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Abstract:
In our study, 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 speech
feedback via earphones. These responses were compared to magnetic
field recordings made while subjects listened to a tape recording
of their production. We observed that responses to self-produced
speech were suppressed in comparison to responses to
tape-recorded speech. To test the specificity of this response
suppression, we looked at the responses to 1KHz tone pulses that
were added to the speech heard by the subject. Compared to the
responses to these tones by themselves, we found significant
suppression of the responses to the tones in the presence of
either self-produced or tape-recorded speech, with slightly more
suppression seen with self-produced speech. We also examined
responses to altered speech feedback: subjects heard noise gated
by either the speech they produced or the tape-playback of their
speech. In this case, there was no response suppression in the
self-produced condition as compared with the tape-recorded
condition. The results of these experiments suggest that during
speech production auditory cortex (1) attenuates its sensitivity
and (2) modulates its activity as a function of the expected
acoustic feedback.
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