Gaze Stabilization Research Articles

A prosthesis utilizing natural vestibular encoding strategies improves sensorimotor performance in monkeys.

Sensory pathways provide complex and multifaceted information to the brain. Recent advances have created new opportunities for applying our understanding of the brain to sensory prothesis development. Yet complex sensor physiology, limited numbers of electrodes, and nonspecific stimulation have proven to be a challenge for many sensory systems. In contrast, the vestibular system is uniquely suited for prosthesis development. Its peripheral anatomy allows site-specific stimulation of 3 separate sensory organs that encode distinct directions of head motion. Accordingly, here, we investigated whether implementing natural encoding strategies improves vestibular prosthesis performance. The eye movements produced by the vestibulo-ocular reflex (VOR), which plays an essential role in maintaining visual stability, were measured to quantify performance. Overall, implementing the natural tuning dynamics of vestibular afferents produced more temporally accurate VOR eye movements. Exploration of the parameter space further revealed that more dynamic tunings were not beneficial due to saturation and unnatural phase advances. Trends were comparable for stimulation encoding virtual versus physical head rotations, with gains enhanced in the latter case. Finally, using computational methods, we found that the same simple model explained the eye movements evoked by sinusoidal and transient stimulation and that a stimulation efficacy substantially less than 100% could account for our results. Taken together, our results establish that prosthesis encodings that incorporate naturalistic afferent dynamics and account for activation efficacy are well suited for restoration of gaze stability. More generally, these results emphasize the benefits of leveraging the brain's endogenous coding strategies in prosthesis development to improve functional outcomes.

Rehabilitation to Improve Gaze and Postural Stability in People With Multiple Sclerosis: A Randomized Clinical Trial

Background People with multiple sclerosis (PwMS) frequently experience dizziness and imbalance that may be caused by central vestibular system dysfunction. Vestibular rehabilitation may offer an approach for improving dysfunction in these people. Objective To test the efficacy of a gaze and postural stability (GPS) retraining intervention compared to a strength and endurance (SAE) intervention in PwMS. Methods About 41 PwMS, with complaints of dizziness or history of falls, were randomized to either the GPS or SAE groups. Following randomization participants completed 6-weeks of 3×/week progressive training, delivered one-on-one by a provider. Following intervention, testing was performed at the primary (6-weeks) and secondary time point (10-weeks). A restricted maximum likelihood estimation mixed effects model was used to examine changes in the primary outcome of the Dizziness Handicap Inventory (DHI) between the 2 groups at the primary and secondary time point. Similar models were used to explore secondary outcomes between groups at both timepoints. Results Thirty-five people completed the study (17 GPS; 18 SAE). The change in the DHI at the primary time point was not statistically different between the GPS and SAE groups (mean difference = 2.33 [95% CI −9.18, 12.85]). However, both groups demonstrated significant improvement from baseline to 6-weeks (GPS −8.73; SAE −7.31). Similar results were observed for secondary outcomes and at the secondary timepoint. Conclusions In this sample of PwMS with complaints of dizziness or imbalance, 6-weeks of GPS training did not result in significantly greater improvements in dizziness handicap or balance compared to 6-weeks of SAE training.

Loss of Flocculus Purkinje Cell Firing Precision Leads to Impaired Gaze Stabilization in a Mouse Model of Spinocerebellar Ataxia Type 6 (SCA6).

