Reward contamination in restrictive anorexia nervosa: A meta-analysis of functional MRI studies

Individuals with anorexia nervosa (AN) are typically anhedonic, leading to the suggestion that intrinsic disturbances of reward processing may represent a trait marker of the disorder. Previous studies have used task-based functional magnetic resonance imaging (fMRI) to investigate reward-related brain activity in AN and reported altered activation in the prefrontal cortex, dorsal posterior cingulate cortex, and rostral anterior cingulate cortex. However, likely due to the varied paradigms and methodologies used, as well as the heterogeneity in sample characteristics, results have proved inconsistent. To determine whether AN patients with the restrictive subtype (AN-r) show different reward-induced activation patterns to matched healthy controls (HCs) at different illness stages, we conducted a meta-analysis of 19 task-based fMRI studies of reward-processing. Using the seed-based differential mapping (SDM) technique, we found differences in reward-related brain activity between AN-r and HCs. Moreover, different brain regions showed differential activation across illness stages, with the direction and magnitude of effects dependent on specific task stimuli. These findings suggest that those with AN-r show distorted reward processing as a consequence of reward contamination and alterations in valence assignment to reward stimuli. In weight-recovered AN-r patients, differences to HCs persisted but were limited to regions known to exhibit significant atrophy in AN-r, indicating that altered reward processing is associated with anorectic undernutrition. These findings have implications for developing pharmacological treatments to aid psychological recovery in AN-r.