Some organizational characteristics of speech movement control.

The neuromotor organization for a class of speech sounds (bilabials) was examined to evaluate the control principles underlying speech as a sensorimotor process. Oral opening and closing actions for the consonants /p/, /b/, and /m/ (C1) in /s V1 C1 V2 C2/ context, where V1 was either /ae/ or /i/, V2 was /ae/, and C2 was /p/, were analyzed from 4 subjects. The timing of oral opening and closing action was found to be a significant variable differentiating bilabial consonants. Additionally, opening and closing actions were found to covary along a number of dimensions implicating the movement cycle as the minimal unit of speech motor programming. The sequential adjustments of the lips and jaw varied systematically with phonetic context reflecting the different functional roles of these articulators in the production of consonants and vowels. The implication of these findings for speech production is discussed.