Summary: Researchers used transcranial magnetic stimulation to both increase and decrease how much people enjoy music and their motivation to hear it again.
Source: McGill University
Musical enjoyment is commonly seen as a subjective experience: what delights one listener may irritate another. Although musical taste varies, theorists have long argued that structural features such as chord progressions and rhythmic patterns create expectations and surprises that contribute to pleasure.
Researchers at the Montreal Neurological Institute and Hospital of McGill University have now shown that it is possible to causally alter how much people enjoy music — and how much they want more of it — by modulating specific brain circuits.
Previous brain imaging studies have shown that listening to music that people find pleasurable activates fronto-striatal networks involved in reward anticipation and surprise. Until now, those findings were correlational: they showed association but not causation. The new study tested whether fronto-striatal circuits are essential to musical reward and whether manipulating them changes subjective experience and physiological markers of musical pleasure.
To target these circuits, the team used transcranial magnetic stimulation (TMS), a non-invasive method that delivers magnetic pulses to temporarily influence the activity of selected brain regions. The researchers applied TMS to the left dorsolateral prefrontal cortex (DLPFC), a cortical area known from imaging studies to influence fronto-striatal pathways and dopamine release, a key neurotransmitter in reward processing.
In a within-subjects design, healthy volunteers attended three separate sessions in which they received either excitatory TMS, inhibitory TMS, or sham (no real) stimulation over the left DLPFC. After each stimulation session, participants listened to music: both songs they personally selected as favorites and a set of tracks chosen by the researchers. While listening, participants provided continuous, real-time ratings of how much they enjoyed the music. The team also recorded psychophysiological responses linked to emotional arousal. Finally, to measure motivation to re-experience the music, participants were given the opportunity to purchase the researcher-selected tracks with real money.
The results were consistent and bidirectional. Excitatory stimulation of the left DLPFC enhanced reported enjoyment, increased psychophysiological indicators of emotional arousal, and raised the monetary value participants placed on the pieces (reflected in greater willingness to purchase them). Conversely, inhibitory stimulation reduced enjoyment, dampened physiological responses, and lowered motivation to buy the music, compared with the sham condition.
“These findings show that fronto-striatal circuitry is not merely associated with musical pleasure but plays an essential causal role,” says Ernest Mas Herrero, a postdoctoral fellow and the study’s first author. “The results suggest that the systems involved in learning and motivation are indispensable for the experience of musical reward.”
Mas Herrero and colleagues are extending this work by combining TMS with functional MRI to pinpoint the specific regions and circuit interactions that drive the observed changes in musical reward processing.
Robert Zatorre, professor of neurology and neurosurgery and the study’s senior author, emphasizes potential clinical relevance: “Demonstrating that musical pleasure and its value can be selectively increased or decreased with TMS is an important step toward understanding the neural circuitry of complex affective responses. Many disorders — including addiction, obesity, and depression — involve dysregulated reward systems. Showing that this circuitry can be modulated in relation to music suggests new possibilities for interventions that aim to up- or down-regulate reward sensitivity.”
Funding: The study was published in Nature Human Behaviour on November 20, 2017. Funding sources included the Natural Sciences and Engineering Research Council (NSERC), the Canadian Institutes of Health Research (CIHR), the Canada Foundation for Innovation (CFI), and the Jeanne Timmins Costello Fellowship.
Source: Shawn Hayward – McGill University
Publisher: NeuroscienceNews.com (organized coverage)
Image Source: Image adapted from the McGill news release.
Original Research: “Modulating musical reward sensitivity up and down with transcranial magnetic stimulation” by Ernest Mas-Herrero, Alain Dagher & Robert J. Zatorre. Nature Human Behaviour. Published online November 20, 2017. DOI: 10.1038/s41562-017-0241-z
Abstract
Modulating musical reward sensitivity up and down with transcranial magnetic stimulation
Humans uniquely derive pleasure from aesthetic experiences such as art and music. Recent neuroimaging research has proposed a model in which mesolimbic striatal circuits interact with cortical systems to form expectancies that produce pleasure. Because neuroimaging is inherently correlational, the present study provides causal evidence by applying TMS to the left dorsolateral prefrontal cortex to bidirectionally modulate fronto-striatal function while measuring pleasure and motivation during music listening. The results show that perceived pleasure, physiological measures of emotional arousal, and the monetary value assigned to musical pieces are all increased by excitatory stimulation of fronto-striatal pathways and decreased by inhibitory stimulation, compared with sham. These findings support the hypothesis that fronto-striatal function causally mediates both affective responses and motivational aspects of music-induced reward, offering insight into how aesthetic experiences arise in the human brain.
Study citation: Ernest Mas-Herrero, Alain Dagher & Robert J. Zatorre, “Modulating musical reward sensitivity up and down with transcranial magnetic stimulation,” Nature Human Behaviour, published online November 20, 2017. DOI: 10.1038/s41562-017-0241-z