MODULATION OF CEREBRAL BLOOD-FLOW IN THE HUMAN AUDITORY-CORTEX DURINGSPEECH - ROLE OF MOTOR-TO-SENSORY DISCHARGES

To investigate mechanisms of audio-vocal interactions in the human bra in, we studied the effect of speech output on modulation of neuronal a ctivity in the auditory cortex, The modulation was assessed indirectly by measuring changes in cerebral blood flow (CBF) during unvoiced spe ech (whispering). Using positron emission tomography (PET), CBF was me asured in eight volunteers as they uttered syllables at each of seven rates (30, 50, 70, 90, 110, 130 or 150/min) during each of the seven 6 0-s PET scans, Low-intensity white noise was used throughout scanning to mask auditory input contingent on the whispering, We found that, as a function of the increasing syllable rate, CBF increased in the left primary face area, the upper pens, the left planum temporale and the left posterior perisylvian cortex. The latter two regions contain seco ndary auditory cortex and previously have been implicated in the proce ssing of speech sounds. We conclude that, in the absence of speech-con tingent auditory input, the modulation of CBF in the auditory cortex i s mediated by motor-to-sensory discharges, As such, it extends our pre vious findings of oculomotor corollary discharges to the audio-vocal d omain.