Reward Neurocircuitry in Autism Spectrum Disorder
Date
2018-09-14
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Abstract
Autism spectrum disorder (ASD) is a common neurodevelopmental disorder with social impairments and restricted interests. Early behavioural interventions often focus on reinforcing desired behaviours (e.g., eye contact) and reducing atypical behaviours (e.g., echoing others' phrases). A recent framework suggests reward system dysfunction to be at the core of ASD symptoms. However, if the reward system is impaired in ASD, it is paradoxical that reward-based strategies are commonly used during interventions. The goal of this thesis was to investigate the reward neurocircuitry to explore whether reward system dysfunction contributes to the ASD phenotype. We conducted a literature review on physiological, behavioural, and neural responses to reinforcers to look for common atypical patterns across all domains. We then investigated structural changes in basal ganglia and the thalamus using advanced surface-based methodology. For this, we modelled effects of diagnosis, age, and their interaction on volume, shape, and surface area on T1-weighted anatomical images of 373 male participants with ASD and 384 typically developing (TD). Finally, we investigated neural responses in the context of learning using rewards that were tailored to participants’ unique interests. 27 adolescents with ASD and 31 TD adolescents performed a reinforcement learning task while we collected fMRI data. Participants had to learn which of two doors showed images of their personal interests. The literature review revealed no consistent pattern of atypical reward responses in ASD. Further, we found that subcortical regions did not differ in volume between individuals with and without ASD. However, we found localized structural changes in shape and surface area of the putamen, globus pallidus and thalamus. Some changes were modulated by age, IQ and symptom severity. Interestingly, when using personal interests as reinforcers during a learning task, we found intact learning performance and similar neural responses in the reward system between ASD and TD groups. Taken together, mixed findings from the literature review and subtle structural changes in subcortical regions of the reward system suggest a role of this neurocircuitry in the ASD phenotype. However, intact learning and typical neural responses towards individual interests suggest that the reward system is not generally impaired in ASD.
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Keywords
Autism Spectrum Disorder, Reinforcement Learning
Citation
Schuetze, M. (2018). Reward Neurocircuitry in Autism Spectrum Disorder (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/33080