Characterization of deficits in pitch perception underlying 'tone deafness'

Congenital amusia is a disorder characterized by life-long, selective deficits in the perception of music. This study examined pitch-perception abilities in a group of 10 adults with this disorder. Tests were administered that assessed fine-grained pitch perception by determining thresholds both for the detection of continuous and segmented pitch changes, and for the recognition of pitch direction. Tests were also administered that assessed the perception of more complex pitch patterns, using pitch-sequence comparison tasks. In addition, the perceptual organization of pitch was also examined, using stream segregation tasks that assess the assignment of sounds differing in pitch to one or two distinct perceptual sources. In comparison with 10 control subjects, it was found that the participants with congenital amusia exhibited deficits both at the level of detecting fine-grained differences in pitch, and at the level of perceiving patterns in pitch. In contrast, no abnormalities were identified in the perceptual organization of pitch. The pitch deficits identified are able to account for the music perception difficulties in this disorder, and implicate deficient cortical processing.