Speech motor control in aphasia.
Published: 2004
Language: eng
Number of pages: 293
Description: The speech motor control system is an important and fundamental component in human verbal communication. The current research aimed to further our understanding of speech motor abilities in individuals with aphasia, and to explore the influence of linguistic complexity on speech motor functions. This thesis describes three experiments, which have utilized physiological measurements to study linguistic processing and speech movements. A total of eight individuals with aphasia and fifteen normal speakers participated in three experiments. Electromagnetic midsagittal articulograph was used to record movements from different articulators (upper lip, lower lip, jaw and tongue) for experiments 1 and 2 (Chapters 2, 3, and 4), and a separate acoustic study was performed to measure reaction time and word duration in experiment 3 (Chapter 5). The selected stimuli provided access to different aspects of linguistic and motor processes and consisted of speech versus nonspeech tasks, nonword sequences with a different number of syllables, and simple monosyllabic words which differed in word and bigram frequency.This research provides new insights into speech motor control in aphasia and a significant step towards a more complete understanding of the verbal expression difficulties in aphasia. The findings indicate that it is important to incorporate both linguistic and speech motor processes in future models of speech/language production.Kinematic analysis of speech versus nonspeech tasks showed that individuals with aphasia demonstrated significantly smaller amplitudes, longer durations and higher variability of individual movements. Unlike normal speakers, the aphasic subjects demonstrated difficulty to implement kinematic changes at the fast rate condition. Kinematic analysis also showed that an increase in linguistic complexity had a direct effect on lip kinematics, and movement duration and variability were significantly different between individuals with aphasia and normal speakers in linguistically more complex conditions (i.e., for longer non-word sequences). Aphasic individuals also demonstrated lower stability in movement coordination for bilabial closure. Reaction time analysis showed that although individuals with aphasia were slower in general, they were qualitatively similar to normal speaker in retrieving words. However, for word duration it was shown that aphasic speakers took longer to produce words with tense vowels compared to words with lax vowels.
Notes: Thesis (Ph.D.)--University of Toronto, 2004.

Electronic version licensed for access by U. of T. users.

Source: Dissertation Abstracts International, Volume: 65-05, Section: B, page: 2383.