Control of speech prosody in Broca's aphasia

A typical clinical description of the speech of Broca's aphasics includes the characteristics of nonfluency, agrammatism, and dysprosody. This study aims to objectively evaluate the subjective impression of dysprosody using computerized techniques to measure fundamental frequency (F0) and segmental timing. We examined three rudimentary aspects of normal speech production: (1) terminal falling F0 contour in utterance-final position, (2) declination of F0 peaks throughout the course of an utterance, and (3) segmental lengthening in utterance-final position. Seventy-five two-word utterances, extracted from the spontaneous speech of three Broca's aphasics, were found to exhibit both terminal falling F0 contours and declination despite interword pauses of up to 3.5 s. However, the timing of these utterances showed no utterance-final lengthening. These results are discussed in terms of the speech planning capabilities of these patients and the apparent dissociation between programming of F0 and timing. A controlled experiment was conducted in order to rule out the possibility that a phonetic influence masked utterance-final lengthening in the spontaneous speech sample; the results confirmed the previous observations for both segmental timing and F0. [Supported by NIH Grants NS 11408, NS 13028, and the MIT Research Laboratory of Electronics.]