Characteristics of Speech as a Motor Control System *

The structural and functional organization of any biophysical system provides potentially important information on the underlying control structure. For speech, the anatomical and physiological components of the vocal tract and the apparent functional nature of speech motor actions suggest a characteristic control structure in which the. entire vocal tract can be viewed as the smallest functional unit. Sounds are coded as different relative vocal tract configurations generated from neuromuscular specifications of characteristic articulatory actions. Sensorimotor processes are applied to the entire vocal tract to scale and sequence changes in vocal tract states. Sensorimotor mechanisms are viewed as a means to predictively adjust speech motor output in the face of continuously changing peripheral conditions. An underlying oscillatory process is hypothesized as the basis for sequential speech movement adjustments in which a centrally-generated rhythm is modulated according to internal (task) requirements and the constantly changing configurational state of the vocal tract.