Functional magnetic resonance imaging of human auditory cortex

Magnetic resonance imaging methods recently demonstrated regional cerebral signal changes in response to limb movement and visual stimulation, attributed to blood flow enhancement. We studied 5 normal subjects scanned while listening to auditory stimuli including nonspeech noise, meaningless speech sounds, single words, and narrative text. Imaged regions included the lateral aspects of both hemispheres. Signal changes in the superior temporal gyrus and superior temporal sulcus were observed bilaterally in all subjects. Speech stimuli were associated with significantly more widespread signal changes than was the noise stimulus, while no consistent differences were observed between responses to different speech stimuli. Considerable intersubject variability in the topography of signal changes was observed. These observations confirm the utility of magnetic resonance imaging in the study of human brain structure-function relationships and emphasize the role of the superior temporal gyrus in perception of acoustic-phonetic features of speech, rather than processing of semantic features.