What seems clear is that the ability to experience and react to music is deeply embedded in the biology of the nervous system. While music tends to be processed mostly in the right hemisphere of the brain, no single set of cells is devoted to the task. Different networks of neurons are activated, depending on whether a person is listening to music or playing an instrument, and whether or not the music involves lyrics. Specific brain disorders can affect the perception of music in very specific ways. Lesions in the temporal lobe can result in so-called musicogenic epilepsy, an extremely rare form of the disorder in which seizures are triggered by the sound of music.
Autism offers an even greater puzzle.
Even simple, familiar tunes such as Frere Jacques and Happy Birthday are mystifying to amusics, but when the lyrics are spoken rather than sung, amusics are able to recognize the song immediately. They all appear to have been born without the wiring necessary to process music. But for instrumentalists, at least, music can evidently trigger physical changes in the brain's wiring. By measuring faint magnetic fields emitted by the brains of professional musicians, a team led by Christo Pantev of the University of Muenster's Institute of Experimental Audiology in Germany has shown that intensive practice of an instrument leads to discernible enlargement of parts of the cerebral cortex, the layer of gray matter most closely associated with higher brain function. Using PET scanners, Zatorre has shown that the parts of the brain involved in processing emotion seem to light up with activity when a subject hears music.