Short-latency labial afferent-to-lingual efferent intended responses: Potential contributions to the spatial-temporal coordination of speech movements

Abstract

Kinesthetic stimuli were applied to the oral angle using a mechanical stimulus generator. Upon sensation of the stimulus subjects were instructed to produce a ‘rapid and forceful’ elevation of the tongue as in the gesture associated with a [d]. EMG responses were obtained from hooked-wire electrodes in the superior longitudinal muscle. Minimal response latencies, free from contamination by reflexes or stimulus overanticipation, ranged from 55–65 ms for all subjects. These data will be discussed in relation to (1) reports in the motor neurophysiology literature suggesting that the timing control of overlapping speech movements may permit interarticulator afferent-to-efferent triggering latencies of up to 75 ms, and (2) a recent model of speech motor control suggesting that speech coordination is achieved via open-loop, feedforward processes operating among the multiple speech structures. [Supported in part by NINCDS Program Project Grant NSq3274.]