Dimensional Anhedonia and the Adolescent brain: Reward and Aversion Anticipation, Effort and Consummation.

Given the heterogeneity of depression the Research Domain Criteria Framework suggests a dimensional approach to understanding the nature of mental health and illness. Neural reward function has been suggested as underpinning the symptom of anhedonia in depression but less is known about how anhedonia is related to aversion processing. We examined how anhedonia relates to neural activity during reward and aversion processing in adolescents and emerging adults (N=84) in the age range 13-21yrs. Using a dimensional approach we examined how anhedonia and depression severity correlated with an fMRI task measuring anticipation, effort and consummation of reward and aversion. We show for the first time that the dimensional experience of anhedonia correlated with neural responses during effort to avoid aversion in the precuneus with a trend in the insula and during aversive consummation in the caudate. Using a categorical approach we also examined how the neural responses during each phase of the task differed in those with depression symptoms compared to healthy controls. We found participants with depression symptoms invested less physical effort to gain reward than controls and had blunted neural anticipation of reward and aversion in the precuneus, insula, and prefrontal cortex and blunted neural effort for reward in the putamen. This work highlights blunted neural responses to reward and aversion in depression and how anticipatory and consummatory anhedonia may be enhanced via dysfunctional neural processing of aversion. Future work will assess if these neural mechanisms can be used to predict blunted behavioural approach to reward and avoidance of negative experiences in adolescents at risk of depression.