Functional specialization of the human auditory cortex in processing phonetic and musical sounds: A magnetoencephalographic (MEG) study

Functional specialization of the human auditory cortex in processing phonet ic vs musical sounds was investigated. While subjects watched a silent self -selected movie, they were presented with sequences consisting of frequent and infrequent phonemes (/e/ and /o/, respectively) or chords (A major and A minor, respectively). The subjects' brain responses to these sounds were recorded with a 122-channel whole-head magnetometer. The data indicated tha t within the right hemisphere, the magnetoencephalographic (MEG) counterpar t MMNm of the mismatch negativity (MMN) elicited by an infrequent chord cha nge was stronger than the MMNm elicited by a phoneme change. Within the lef t hemisphere, the MMNm strength for a chord vs phoneme change did not signi ficantly differ. Furthermore, the MMNm sources for the phoneme and chord ch anges were posterior to the Plm sources generated at or near the primary au ditory areas. In addition, the MMNm source for a phoneme change was superio r to that for the chord change in both hemispheres. The data thus provide e vidence for spatially distinct cortical areas in both hemispheres specializ ed in representing phonetic and musical sounds. (C) 1999 Academic Press.