Neural Mechanisms of Reward Prediction Error in Autism Spectrum Disorder

Strategic decision making and prediction differences in autism

Background

Several theories in autism posit that common aspects of the autism phenotype may be manifestations of an underlying differentiation in predictive abilities. The present study investigates this hypothesis in the context of strategic decision making in autistic participants compared to a control group.

Method

Autistic individuals (43 adults, 35 male) and a comparison group (42 adults, 35 male) of age and gender matched individuals, played a modified version of the prisoner's dilemma (PD) task where they were asked, if capable, to predict their opponents' move. The predictive performance of the two groups was assessed.

Results

Overall, participants in the autism group had a significantly lower number of correct predictions. Moreover, autistic participants stated, significantly more frequently than the comparison group, that they were unable to make a prediction. When attempting a prediction however, the success ratio did not differ between the two groups.

Conclusions

These findings indicate that there is a difference in prediction performance between the two groups. Although our task design does not allow us to identify whether this difference is due to difficulty to form a prediction or a reluctance in registering one, these findings could justify a role for prediction in strategic decision making during the PD task.

VTA dopamine neuron activity encodes social interaction and promotes reinforcement learning through social prediction error

Social interactions are motivated behaviors that in many species facilitate learning. However, how the brain encodes the reinforcing properties of social interactions remains elusive. Here, using in vivo recording in freely moving mice, we show that dopamine (DA) neurons of the ventral tegmental area (VTA) increase their activity during interactions with an unfamiliar conspecific and display heterogeneous responses. Using a social instrumental task (SIT), we then show that VTA DA neuron activity encodes social prediction error and drives social reinforcement learning. Thus, our findings suggest that VTA DA neurons are a neural substrate for a social learning signal that drives motivated behavior.

The functional neural architecture of dysfunctional reward processing in autism

Functional imaging studies have found differential neural activation patterns during reward-paradigms in patients with autism spectrum disorder (ASD) compared to neurotypical controls. However, publications report conflicting results on the directionality and location of these aberrant activations. We here quantitatively summarized relevant fMRI papers in the field using the anatomical likelihood estimation (ALE) algorithm. Patients with ASD consistently showed hypoactivations in the striatum across studies, mainly in the right putamen and accumbens. These regions are functionally involved in the processing of rewards and are enrolled in extensive neural networks involving limbic, cortical, thalamic and mesencephalic regions. The striatal hypo-activations found in our ALE meta-analysis, which pooled over contrasts derived from the included studies on reward-processing in ASD, highlight the role of the striatum as a key neural correlate of impaired reward processing in autism. These changes were present for studies using social and non-social stimuli alike. The involvement of these regions in extensive networks associated with the processing of both positive and negative emotion alike might hint at broader impairments of emotion processing in the disorder.

Prediction in Autism Spectrum Disorder: A Systematic Review of Empirical Evidence

According to a recent influential proposal, several phenotypic features of autism spectrum disorder (ASD) may be accounted for by differences in predictive skills between individuals with ASD and neurotypical individuals. In this systematic review, we describe results from 47 studies that have empirically tested this hypothesis. We assess the results based on two observable aspects of prediction: learning a pairing between an antecedent and a consequence and responding to an antecedent in a predictive manner. Taken together, these studies suggest distinct differences in both predictive learning and predictive response. Studies documenting differences in learning predictive pairings indicate challenges in detecting such relationships especially when predictive features of an antecedent have low salience or consistency, and studies showing differences in habituation and perceptual adaptation suggest low-level predictive processing differences in ASD. These challenges may account for the observed differences in the influence of predictive priors, in spontaneous predictive movement or gaze, and in social prediction. An important goal for future research will be to better define and constrain the broad domain-general hypothesis by testing multiple types of prediction within the same individuals. Additional promising avenues include studying prediction within naturalistic contexts and assessing the effect of prediction-based intervention on supporting functional outcomes for individuals with ASD. LAY SUMMARY: Researchers have suggested that many features of autism spectrum disorder (ASD) may be explained by differences in the prediction skills of people with ASD. We review results from 47 studies. These studies suggest that ASD may be associated with differences in the learning of predictive pairings (e.g., learning cause and effect) and in low-level predictive processing in the brain (e.g., processing repeated sounds). These findings lay the groundwork for research that can improve our understanding of ASD and inform interventions. Autism Res 2021, 14: 604-630. © 2021 International Society for Autism Research and Wiley Periodicals LLC.

A Systematic Review of the Positive Valence System in Autism Spectrum Disorder

This review synthesized current literature of behavioral and cognitive studies targeting reward processing in autism spectrum disorder (ASD). The National Institute of Mental Health's Research Domain Criteria (RDoC) Positive Valence System (PVS) domain was used as an overarching framework. The objectives were to determine which component operations of reward processing may be atypical in ASD and consequently postulate a heuristic model of reward processing in ASD that could be evaluated with future research. 34 studies were identified from the Embase, PubMed, PsycINFO, and Web of Science databases and included in the review using guidelines from the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (also known as PRISMA guidelines). The extant literature suggested potential relationships between social symptoms of ASD and PVS sub-constructs of reward anticipation, probabilistic and reinforcement learning, reward prediction error, reward (probability), delay, and effort as well as between restricted and repetitive behaviors and interests (RRBIs) and PVS-sub constructs of initial response to reward, reward anticipation, reward (probability), delay, and effort. However, these findings are limited by a sparse and mixed literature for some sub-constructs. We put forward a developmentally informed heuristic model that posits how these component reward processes may be implicated in early ASD behaviors as well as later emerging and more intransigent symptoms. Future research is needed to comprehensively evaluate the proposed model.

Neural Mechanisms of Social and Nonsocial Reward Prediction Errors in Adolescents with Autism Spectrum Disorder

Autism spectrum disorder (ASD) is characterized by impaired predictive abilities; however, the neural mechanisms subsuming reward prediction errors in ASD are poorly understood. In the current study, we investigated neural responses during social and nonsocial reward prediction errors in 22 adolescents with ASD (ages 12-17) and 20 typically developing control adolescents (ages 12-18). Participants performed a reward prediction error task using both social (i.e., faces) and nonsocial (i.e., objects) rewards during a functional magnetic resonance imaging scan. Reward prediction errors were defined in two ways: (a) the signed prediction error, the difference between the experienced and expected reward; and (b) the thresholded unsigned prediction error, the difference between expected and unexpected outcomes regardless of magnitude. During social reward prediction errors, the ASD group demonstrated the following differences relative to the TD group: (a) signed prediction error: decreased activation in the right precentral gyrus and increased activation in the right frontal pole; and (b) thresholded unsigned prediction error: increased activation in the right anterior cingulate gyrus and bilateral precentral gyrus. Groups did not differ in brain activation during nonsocial reward prediction errors. Within the ASD group, exploratory analyses revealed that reaction times and social-communication impairments were related to precentral gyrus activation during social prediction errors. These findings elucidate the neural mechanisms of social reward prediction errors in ASD and suggest that ASD is characterized by greater neural atypicalities during social, relative to nonsocial, reward prediction errors in ASD. Autism Res 2020, 13: 715-728. © 2020 International Society for Autism Research, Wiley Periodicals, Inc. LAY SUMMARY: We used brain imaging to evaluate differences in brain activation in adolescents with autism while they performed tasks that involved learning about social and nonsocial information. We found no differences in brain responses during the nonsocial condition, but differences during the social condition of the learning task. This study provides evidence that autism may involve different patterns of brain activation when learning about social information.