Relationship between maternal biological features, environmental factors, and newborn neuromotor development associated with visual fixation abilities.

Newborn visual fixation abilities predict future cognitive, perceptive, and motor skills. However, little is known about the factors associated with the newborn visual fixation, which is an indicator of neurocognitive abilities. We analyzed maternal biological and environmental characteristics associated with fine motor skills (visual tracking) in 1 month old infants. Fifty-one infants were tested on visual tracking tasks (Infant Visuomotor Behavior Assessment Scale/ Guide for the Assessment of Visual Ability in Infants) and classified according to visual conducts scores. Differences between groups were compared considering motor development (Alberta Infant Motor Scale) maternal mental health (Edinburgh Postnatal Depression Scale and Hamilton Anxiety Scale); home environment (Affordances in the Home Environment for Development Scale); maternal care (Coding Interactive Behavior); breastmilk composition (total fatty acids, proteins, and cortisol); and maternal metabolic profile (serum hormones and interleukins). Mothers of infants with lower visual fixation scores had higher levels of protein in breastmilk at 3 months. Mothers of infants with better visual conduct scores had higher serum levels of T4 (at 1 month) and prolactin (at 3 months). There were no associations between visual ability and motor development, home environment, or maternal care. Early newborn neuromotor development, especially visual and fine motor skills, is associated with maternal biological characteristics (metabolic factors and breastmilk composition), highlighting the importance of early detection of maternal metabolic changes for the healthy neurodevelopment of newborns.

Spatial and Temporal Abnormalities of Spontaneous Fixational Saccades and Their Correlates With Positive and Cognitive Symptoms in Schizophrenia.

BACKGROUND AND HYPOTHESIS: Visual fixation is a dynamic process, with the spontaneous occurrence of microsaccades and macrosaccades. These fixational saccades are sensitive to the structural and functional alterations of the cortical-subcortical-cerebellar circuit. Given that dysfunctional cortical-subcortical-cerebellar circuit contributes to cognitive and behavioral impairments in schizophrenia, we hypothesized that patients with schizophrenia would exhibit abnormal fixational saccades and these abnormalities would be associated with the clinical manifestations. STUDY DESIGN: Saccades were recorded from 140 drug-naïve patients with first-episode schizophrenia and 160 age-matched healthy controls during ten separate trials of 6-second steady fixations. Positive and negative symptoms were assessed using the Positive and Negative Syndrome Scale (PANSS). Cognition was assessed using the Measurement and Treatment Research to Improve Cognition in Schizophrenia Consensus Cognitive Battery (MCCB). STUDY RESULTS: Patients with schizophrenia exhibited fixational saccades more vertically than controls, which was reflected in more vertical saccades with angles around 90° and a greater vertical shift of horizontal saccades with angles around 0° in patients. The fixational saccades, especially horizontal saccades, showed longer durations, faster peak velocities, and larger amplitudes in patients. Furthermore, the greater vertical shift of horizontal saccades was associated with higher PANSS total and positive symptom scores in patients, and the longer duration of horizontal saccades was associated with lower MCCB neurocognitive composite, attention/vigilance, and speed of processing scores. Finally, based solely on these fixational eye movements, a K-nearest neighbors model classified patients with an accuracy of 85%. Conclusions: Our results reveal spatial and temporal abnormalities of fixational saccades and suggest fixational saccades as a promising biomarker for cognitive and positive symptoms and for diagnosis of schizophrenia.

Visual fixation suppression of caloric nystagmus in progressive supranuclear palsy - A comparison with Parkinson's disease.

BACKGROUND: Impairment of visual fixation suppression (VS) in progressive supranuclear palsy (PSP) is not well documented. OBJECTIVE: To evaluate the usefulness of impaired VS of caloric nystagmus as an index for differential diagnosis between PSP and Parkinson's disease (PD), which is often difficult, especially in the early stage. METHODS: Subjects comprised 26 PSP patients and 26 PD patients clinically diagnosed at Tokyo Metropolitan Neurological Hospital. We retrospectively investigated VS of caloric nystagmus, horizontal pursuit, saccades, and horizontal optokinetic nystagmus recorded on direct-current-electronystagmography, and neuroradiological findings. RESULTS: The median of the average VS% was 0% and 50.0% in PSP and PD patients, respectively. In PSP, VS was impaired even in the early stage of disease. We found a significant correlation between VS and velocity of saccades or maximum slow phase velocity of optokinetic nystagmus only in PSP patients. PSP patients with atrophy of the subthalamic nucleus or with decreased blood flow in the frontal lobe showed significantly more severe impairment of VS. CONCLUSIONS: VS may be a useful biomarker to differentiate patients with PSP from those with PD. Cerebellar networks that connect with the cerebral cortex and basal ganglia may contribute to impaired VS of caloric nystagmus in PSP.

