What makes a song like "Jingle Bells" stick in your head, and why does a wrongly played note sound so jarring?
New research suggests the brain has and develops structures designed to perceive musical patterns and then remember them.
Although the brain appears to tap several areas to hear music, the study determined its musical ear, so to speak, is made up of set circuits, many of which connect to the rostromedial prefrontal cortex, a region located just behind the forehead.
It's the existence of these circuits that gives people their innate sense of melody (some more than others) and why familiar musical harmonics and ditties like "Jingle Bells" can literally become branded in the brain.
"As a piece of music fulfills or violates our expectations, it moves around in this space. And it's this violation of expectations that drives our underlying response to music," said Petr Janata, an assistant professor at Dartmouth College's Center for Cognitive Neuroscience in Hanover, N.H., and author of the study appearing in the journal Science.
"So if we're hearing a lot of things we're not expecting to hear, it sounds unpleasant. But if we're never surprised, it can start to sound simple."
Watching Brains Listen
To map the brain's response to music, Janata and colleagues had eight students with musical experience listen to a piece of originally composed music while a functional magnetic resonance imaging scanner snapped detailed pictures of their brains. The eight-minute melody was composed by a Dartmouth graduate, Jeffrey Birk, who designed the tune to move through all 24 major and minor keys.
As the students listened to the music, Janata had them perform two simple tasks. He noted their brain activity as they performed the tasks and used them as markers to detect how their brains were responding to key changes in the music.
Janata found that while several areas of the brain lighted up as the students listened, only the rostromedial prefrontal cortex regularly tracked fluctuations in the music. This suggested that this area is where the brain maintains maps of melodies.
The work is the first to confirm what neuroscientists had long suspected about where and how music is interpreted within the brain. Mark Tramo, head of the Institute for Music and Brain Science at Harvard University, had argued in earlier work that the rostromedial prefrontal cortex likely had a role in interpreting and predicting melodies.
Programmed for Music?
Tramo says the new study not only backs up that idea, it also helps explain why some people show musical intuition.
"Four of the greatest songwriters of the 20th century — Stevie Wonder, Irving Berlin, John Lennon and Paul McCartney — wrote most of their music without musical training or before they had studied music theory," says Tramo, who is both a neurobiologist and a published songwriter. "That's because they could rely on implicit knowledge about how to become the most effective manipulators of music."
One thing that is not yet clear is to what extent the brain's hardware for music is there at birth and how much is acquired through exposure to music. Tramo says it's likely a combination of both.
This might explain why music traditions around the world share features, such as octaves (scales of eight notes), but also exhibit key differences, like an emphasis on major or minor keys.
"There's fairly good evidence that it's possible to acquire structures through repeated exposure to music," said Janata.
One way to test this question in the future could be to scan and compare brain activities of experienced musicians and people with no musical background as well as people who come from Western musical traditions and those with Eastern musical upbringings.
Moving to Music
Janata says his work might also explain one other aspect of music perception — our impulse to dance.
He explains the rostromedial prefrontal cortex is not only where we seem to interpret music, it has also been identified as a region that plays a role in directing motion. As the brain perceives music, he says, it could also be sending out signals to groove.