Eye movements, sensorimotor adaptation and cerebellar-dependent learning in autism: toward potential biomarkers and subphenotypes

No evidence for differential saccadic adaptation in children and adults with an autism spectrum diagnosis

Background

Altered patterns of eye-movements during scene exploration, and atypical gaze preferences in social settings, have long been noted as features of the Autism phenotype. While these are typically attributed to differences in social engagement and interests (e.g., preferences for inanimate objects over face stimuli), there are also reports of differential saccade measures to non-social stimuli, raising the possibility that fundamental differences in visuo-sensorimotor processing may be at play. Here, we tested the plasticity of the eye-movement system using a classic saccade-adaptation paradigm to assess whether individuals with ASD make typical adjustments to their eye-movements in response to experimentally introduced errors. Saccade adaptation can be measured in infants as young as 10 months, raising the possibility that such measures could be useful as early neuro-markers of ASD risk.

Methods

Saccade amplitudes were measured while children and adults with ASD (N = 41) and age-matched typically developing (TD) individuals (N = 68) made rapid eye-movements to peripherally presented targets. During adaptation trials, the target was relocated from 20-degrees to 15-degrees from fixation once a saccade to the original target location was initiated, a manipulation that leads to systematic reduction in saccade amplitudes in typical observers.

Results

Neither children nor adults with ASD showed any differences relative to TD peers in their abilities to appropriately adapt saccades in the face of persistently introduced errors.

Conclusion

Of the three studies to date of saccade adaptation in ASD, none have shown deficits in saccade adaptation that are sufficient to generalize to the whole or a subgroup of the ASD population. Unlike prior studies, we found no evidence for a slower adaptation rate during the early adaptation phase, and no of evidence greater variance of saccade amplitudes in ASD. In post hoc analysis, there was evidence for larger primary saccades to non-adapted targets, a finding requiring replication in future work.

Neurocognitive and cerebellar function in ADHD, autism and spinocerebellar ataxia

The cerebellum plays a major role in balance, motor control and sensorimotor integration, but also in cognition, language, and emotional regulation. Several neuropsychiatric disorders such as attention deficit-hyperactivity disorder (ADHD), autism spectrum disorder (ASD), as well as neurological diseases such as spinocerebellar ataxia type 3 (SCA3) are associated with differences in cerebellar function. Morphological abnormalities in different cerebellar subregions produce distinct behavioral symptoms related to the functional disruption of specific cerebro-cerebellar circuits. The specific contribution of the cerebellum to typical development may therefore involve the optimization of the structure and function of cerebro-cerebellar circuits underlying skill acquisition in multiple domains. Here, we review cerebellar structural and functional differences between healthy and patients with ADHD, ASD, and SCA3, and explore how disruption of cerebellar networks affects the neurocognitive functions in these conditions. We discuss how cerebellar computations contribute to performance on cognitive and motor tasks and how cerebellar signals are interfaced with signals from other brain regions during normal and dysfunctional behavior. We conclude that the cerebellum plays a role in many cognitive functions. Still, more clinical studies with the support of neuroimaging are needed to clarify the cerebellum's role in normal and dysfunctional behavior and cognitive functioning.

Quotidian Profile of Vergence Angle in Ambulatory Subjects Monitored With Wearable Eye Tracking Glasses

Purpose

Wearable eye trackers record gaze position as ambulatory subjects navigate their environment. Tobii Pro Glasses 3 were tested to assess their accuracy and precision in the measurement of vergence angle.

Methods

Four subjects wore the eye tracking glasses, with their head stabilized, while fixating at a series of distances corresponding to vergence demands of: 0.25, 0.50, 1, 2, 4, 8, 16, and 32°. After these laboratory trials were completed, 10 subjects wore the glasses for a prolonged period while carrying out their customary daily pursuits. A vergence profile was compiled for each subject and compared with interpupillary distance.

