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 phonetic 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 that within the right hemisphere, the magnetoencephalographic (MEG) counterpart MMNm of the mismatch negativity (MMN) elicited by an infrequent chord change was stronger than the MMNm elicited by a phoneme change. Within the left hemisphere, the MMNm strength for a chord vs phoneme change did not significantly differ. Furthermore, the MMNm sources for the phoneme and chord changes were posterior to the P1m sources generated at or near the primary auditory areas. In addition, the MMNm source for a phoneme change was superior to that for the chord change in both hemispheres. The data thus provide evidence for spatially distinct cortical areas in both hemispheres specialized in representing phonetic and musical sounds.