Are smooth pursuit eye movements influenced by perceptual experience?

Are smooth pursuit eye movements influenced by perceptual experience?

Tuning in to a hip-hop beat: Pursuit eye movements reveal processing of biological motion

Smooth pursuit eye movements are mainly driven by motion signals to achieve their goal of reducing retinal motion blur. However, they can also show anticipation of predictable movement patterns. Oculomotor predictions may rely on an internal model of the target kinematics. Most investigations on the nature of those predictions have concentrated on simple stimuli, such as a decontextualized dot. However, biological motion is one of the most important visual stimuli in regulating human interaction and its perception involves integration of form and motion across time and space. Therefore, we asked whether there is a specific contribution of an internal model of biological motion in driving pursuit eye movements. Unlike previous contributions, we exploited the cyclical nature of walking to measure eye movement's ability to track the velocity oscillations of the hip of point-light walkers. We quantified the quality of tracking by cross-correlating pursuit and hip velocity oscillations. We found a robust correlation between signals, even along the horizontal dimension, where changes in velocity during the stepping cycle are very subtle. The inversion of the walker and the presentation of the hip-dot without context incurred the same additional phase lag along the horizontal dimension. These findings support the view that information beyond the hip-dot contributes to the prediction of hip kinematics that controls pursuit. We also found a smaller phase lag in inverted walkers for pursuit along the vertical dimension compared to upright walkers, indicating that inversion does not simply reduce prediction. We suggest that pursuit eye movements reflect the visual processing of biological motion and as such could provide an implicit measure of higher-level visual function.

Curriculum in Neuro-Ophthalmic Principles for National Football League Game Officials: Comparison of Pretraining and Posttraining Ratings of Knowledge.

We hypothesize that creation of a structured curriculum in neuro-ophthalmology principles might improve self-rated learner satisfaction and knowledge base of National Football League (NFL) game officials. Our initial objective is to create the said curriculum in coordination with game official experts and staff at the NFL to increase levels of understanding of neuro-ophthalmology principles. We reviewed the prior published literature on applicable neuro-ophthalmic principles in professional sports. Major neuro-ophthalmic principles reviewed include both the efferent (e.g., saccadic and pursuit eye movements and vestibulo-ocular reflex) and afferent (visual field, dynamic visual acuity during body movement, and selective attention deficits). A 6-question survey pertaining to levels of understanding, future applicability, relevance, satisfaction, and interest in additional training was then given to 26 individuals before and after a lecture given by Dr. Andrew Lee in Plano, TX. The primary outcome measure was the creation of the curriculum followed by real-world testing for face and content validity and ending with a self-rated assessment. Twenty-one individuals completed the prelecture and postlecture survey out of 26 individuals who attended. Prelecture means for the level of understanding of oculomotor terms and the likelihood of using said terms were 3.4 and 3.2, respectively. Postlecture means were 8.9 and 8.8, respectively. The lecture was rated 9.2 of 10 for relevance to coaching and teaching officials, and individuals rated their interest in further content as 9.4 of 10. This study found that NFL game officials are interested in learning more about the science behind play-calling in terms of neuro-ophthalmology principles and practices. In addition, from our pilot survey, it is evident that even one lecture can improve participants' level of understanding and likelihood of learning more about neuro-ophthalmic principles.

Visual attentional guidance during smooth pursuit eye movements: Distractor interference is independent of distractor-target similarity.

In the current study, we used abrupt-onset distractors similar and dissimilar in luminance to the target of a smooth pursuit eye-movement to test if abrupt-onset distractors capture attention in a top-down or bottom-up fashion while the eyes track a moving object. Abrupt onset distractors were presented at different positions relative to the current position of a pursuit target during the closed-loop phase of smooth pursuit. Across experiments, we varied the duration of the distractors, their motion direction, and task-relevance. We found that abrupt-onset distractors decreased the gain of horizontally directed smooth-pursuit eye-movements. This effect, however, was independent of the similarity in luminance between distractor and target. In addition, distracting effects on horizontal gain were the same, regardless of the exact duration and position of the distractors, suggesting that capture was relatively unspecific and short-lived (Experiments 1 and 2). This was different with distractors moving in a vertical direction, perpendicular to the horizontally moving target. In line with past findings, these distractors caused suppression of vertical gain (Experiment 3). Finally, making distractors task-relevant by asking observers to report distractor positions increased the pursuit gain effect of the distractors. This effect was also independent of target-distractor similarity (Experiment 4). In conclusion, the results suggest that a strong location signal exerted by the pursuit targets led to very brief and largely location-unspecific interference through the abrupt onsets and that this interference was bottom-up, implying that the control of smooth pursuit was independent of other target features besides its motion signal.