Spinocerebellar Ataxia Type 6 (SCA6) is a mid-life onset neurodegenerative disease characterized by progressive ataxia, dysarthria, and eye movement impairment. This autosomal dominant disease is caused by the expansion of a CAG repeat tract in the CACNA1A gene that encodes the α1A subunit of the P/Q type voltage-gated Ca2+ channel. Mouse models of SCA6 demonstrate impaired locomotive function and reduced firing precision of cerebellar Purkinje in the anterior vermis. Here, to further assess deficits in other cerebellar-dependent behaviors, we characterized the oculomotor phenotype of a knock-in mouse model with hyper-expanded polyQ repeats (SCA684Q). We found a reduction in the efficacy of the vestibulo-ocular reflex (VOR) and optokinetic reflex (OKR) in SCA6 mutant mice, without a change in phase, compared to their litter-matched controls. Additionally, VOR motor learning was significantly impaired in SCA684Q mice. Given that the floccular lobe of the cerebellum plays a vital role in the generation of OKR and VOR calibration and motor learning, we investigated the firing behavior and morphology of floccular cerebellar Purkinje cells. Overall, we found a reduction in the firing precision of floccular lobe Purkinje cells but no morphological difference between SCA684Q and wild-type mice. Taken together, our findings establish that gaze stabilization and motor learning are impaired in SCA684Q mice and suggest that altered cerebellar output contributes to these deficits.

Perinatal development of central vestibular neurons in mice.

Central circuitry of the vestibular nuclei integrates sensory inputs in the adaptive control of motor behaviors such as posture, locomotion, and gaze stabilization. Thus far, such circuits have been mostly examined at mature stages, whereas their emergence and early development have remained poorly described. Here, we focused on the perinatal period of murine development, from embryonic day E14.5 to post-natal day P5, to investigate the ontogeny of two functionally distinct vestibular neuronal groups, neurons projecting to the spinal cord via the lateral vestibulospinal tract (LVST) and commissural neurons of the medial vestibular nucleus that cross the midline to the contralateral nucleus. Using transgenic mice and retrograde labeling, we found that network-constitutive GABAergic and glycinergic neurons are already established in the two vestibular groups at embryonic stages. Although incapable of repetitive firing at E14.5, neurons of both groups can generate spike trains from E15.5 onward and diverge into previously established A or B subtypes according to the absence (A) or presence (B) of a two-stage spike after hyperpolarization. Investigation of several voltage-dependent membrane properties indicated that solely LVST neurons undergo significant maturational changes in their electrophysiological characteristics during perinatal development. The proportions of A vs B subtypes also evolve in both groups, with type A neurons remaining predominant at all stages, and type B commissural neurons appearing only post-natally. Together, our results indicate that vestibular neurons acquire their distinct morpho-functional identities after E14.5 and that the early maturation of membrane properties does not emerge uniformly in the different functional subpopulations of vestibulo-motor pathways.

Conserved subcortical processing in visuo-vestibular gaze control

Gaze stabilization compensates for movements of the head or external environment to minimize image blurring. Multisensory information stabilizes the scene on the retina via the vestibulo-ocular (VOR) and optokinetic (OKR) reflexes. While the organization of neuronal circuits underlying VOR is well-described across vertebrates, less is known about the contribution and evolution of the OKR and the basic structures allowing visuo-vestibular integration. To analyze these neuronal pathways underlying visuo-vestibular integration, we developed a setup using a lamprey eye-brain-labyrinth preparation, which allowed coordinating electrophysiological recordings, vestibular stimulation with a moving platform, and visual stimulation via screens. Lampreys exhibit robust visuo-vestibular integration, with optokinetic information processed in the pretectum that can be downregulated from tectum. Visual and vestibular inputs are integrated at several subcortical levels. Additionally, saccades are present in the form of nystagmus. Thus, all basic components of the visuo-vestibular control of gaze were present already at the dawn of vertebrate evolution.

