Music agnosia and auditory agnosia. Dissociations in stroke patients.

A review and an experimental study were carried out in search of dissociations between the recognition of music (music agnosia) and that of environmental sounds (auditory agnosia) in stroke patients. The review focused on 45 adequately studied cases published since 1883. The experimental study consisted of administering standard tests of music and environmental sound recognition to 40 unselected patients with unilateral stroke. Among case reports, music was selectively impaired more frequently than environmental sounds, whereas the reverse occurred in the experimental study. In this, right hemisphere lesions tended either to disrupt the apperception of environmental sounds, sparing music entirely, or to disrupt both environmental sounds and melody, sparing rhythm, whereas left hemisphere lesions tended to spare melody and to disrupt rhythm, either selectively or in association with the semantic identification of environmental sounds.