Functional organization of velar movements following jaw perturbation.

Abstract

Mechanical perturbation of the articulators has been used to examine motor control principles underlying speech production. One common observation is that if one member of a group of functionally related articulators is perturbed during articulation, the other members compensate. The compensatory response patterns reflect sensorimotor organization for speech, and thus have implications for speech production theories. The present experiment examines such linkages by analyzing the spatiotemporal response patterns to jaw perturbation displayed by the anatomically linked and remote jaw, upper lip, lower lip, and velum. Subjects were fitted with a mandibular prosthesis to allow delivery of jaw-lowering, random (20% of the trials) perturbations during productions of the utterance /mabnab/. Lip, jaw, and velar kinematics were recorded optoelectronically and simultaneously with the acoustic signal. These movements exhibited compensatory actions including increased movement displacement and oral closing velocity. Movement duration changes were also observed. Coordinative timing among lips, jaw, and velum was generally maintained following the perturbation. Variations in that timing appear to depend on the temporal relations between the onset of the perturbation and the onset of the component speech event. [Work supported by NIH Grant Nos. DC-00121, and DC-00594 to Haskins Laboratories.]