Premotion silence in rapid voluntary movements for speech: Implications for suprabulbar control mechanisms

Abstract

In unprocessed speech EMG we have often observed a short‐duration silent period immediately preceding phasic activity for rapid voluntary movement [e.g., K. J. Cole and J. H. Abbs, J. Acoust. Soc. Am. Suppl. 1 66, S11 (1979)]. In the limbs, similar observations have been interpreted to indicate supraspinal control mechanisms for rapid voluntary and/or highly skilled movements. For example, premotion silence has been suggested to reflect differential control of tonic and phasic motoneurons, or preemption of peripheral reflex circuits, to facilitate initial movement acceleration [R. E. Burke, Prog. Clin. Neurophysiol. 9, 59–84 (1981); K. Yabe, J. Appl. Physiol. 41, 470–473 (1976)]. Such mechanisms offer alternative explanations for paradoxical changes in firing rates of neighboring single motor units for labial closure gestures, and for apparent reductions of perioral reflex excitability prior to labial closure [e.g., R. Netsell and J. H. Abbs, J. Acoust. Soc. Am. Suppl. I 58, S41 (1975)]. A series of experiments were initiated to determine the conditions under which premotion silent periods are observed for speech and nonspeech movements, particularly for various movement parameters. Potential underlying mechanisms and the implications of premotion silence for speech motor control are discussed. [This research was supported by NIH grant 13274.]