Homeostatic plasticity of eye movement performance in Xenopus tadpoles following prolonged visual image motion stimulation

Visual image motion-driven ocular motor behaviors such as the optokinetic reflex (OKR) provide sensory feedback for optimizing gaze stability during head/body motion. The performance of this visuo-motor reflex is subject to plastic alterations depending on requirements imposed by specific eco-physiological or developmental circumstances. While visuo-motor plasticity can be experimentally induced by various combinations of motion-related stimuli, the extent to which such evoked behavioral alterations contribute to the behavioral demands of an environment remains often obscure. Here, we used isolated preparations of Xenopus laevis tadpoles to assess the extent and ontogenetic dependency of visuo-motor plasticity during prolonged visual image motion. While a reliable attenuation of large OKR amplitudes can be induced already in young larvae, a robust response magnitude-dependent bidirectional plasticity is present only at older developmental stages. The possibility of older larvae to faithfully enhance small OKR amplitudes coincides with the developmental maturation of inferior olivary–Purkinje cell signal integration. This conclusion was supported by the loss of behavioral plasticity following transection of the climbing fiber pathway and by the immunohistochemical demonstration of a considerable volumetric extension of the Purkinje cell dendritic area between the two tested stages. The bidirectional behavioral alterations with different developmental onsets might functionally serve to standardize the motor output, comparable to the known differential adaptability of vestibulo-ocular reflexes in these animals. This homeostatic plasticity potentially equilibrates the working range of ocular motor behaviors during altered visuo-vestibular conditions or prolonged head/body motion to fine-tune resultant eye movements.

Stroboscopic lighting with intensity synchronized to rotation velocity alleviates motion sickness gastrointestinal symptoms and motor disorders in rats.

Motion sickness (MS) is caused by mismatch between conflicted motion perception produced by motion challenges and expected “internal model” of integrated motion sensory pattern formed under normal condition in the brain. Stroboscopic light could reduce MS nausea symptom via increasing fixation ability for gaze stabilization to reduce visuo-vestibular confliction triggered by distorted vision during locomotion. This study tried to clarify whether MS induced by passive motion could be alleviated by stroboscopic light with emitting rate and intensity synchronized to acceleration–deceleration phase of motion. We observed synchronized and unsynchronized stroboscopic light (SSL: 6 cycle/min; uSSL: 2, 4, and 8 cycle/min) on MS-related gastrointestinal symptoms (conditioned gaping and defecation responses), motor disorders (hypoactivity and balance disturbance), and central Fos protein expression in rats receiving Ferris wheel-like rotation (6 cycle/min). The effects of color temperature and peak light intensity were also examined. We found that SSL (6 cycle/min) significantly reduced rotation-induced conditioned gaping and defecation responses and alleviated rotation-induced decline in spontaneous locomotion activity and disruption in balance beam performance. The efficacy of SSL against MS behavioral responses was affected by peak light intensity but not color temperature. The uSSL (4 and 8 cycle/min) only released defecation but less efficiently than SSL, while uSSL (2 cycle/min) showed no beneficial effect in MS animals. SSL but not uSSL inhibited Fos protein expression in the caudal vestibular nucleus, the nucleus of solitary tract, the parabrachial nucleus, the central nucleus of amygdala, and the paraventricular nucleus of hypothalamus, while uSSL (4 and 8 cycle/min) only decreased Fos expression in the paraventricular nucleus of hypothalamus. These results suggested that stroboscopic light synchronized to motion pattern might alleviate MS gastrointestinal symptoms and motor disorders and inhibit vestibular-autonomic pathways. Our study supports the utilization of motion-synchronous stroboscopic light as a potential countermeasure against MS under abnormal motion condition in future.

Oculomotor plant and neural dynamics suggest gaze control requires integration on distributed timescales.

