Congenital amusias.

In contrast to the sophisticated music processing reported in the general population, individuals with congenital amusia show deficits in music perception and production. Congenital amusia occurs without brain damage, sensory or cognitive deficits, and has been suggested as a lifelong deficit with genetic origin. Even though recognized for a long time, this disorder has been systematically studied only relatively recently for its behavioral and neural correlates. The currently most investigated hypothesis about the underlying deficits concerns the pitch dimension, notably with impaired pitch discrimination and memory. Anatomic and functional investigations of pitch processing revealed that the amusic brain presents abnormalities in the auditory and inferior frontal cortices, associated with decreased connectivity between these structures. The deficit also impairs processing of pitch in speech material and processing of the time dimension in music for some of the amusic individuals, but does not seem to affect spatial processing. Some studies suggest at least partial dissociation in the disorder between perception and production. Recent studies revealed spared implicit pitch perception in congenital amusia, supporting the power of implicit cognition in the music domain. Current challenges consist in defining different subtypes of congenital amusia as well as developing rehabilitation programs for this "musical handicap."