They had to listen to 32 previously rated musical excerpts (10 pleasant, 10 neutral, 10 unpleasant, and 2 pleasant excerpts selected by the participant). In the first session, participants engaged in a music listening task, similar to the task used by Mas-Herrero et al. This study specifically addresses the neural mechanisms underpinning the phenomenon of specific musical anhedonia. Moreover, we hypothesized that the activation of these areas would be similar in the three groups in response to monetary rewards and punishments, demonstrating the specificity of this phenomenon for music reward processing. We hypothesized that specific musical anhedonia would be associated with reduced activity in the ventral striatum (VS especially the NAcc) in response to pleasant music, and also a down-regulation in the interaction between auditory cortices and reward-related regions, compared with people with high and average sensitivity to music. In the second session, subjects were scanned with fMRI while performing two different tasks: a music listening paradigm in which online pleasure ratings for 16 excerpts were given and a monetary gambling task used as a control. In the first session, SCRs were recorded while participants listened to excerpts of previously rated pleasant, neutral, and unpleasant music by an independent group of subjects to validate the group classification via an objective index of musical reward sensitivity. Three groups of subjects (musical anhedonia and average or high sensitivity to musical reward) engaged in two separate experimental sessions. To reach this goal, we selected 45 healthy subjects who differed in their sensitivity to music reward using a previously developed psychometric instrument, the Barcelona Musical Reward Questionnaire (BMRQ) ( 18), which is known to be a reliable indicator of interindividual variability in music reward sensitivity. In the present study, we aim to unravel the brain mechanisms responsible for the specific impairment in music reward processing observed in people with specific musical anhedonia. Therefore, individuals with specific musical anhedonia represent an ideal population in which to test models of music reward processing. Notably, they showed normal responses to other types of reward. When listening to music rated as pleasant by others, people with specific musical anhedonia showed a reduced emotional arousal as indexed by autonomic nervous system activity compared with people having standard or high sensitivity to music. A detailed study on this population revealed that this phenomenon cannot be explained by perceptual problems or by general anhedonia (lack of pleasure for all types of rewarding stimuli). Paradoxically, not everybody loves music: A small percentage of healthy individuals do not find music pleasurable, a phenomenon known as specific musical anhedonia ( 4).
Thus, our results suggest that specific musical anhedonia may be associated with a reduction in the interplay between the auditory cortex and the subcortical reward network, indicating a pivotal role of this interaction for the enjoyment of music. In contrast, individuals with greater than average response to music showed enhanced connectivity between these structures. Furthermore, this group also exhibited decreased functional connectivity between the right auditory cortex and ventral striatum (including the NAcc). We demonstrate that the music anhedonic participants showed selective reduction of activity for music in the nucleus accumbens (NAcc), but normal activation levels for a monetary gambling task. In the current study, we addressed this question using fMRI in three groups of 15 participants, each with different sensitivity to music reward. If such interaction is critical for music-induced pleasure to emerge, then those individuals who do not experience it should show alterations in the cortical-mesolimbic response. Previous neuroimaging studies have shown that musically induced pleasure may arise from the interaction between auditory cortical networks and mesolimbic reward networks. The study of these individuals with specific musical anhedonia may be crucial to understand better the neural correlates underlying musical reward. Although music is ubiquitous in human societies, there are some people for whom music holds no reward value despite normal perceptual ability and preserved reward-related responses in other domains.
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