A fundamental principle of biological motor control is that the neural commands driving movement must conform to the response properties of the motor plants they control. In the oculomotor system, characterizations of oculomotor plant dynamics traditionally supported models in which the plant responds to neural drive to extraocular muscles on exclusively short, subsecond timescales. These models predict that the stabilization of gaze during fixations between saccades requires neural drive that approximates eye position on longer timescales and is generated through the temporal integration of brief eye velocity-encoding signals that cause saccades. However, recent measurements of oculomotor plant behaviour have revealed responses on longer timescales. Furthermore, measurements of firing patterns in the oculomotor integrator have revealed a more complex encoding of eye movement dynamics. Yet, the link between these observations has remained unclear. Here we use measurements from the larval zebrafish to link dynamics in the oculomotor plant to dynamics in the neural integrator. The oculomotor plant in both anaesthetized and awake larval zebrafish was characterized by a broad distribution of response timescales, including those much longer than 1s. Analysis of the firing patterns of oculomotor integrator neurons, which exhibited a broadly distributed range of decay time constants, demonstrates the sufficiency of this activity for stabilizing gaze given an oculomotor plant with distributed response timescales. This work suggests that leaky integration on multiple, distributed timescales by the oculomotor integrator reflects an inverse model for generating oculomotor commands, and that multi-timescale dynamics may be a general feature of motor circuitry. KEY POINTS: Recent observations of oculomotor plant response properties and neural activity across the oculomotor system have called into question classical formulations of both the oculomotor plant and the oculomotor integrator. Here we use measurements from new and published experiments in the larval zebrafish together with modelling to reconcile recent oculomotor plant observations with oculomotor integrator function. We developed computational techniques to characterize oculomotor plant responses over several seconds in awake animals, demonstrating that long timescale responses seen in anaesthetized animals extend to the awake state. Analysis of firing patterns of oculomotor integrator neurons demonstrates the sufficiency of this activity for stabilizing gaze given an oculomotor plant with multiple, distributed response timescales. Our results support a formulation of gaze stabilization by the oculomotor system in which commands for stabilizing gaze are generated through integration on multiple, distributed timescales.

Ocular counter-roll is less affected in experienced versus novice space crew after long-duration spaceflight

Otoliths are the primary gravity sensors of the vestibular system and are responsible for the ocular counter-roll (OCR). This compensatory eye torsion ensures gaze stabilization and is sensitive to a head roll with respect to gravity and the Gravito-Inertial Acceleration vector during, e.g., centrifugation. To measure the effect of prolonged spaceflight on the otoliths, we quantified the OCR induced by off-axis centrifugation in a group of 27 cosmonauts in an upright position before and after their 6-month space mission to the International Space Station. We observed a significant decrease in OCR early postflight, larger for first-time compared to experienced flyers. We also found a significantly larger torsion for the inner eye, the eye closest to the rotation axis. Our results suggest that experienced cosmonauts have acquired the ability to adapt faster after G-transitions. These data provide a scientific basis for sending experienced cosmonauts on challenging missions that include multiple g-level transitions.

A-37 Ocular Motor Impairments in Concussion Professional Football Players

Abstract Purpose: The purpose of this study was to examine baseline and post-concussion injury characteristics of ocular eye movements using the Sync Think visual eye tracking apparatus in professional football players in the Canadian Football League (CFL). Methods: The visual tracking testing protocol uses an integrated stimulus presentation-eye tracking apparatus (EyeLink CL; SR Research, Ontario, Canada) with which eye movements were recorded at 500 Hz using infrared video-oculography. The standard deviation of radial errors (SDRE) and tangential errors (SDTE) were used to determine poor visual tracking. Participants were (n = 748) rostered players in the Canadian Football League. All participants completed assessments at baseline. Sixteen players completed post-concussion assessments and 98 players completed post-exertional assessments during the 2021 season to evaluate the impact of physical exertion on ocular movement metrics. Results: Participants with diagnosed concussions (n = 16+) demonstrated significantly poorer performance on measures of both gaze stability and smooth pursuit (p < 0.001). The poorer results were correlated with significantly higher subjective ratings of dizziness (p < 0.01) and fogginess (p < 0.001). In contrast, healthy participants who completed the same ocular motor assessments demonstrated no significant differences compared to baseline test performance. Conclusions: Findings suggest that subtle differences in oculomotor functioning arise from sport concussion in professional football players. Further research with larger sample sizes and correlation with other cognitive and physical outcomes is warranted.