Characteristics of Visual Fixation in Chinese Children with Autism During Face-to-Face Conversations.

Few eye tracking studies have examined how people with autism spectrum disorder (ASD) visually attend during live interpersonal interaction, and none with the Chinese population. This study used an eye tracker to record the gaze behavior in 20 Chinese children with ASD and 23 children with typical development (TD) when they were engaged in a structured conversation. Results demonstrated that children with ASD looked significantly less at the interlocutor's mouth and whole-face, and more at background. Additionally, gaze behavior was found to vary with the conversational topic. Given the great variability in eye tracking findings in existing literature, future explorations might consider investigating how fundamental factors (i.e., participant's characteristics, tasks, and context) influence the gaze behavior in people with ASD.

Nystagmus only with fixation in the light: a rare central sign due to cerebellar malfunction.

Fixation nystagmus refers to the nystagmus that appears or markedly increases with fixation. While relatively common in infantile (congenital) nystagmus, acquired fixation nystagmus is unusual and has been ascribed to lesions involving the cerebellar nuclei or the fibers projecting from the cerebellum to the brainstem. We aimed to report the clinical features of patients with acquired fixation nystagmus and discuss possible mechanisms using a model simulation and diagnostic significance. We describe four patients with acquired fixation nystagmus that appears or markedly increases with visual fixation. All patients had lesions involving the cerebellum or dorsal medulla. All patients showed direction-changing gaze-evoked nystagmus, impaired smooth pursuit, and decreased vestibular responses on head-impulse tests. The clinical implication of fixation nystagmus is that it may occur in central lesions that impair both smooth pursuit and the vestibulo-ocular reflex (VOR) but without creating a spontaneous nystagmus in the dark. We develop a mathematical model that hypothesizes that fixation nystagmus reflects a central tone imbalance due to abnormal function in cerebellar circuits that normally optimize the interaction between visual following (pursuit) and VOR during attempted fixation. Patients with fixation nystagmus have central lesions involving the cerebellar circuits that are involved in visual-vestibular interactions and normally eliminate biases that cause a spontaneous nystagmus.

Visual interpretation of panoramic radiographs in dental students using eye-tracking technology.

PURPOSE: While eye-tracking technology is a validated tool in the field of education it is still in its infancy in the field of Pediatric Dentistry. The primary aim of this study was to determine dental undergraduates' search patterns and visual fixations while viewing panoramic radiographs (PR) using an eye-tracker. The secondary aim was to decide on the potential opportunities to enhance teaching-learning strategies when studying these radiographs. METHODS: Sixty-five dental undergraduates in the final year of their dental education consented to and participated in this study. A Tobii Pro Nano screen-based eye-tracking camera was mounted to the lower edge of a laptop with five different PR uploaded onto the Tobii Studio software. Regions of Interest (ROIs) were pre-determined for the five PR. The participants (17 males and 48 females) viewed all the PR images with no time restrictions and a "think-aloud" protocol was exercised. RESULTS: The average view time for the PR was 245.58 ± 106.7 s. Participants spent significantly less time examining the surrounding structures (14.85 s) than the dentitions (primary: 97.58 s and permanent: 37.58 s). Males demonstrated a slightly higher view time (290.88 ± 97.7 s) than females (229.53 ± 106.05 s). CONCLUSIONS: The results revealed that though the participants focused on the ROI, most of them failed to make the correct diagnosis. In addition, the search patterns of the participants unveiled no sequential viewing of PR. Hence the need to revise the teaching-learning strategies for the systematic interpretation of PR images in the dental curriculum is warranted.

Towards consensus on visual pursuit and visual fixation in patients with disorders of consciousness. A Delphi study.