Results

In the laboratory, the eye tracking glasses were comparable in accuracy to remote video eye trackers, outputting a mean vergence value within 1° of demand at all angles except 32°. In ambulatory subjects, the glasses were less accurate, due to tracking interruptions and measurement errors, partly mitigated by the application of data filters. Nonetheless, a useful record of vergence behavior was obtained in every subject. Vergence profiles often had a bimodal distribution, reflecting a preponderance of activities at near (mobile phone and computer) or far (driving and walking). As expected, vergence angle correlated with interpupillary distance.

Conclusions

Wearable eye tracking glasses make it possible to compile a nearly continuous record of vergence angle over hours, which can be correlated with the corresponding visual scene viewed by ambulatory subjects.

Translational Relevance

This technology provides new insight into the diversity of human ocular motor behavior and may become useful for the diagnosis of disorders that affect vergence function such as: convergence insufficiency, Parkinson disease, and strabismus.

A Prospective Evaluation of Infant Cerebellar-Cerebral Functional Connectivity in Relation to Behavioral Development in Autism Spectrum Disorder

Background

Autism spectrum disorder (ASD) is a neurodevelopmental disorder diagnosed based on social impairment, restricted interests, and repetitive behaviors. Contemporary theories posit that cerebellar pathology contributes causally to ASD by disrupting error-based learning (EBL) during infancy. The present study represents the first test of this theory in a prospective infant sample, with potential implications for ASD detection.

Methods

Data from the Infant Brain Imaging Study (n = 94, 68 male) were used to examine 6-month cerebellar functional connectivity magnetic resonance imaging in relation to later (12/24-month) ASD-associated behaviors and outcomes. Hypothesis-driven univariate analyses and machine learning-based predictive tests examined cerebellar-frontoparietal network (FPN; subserves error signaling in support of EBL) and cerebellar-default mode network (DMN; broadly implicated in ASD) connections. Cerebellar-FPN functional connectivity was used as a proxy for EBL, and cerebellar-DMN functional connectivity provided a comparative foil. Data-driven functional connectivity magnetic resonance imaging enrichment examined brain-wide behavioral associations, with post hoc tests of cerebellar connections.

Results

Cerebellar-FPN and cerebellar-DMN connections did not demonstrate associations with ASD. Functional connectivity magnetic resonance imaging enrichment identified 6-month correlates of later ASD-associated behaviors in networks of a priori interest (FPN, DMN), as well as in cingulo-opercular (also implicated in error signaling) and medial visual networks. Post hoc tests did not suggest a role for cerebellar connections.

Conclusions

We failed to identify cerebellar functional connectivity-based contributions to ASD. However, we observed prospective correlates of ASD-associated behaviors in networks that support EBL. Future studies may replicate and extend network-level positive results, and tests of the cerebellum may investigate brain-behavior associations at different developmental stages and/or using different neuroimaging modalities.

Atypical visual motion prediction abilities in autism spectrum disorder

A recent theory posits that prediction deficits may underlie the core symptoms in autism spectrum disorder (ASD). However, empirical evidence for this hypothesis is minimal. Using a visual extrapolation task, we tested motion prediction abilities in children and adolescents with and without ASD. We examined the factors known to be important for motion prediction: the central-tendency response bias and smooth pursuit eye movements. In ASD, response biases followed an atypical trajectory that was dominated by early responses. This differed from controls who exhibited response biases that reflected a gradual accumulation of knowledge about stimulus statistics. Moreover, while better smooth pursuit eye movements for the moving object were linked to more accurate motion prediction in controls, in ASD, better smooth pursuit was counterintuitively linked to a more pronounced early response bias. Together, these results demonstrate atypical visual prediction abilities in ASD and offer insights into possible mechanisms underlying the observed differences.

The impact of social complexity on the visual exploration of others' actions in preschoolers with autism spectrum disorder

BACKGROUND

Typical development of socio-communicative skills relies on keen observation of others. It thus follows that decreased social attention negatively impacts the subsequent development of socio-communicative abilities in children with autism spectrum disorders (ASD). In addition, studies indicate that social attention is modulated by context and that greater social difficulties are observed in more socially demanding situations. Our study aims to investigate the effect of social complexity on visual exploration of others' actions in preschoolers.