To Design and Investigate the Effectiveness of a Gaze Stabilization Application on Patients with Impaired Visual Vestibulo-ocular Reflex

Purpose: Vestibulo-ocular Reflex is the main vision stabilizing system during rapid head movements. In keeping the eyes still during head motion which is referred to as the gaze stability, the VOR has a censorious role. Loss of this vestibular function produces instability of gaze which worsens on motion and activity. Vestibular rehabilitation is one of the treatment modalities for patients with vestibular insufficiency. These exercises include gaze stability, central programming and balance exercise. Here this study is an instrument-based study and this device focuses on visually tracking, using smooth pursuit eye movements on a moving object. It shall not only provide a combined gaze stability adaptive exercise but it will also provide various progressions and biofeedback to the patients. Methods: An interventional study, with a sum of 30 participants having significant vestibular hypofunction or dysfunction who voluntarily participated in the study. It was a comparative study and it took place in Krishna Institute of Medical Sciences deemed to be University, Karad city in Maharashtra, India. 6 months was the total time span required to complete this trial. Consecutive sampling with random allocation was done. Those fulfilling the inclusion criteria were recruited and divided into two groups: control and interventional. Results and Conclusion: Vestibular dysfunction significantly affected the quality of life and lead to serious disability. Virtual mode of rehabilitation training by tracking the object with the eye, built interest and motivated the patient to regularly exercise as well as to perform smooth eye movements with lower range of saccades.

Low Gain Values of the Vestibulo-Ocular Reflex Can Optimize Retinal Image Slip.

The angular vestibulo-ocular reflex (aVOR) stabilizes retinal images by counter-rotating the eyes during head rotations. Perfect compensatory movements would thus rotate the eyes exactly opposite to the head, that is, eyes vs. head would exhibit a unity gain. However, in many species, but also in elderly humans or patients with a history of vestibular damage, the aVOR is far from compensatory with gains that are in part considerably lower than unity. The reason for this apparent suboptimality is unknown. Here, we propose that low VOR gain values reflect an optimal adaptation to sensory and motor signal variability. According to this hypothesis, gaze stabilization mechanisms that aim at minimizing the overall retinal image slip must consider the effects of (1) sensory and motor noise and (2) dynamic constraints of peripheral and central nervous processing. We demonstrate that a computational model for optimizing retinal image slip in the presence of such constraints of signal processing in fact predicts gain values smaller than unity. We further show specifically for tadpoles of the clawed toad, Xenopus laevis with particularly low gain values that previously reported VOR gains quantitatively correspond to the observed variability of eye movements and thus constitute an optimal adaptation mechanism. We thus hypothesize that lower VOR gain values in elderly human subjects or recovered patients with a history of vestibular damage may be the sign of an optimization given higher noise levels rather than a direct consequence of the damage, such as an inability of executing fast compensatory eye movements.

Association of Postural Sway with Kellengren Lawrence Grade II and III of Osteoarthritis of Knee Joint among Elderly Population.

Background: Postural sway is very common in elderly population. It is mainly associated with balance. There are two factors, Decreased proprioception –which leads to sway when walking and increased reliance on vision. Vestibular weakness – as the person ages it’s common to have vestibular deficits which affects gaze stability and ability to turn head which affects balance. This may cause fall and increase the risk of injury. Objective: 1. To investigate the postural sway in elderly OA knee patients. To investigate the postural sway according to different grades of OA. Methodology: It was a cross-sectional study. Total 60 elderly individuals with OA knee were included using simple random sampling method. Result: The data was collected in OA Knee patients for sway in all four directions was analyzed with eyes open and eyes closed conditions. All 60 subjects having more sway in anterior and left lateral direction with both eyes open and eyes closed condition compared to their sway in posterior and right lateral direction. Conclusion: This study concludes that more sway was observed in anterior and left lateral direction both with eyes opened and eyes closed compared to posterior and right lateral direction in all Grade I, Grade II ,Grade III patients, all males and females, young old and middle old subjects. While in old old subjects the sway was found more in anterior and right lateral direction compared to posterior and left lateral direction.

