Identifying neurocognitive endophenotypes in ASD: A multi-method, family study of visual perception and attention

Nayar, Kritika

doi:https://doi.org/10.21985/n2-x67d-ej45

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Identifying neurocognitive endophenotypes in ASD: A multi-method, family study of visual perception and attention

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Background: The way in which one perceives their visual world (i.e., bottom-up visual perception) and what one pays attention to in their surroundings (i.e., top-down attention), are critical to uncovering underlying thoughts and cognitions, and impact how one operates in the social world. Individuals with autism spectrum disorder (ASD), a neurodevelopmental disorder, demonstrate a local visual processing bias (i.e., tendency to perceive details) and social attention atypicalities (i.e., showing reduced attention allocated towards social information) compared to controls, which have been shown to relate to clinical-behavioral features of the disorder. As such, differences in visual perception and social attentional styles may be contributing to increased autism severity, suggesting a possible underlying biological mechanism related to ASD. Such differences in visual attention and perception have also been implicated more subtly in parents of individuals with ASD, suggesting a potential genetic influence on visual perception/attention. However, prior studies involving parents do not assess local/global visual processing explicitly nor do they comprehensively examine dynamic looking patterns of social attention, which are critical to uncovering processing strategies that may be contributing to clinical and sub-clinical ASD-related features. As such, the extent to which visual perception/attention constitute endophenotypes (i.e., measurable intermediate traits with closer ties to underlying biology) and whether differences are linked to underlying neurobiology, remains unknown. Because endophenotypes can be linked to observed behavior and clinical functioning, as well as to underlying gene networks and neurobiology, the study of endophenotypes offers a bridge for connecting gene-brain-behavior relationships, to help increase an understanding of the biology of a disorder, which may offer an opportunity to inform treatment among affected individuals. This dissertation takes an endophenotype approach and deeply characterizes social attention by extrapolating dynamic looking patterns and uncovering underlying mechanistic properties including behavioral (i.e., performance-based measures and eye-tracking variables) and neural bases of bottom-up visual perception in individuals with ASD and their first-degree relatives in three separate, but theoretically related, studies. Methods: Across tasks, participants included a maximum of 32 individuals with ASD and 30 controls, as well as 56 parents of individuals with ASD and 43 parent controls. Top-down social attention was assessed using a suite of analytical methods applied to eye tracking during presentation of a social-emotional scene, characterizing where and how participants looked. To examine bottom-up visual processing, Global and Local composite scores were generated from several eye-tracking variables obtained during two interactive tasks administered on an eye-tracker. Finally, neural correlates of local/global processing were assessed with event-related potentials (ERPs, i.e., time-locked EEG responses to visual stimuli), including P1, N1, and N2 components. Results: The ASD and ASD parent groups showed reduced social attention over the course of the task, with a linear decrease and a dynamic looking pattern (i.e., shifting away earlier from social information and decreasing social attention later) in the ASD and ASD parent groups, respectively. Both groups also refixated more toward non-salient, background objects compared to controls, but there were no group significant differences in the transitions away from and towards social and non-social information, percentage of area explored, first fixation durations and type of information first explored, regressive fixations, or number of fixations per second. Autistic individuals demonstrated a greater local than global visual processing style. While parent groups did not differ in Local/Global composite scores, ASD parents attended less towards global features of the stimuli than parent controls. Finally, atypical N1 amplitudes and latencies in the occipital-parietal region were found in the ASD group, with observable opposite patterns of neural responses occurring in the N2 component in both the ASD and ASD parent groups compared to controls. Social attention, and local and global gaze and neural components were related to clinical and sub-clinical features of the ASD phenotype. Conclusions: Eye-tracking and neural results demonstrated parallel patterns of reduced social attention and global perception between individuals with ASD and, more subtly, parents of individuals with ASD, compared to controls. The eye-tracking variables examined in this study are thought to effectively reveal different aspects of underlying cognition, therefore revealing key mechanistic insights into the roots of social functioning differences in ASD. Furthermore, findings of local/global visual processing differences both behaviorally and neurally point to underlying neurobiological differences shaped by ASD-related genetic variation. Importantly, relationships with clinical and sub-clinical features of autistic individuals and parents support the utility of studying social and non-social visual perception and attention to enhance an understanding of underlying biological mechanisms contributing to ASD-related traits, potentially reflecting genetic liability to ASD. Findings further highlight the investigation of biological and mechanistic underpinnings using eye-tracking and EEG methodology to the study of visual perception/attention, which may help to elucidate the gene-brain-behavior basis of the disorder. Finally, stimuli and methodologies applied to the present work will help to inform future studies of vision and cognitive science.

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