Music and the neurologist. A historical perspective.

Neurological disorders affecting musical function can produce either positive or negative symptoms. Positive phenomena include musicogenic epilepsy (seizures triggered by music), musical partial seizures (hallucinated music as the expression of the seizure), musical release hallucinations (nonepileptic musical hallucinations, usually associated with impaired hearing), and synesthesia (hallucinated colors triggered by musical tones). Negative phenomena comprise the amusias, which can be receptive, expressive, or both, and can selectively involve particular components of musical processing, including pitch, interval, contour, rhythm, meter, timbre, and emotional response. Amusia is often accompanied by aphasia, but each can occur in the absence of the other. Neurological disorders provide evidence that musical processing is multimodal and widely distributed in both cerebral hemispheres.