H. Betty Kollia
City Univ. of New York
Haskins Labs., 270 Crown St., New Haven, CT 06510
It is an established notion that the actions of the articulators are functionally constrained during speech production. Articulator tasks toward attainment of a specific goal appear to be distributed to the structures involved. This implies a global organization of the speech motor control mechanism. The present kinematic study examines the time dependence of articulator responses to jaw perturbation. Jaw-lowering perturbations were applied randomly during speech with the use of a mandibular prosthesis. Following the perturbation the coordinative timing among the articulators was generally maintained. It appears that the responses of the articulators to perturbations of the jaw were differentially affected by the time of the load application of the jaw and appeared to depend on the temporal relation between the onset of the perturbation and the onset of the component speech event. These load-induced modifications were effected in a manner such that the adjustments performed to counterbalance the perturbation and attain the specified target (/b/ production) were carried out in a modulated way. The jaw was the major contributor of compensatory adjustments to its mechanical perturbation, while the lower lip and upper lip supplemented these modifications in an almost reciprocal manner. Of the articulator kinematic variables (displacement, velocity, and duration), velocity was most sensitive to the temporal onset of the perturbation. [Work supported by NIH Grant Nos. DC-00121 and DC-00594 to Haskins Laboratories.]