My workday is full of people wearing headphones. Almost everybody on the bus to work is plugged into a music player or a smartphone. The bicyclists pushing pedals along the busy El Camino Real road that bisects Silicon Valley are also almost universally equipped with devices that occupy their ears, though arguably they would be better off paying attention to the sounds of traffic (for a summary of American laws regulating this matter, see here). Once I get to my laboratory, I have no one to say good morning to, as the hearing of my co-workers is engrossed by whatever is playing on their computers. Pretty soon, I also feel the urge to plug in to my Internet radio station and tune out the world. Once I do, I’m happier. And that got me wondering. How much do we know about the neurobiology behind compulsive behavior that generates pleasure and does the craving for music exhibited by many people around me share this neurobiology?
I should first confess that I am a cell biologist, not a neuroscientist, and the behavioral neuroscience I had to delve into to answer my questions is a difficult discipline. The answer I got is neither satisfying, nor, I suspect, comprehensive, but I did get a general sense of what has been studied to date. I also acquired an opinion about what could be changed in future experiments to make them more easily interpretable.
For decades, the one-word answer to what regulates compulsive behavior in the brain has been “dopamine.” First discovered in the 1960s this brain chemical and the neurons that respond to it have gone on to become possibly the most studied and most sensationalized (for a much more specialized and detailed discussion of dopamine neurons, see Talia Lerner’s post "Are you there, God? It’s me, dopamine neuron" ). And that’s got many neuroscientists, including my fellow Neuroblog contributors, a bit annoyed. If you, like me, know little about dopamine and the controversy that surrounds it, Bethany Brookshire, a neuroscientist-turned-blogger, has a highly readable exposition and opinion piece on Slate.com. Basically, dopamine has been implicated in a variety of phenomena, including pleasure, reward, addiction, and attention. To make matters worse, these phenomena are hard to precisely define and even harder to measure, so performing interpretable experiments is no easy task. But because people care about pleasure, addiction, and all the various dopamine-related phenomena, public opinion has seized on dopamine as a simple, too simple, “scientific” explanation of diverse human experiences.
Unsurprisingly, given the experimental limitations in behavioral neuroscience, the role of dopamine in regulating the response to music is controversial. Participants in one study showed increased dopamine release, measured by positron emission tomography, and reported more thrilling chills down the spine when they listened to their favorite music than when they listened to neutral music. But another study that exposed Japanese college students to music they considered highly uplifting or not-so-uplifting after they performed stressful tasks found no changes in dopamine (the abstract doesn’t mention the method used to measure dopamine, and the Stanford library doesn’t subscribe to the Journal of Music Therapy, which published the study). In a recent review in Trends in Cognitive Sciences, Mona Lisa Chanda and Daniel J. Levitin of McGill University point out that disparate experimental designs and lack of comprehensive controls for confounding factors make the various studies difficult to compare.
One confounding factor that muddles conclusions about the brain’s response to music is locus of control. That’s a technical term psychologists use to describe who has control of a situation. For instance, if I am just sitting at my desk in lab and my co-workers decide to start discussing baseball—the American fascination with which I shall never understand—or the freezer emits a jittering groan, I am forced to listen and get irritated. But if I plug in my headphones and start blasting Rihanna, all these irksome sounds blissfully disappear. And if I get sick of Rihanna, I can switch to Beethoven because the locus of control resides with me. According to Chanda and Levitin, no studies conducted to date adequately discriminate between the pleasure people derive from music per se and the pleasure they derive from controlling their aural environment. They suggest that future studies should always let the participants select their own music, instead of using experimenter-selected music, to control for this factor.
An alternative hypothesis for the effect of music is that it brings pleasure through social bonding. Though listening through headphones seems anti-social because it excludes communication from the surrounding people, it does connect the listener to the composer and the artist and whatever emotions they sought to transmit. Again, according to Chanda and Levitin, no studies conclusively rule in or rule out this hypothesis. One way to control for social bonding would be to compare people engaged in a group musical activity to people also engaged in a group activity, but of a non-musical nature.
So, our understanding of the neurobiology of music is incomplete and inconclusive. It may be that the brain of the music lover has some as-yet-undiscovered qualities or it may be that it is just like the brain of a control freak or a social butterfly. Dopamine may be involved. Or it may not be, though if dopamine isn’t it, I haven’t found any ideas about what could be the regulator. But I do think that music, which humans have used to regulate mood since ancient times, is well worth further study by neurobiologists.