Different motor strategies for increasing speaking rate: Data and modeling

Abstract

Different motor strategies for increasing speaking rate: data and modeling EMG, kinematic and acoustic signals were recorded from two male subjects as they pronounced multiple repetitions of simple nonsense utterances. The resulting data indicate that the two subjects employed different motor strategies to increase speaking rate. When speaking faster, S1 significantly increased the size of the articulatory target region for his tongue movements, increased the speed of the tongue movements and the rate of EMG rise somewhat, while decreasing the movement duration significantly and movement distance slightly. In contrast, at the fast rate, S2 had the same size articulatory target region and rate of EMG rise as at the normal rate, but decreased the speed, distance, and duration of tongue movement slightly. Each subject had similar dispersions of acoustic targets in F1–F2 space at fast versus normal rates, but both shifted target centroids toward the center of the vowel space at the fast rate. Simulations with a biomechanical model of the vocal tract show how modulations of motor commands may account for such effects of speaking rate on EMG, kinematics, and acoustic outputs. [Work supported by NIDCD, NIH.]