Academic journal article Cognitive, Affective and Behavioral Neuroscience

Neurophysiological Differences in Reward Processing in Anhedonics

Academic journal article Cognitive, Affective and Behavioral Neuroscience

Neurophysiological Differences in Reward Processing in Anhedonics

Article excerpt

Published online: 12 September 2012

# Psychonomic Society, Inc. 2012

Abstract Anhedonia is characterized by a reduced capacity to experience pleasure in response to rewarding stimuli and has been considered a possible candidate endophenotype in depression and schizophrenia. However, it is still not well understood whether these reward deficits are confined to anticipatory and/or to consummatory experiences of pleasure. In the present study, we recorded electrophysiological responses (event-related brain potentials [ERPs] and oscillatory activity) to monetary gains and losses in extreme groups of anhedonic and nonanhedonic participants. The anhedonic participants showed reduced motivation to incur risky decisions, especially after monetary rewards. These sequential behavioral effects were correlated with an increased sensitivity to punishment, which psychometrically characterized the anhedonic group. In contrast, both electrophysiological measures associated with the impacts of monetary losses and gains-the feedback-related negativity (FRN) and the beta-gamma oscillatory component- clearly revealed preserved consummatory responses in anhedonic participants. However, anhedonics showed a drastic increase in frontal medial theta power after receiving the maximum monetary gain. This increase in theta oscillatory activity could be associated with an increase in conflict and cognitive control for unexpected large positive rewards, thus indexing the violation of default negative expectations built up across the task in anhedonic participants. Thus, the present results showed that participants with elevated scores on Chapman's Physical Anhedonia Scale were more sensitive to possible punishments, showed deficits in the correct integration of response outcomes in their actions, and evidenced deficits in sustaining positive expectations of future rewards. This overall pattern suggests an effect of anhedonia in the motivational aspects of approach behavior rather than in consummatory processes.

Keywords Anhedonia . Reward processing . Feedbackrelated Negativity . Medial-frontal theta oscillatory activity . Beta-gamma oscillatory activity . Motivation

Recent years have shown a renewed interest in the study of affective processes, and particularly in the psychological and neural mechanisms that explain the interaction between goal-directed behavior, reward, and motivation. One of the most important aspects that has been somehow neglected, yet is crucial to understanding motivated behavior, is individual differences in anhedonia. The concept of "anhedonia" refers to a reduction of the ability to experience pleasure (Meehl, 1975), as reflected in a diminished interest in rewarding stimuli and pleasurable events. Anhedonia has been described as a prominent symptom and potential trait marker of major depression (Loas, 1996) and is broadly studied in relation to schizophrenia and the negative- symptoms spectrum (Foussias & Remington, 2008). While the importance of this concept is well established in psychopathology (Berrios & Olivares, 1995), the neurophysiological mechanisms associated with it are still ambiguous. A possible dysfunction in the reward and motivation systems has been lately proposed to explain the link between anhedonia and depression (Keedwell, Andrew, Williams, Brammer, & Phillips, 2005; Naranjo, Tremblay, & Busto, 2001; Nestler & Carlezon, 2006; Pizzagalli et al., 2009; Treadway & Zald, 2011).

Anhedonia as a trait has also been characterized in clinical and nonclinical populations, showing stable individual differences across time (Blanchard, Horan, & Brown, 2001; Herbener, Harrow, & Hill, 2005; Shankman, Nelson, Harrow, & Faull, 2010). Considering its clinical importance and substantial heritability (Bogdan & Pizzagalli, 2009), the anhedonia trait has been proposed as a very promising endophenotype for depression (Hasler, Drevets, Manji, & Charney, 2004) and has been used already to disentangle reward abnormalities observed in depression (Harvey, Pruessner, Czechowska, & Lepage, 2007; Pizzagalli, Jahn, & O'Shea, 2005) and schizophrenia (Harvey, Armony, Malla, & Lepage, 2010; Herbener & Harrow, 2002). …

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