REFLEX AND FINE FORCE DYNAMICS OF THE PERIORAL SYSTEM

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Afferent information derived from proprioceptive and cutaneous mechanosensitive inputs is considered important for the moment-to-moment coordination of movement. Small movements and forces, associated with skilled motor behavior, have been shown to be more dependent on peripheral inputs than large movements and forces. A number of cutaneous and muscle receptors exhibit their greatest sensitivity to small amplitude input signals. Speech production, considered a fine motor skill consisting of small movements and forces, is hypothesized to be highly dependent upon afferent information for ongoing motor control in the developing and mature nervous system. To date, detailed information concerning the neural integration of mechanosensory inputs during the production of fine motor behaviors in the perioral complex remains unknown. We propose to approach the problem of sensorimotor integration in the perioral complex during fine motor control from a new direction in consideration of the hypothesis that small movements and small forces are more dependent on peripheral inputs than large movements and forces. This hypothesis is especially appealing for studies of speech motor control since movements of the articulators are generally considered to require precise spatial and temporal adjustments in force recruitment among the complex array of muscles within the perioral complex. This proposal outlines a series of studies intended to quantify the interactions between controlled mechanosensory input and reflexively driven perioral motor units during the production of skilled motor behaviors, including 1) FINE FORCE CONTROL, (2) FINE POSITION CONTROL, and (3) SPEECH MOVEMENT CONTROL. The experiments will provide new and valuable information on fundamental physiologic properties of the perioral mechanism. This information should lead to a better understanding of basic sensorimotor mechanisms involved in fine motor control, including speech production, and more importantly, provide a conceptual framework and extensive normative database for use in future investigations of neuromotor speech disorders.