Labial movement dynamics for speech

Abstract

Interpreting central nervous system control of speech movement depends in part on understanding the detailed parameters of that movement. For example, the motor control significance of the often‐reported reflex responses elicited during speech depends upon whether the external eliciting stimuli generate mechanoreceptor activity that is comparable to that generated naturally by speech movements [cf., Caligiuri and Abbs, Society for Neurosciences (1984)]. Similarly, kinematic analyses of articulatory movement confined to average velocity without considering instantaneous velocity and acceleration are likely to be misleading insofar as the critical neuromotor actions are likely to be misinterpreted. For these reasons the labial dynamics for speech were investigated in five young adults. The maximum peak acceleration and velocity obtained during normal speech production were 544.9 cm/s2 and 39.7 cm/s, respectively, with means of 260.7 cm/s2 and 25.5 cm/s. Further analyses of the effects of increasing speaking rate revealed that peak velocity and acceleration were not scaled proportionately. That is, for the labial closing gesture, peak acceleration increased up to 47%, while peak velocity increased only 12%. These and related findings underscore the importance of considering peak acceleration as well as peak velocity when assessing the motor control of speech movements. [Research supported by NS‐13274 and NS‐18797.]