Disordered Speech Production Research Articles

Electropalatographic and perceptual analysis of the speech of Cantonese children with cleft palate.

This study used electropalatographic and perceptual analysis to investigate the speech of two Cantonese children with repaired cleft palate. Some features of their speech, as identified from the perceptual analysis, have been previously reported as being typical of children with cleft palate. For example, fricatives and affricates were vulnerable to disruption, and obstruent sounds were judged by listeners to have posterior placement. However, some apparently language-specific characteristics were identified in the Cantonese-speaking children. First there was a relatively high incidence of initial consonant deletion, and for one subject /s/ and /f/ targets were produced as bilabial fricatives. EPG error patterns for target lingual obstruents were largely similar to those reported to occur in English- and Japanese-speaking children. In particular, broader and more posterior tongue-palate contact was observed, and intrasubject variability was noted. There was also evidence of simultaneous labial/velar and alveolar/velar constriction for labial and velar targets respectively. The clinical implications of the findings are discussed.

Can articulatory behavior in motor speechdisorders be accounted for by theories of normal speech production?

This paper deals with the relationship of speech production theoriesto articulatory behavior in motor speech disorders. The ability of translation and gesture theories to account for some selected facts of motor speech disorders is first considered, followed by a report of a small-scale experiment designed to demonstrate a specific application of certain aspects of gesture theory to articulatory variability in apraxia of speech. The results of this experiment seem to indicate that a gesture perspective on the speech production deficit in motor speech disorders may yield important insights for both normal and disordered speech production.

Disordered Speech Production in Aphasic and Normal Speakers

Two empirical studies are presented which seek to extend the parallels between disordered speech production in aphasia and in normals. Study 1 compares the rate and distribution of some theoretically interesting error types in a jargon aphasic and a normal error corpus. Study 2 is an investigation of how the error pattern of normal speakers evolves as utterances become more practiced. On the basis of these studies, we offer a hypothesis about the nature of the variation between more and less disordered systems. Our claim, which is developed in the context of spreading activation models of production, is that such variation is tied to the ability of the system to deliver activation to intended units, relative to that of unintended units, within the time required by the task at hand.

Surface EMG recording of the perioral reflexes: preliminary observations on stutterers and nonstutterers.

The capability to record muscle-specific reflexes in the perioral muscles with surface electrodes could have practical significance for the study of speech production disorders. In the present study, surface electrodes were used to describe the perioral reflexes in 7 stutterers and 5 nonstutterers. Electromyographic (EMG) recordings were obtained at electrode sites associated with the orbicularis oris inferior muscle (OOI) and depressor labii inferior muscle (DLI) during lower-lip press and depression gestures. During postural maintenance of these gestures, innocuous mechanical stimuli were applied at the corner of the mouth. Signal averages on the two EMG signals for the two gestures and electrode sites revealed four distinct reflex response components: two excitatory (E1 and E2) and two suppression components (S1 and S2). During lip pressing, the OOI electrode site showed a prominent E1 response in all subjects, and, during lip depression, the DLI site showed an initial S1-E2 response pattern in the nonstutterers. These observations are consistent with previous descriptions of the perioral reflexes involving intramuscular electrodes. Quantitative differences in the perioral reflexes were not seen in the stutterers and nonstutterers. However, a difference was noted in the pattern of reflex response between the two groups during lip depression at the DLI electrode site.

Studies of phrase-level speech timing

In a previous presentation [G. Weismer, Speech Motor Control Conference, Madison, WI (April-May 1982)] data were presented which suggested that temporal ratios of acoustically defined events in a five-syllable utterance were approximately constant across speaking rate adjustments. These findings were related to similar results from typing sequence research, and to general notions of temporal sequence organization by the central nervous system. For the present paper additional data on relative phrase-level timing are described, both from the perspective of normal and disordered speech production. In particular, phrase-level timing characteristics of speakers with neurogenically based disorders are described, because the specific disorders are often thought to involve aberrant motor programming. Discussion will not only be devoted to the implications of the results, but also to the selection of “events” in a phrase-level sequence for use in the construction of temporal ratios. Finally, some attempt will be made to relate this work to a model of speech timing proposed by Fujimura [In Honor of Ilse Lehiste, edited by R. Channon and L. Shockey (in press)]. [Supported by NINCDS Award NS 13274.]

Studies of apraxic speech production

A series of five studies of apraxic speakers generated the following conclusions: (1) The major residual errors for an apraxic with ten years of therapy appeared to result from poor temporal coordination of expiration, vocal fold adduction, and articulatory gesture. (2) VOTs for this patient differed markedly from those of normals, and related to perceived voicing errors for stops. (3) VOTs for four other apraxic speakers were also abnormal. (4) Therapy directed toward teaching the first patient to produce more appropriate voice onset times succeeded in establishing two discreet categories of stops, but VOTs still differed from those of normals and lacked “natural quality.” (5) Lack of success in teaching the patient to produce normal stops may result from the categorical perception of clinicians providing feedback for modification. Results of these studies have implications relating to (1) the nature of the apraxic disorder, (2) use of acoustic analysis procedures for diagnosis and management of speech production disorders, (3) limitations of clinician perception in providing feedback for modification of in‐category (distorted) phoneme production errors. [This work was supported in part by NIDR Grant DE‐01774.]