BACKGROUND: The aim of this Delphi study was to reach consensus about definition, operationalization and assessment of visual pursuit (VP) and visual fixation (VF). METHODS: In a three-round international Delphi study, clinical and research experts on disorders of consciousness indicated their level of agreement on 87 statements using a 5-point Likert scale. Consensus for agreement was defined by a median of 5, an interquartile range (IQR) ≤ 1, and ≥ 80% indicating moderate or strong agreement. RESULTS: Forty-three experts from three continents participated, 32 completed all three rounds. For VP, the consensus statements with the highest levels of agreement were on the term 'pursuit of a visual stimulus', the description 'ability to follow visually in horizontal and/or vertical plane', a duration > 2 s, tracking in horizontal and vertical planes, and a frequency of more than 2 times per assessment. For VF, consensus statements with the highest levels of agreement were on the term 'sustained VF', the description 'sustained fixation in response to a salient stimulus', a duration of > 2 s and a frequency of 2 or more times per assessment. The assessment factors with the highest levels of agreement were personalized stimuli, the use of eye tracking technology, a patient dependent time of assessment, sufficient environmental light, upright posture, and the necessity to exclude ocular/oculomotor problems. CONCLUSION: This first international Delphi study on VP and VF in patients with disorders of consciousness provides provisional operational definitions and an overview of the most relevant assessment factors.

Dissociations between performance and visual fixations after subordinate- and basic-level training with novel objects.

Previous work suggests that subordinate-level object training improves exemplar-level perceptual discrimination over basic-level training. However, the extent to which visual fixation strategies and the use of visual features, such as color and spatial frequency (SF), change with improved discrimination was not previously known. In the current study, adults (n = 24) completed 6 days of training with 2 families of computer-generated novel objects. Participants were trained to identify one object family at the subordinate level and the other object family at the basic level. Before and after training, discrimination accuracy and visual fixations were measured for trained and untrained exemplars. To examine the impact of training on visual feature use, image color and SF were manipulated and tested before and after training. Discrimination accuracy increased for the object family trained at the subordinate-level, but not for the family trained at the basic level. This increase was seen for all image manipulations (color, SF) and generalized to untrained exemplars within the trained family. Both subordinate- and basic-level training increased average fixation duration and saccadic amplitude and decreased the number of total fixations. Collectively, these results suggest a dissociation between discrimination accuracy, indicative of recognition, and the associated pattern of changes present for visual fixations.

Classification of Children With Autism and Typical Development Using Eye-Tracking Data From Face-to-Face Conversations: Machine Learning Model Development and Performance Evaluation.

BACKGROUND: Previous studies have shown promising results in identifying individuals with autism spectrum disorder (ASD) by applying machine learning (ML) to eye-tracking data collected while participants viewed varying images (ie, pictures, videos, and web pages). Although gaze behavior is known to differ between face-to-face interaction and image-viewing tasks, no study has investigated whether eye-tracking data from face-to-face conversations can also accurately identify individuals with ASD. OBJECTIVE: The objective of this study was to examine whether eye-tracking data from face-to-face conversations could classify children with ASD and typical development (TD). We further investigated whether combining features on visual fixation and length of conversation would achieve better classification performance. METHODS: Eye tracking was performed on children with ASD and TD while they were engaged in face-to-face conversations (including 4 conversational sessions) with an interviewer. By implementing forward feature selection, four ML classifiers were used to determine the maximum classification accuracy and the corresponding features: support vector machine (SVM), linear discriminant analysis, decision tree, and random forest. RESULTS: A maximum classification accuracy of 92.31% was achieved with the SVM classifier by combining features on both visual fixation and session length. The classification accuracy of combined features was higher than that obtained using visual fixation features (maximum classification accuracy 84.62%) or session length (maximum classification accuracy 84.62%) alone. CONCLUSIONS: Eye-tracking data from face-to-face conversations could accurately classify children with ASD and TD, suggesting that ASD might be objectively screened in everyday social interactions. However, these results will need to be validated with a larger sample of individuals with ASD (varying in severity and balanced sex ratio) using data collected from different modalities (eg, eye tracking, kinematic, electroencephalogram, and neuroimaging). In addition, individuals with other clinical conditions (eg, developmental delay and attention deficit hyperactivity disorder) should be included in similar ML studies for detecting ASD.

How Task Constraints Influence the Gaze and Motor Behaviours of Elite-Level Gymnasts.

Perception-action coupling is fundamental to effective motor behaviour in complex sports such as gymnastics. We examined the gaze and motor behaviours of 10 international level gymnasts when performing two skills on the mini-trampoline that matched the performance demands of elite competition. The presence and absence of a vaulting table in each skill served as a task-constraint factor, while we compared super-elite and elite groups. We measured visual search behaviours and kinematic variables during the approach run phase. The presence of a vaulting table influenced gaze behaviour only in the elite gymnasts, who showed significant differences in the time spent fixating on the mini-trampoline, when compared to super-elite gymnasts. Moreover, different approach run characteristics were apparent across the two different gymnastic tasks, irrespective of the level of expertise, and take-off velocity was influenced by the skill being executed across all gymnasts. Task constraints and complexity influence gaze behaviours differed across varying levels of expertise in gymnastics, even within a sample of international level athletes. It appears that the time spent fixating their gazes on the right areas of interest during the approach run is crucial to higher-level performance and therefore higher scores in competition, particularly on the mini-trampoline with vaulting table.

