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Studies conducted in rodents indicate a crucial role of the opioid circuit in mediating objective hedonic reactions to primary rewards. However, it remains unclear whether opioid transmission is also essential to experience pleasure with more abstract rewards, such as music. We addressed this question using a double-blind within-subject pharmacological design in which opioid levels were up- and downregulated by administering an opioid agonist (oxycodone) and antagonist (naltrexone), respectively, before healthy participants (n = 21) listened to music. Participants also performed a monetary incentive delay (MID) task to control for the effectiveness of the treatment and the specificity of the effects. Our results revealed that the pharmacological intervention did not modulate subjective reports of pleasure, nor the occurrence of chills. On the contrary, psychophysiological (objective) measures of emotional arousal, such as skin conductance responses (SCRs), were bidirectionally modulated in both the music and MID tasks. This modulation specifically occurred during reward consumption, with greater pleasure-related SCR following oxycodone than naltrexone. These findings indicate that opioid transmission does not modulate subjective evaluations but rather affects objective reward-related psychophysiological responses. These findings raise new caveats about the role of the opioidergic system in the modulation of pleasure for more abstract or cognitive forms of rewarding experiences, such as music.

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Interindividual differences in music-related reward have been characterized as involving five main facets: musical seeking, emotion evocation, mood regulation, social reward, and sensory-motor. An interesting concept related to how humans decode music as a rewarding experience is music transcendence or absorption (i.e., music-driven states of complete immersion, including momentary loss of self-consciousness or even time-space disorientation). Here, we investigated the relation between previously characterized facets of music reward and individual differences in music absorption. A first sample of participants (N = 370) completed both the Barcelona Music Reward Questionnaire (BMRQ) and the Absorption in Music Scale (AIMS). Results showed that both constructs were highly interrelated (r = 0.78, p < 0.001), indicating that higher music reward sensitivity is associated with a greater tendency to music-related absorption states. In addition, four items from the AIMS were identified as suitable to be added to an extended version of the BMRQ (eBMRQ). A second sample (N = 550) completed the eBMRQ for a validation study. Exploratory and confirmatory factor analyses on the whole sample (N = 920) showed the reliable psychometric properties of the eBMRQ and suggested that taking into account an absorption facet could contribute to a better characterization of individual differences in the sensitivity to experience music-related reward and pleasure.

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Forkhead box (Fox) genes belong to the "winged helix" transcription factor superfamily. The function of some Fox genes is well known, such as the role of foxO in controlling metabolism and longevity and foxA in controlling differentiation of endodermal tissues. However, the role of some Fox factors is not yet well characterized. Such is the case of FoxK genes, which are mainly studied in mammals and have been implicated in diverse processes including cell proliferation, tissue differentiation and carcinogenesis. Planarians are free-living flatworms, whose importance in biomedical research lies in their regeneration capacity. Planarians possess a wide population of pluripotent adult stem cells, called neoblasts, which allow them to regenerate any body part after injury. In a recent study, we identified three foxK paralogs in the genome of Schmidtea mediterranea. In this study, we demonstrate that foxK1 inhibition prevents regeneration of the ectodermal tissues, including the nervous system and the epidermis. These results correlate with foxK1 expression in neoblasts and in neural progenitors. Although the triggering of wound genes expression, polarity reestablishment and proliferation was not affected after foxK1 silencing, the apoptotic response was decreased. Altogether, these results suggest that foxK1 would be required for differentiation and maintenance of ectodermal tissues.

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Music listening provides one of the most significant abstract rewards for humans because hearing music activates the dopaminergic mesolimbic system. Given the strong link between reward, dopamine, and memory, we aimed here to investigate the hypothesis that dopamine-dependent musical reward can drive memory improvements. Twenty-nine healthy participants of both sexes provided reward ratings of unfamiliar musical excerpts that had to be remembered following a consolidation period under three separate conditions: after the ingestion of a dopaminergic antagonist, a dopaminergic precursor, or a placebo. Linear mixed modeling of the intervention data showed that the effect of reward on memory-i.e., the greater the reward experienced while listening to the musical excerpts, the better the memory recollection performance-was modulated by both dopaminergic signaling and individual differences in reward processing. Greater pleasure was consistently associated with better memory outcomes in participants with high sensitivity to musical reward, but this effect was lost when dopaminergic signaling was disrupted in participants with average or low musical hedonia. Our work highlights the flexibility of the human dopaminergic system, which can enhance memory formation not only through explicit and/or primary reinforcers but also via abstract and aesthetic rewards such as music.

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Music listening is one of the most pleasurable activities in our life. As a rewarding stimulus, pleasant music could induce long-term memory improvements for the items encoded in close temporal proximity. In the present study, we behaviourally investigated (1) whether musical pleasure and musical hedonia enhance verbal episodic memory, and (2) whether such enhancement takes place even when the pleasant stimulus is not present during the encoding. Participants (N = 100) were asked to encode words presented in different auditory contexts (highly and lowly pleasant classical music, and control white noise), played before and during (N = 49), or only before (N = 51) the encoding. The Barcelona Music Reward Questionnaire was used to measure participants' sensitivity to musical reward. 24 h later, participants' verbal episodic memory was tested (old/new recognition and remember/know paradigm). Results revealed that participants with a high musical reward sensitivity present an increased recollection performance, especially for words encoded in a highly pleasant musical context. Furthermore, this effect persists even when the auditory stimulus is not concurrently present during the encoding of target items. Taken together, these findings suggest that musical pleasure might constitute a helpful encoding context able to drive memory improvements via reward mechanisms.

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