H. Betty Kollia
City Univ. of New York, New York, NY 10036 and Haskins Labs., 270 Crown St., New Haven, CT 06510
It was recently shown that anatomically linked and remote articulators such as the jaw, the lips, and the velum are functionally constrained during bilabial closing, exhibiting temporal stability in the patterns of interarticulatory cohesion [Kollia et al., J. Acoust. Soc. Am. 92, 2390 (A) (1992)]. Further, it was found that, when functionally related for speech, jaw, lips, and velum show compensatory kinematic adjustments to a mechanical jaw perturbation, such as increased movement displacement and oral closing velocity, thereby maintaining interarticulator cohesion [Kollia et al., J. Acoust. Soc. Am. 91, 2474 (A) (1992)]. The interpretation is that speech movements are controlled in a global manner, rather than independently, reflecting large scale vocal tract actions. The present study aims at untangling the gradient effects of the perturbation on the articulators and their kinematic parameters. Overall load effects depended on the distance of the articulator from the site of the perturbation. Load effects were heightened in structures that were more proximal to the perturbation such as the jaw and the lower lip, and diminished in more remote structures, such as the upper lip and the velum. Moreover, load effects depended on the load onset time and had a variable effect on the different kinematic parameters. [Work supported by NIH Grant Nos. DC-00121 and DC-00594 to Haskins Laboratories.]