Age Differences in Visual Attention and Responses to Intergenerational and Non-intergenerational Workplace Conflicts.

Intergenerational conflict occurs commonly in the workplace because of age-related differences in work attitudes and values. This study aimed to advance the current literature on aging and work by examining whether younger and older workers differ in their visual attention, emotional responses, and conflict strategies when observing hypothetical conflict vignettes involving a coworker from a similar or dissimilar age group. The indirect effect of age group on emotional responses and conflict strategies through visual fixation on conflict scenes was also examined. Utilizing eye tracking, the visual attention of younger and older workers while watching two hypothetical workplace task conflict videos was recorded and compared. The participants were also asked to imagine how they would respond if they were the main actor in the vignettes. A total of 94 working adults, including 48 younger workers and 46 older workers, participated in the eye tracking experiment. Older workers reported fewer negative and more positive emotions than their younger counterparts after watching the conflict videos, particularly those on the non-intergenerational conflict. Younger workers used more dominating in the intergenerational conflict than in the non-intergenerational conflict; such discrepancy between conflict types was relatively small in older workers. Compared with younger workers, older workers fixated significantly less on the coworker during the intergenerational conflict scenes. A significant indirect effect of age group through visual fixation on the coworker was observed for positive emotions and avoiding. Results revealed that older workers may regulate their emotional reactions and conflict strategies to workplace conflicts by reducing their attention to negative stimuli.

Introducing BITTSy: The Behavioral Infant & Toddler Testing System.

This manuscript introduces BITTSy, the Behavioral Infant & Toddler Testing System. This software system is capable of running the headturn preference procedure, preferential looking, conditioned headturn, and visual fixation/habituation procedures. It uses only commercial-off-theshelf (COTS) hardware to implement the procedures in an affordable and space-efficient setup. The software package, example protocols and data sets, and manual are freely available and downloadable from go.umd.edu/BITTSy, making this entire set of procedures available to resource-limited labs. Researchers can easily use BITTSy at multiple sites in a uniform manner, resulting in a standardized, powerful research tool that can enhance cross-site research collaborations.

Evaluation of Fixational Behavior throughout Life.

BACKGROUND: To quantify development of gaze stability throughout life during short and long fixational tasks using eye tracking technology. METHODS: Two hundred and fifty-nine participants aged between 5 months and 77 years were recruited along the study. All participants underwent a complete ophthalmological assessment. Fixational behavior during long and short fixational tasks was analyzed using a DIVE (Device for an Integral Visual Examination), a digital test assisted with eye tracking technology. The participants were divided into ten groups according to their age. Group 1, 0-2 years; group 2, 2-5 years; group 3, 5-10 years; group 4, 10-20 years; group 5, 20-30 years; group 6, 30-40 years; group 7, 40-50 years; group 8, 50-60 years; group 9, 60-70 years; and group 10, over 70 years. RESULTS: Gaze stability, assessed by logBCEA (log-transformed bivariate contour ellipse area), improved with age from 5 months to 30 years (1.27 vs. 0.57 deg2 for long fixational task, 0.73 vs. -0.04 deg2 for short fixational task), while fixations tend to be longer (1.95 vs. 2.80 msec for long fixational tasks and 0.80 vs. 1.71 msec for short fixational tasks). All fixational outcomes worsened progressively from the fifth decade of life. Log-transformed bivariate contour ellipse area (0.79, 0.83, 0.91, 1.42 deg2 for long fixational task and 0.01, 0.18, 0.28, 0.44 deg2 for short fixational task, for group 7, 8, 9, and 10 respectively). Stimuli features may influence oculomotor performance, with smaller stimuli providing prolonged fixations. CONCLUSIONS: Fixational behavior can be accurately assessed from 5 months of age using a DIVE. We report normative data of gaze stability and duration of fixations for every age group. Currently available technology may increase the accuracy of our visual assessments at any age.

Saccadic Eye Movements Attenuate Postural Sway but Less in Sleep-Deprived Young Adults.