METHODS

To investigate the impact of social complexity, we used an eye-tracking paradigm with 26 typically developing preschoolers (TD, age = 3.60 ± 1.55) and 37 preschoolers with ASD (age = 3.55 ± 1.21). Participants were shown videos of two children engaging in socially simple play (parallel) versus socially complex play (interactive). We subsequently quantified the time spent and fixation duration on faces, objects, bodies, as well as the background and the number of spontaneous gaze shifts between socially relevant areas of interest.

RESULTS

In the ASD group, we observed decreased time spent on faces. Social complexity (interactive play) elicited changes in visual exploration patterns in both groups. From the parallel to the interactive condition, we observed a shift towards socially relevant parts of the scene, a decrease in fixation duration, as well as an increase in spontaneous gaze shifts between faces and objects though there were fewer in the ASD group.

LIMITATIONS

Our results need to be interpreted cautiously due to relatively small sample sizes and may be relevant to male preschoolers, given our male-only sample and reported phenotypic differences between males and females.

CONCLUSION

Our results suggest that similar to TD children, though to a lesser extent, visual exploration patterns in ASD are modulated by context. Children with ASD that were less sensitive to context modulation showed decreased socio-communicative skills or higher levels of symptoms. Our findings support using naturalistic designs to capture socio-communicative deficits in ASD.

Evidence of inverted gravity-driven variation in predictive sensorimotor function

We move our eyes to place the fovea into the part of a viewed scene currently of interest. Recent evidence suggests that each human has signature patterns of eye movements like handwriting which depend on their sensitivity, allocation of attention and experience. Use of implicit knowledge of how earth's gravity influences object motion has been shown to aid dynamic perception. We used a projected ball-tracking task with a plain background offering no context cues to probe the effect of acquired experience about physical laws of gravitation on performance differences of 44 participants under a simulated gravity and an atypical (upward) antigravity condition. Performance measured by the unsigned difference between instantaneous eye and stimulus positions (RMSE) was consistently worse in the antigravity condition. In the vertical RMSE, participants took about 200 ms longer to improve to the best performance for antigravity compared to gravity trials. The antigravity condition produced a divergence of individual performance which was correlated with levels of questionnaire-based quantified traits of schizotypy but not control traits. Grouping participants by high or low traits revealed a negative relationship between schizotypy trait level and both initiation and maintenance of tracking, a result consistent with trait-related impoverished sensory prediction. The findings confirm for the first time that where cues enabling exact estimation of acceleration are unavailable, knowledge of gravity contributes to dynamic prediction improving motion processing. With acceleration expectations violated, we demonstrate that antigravity tracking could act as a multivariate diagnostic window into predictive brain function.

Towards the automatic detection of social biomarkers in autism spectrum disorder: introducing the simulated interaction task (SIT)

Social interaction deficits are evident in many psychiatric conditions and specifically in autism spectrum disorder (ASD), but hard to assess objectively. We present a digital tool to automatically quantify biomarkers of social interaction deficits: the simulated interaction task (SIT), which entails a standardized 7-min simulated dialog via video and the automated analysis of facial expressions, gaze behavior, and voice characteristics. In a study with 37 adults with ASD without intellectual disability and 43 healthy controls, we show the potential of the tool as a diagnostic instrument and for better description of ASD-associated social phenotypes. Using machine-learning tools, we detected individuals with ASD with an accuracy of 73%, sensitivity of 67%, and specificity of 79%, based on their facial expressions and vocal characteristics alone. Especially reduced social smiling and facial mimicry as well as a higher voice fundamental frequency and harmony-to-noise-ratio were characteristic for individuals with ASD. The time-effective and cost-effective computer-based analysis outperformed a majority vote and performed equal to clinical expert ratings.