Challenging the Vestibular System Affects Gait Speed and Cognitive Workload in Chronic Mild Traumatic Brain Injury and Healthy Adults.

People with persistent symptoms after mild traumatic brain injury (mTBI) report imbalance during walking with head movements. The purpose of this study was (1) to compare usual walk gait speed to walking with head turns (HT) between people with mTBI and controls, (2) to compare the cognitive workload from usual walk to HT walk between groups, and (3) to examine if gaze stability deficits and mTBI symptoms influence gait speed. Twenty-three individuals (mean age 55.7 ± 9.3 years) with persistent symptoms after mTBI (between 3 months to 2 years post-injury) were compared with 23 age and sex-matched controls. Participants walked a 12-inch wide, 60-foot walkway when looking ahead and when walking with HT to identify letters and their colors. Gait speed during usual walk and HT walk were calculated. Pupillary responses during both walks were converted to the Index of Cognitive Activity (ICA) as a measure of cognitive workload. Gaze stability was examined by the dynamic visual acuity (DVA) test in the yaw plane. The post-concussion symptom scale (PCSS) was used to collect symptom severity. Within group analysis showed that gait speed was lower during HT walk compared to usual walk in the people with mTBI (p < 0.001) as well as in controls (p < 0.001). ICA was higher with HT compared to usual walk in the mTBI group in the right eye (p = 0.01) and left eye (p = 0.001), and in controls in the right eye (p = 0.01) and left eye (p = 0.01). Participants in the mTBI group had slower usual (p < 0.001), and HT gait speed (p < 0.001) compared to controls. No differences were noted in ICA in the right or left eye during usual walk and HT walk between groups (p > 0.05). DVA loss in the yaw plane to the right and left was not different between groups (p > 0.05) and were not correlated with gait speed. PCSS scores were correlated with usual walk (r = −0.50, p < 0.001) and HT gait speed (r = −0.44, p = 0.002). Slower gait speed, poorer stability, and higher cognitive workload during walking with head turns may reduce community participation in people with mTBI and persistent symptoms.

IGST Combined with Conventional Drug Therapy and TCM Therapy for Treatment of Bilateral Vestibular Hypofunction.

Objective To investigate the effects of intensive gaze stability training (IGST) combined with conventional drug therapy and traditional Chinese medicine (TCM) therapy on hearing recovery and quality of life (QOL) in patients with bilateral vestibular dysfunction. Materials and Methods A total of 120 patients with bilateral vestibular dysfunction admitted to our hospital from January 2019 to January 2020 were recruited and assigned to group A (n = 60) and group B (n = 60) based on the order of admission. Group B received conventional medication and TCM therapy, and group A received IGST plus conventional medication and TCM therapy. The serum biochemical indexes, blood rheology indexes, symptoms disappearance time, hearing recovery time, pure-tone hearing threshold, vestibular symptom index (VSI), and QOL of the two groups were compared. Results The serum biochemical indexes and blood rheology indexes in group A were lower than those in group B after treatment (P < 0.001). Patients in group A had a shorter time lapse before symptoms disappearance and hearing recovery than those in group B (P < 0.001). Group A had lower results of the pure-tone hearing threshold (P < 0.001) and of VSI (P < 0.05) than group B. Patients in group A had higher QOL scores than those in group B after treatment (P < 0.001). Conclusion IGST plus conventional drug therapy effectively improves the serum biochemical indexes and blood rheological indexes of patients with bilateral vestibular hypofunction, accelerates their hearing recovery process, and alleviates their clinical symptoms, thereby improving their QOL, which shows good potential in clinical application.