Sleep deprivation affects the performance of postural control and several other aspects related to attentional mechanisms that may alter sensory cue acquisition strategies. This study aimed to examine the possible effects of horizontal saccades and ocular fixation on a target in the performance of postural control in young adults with sleep deprivation. Twenty-six adults formed two groups, tested in two evaluations. In the first evaluation, participants slept normally on the night before. In the second evaluation, 13 participants were sleep deprived (SD) and 13 slept normally (control group [CG]) on the night before. In both evaluations, each participant stood upright as still as possible, in two experimental conditions: fixating the eye on a target and performing saccadic movement toward a target presented in two different locations (0.5 Hz). Each participant performed 3 trials in each condition, lasting 62 s each. Body oscillation was obtained in both anterior-posterior and medial-lateral directions. Results showed that SD participants swayed with a larger magnitude and higher velocity after sleep deprivation in the fixation condition. In the saccadic condition, body sway magnitude and velocity were reduced but were still larger/higher in the SD participants. Sleep deprivation deteriorates the performance of postural control. Saccadic eye movements improve postural control performance even in sleep-deprived participants but are still not sufficient to avoid postural control deterioration due to sleep deprivation.

Traumatic Brain Injury in Children: Sport-related Concussions in Children.

Concussion is a worldwide health concern among children and adolescents. Over the decades concussion has been gradually better recognized as an entity that accounts for a significant disability post head trauma in patients. Patients present with cognitive, somatic and oculo-vestibular symptoms that can be incapacitating. Most concussion symptoms are transient and resolve within 1-2 weeks but can persist for years. Concussion pathophysiology is complex and may not be fully understood but it involves numerous mechanisms including cellular metabolic derangements, cerebral blood inflow, and axonal disruption. With no associated objective biomarkers or visible pathologic brain changes, diagnosis of concussion can be challenging. Many organizations and collaborative groups have suggested numerous definitions and diagnostic criteria for concussion in an attempt to improve the evidence-based clinical assessments and therapies for concussion. Proper assessment and evaluation is crucial starting from counseling of the patient, gradual return to cognitive and physical activity in an individualized treatment plan to ensure a timely return to daily activities and full sport participation. This report provides a grasp over the current state of sport-related concussion knowledge, diagnosis, and clinical evaluation in children and adolescent, with a focus on the ocular symptoms and signs.

Suppressive control of optokinetic and vestibular nystagmus by the primate frontal eye field.

When the eyes are fixated on a spot, fixation neurons in the frontal eye field (FEF) show an increase in activity. Our previous study suggested that fixation neurons in the FEF contribute to the suppression of saccades and smooth pursuit eye movements to maintain active fixation. The present study examined the role of the FEF in the suppressive control of reflexive eye movements, optokinetic and vestibular nystagmus, in trained monkeys. Electrical stimulation in the FEF suppressed the quick and slow phases of optokinetic and vestibular nystagmus at an intensity lower than the threshold for eliciting electrically evoked saccades. Relatively weak suppression influenced the slow phase of vestibular nystagmus. During optokinetic or vestibular nystagmus, presentation of a stationary small spot to the eyes followed by fixation is known to suppress both the quick and slow phases of eye movements. We recorded the activity of fixation neurons in the FEF and found that fixation neurons usually showed a decrease in activity during optokinetic and vestibular nystagmus and an increase in activity during the suppression of nystagmus by visual fixation. The present results show that the activity of fixation neurons in the FEF is related to the suppressive control of optokinetic and vestibular nystagmus for maintaining active fixation. We discuss the role of a generalized visual fixation system that can maintain visual attention on an interesting object.NEW & NOTEWORTHY In this study, electrical stimulation in the frontal eye field (FEF) suppressed the quick and slow phases of optokinetic and vestibular nystagmus at an intensity subthreshold for eliciting saccades. Furthermore, the activity of fixation neurons in the FEF was related to the suppression of optokinetic and vestibular nystagmus by visual fixation. This suggests that a common neuronal assembly in the FEF may contribute to the suppressive control of different functional classes of eye movements.

Drivers' Visual Attention Characteristics under Different Cognitive Workloads: An On-Road Driving Behavior Study.

