Neurophysiological differences in reward processing in anhedonics

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 componentclearly 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-

Beta oscillations and reward processing: Coupling oscillatory activity and hemodynamic responses

“…However, the effects of monetary gains in gambling tasks-which we replicate here-are very robust and have been widely studied both in EEG and fMRI (Camara et al, , 2010Ripollés et al, 2014;Carlson et al, 2011;Marco-Pallarés et al, 2008Sescousse et al, 2013;Cohen et al, 2007;Padrao et al, 2013). In addition, in the gambling task used in this study, the amounts of overall monetary gains and losses were fixed and equal for all participants and sessions.…”

“…Previous Electroencephalography (EEG) and Magnetoencephalography (MEG) human studies using time-frequency (TF) decomposition have revealed a mid-frontal BOA elicited by positive outcomes (20-30 Hz, peaking 200-400 ms after positive feedback; Cohen et al, 2007;Marco-Pallarés et al, 2008;Marco-Pallarés et al, 2009;Cunillera et al, 2012;HajiHosseini et al, 2012;Leicht et al, 2013;Luft et al, 2013;Padrao et al, 2013) and reward-predicting cues (Bunzeck et al, 2011;Kawasaki and Yamaguchi, 2013;Apitz and Bunzeck, 2014). This gain-related signal has been associated to the engagement of rewardrelated brain networks due to the fact that BOA shows a similar pattern in response to rewards than that observed in midbrain dopaminergic and striatal neurons.…”

Associations between Electrophysiological Evidence of Reward and Punishment-Based Learning and Psychotic Experiences and Social Anhedonia in At-Risk Groups

“…In contrast to the PE group, the social anhedonia group did not differ from the control group in their behavioral performance or in their FRN for unexpected trials on the RLT, suggesting that some aspects of reward and punishment-based learning may to some extent be intact in people with extremely elevated social anhedonia who are at increased risk for schizophrenia-spectrum disorders (Karcher et al, 2015b;Padrao et al, 2013). Future research should continue to examine whether some particular aspect of reward and punishment-based learning, perhaps reward anticipation (Dowd and Barch, 2012;Juckel et al, 2006), is associated with anhedonia in at risk groups.…”

Crossing the Worm-Brain Barrier by Using <b><i>Caenorhabditis elegans</i></b> to Explore Fundamentals of Human Psychiatric Illness

“…In MDD, anhedonia and apathy are considered biological markers contributing to the overall picture of depression [26,27]. In schizophrenia, avolition is considered an endophenotype that contributes to the negative symptoms [15,28,29].…”