Thursday, February 26, 2009

Rockin' the Nucleus Accumbens

It's really quite simple, actually:
The rewarding and reinforcing aspects of listening to music seem, then, to be mediated by increasing dopamine levels in the nucleus accumbens, and by the cerebellum's contribution to regulating emotion through its connections to the frontal lobe and the limbic system. Current neuropsychological theories associate positive mood and affect with increased dopamine levels, one of the reasons that many of the newer antidepressents act on the dopaminergic system. Music is clearly a means for improving people's moods. Now we think we know why.
Now go make a hit record! OK, maybe it's not that simple, but this is one of the key lessons of This Is Your Brain On Music, though fortunately most of it is more about music than brain chemicals. Daniel Levitin was a musician and a professional music producer before he became a neuroscientist, so he knows both sides of the territory he covers here. I was jealous that he was able to discuss over dinner with Joni Mitchell the musical ambiguity that can be triggered by her "unschooled" use of alternate guitar tunings - but I was glad he could bring that knowledge into this book.

I finished the book a few weeks ago, and I really learned a lot of cool stuff from it. It has even slightly changed the way I approach listening to music. Now I pay a lot more explicit attention to timbre in music, the "texture" of the sounds that make up the music. Paul Simon says that this is the main thing he pays attention to in his own music - as if great melody, rhythm, and lyrics are the easy stuff (Paul Simon makes it sound easy, but I've read about his process, and he works very hard to make it sound that easy). Timbre is many things in music - the gravelly or smooth and sexy quality of a singer's voice, the "crispness" of a well recorded acoustic guitar, the "blended" quality of the Beach Boys' or CSNY's harmonies, even the alterations in sound quality that come from reverb or other audio effects. Plus all the different sounds of the natural and synthesized instruments that are available to the modern recording artist or performer.

Of course it's not all timbre. Levitin also talks a lot about prediction and expectations. When a certain part of your brain latches onto the "pulse" of a song, it begins predicting where the next strong and weak beats will occur, and part of the pleasure of music is in the artful violation of these expectations about the timing of the sound. This is sometimes called "groove" and the neural pathway that responds to this seems to be directly emotional, involving the "lower" brain that also is connected with movement (part of the music-dance connection). It goes via the ear-cerebellum-nucleus accumbens limbic circuit rather than via the ear-auditory cortex circuit. It's amazing that all this distributed activity is seamlessly integrated so we can just say, "hey, cool song" as we unconsciously respond to the rhythm.

Whether music was an evolutionary adaptation or "merely" an accidental re-purposing of the language and motion capabilities of our brain is not completely clear (Levitin discusses this controversy). However it happened, and however complicated it is down there in the synapses and neurochemical soups of our brains, I'm glad we ended up a musical species. Knowing something of how the trick works doesn't make it any less wondrous and enjoyable.

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