Speech Timing at the Sentence Level in Thai After Unilateral Brain Damage

Abstract

The present study examined temporal characteristics of spoken sentences in Thai to evaluate timing control in brain-damaged patients with unilateral left and right hemisphere lesions. Subjects included 10 young and 10 old normal adults, 14 right hemisphere patients, and 2 left hemisphere nonfluent and 7 fluent aphasic patients. Utterances were produced at a conversational speaking rate. Duration measures were taken from wide-band spectrograms. Results indicated that left hemisphere patients exhibited abnormal timing on both absolute and relative timing measures, whereas right hemisphere patients did not. Among left hemisphere patients, fluent as well as nonfluent aphasics exhibited aberrant temporal patterns. Left hemisphere patients were also more variable than right hemisphere patients which, in turn, were more variable than normals in their production of sentences. In comparison to earlier findings on timing at segment and word levels, it was found that deficit profiles varied between fluent and nonfluent aphasics as a function of the size of the linguistic unit with nonfluent aphasics being affected at the segment, word, and sentence level but fluent aphasics affected at the sentence level only. Findings are discussed in relation to issues pertaining to hemispheric specialization and the nature of timing deficits in nonfluent and fluent aphasic patients.