Amusia due to rhythm agnosia in a musician with left hemisphere damage: a non-auditory supramodal defect.

A case of a severe receptive and expressive amusia in a professional musician following a left hemisphere vascular stroke is reported. Recognition and production of single tones and random tone sequences were found to be surprisingly well preserved. In contrast, the recognition and production of simple rhythm patterns were grossly disturbed. It is suggested that amusia is due to the demonstrated rhythm disturbance. Moreover, it has been found that the defect in recognition and reproduction of rhythms was manifested regardless of the modality of perception, i.e. whether rhythm patterns were perceived by audition, vision, or touch. Therefore, the disturbance of rhythm abilities is supramodal in nature, based probably on the perception of time microintervals. Thus, this type of amusia is a result of a non-auditory supramodal defect, i.e., an impairment of temporal pattern recognition.