Effects of balance training with and without gaze stabilization exercises on clinical outcomes in elderly patients with chronic dizziness: A randomized controlled trial

ObjectiveTo compare the effects of balance training with and without Gaze Stabilization exercises on clinical outcomes in elderly patient with chronic dizziness. MethodTotal 64 participants after referral from neurologist at Lahore General Hospital were recruited in this study. These participants were randomly assigned into two groups i.e. Group A (Gaze group) and Group B (control group) with 32 participants in each group by sealed envelope method. Gaze group performed balance exercises with gaze stability exercise whereas, group B performed balance exercises with saccade eye exercises. Berg Balance Scale, Disability Handicapped Inventory, and Activity Specific Balance Confidence Scale were used to measure outcome variables. ResultsDemographic variables were represented by mean, standard deviation and frequency distribution. Results showed that there was no baseline difference between gaze and control group (p > 0.05). Both groups showed improved results with the gaze group showing significantly more improvement as compare to the control group on balance (p < 0.05, Mean Group A = 44.1, Mean group B = 40.91), perceived disability (p < 0.05, Mean Group A = 52.84, Group B = 56.09), and risk of fall (p < 0.05, Mean Group A = 53.84, Mean Group B = 50.72) respectively. ConclusionThis study concluded that gaze stability exercises with balance training are effective in improving balance, level of perceived disability, and risk of fall prevention among elderly patients with chronic dizziness.

Complementary feedback control enables effective gaze stabilization in animals

Visually active animals coordinate vision and movement to achieve spectacular tasks. An essential prerequisite to guide agile locomotion is to keep gaze level and stable. Since the eyes, head and body can move independently to control gaze, how does the brain effectively coordinate these distinct motor outputs? Furthermore, since the eyes, head, and body have distinct mechanical constraints (e.g., inertia), how does the nervous system adapt its control to these constraints? To address these questions, we studied gaze control in flying fruit flies (Drosophila) using a paradigm which permitted direct measurement of head and body movements. By combining experiments with mathematical modeling, we show that body movements are sensitive to the speed of visual motion whereas head movements are sensitive to its acceleration. This complementary tuning of the head and body permitted flies to stabilize a broader range of visual motion frequencies. We discovered that flies implement proportional-derivative (PD) control, but unlike classical engineering control systems, relay the proportional and derivative signals in parallel to two distinct motor outputs. This scheme, although derived from flies, recapitulated classic primate vision responses thus suggesting convergent mechanisms across phyla. By applying scaling laws, we quantify that animals as diverse as flies, mice, and humans as well as bio-inspired robots can benefit energetically by having a high ratio between head, body, and eye inertias. Our results provide insights into the mechanical constraints that may have shaped the evolution of active vision and present testable neural control hypotheses for visually guided behavior across phyla.

The Effect of A Home Exercise Program on Visio-Vestibular Function in Concussed Pediatric Patients

