Towards a better understanding of the reward system in autism spectrum disorders: empirical tests of the social motivation hypothesis

This dissertation examined the reward system in children with autism spectrum disorders (ASD). I empirically tested the social motivation hypothesis as a potential explanation for social impairments in ASD. Chapter 1 investigated typically developing (TD) children's electrophysiological responses to rewards accompanied by incidental social versus nonsocial stimuli. This chapter introduced a paradigm that allows reward anticipation to be measured while controlling for both reward and stimulus properties. TD children had increased activation while anticipating rewards accompanied by social versus nonsocial stimuli, suggesting that TD children find social stimuli more rewarding than nonsocial stimuli. Chapter 2 investigated how children with ASD compare to TD children on reward anticipation and processing using the paradigm described in Chapter 1. TD children had larger reward anticipation for social versus nonsocial stimuli, while children with ASD did not. Children with ASD also processed social versus nonsocial stimuli differently than their TD peers. These results suggest that children with ASD have selective deficits in anticipation and processing of social rewards. Chapter 3 examined whether familiarity might normalize social reward anticipation for children with ASD. Neither children with nor without ASD had different magnitudes of reward anticipation for familiar versus unfamiliar faces, or scrambled versions of those pictures. However, when collapsing across familiarity, results from Chapter 2 were replicated—TD children had larger reward anticipation for social versus nonsocial stimuli, while children with ASD did not. Chapter 3 also found evidence for an Nc-like component that occurred prior to social stimuli. This component was larger for TD children versus those with ASD. To explore possible mechanisms for these differences in social reward processing, Chapter 4 proposes oxytocin as a potential neuropeptide involved in social motivation. Chapter 4 reviews research on oxytocin's effect on social behavior in individuals with and without ASD, as well as implications for treatment of joint attention deficits in ASD. This chapter makes suggestions for future research that combine pharmacological and behavioral interventions in order to optimize outcomes. Collectively, this dissertation provides evidence in favor of the social motivation hypothesis, and important information about the nature of the reward system in children with ASD.