Cortices in C Minor

This is your brain on music: lighting up all over the place. Mark Jude Tramo, M.D., Ph.D. '98, an assistant professor of neurology at Harvard Medical School, and others in his field are studying what happens in the brain as it listens to and processes music. They have found that the music experience, unlike more localized activities such as speaking or silent reading, "maps" everywhere. As our brain makes sense of and enjoys a tune, it is involved in a complex process of interrelated tasks, using many of its regions.

Tramo's studies have used magnetic resonance imaging (MRI) on epilepsy and stroke patients, portions of whose brains have been damaged. By determining which music-processing functions patients are unable to perform, Tramo has deduced which parts of the brain are involved in certain music-related activities.

First and primary in music perception are the auditory cortices. Lying near our ears, each about the size of a thumb, the auditory cortices process such elements of music as melody, harmony, and timbre. It is primarily the auditory cortex in the brain's right hemisphere, Tramo has found, that distinguishes one pitch from another, particularly if the pitches are very close. The right auditory cortex also appears to play an important role in the perception of harmony, most likely because of its ability to distinguish pitches and relate them to each other. Both the left and the right cortices, he says, help us recognize the distinctive timbre of musical instruments--in distinguishing a middle C played on a trumpet from one played on an electric guitar.

But because listening to music involves, happily, more than simply processing sound and sound patterns, it engages much more of our brains than the auditory cortices. ("Imagine how much of the brain lights up when we dance!" wrote Tramo in a 2001 article for Science.) If a swing band spurs us across the floor or we simply tap out its rhythm with our fingers, the motor areas in the frontal cortex and cerebellum, as well as the auditory cortex, become active. But researchers in Japan have found that the motor areas are also active when we are listening and merely thinking about tapping our fingers. Different types of rhythms trigger different areas of the brain. If the rhythm is metrical (i.e., it can be expressed by an integer ratio such as 1:2), as is the case with most Western music, we use the left frontal cortex, the left parietal cortex, and the right cerebellum. For nonmetrical rhythms (a ratio of 1:2.5, for example), which are more difficult to tap out, more of the brain is involved: both the left and right parietal cortices and the left and right cerebellum, activity in the frontal cortex shifting to the right hemisphere.

In addition to motor activity, a piece of music is likely to evoke emotion and, if the piece is familiar, memories as well. These activities involve still other parts of our brains. The parts of the brain that process emotion are also involved if the music makes us feel joy, break out in a sweat, or get goosebumps. The medial temporal lobe is active in memory, so we use that when a piece triggers memories: of a lost love, say, or just the music exam we took junior year. Yet another area dampens our responses to music: Tramo has found that the anterior, inferior portion of the frontal lobe helps to inhibit intense emotional and visceral responses to a familiar piece or song, helping to ensure that we behave in socially acceptable ways.

All of the structures in the brain that process music, Tramo and other researchers have found, also contribute to other forms of cognition. Could music, then, make us smarter? The question has interested educators and parents in recent years. While the famous "Mozart effect" (the claim that passive listening to Mozart boosted children's intelligence) has largely been discredited, there is preliminary evidence that certain kinds of music study can improve performance in other subjects, like math. Such findings make sense in light of the wide array of brain structures that music stimulates. "Many of the mental operations involved in music cognition generalize to other aspects of cognition, such as memory and abstraction," says Tramo, a guitarist himself. "Active participation in music is a good way to exercise the brain."

~Nell Lake

Mark Jude Tramo e-mail address: [email protected]

       

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