Effects of Eye Movement Exercise on Cognitive Function and Prefrontal Cortex Connectivity for the Elderly with Mild Cognitive Impairment: An fNIRS Study

PURPOSE The purpose of this study was to examine the effects of an eye movement exercise intervention on cognitive function and prefrontal cortex connectivity in the elderly with mild cognitive impairment.METHODS Ten older adults with mild cognitive impairment participated in eye movement exercise consisting of saccadic eye movement, pursuit eye movement, vestibular-ocular eye movement, and vergence eye movement for 4 weeks. Cognitive function (MoCA-K), reaction time during stroop task, and prefrontal cortex connectivity were measured using the functional near-infrared spectrometric analyzer (fNIRS) before and after the intervention.RESULTS First, cognitive function of the elderly with mild cognitive impairment showed significant improvement after the eye movement exercise (p &lt; .05). Second, reaction time decreased significantly from 1.16 to 0.91 ms after eye movement exercise. Third, the strength of prefrontal cortex connectivity (left OFC - right FPC, right OFC - right FPC) increased after the intervention in the older adults with mild cognitive impairment.CONCLUSIONS The results of this study suggest that eye movement exercise is an effective intervention for improving cognitive function through improvement of brain functional connection in the elderly patients with mild cognitive impairment.

Age-related decline of online visuomotor adaptation: a combined effect of deteriorations of motor anticipation and execution.

The literature has established that the capability of visuomotor adaptation decreases with aging. However, the underlying mechanisms of this decline are yet to be fully understood. The current study addressed this issue by examining how aging affected visuomotor adaptation in a continuous manual tracking task with delayed visual feedback. To distinguish separate contributions of the declined capability of motor anticipation and deterioration of motor execution to this age-related decline, we recorded and analyzed participants' manual tracking performances and their eye movements during tracking. Twenty-nine older people and twenty-three young adults (control group) participated in this experiment. The results showed that the age-related decline of visuomotor adaptation was strongly linked to degraded performance in predictive pursuit eye movement, indicating that declined capability motor anticipation with aging had critical influences on the age-related decline of visuomotor adaptation. Additionally, deterioration of motor execution, measured by random error after controlling for the lag between target and cursor, was found to have an independent contribution to the decline of visuomotor adaptation. Taking these findings together, we see a picture that the age-related decline of visuomotor adaptation is a joint effect of the declined capability of motor anticipation and the deterioration of motor execution with aging.

Istradefylline Improves Impaired Smooth Pursuit Eye Movements in Parkinson's Disease.

Patients with Parkinson's disease (PD) exhibit alterations in eye movement control, primarily diverse oculomotor deficits which include hypometric saccade and impaired smooth pursuit with reduced pursuit-gain necessitating catch-up saccades. The effects of dopaminergic treatment of PD on eye movements are controversial. Previous studies suggest that smooth pursuit eye movements (SPEMs) are not directly influenced by the dopaminergic system. The nondopaminergic drug istradefylline, a selective adenosine A2A receptor antagonist, reduces the OFF time and improves somatomotor function in levodopa-treated PD. Here, we investigated whether istradefylline improves SPEMs in PD, and determined whether oculomotor performance is associated with somatomotor performance. Using an infrared video eye tracking system, we quantified horizontal SPEMs in six patients with PD before and 4-8weeks after initiation of istradefylline administration. A further five patients with PD were tested before and after a 4-week interval without istradefylline to control for practice effects. We evaluated smooth pursuit gain (eye velocity/target velocity), accuracy of smooth pursuit velocity, and saccade rate during pursuitbefore and after istradefylline administration during the ON state. Patients received istradefylline by single daily oral administration at 20 to 40mg. Eye tracking data were obtained 4-8weeks after initiation of istradefylline administration. Istradefylline increased smooth pursuit gain and the accuracy of smooth pursuit velocity, and tended to decrease saccade rates during pursuit. Istradefylline ameliorated the oculomotor deficit in SPEM of patients with PD, although differences in somatomotor performance before and after istradefylline treatment were not significant during ON periods. The discrepancy observed between the oculomotor and somatomotor responses to istradefylline supports previous findings that SPEM is at least partially under nondopaminergic control.