Background:A home exercise program (HEP) can provide an equitable and cost-effective method for therapy targeted towards visio-vestibular deficits that are common following concussion. It is unclear if pediatric patients prescribed a HEP demonstrate improved visio-vestibular function.Purpose:To explore if a HEP affects visio-vestibular function in concussed pediatric patients.Methods:This observational study included 1,041 patients (614 female(59.0%); age=14.0±2.5 years) reporting to a specialty care concussion center for an initial visit within 28 days of injury and a first follow-up visit within 60 days of injury. All patients completed a Visio-Vestibular Examination (VVE) at both time points, which consisted of 9 maneuvers: smooth pursuit, horizontal/vertical saccades and gaze stability, binocular convergence, left/right monocular accommodation, and complex tandem gait. Patients were given a HEP at initial visit which consisted of exercises, including saccades, gaze stability, convergence, and balance, and instructed to complete these exercises 1-2 times daily. At follow-up, patients were asked to report their progress with the HEP, which was categorized as 1) has not done the HEP, 2) is currently doing the HEP, or 3) has completed the HEP. Primary outcomes included HEP status at first follow-up, VVE subtests (normal/abnormal), and total VVE (abnormal=2+ abnormal subtests). Separate chi-square tests with Bonferroni corrections were used to determine if the proportion of abnormal VVE outcomes was associated with HEP status (α=0.017 a priori).Results:At initial visit, 812 (77.6%) patients presented with abnormal total VVE. The proportion of abnormal subtests at initial visit ranged from 16.0% (right monocular accommodation) to 77.4% (horizontal gaze stability). At first follow-up, the proportion of abnormal total VVE did not differ among patients reporting not doing the HEP (101(62.0%)), patients currently doing the HEP (516(69.0%)), and patients who had completed the HEP (51(69.0%)). However among VVE subtests, a lower proportion of patients who completed the HEP presented with abnormal smooth pursuit (7.5%), horizontal (3.8%) and vertical (3.8%) saccades, and complex tandem gait (0%) relative to patients who were currently doing the HEP (P≤0.003) and to patients not doing the HEP (P≤0.01).Conclusions:Our findings indicate that patients who completed the HEP presented with better aspects of visio-vestibular function (smooth pursuit, saccades, and complex tandem gait) relative to those who did not start or were currently doing the HEP. This suggests that a HEP may be effective in reducing visio-vestibular dysfunction following concussion. Additional research investigating cost-effective concussion management tools is needed to improve patient outcomes.

Stable Gaze Tracking with Filtering Based on Internet of Things.

Gaze tracking is basic research in the era of the Internet of Things. This study attempts to improve the performance of gaze tracking in an active infrared source gaze-tracking system. Owing to unavoidable noise interference, the estimated points of regard (PORs) tend to fluctuate within a certain range. To reduce the fluctuation range and obtain more stable results, we introduced a Kalman filter (KF) to filter the gaze parameters. Considering that the effect of filtering is relevant to the motion state of the gaze, we design the measurement noise that varies with the speed of the gaze. In addition, we used a correlation filter-based tracking method to quickly locate the pupil, instead of the detection method. Experiments indicated that the variance of the estimation error decreased by 73.83%, the size of the extracted pupil image decreased by 93.75%, and the extraction speed increased by 1.84 times. We also comprehensively discussed the advantages and disadvantages of the proposed method, which provides a reference for related research. It must be pointed out that the proposed algorithm can also be adopted in any eye camera-based gaze tracker.

Эффективность применения световой нервно-зрительной стимуляции у детей младенческого возраста с задержкой зрительного созревания

Purpose. To study the effectiveness of neuro-visual light stimulation in infants with delayed visual maturation (DVM). Material and methods. The study involved 22 infants with DVM at the age of 2–3 months. In all children, the movements of the eyeballs were insufficiently coordinated; there were also no visual reflexes of tracking and stable fixation. All patients were divided into two groups – the main (12 people) and comparison (10 people). Children of both groups received neurotropic therapy. Additionally, patients of the main group were prescribed light therapy of fontanelles with the Bioptron device daily for 30 seconds in one session (15 seconds for each fontanel). The duration of the course was 15 days with a frequency of course treatment every 1–1.5 months until the desired therapeutic effect is obtained. Efficiency criteria: the rate of development of visual functions and behavioral reactions corresponding to the variant of the age norm. Results. After the first course of using the Bioptron device, 8 out of 12 children of the main group developed a tracking reaction, gaze fixation, and consistency in the movements of the eyeballs. In three children – only after the second course of light therapy, and in one child – after the third course of treatment. In the control group, two out of 10 children after 15 days from the start of neurotropic therapy developed eye movement coordination, a stable reaction to tracking objects, and stable gaze fixation; in the remaining 8 children, these reactions appeared only 5 months after the start of treatment. Conclusion. Neuro-visual light stimulation, as an addition to pharmaconeuroprotection, significantly reduces the time for the formation of normal visual functions in case of DVM. Keywords: neuro-visual light stimulation, delayed visual maturation, Bioptron.