13 - Neurophysiological Assessment of Anhedonia in Depression and Schizophrenia

Abstract

Anhedonia, broadly defined as the absence of pleasure, is considered a prominent feature of both depression and schizophrenia. However, despite analogous clinical descriptions, differences in symptomatology between the disorders suggest that the term anhedonia in each disorder may capture clinically and neurobiologically distinct phenomena. Particularly, depression seems to be characterized by an episodic deficit in hedonic capacity, while schizophrenia may be characterized by a relatively stable deficit in the retrieval of noncurrent emotional states. In this chapter, we provide an overview of anhedonia, the demonstrated nuances between depression and schizophrenia, and plausible mechanisms including reward sensitivity and emotional reactivity. We describe neurophysiological methodologies utilized to tease apart the time course and intricate nature of these mechanisms, primarily focusing on two neurophysiological components—event-related potentials termed the reward positivity and late positive potential. Reviewing the research, we propose that depression is characterized by experiential deficits in reward consumption and momentary affective experiences, while schizophrenia is distinctly characterized by cognitive deficits rather than deficient experiential capacity in either reward or emotional reactivity.