Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Master of Education

Program

Education

Supervisor

Duerden, Emma G.

Abstract

Children diagnosed with Autism Spectrum Disorder (ASD) show impairments in gaze-following and will seldom engage in joint attention (JA). The ability to initiate JA (IJA) can be more impaired than the ability to respond to JA (RJA). In a longitudinal study, 101 high-risk infants for ASD (62% males) completed MRI scans at 4 or 6 months of age. Subcortical volumes (thalamus, basal ganglia, hippocampus, amygdala) were extracted. Gaze and JA behaviours were assessed with standardized measures. The majority of infants were IJA non-responders (n=93, 92%), and over half were RJA non-responders (n=50, 52%). In the non-responder groups, models testing the association of subcortical volumes with later ASD diagnosis accounted for age, sex, and cerebral volumes. It was found that hippocampal and thalamic volumes predicted later ASD diagnosis. Findings suggest that these brain regions may present increased vulnerability early in life and might be key predictors of the development of ASD.

Summary for Lay Audience

Children diagnosed with Autism Spectrum Disorder (ASD) are more likely to present difficulties in following where the gaze of others is being directed and in engaging in shared attention with another person and a third object. These behaviours are called joint attention (JA). The ability to follow the gaze of another person, responding to joint attention (RJA), is different from initiating joint attention (IJA), which is when the child looks or points to something for the purpose of sharing interests with others. Difficulties in joint attention are observed in young children with ASD. These children have a harder time initiating shared interest than following somebody’s gaze. In this study, 101 babies who had an older sibling diagnosed with ASD were assessed (62% males). Because ASD is considered a genetic disorder, these babies are considered to be at higher risk for developing ASD. Babies completed image exams when they were 4 or 6 months of age. From these images, volumes of some specific areas of the brain were extracted. Behavioural measures of early gaze and joint attention were assessed using 2 questionnaires. It was found that the majority of babies were non-responders to Initiating Joint Attention (n=93, 92%), and over half were non-responders to Responding to Joint Attention (n=50, 52%). We separated them into groups, responders and non-responders, and we tested the association of subcortical brain volumes with later ASD diagnosis. In the group that did not respond to Initiate Joint Attention, we found that volumes of some specific areas (hippocampus and thalamus) predicted later ASD diagnosis. Findings suggest that these brain areas might be key predictors of the development of ASD.

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