Petr Janata of Dartmouth University and his colleagues used functional magnetic resonance imaging (fMRI) to track the brain activity of eight volunteers while they listened to music. Study co-author Jeffrey Birk composed a melody that moved through all 24 major and minor keys in a pattern representative of Western music. Depicted as a geometric shape, this pattern conforms to a donut-shaped figure known as a torus. By asking the subjects to identify test tones and the sound of a different instrument buried within the tune, the researchers were able to determine that the rostromedial prefrontal cortex was primarily responsible for tracing the music as it "moved" over the surface of the torus. "This region in the front of the brain where we mapped musical activity is important for a number of functions, like assimiliating information that is important to one's self, or mediating interactions between emotional and non-emotional information," Janata notes. The results, he says, help "provide a stronger foundation for explaining the link between music, emotion and the brain."