Magnetic field responses of auditory cortex to produced speech

Abstract

Several behavioral and brain imaging studies have demonstrated a significant interaction between speech reception and speech production. In this study, the dynamics of modulation of auditory cortical responses to speech during self-production and feedback alteration were examined. Magnetic field recordings were obtained from both hemispheres of subjects who spoke while hearing controlled versions of their feedback via earphones. These responses were compared to magnetic field recordings made while subjects listened to a tape recording of their production. The amplitude of the tape playback was adjusted to be equal to the amplitude of produced speech. Successful recordings of evoked responses to both self-produced and tape-recorded speech were obtained free of movement-related artifacts. In all subjects, a progressive differentiation in the dynamics of the responses to self-produced speech and to recorded speech was observed. In several subjects, a clear bilateral suppression of amplitude of the peak response 100 ms after stimulus onset was also observed. Feedback alteration enhanced the evoked response to produced speech. [Work supported by the McDonnell-Pew Foundation, the Coleman Fund, HRI, and Scientific Learning Corp.]