In this study, an on-road driving experiment was designed to investigate the visual attention fixation and transition characteristics of drivers when they are under different cognitive workloads. First, visual attention was macroscopically analyzed through the entropy method. Second, the Markov glance one- and two-step transition probability matrices were constructed, which can study the visual transition characteristics under different conditions from a microscopic perspective. Results indicate that the fixation entropy value of male drivers is 23.08% higher than that of female drivers. Under the normal driving state, drivers' fixation on in-vehicle systems is not continuous and usually shifts to the front and left areas quickly after such fixation. When under cognitive workload, drivers' vision transition is concentrated only in the front and right areas. In mild cognitive workload, drivers' sight trajectory is mainly focused on the distant front area. As the workload level increases, the transition trajectory shifts to the junction near the front and far sides. The current study finds that the difference between an on-road test and a driving simulation is that during the on-road driving process, drivers are twice as attentive to the front area than to the driving simulator. The research provides practical guidance for the improvement of traffic safety.

[Comparative assessment of the parameters of visual fixation in amblyopia of different origin]. / Sravnitel'naya otsenka parametrov zritel'noi fiksatsii pri ambliopii razlichnogo geneza.

INTRODUCTION: Examination of visual fixation parameters is an important diagnostic method in patients with amblyopia of different origin. PURPOSE: To study the visual fixation parameters for various types of amblyopia. MATERIAL AND METHODS: The study included 108 patients (213 eyes) aged 5-11 years with moderate and high amblyopia: 27 patients (54 eyes) with strabismic amblyopia, 45 patients (87 eyes) with refractive and anisometropic amblyopia, and 36 patients (72 eyes) with relative amblyopia caused by deprivation nystagmus. All examinations were performed on the NIDEK MP-1 Microperimeter. RESULTS: Fixation density within 2° and 4°, the amplitude of the horizontal and vertical fixation point displacement, the averaged value of the fixation point displacement and the average velocity of displacement were evaluated. There was a positive correlation between visual acuity and fixation density for all types of amblyopia, the higher the visual acuity, the higher the fixation density in the area of 2° and 4°. The maximum values of the displacement point amplitude were registered in patients with nystagmus. In patients with strabismic amblyopia, hyperopia and myopia values of displacement point amplitude were lower. The highest average displacement and rate of displacement of the fixation point were found in the group of patients with nystagmus. The differences were much less significant in other groups. CONCLUSION: A comparative objective study of visual fixation parameters for various types of amblyopia was performed using the NIDEK MP-1 Microperimeter. There was a positive correlation between fixation density decrease, the increase of amplitude and average displacement of the fixation point, and visual acuity decrease for all types of amblyopia. There was no significant correlation between average rate of displacement and visual acuity. The maximum disturbance of fixation parameters, including the average rate of the fixation point displacement, was registered in nystagmus.

Fourier-Domain OCT Imaging of the Ocular Surface and Tear Film Dynamics: A Review of the State of the Art and an Integrative Model of the Tear Behavior During the Inter-Blink Period and Visual Fixation.

In the last few decades, the ocular surface and the tear film have been noninvasively investigated in vivo, in a three-dimensional, high resolution, and real-time mode, by optical coherence tomography (OCT). Recently, OCT technology has made great strides in improving the acquisition speed and image resolution, thus increasing its impact in daily clinical practice and in the research setting. All these results have been achieved because of a transition from traditional time-domain (TD) to Fourier-domain (FD) technology. FD-OCT devices include a spectrometer in the receiver that analyzes the spectrum of reflected light on the retina or ocular surface and transforms it into information about the depth of the structures according to the Fourier principle. In this review, we summarize and provide the state-of-the-art in FD-OCT imaging of the ocular surface system, addressing specific aspects such as tear film dynamics and epithelial changes under physiologic and pathologic conditions. A theory on the dynamic nature of the tear film has been developed to explain the variations within the individual compartments. Moreover, an integrative model of tear film behavior during the inter-blink period and visual fixation is proposed.

Uncertainty in learning, choice, and visual fixation.

Uncertainty plays a critical role in reinforcement learning and decision making. However, exactly how it influences behavior remains unclear. Multiarmed-bandit tasks offer an ideal test bed, since computational tools such as approximate Kalman filters can closely characterize the interplay between trial-by-trial values, uncertainty, learning, and choice. To gain additional insight into learning and choice processes, we obtained data from subjects' overt allocation of gaze. The estimated value and estimation uncertainty of options influenced what subjects looked at before choosing; these same quantities also influenced choice, as additionally did fixation itself. A momentary measure of uncertainty in the form of absolute prediction errors determined how long participants looked at the obtained outcomes. These findings affirm the importance of uncertainty in multiple facets of behavior and help delineate its effects on decision making.