Magnitude of perioral reflexes as a function of stimulus velocity and isometric lip force

Abstract

A quantitative description of peripheral nervous‐system function may enhance our ability to analyze speech motor control. With respect to lip motor control, recent evidence [R. Netsell and J. Abbs, J. Acoust. Soc. Am. 58, S41 (1975)] suggests that perioral reflexes may be actively modulated throughout lip movement for speech. In the present study, factors explored to clarify the manner in which these reflexes may be modulated during control of lip movement. Previous studies of perioral reflexes have been handicapped by the inability to systematically vary the characteristics of the mechanical simulus. The present investigation utilized an electromagnet under displacement sensitive servo control, coupled to a force transduction system, which delivered mechanical stimuli of different velocities against the lip of normal adult subjects. Reflexes were recorded from hooked‐wire EMG electrodes inserted into the orbicularis oris muscle while the lip was either passive or exerting an isometric force. Perioral reflexes were found to increase in magnitude as a function of both stimulus velocity and the level of isometric force. [Work supported by NIH.]