A song in your head

Singing evokes a unique response in the human brain, MIT neuroscientists have found.

The researchers, led by Nancy Kanwisher and collaborator Josh McDermott, had previously identified a population of neurons in the auditory cortex that respond specifically to music by using functional magnetic resonance imaging (fMRI) on subjects as they listened to a recording of 165 sounds. But they were able to gather much more precise information by directly recording electrical activity in the brains of 15 people via electrodes placed inside their skulls to monitor epileptic seizures in the days leading up to surgery, during which time these participants listened to the same selection of sounds.

Using a novel statistical analysis that they developed to combine the new results with the fMRI data, which covered a larger portion of the brain at lower resolution, the researchers were able to infer the types of neural populations that produced the data recorded by each electrode. They were surprised to find that a population of neurons at the top of the temporal lobe lit up in response to songs but not to speech, instrumental music, or other types of sounds.

“The work provides evidence for relatively fine-grained segregation of function within the auditory cortex, in a way that aligns with an intuitive distinction within music,” says former MIT postdoc Sam Norman-Haignere, an assistant professor of neuroscience at the University of Rochester Medical Center and the lead author of the study on the new research.

The song-specific neurons may be responding to features such as the perceived pitch, or the interaction between words and perceived pitch, before sending information to other parts of the brain for further processing, the researchers say. They now hope to learn more about what aspects of singing drive the response.