Music is literally the most universally popular thing among people. Humans have been fashioning ancient musical instruments such as flutes made from bird bone and mammoth ivory as far back as 43,000 years ago, long before we invented agriculture. Scientists have always been fascinated with why humans seem to be so drawn to music. Many studies have probed this question, and thanks to recent developments in neuroscience, we’re nearing a complete picture. Previously, neuroimaging studies that scanned the brains of participants while they listened to music found that the brain’s reward circuits responded similarly to when we experience other pleasurable stimuli such as food, money, or alcohol. But in a new study, researchers at McGill University took things a step further, showing there’s a causal link between the brain’s reward circuit and the way we experience music. “Prior studies had shown a correlation between brain activity in a structure called the striatum and the experience of musical pleasure. But that does not demonstrate that one causes the other, just that they are correlated. In the present paper we show that when you stimulate the brain with excitation or inhibition you change the response of the striatum up or down, and that in turn causes people to experience more or less pleasure to music,” Robert Zatorre, a cognitive neuroscientist at the Montreal Neurological Institute at McGill University and senior author of the new study, told ZME Science. Zatorre and colleagues recruited volunteers who had to listen to pop songs while their brain activity was being measured with fMRI. Right before the scanning commenced, the volunteers’ reward circuit was either excited or inhibited using transcranial magnetic stimulation, a harmless procedure that uses magnetic fields to stimulate nerve cells in the brain. When the reward circuit was excited prior to the music listening session, the participants reported more pleasure. Conversely, when the reward circuit was inhibited, people reported less pleasure out of listening to music. And for those who had their reward circuits light up when music was blasting, the pleasure they feel may be on par with that of eating good food or drinking alcohol. Particularly, pleasure induced by music was mediated by activity in the nucleus accumbens, a key brain region of the reward circuit. “If we look at how much the reward system is stimulated by music vs other stimuli, we find it is in a similar range in terms of percent activity change for instance. And if we look at measures like how much time, effort, and money people are willing to spend on music, it seems commensurate with other stimuli like food or alcohol,” Zatorre said. These findings are important in the context of previous research. In another study published in the Proceedings of the National Academy of Sciences in 2017, Zatorre and colleagues used fMRI scans to measure participants’ brain response to music. This study found that the brain’s auditory and reward regions are closely coupled and, resulting in joy and pleasure — well, at least for most people. There’s a tiny fraction of the population, maybe 3%-5% of all people, who have musical anhedonia, meaning they get no pleasure out of music, finding it boring instead. The new study published by Zatorre and colleagues confirmed these findings, showing that those with the greatest differences in reported pleasure also showed the greatest difference in synchronized activity between auditory and reward regions. Greater induced pleasure differences were associated with increased synchronized activity between auditory and reward regions. “It sort of closes the loop from previous research, because previously we and others had shown that music activates the reward system, and that brain stimulation changes pleasure responses, so we still had to demonstrate that brain stimulation changes the striatum activity, which in turn changes the way we experience the music,” Zatorre said. The scientists aren’t stopping here. They have plans to follow up using the same techniques on people with poor regulation of the reward system, such as those with disorders of mood or motivation, to see if they might benefit from music therapy in any way. The findings appeared in the Journal of Neuroscience. Source