Are early visual behavior impairments involved in the onset of autism spectrum disorders? Insights for early diagnosis and intervention

A correct use of the visual behavior (VB), and its integration with motor function, represents the earliest mean used by infants to explore and act on the social and non-social surrounding environment. The aim of this mini review is to present influential evidence of abnormalities in the VB domain in ASD individuals and to discuss the implication of these findings for early identification and intervention. We analyzed the possible anomalies in oculomotor abilities, visual attention, and visual-motor integration, as parts of a wider visual behavior defect, that could affect children with autism spectrum disorders (ASD) since the early stages of development.Conclusion: According to the literature, difficulties in these three areas have been often reported in children with ASD, and the visual-perception deficit could have cascading effects on learning processes and on social development. Despite this evidence of atypical VB in ASD, their investigation is not yet included into diagnostic processes, and they are not yet considered a specific treatment target.What is Known:•Atypical social use of visual behavior is one the first symptoms in children with autism spectrum disorders•Individuals with autism spectrum disorders often show unusual visual exploration of the surrounding environmentWhat is New:•It is possible to hypothesize that early visual behavior abnormalities may affect experiences that permit learning processes and social and communicative development in infants•An early assessment of visual behavior, as a core symptom of ASD, might improve the diagnostic processes and might help to developing more individualized treatments.

Saccade Latency Provides Evidence for Reduced Face Inversion Effects With Higher Autism Traits

Individuals on the autism spectrum are reported to show impairments in the processing of social information, including aspects of eye-movements towards faces. Abnormalities in basic-level visual processing are also reported. In the current study, we sought to determine if the latency of saccades made towards social targets (faces) in a natural scene as opposed to inanimate targets (cars) would be related to sub-clinical autism traits (ATs) in individuals drawn from a neurotypical population. The effect of stimulus inversion was also examined given that difficulties with processing inverted faces are thought to be a function of face expertise. No group differences in saccadic latency were established for face or car targets, regardless of image orientation. However, as expected, we found that individuals with higher autism-like traits did not demonstrate a saccadic face inversion effect, but those with lower autism-like traits did. Neither group showed a car inversion effect. Thus, these results suggest that neurotypical individuals with high autism-like traits also show anomalies in detecting and orienting to faces. In particular, the reduced saccadic face inversion effect established in these participants with high ATs suggests that speed of visual processing and orienting towards faces may be associated with the social difficulties found across the broader autism spectrum.

Early-life stress induces motor coordination dysfunction in adult mice

Although child abuse has become a serious social problem in most countries, the neural mechanisms by which it induces adulthood mental disorders is not yet fully understood. Mice exposed to early-life stresses, such as maternal deprivation (MD) during lactation, are a good model for studying the effects of neglect of humans in early life. Early-life stress induces structural/functional changes of neurons in the hippocampus, prefrontal cortex, and amygdala, and causes mental disorders in adulthood. In this study, we found motor coordination dysfunction in male MD mice. We also found that the expression levels of the aminomethylphosphonic acid receptor subunits GluA1 and GluA3 were high in the cerebellum of male MD mice. The basal activity of the cerebellum detected by field-potential analysis was higher in male MD mice than in male control mice. Caloric stimulation increased the activity of the cerebellum of control mice, but it did not significantly increase the activity of the cerebellum in male MD mice. We concluded that early-life stress induced a functional change in the cerebellum of MD mice and that this change induced motor coordination dysfunctions.

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

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

Biomarkers in Autism Spectrum Disorder: Challenges, Advances, and the Need for Biomarkers of Relevance to Public Health

Although autism spectrum disorder (ASD) is the most strongly genetic of all complex neuropsychiatric disorders, it is still defined and diagnosed behaviorally. The vast genotypic and phenotypic heterogeneity of the condition necessitate a vigorous search for biological markers capable of aiding in diagnosis, identifying more homogeneous subgroups for biological study, individualizing treatment, and measuring treatment response. Many candidate biomarkers are available, spanning genetic, metabolic, electroencephalographic, magnetic resonance imaging, and neuropsychological methods. Although biomarker research has focused primarily on mechanistic etiologic hypotheses, the biomarkers more likely to result in optimized clinical outcomes in the near term are cost-effective and community-viable measures obtained through eye-tracking technology involving infants and toddlers. Although these tools are still far from being ready for widespread application, the goal is to develop objective procedures and measures for population-based screening and diagnosis to increase access to early treatment and intervention.