Music processing ability was studied in 65 right-handed patients following unilateral temporal cortectomy and compared to 24 matched normal controls at the Clinique Neurologique, Ponchaillou, Rennes, France; Departement de Psychologie, Universite de Montreal; and Centre de Reserche, Centre Hospitalier Cote-des-Neiges, Montreal, Quebec, Canada. Sequences of simple musical phrases were presented, with variations in either pitch or timing, to test ability to recognize changes in note intervals, rhythms, and metres. Deficits in discrimination of melodies were associated with right temporal lesions, and impairment of interval processing occurred with left temporal cortectomy. Pitch and timing were particularly affected by excision of the posterior superior temporal gyrus, part of the auditory cortex. Damage to the anterior part of the superior temporal gyrus caused impairment of metric processing, with preservation of rhythm. 
COMMENT. The positive effects of music on learning in children are supported by neuroanatomical and electrophysiological studies, using high resolution PET scanners, EEG analysis, and observations of patients undergoing temporal cortectomy. Platel, Frackowiak and coworkers, in PET studies, found the left hemisphere dominant for rhythm, tune recognition, and pitch perception, while the right hemisphere is involved in timbre or quality of tone perception (Ped Neur Briefs April 1997;11:29-30). Listening to Mozart induces cortical right frontal and left hemisphere cerebral activity and enhances spatial-temporal reasoning (Ped Neur Briefs April 1998;4:32); it also lessens epileptic activity in the EEG of patients with epilepsy, both left or right temporal lobe focal discharges being suppressed (Ped Neur Briefs July 1998;7:52-53).
Meter is usually defined as the recurrent rhythmical pattern of notes, accents, and beats per measure in music. The above neuroanatomical study dissociates meter and rhythm, identifying separate cerebral locations for these cognitive musical processes. The metric organization of a sequence, involving the anterior part of the superior temporal gyrus, is not dependent on rhythmical organization or relative duration of notes. Functional MRI studies and music appreciation in children with ADHD would be of interest (Brain Dev Sept 1998;437)