Oculomotor abnormalities indicate early executive dysfunction in prodromal X-linked dystonia-parkinsonism (XDP)

BackgroundX-Linked dystonia-parkinsonism (XDP) is a movement disorder characterized by the presence of both dystonia and parkinsonism with one or the other more prominent in the initial stages and later on manifesting with more parkinsonian features towards the latter part of the disease. XDP patients show oculomotor abnormalities indicating prefrontal and striatal impairment. This study investigated oculomotor behavior in non-manifesting mutation carriers (NMC). We hypothesized that oculomotor disorders occur before the appearance of dystonic or parkinsonian signs. This could help to functionally identify brain regions already affected in the prodromal stage of the disease.MethodsTwenty XDP patients, 13 NMC, and 28 healthy controls (HC) performed different oculomotor tasks typically affected in patients with parkinsonian signs.ResultsThe error rate for two types of volitional saccades, i.e., anti-saccades and memory-guided saccades, was increased not only in XDP patients but also in NMC compared to HC. However, the increase in error rates of both saccade types were highly correlated in XDP patients only. Hypometria of reflexive saccades was only found in XDP patients. Initial acceleration and maintenance velocity of smooth pursuit eye movements were only impaired in XDP patients.ConclusionsDespite being asymptomatic, NMC already showed some oculomotor deficits reflecting fronto-striatal impairments, typically found in XDP patients. However, NMC did not show saccade hypometria and impaired smooth pursuit as seen in advanced Parkinson’s disease and XDP, suggesting oculomotor state rather than trait signs in these mutation carriers. Neurodegeneration may commence in the striatum and prefrontal cortex, specifically the dorsolateral prefrontal cortex.

Development of a New Eye Movement Measurement Device Using Eye-Tracking Analysis Technology

Smooth pursuit eye movements and saccadic eye movements are vital for precise vision. Therefore, tests for eye movement are important for assessing nervous or muscular diseases. However, objective measurements are not frequently performed due to the need for a polygraph system, electrodes, amplifier, and personal computer for data analysis. To address this, we developed an all-in-one eye-movement-measuring device that simultaneously presents visual stimuli, records eye positions, and examines its feasibility for evaluating eye movements. This device generates stimulus that induces eye movements and records those movements continuously. The horizontal or vertical eye movements of 16 participants were measured at various visual target speeds of 20–100 deg/s. The maximum cross-correlation coefficient (rho max) between the eye and visual target positions was used as an index of eye movement accuracy. A repeated-measures multi-way analysis of variance was performed, with the main effect being that rho max significantly decreased as the visual target speed increased. The average (±standard deviation) rho max values across all velocities were 0.995 ± 0.008 and 0.967 ± 0.062 in the horizontal and vertical directions, respectively, and were significantly higher for horizontal eye movements than for vertical eye movements. Moreover, rho max and saccadic frequency were significantly correlated for the slowest and fastest visual target motions. These suggest that our device enables accurate measurements of eye movements. We believe our new measurement device can be applied clinically for easily and objectively evaluating eye movements.

Progressive Supranuclear Palsy

Progressive supranuclear palsy (PSP) has been reported as a disorder mainly characterized by a tendency to fall, vertical supranuclear gaze palsy, and constriction of the body axis, akinesia, and cognitive impairment. Patients presenting with these typical clinical features are diagnosed as having the PSP-Richardson syndrome (PSP-RS). Electronystagmography (ENG) is useful for the detection of ocular motility disorder, which is the main feature of PSP. In cases of PSP, ocular motility disorder in the vertical direction occurs from the initial stage of the disease, and is characterized by prolonged latency and reduced velocity of the saccadic eye movement in the vertical direction. Horizontal saccadic eye movement disorder also occurs after the intermediate stage. Square wave jerks (SWJ) are often recognized from the initial stage of the disease. In terms of nystagmus, the quick phase is impaired due to impaired saccadic eye movements, and impairment of optokinetic nystagmus also starts from the quick phase movements. Pursuit (smooth) eye movement may also be impaired as the disease progresses. On the other hand, the vestibulo-ocular reflex is maintained even after disease progression to a late stage.