Interaction between tone and intonation in Thai after unilateral brain damage

Intonational characteristics of Thai sentences were used to evaluate fundamental frequency (F(0)) control in brain-damaged patients with unilateral left and right hemisphere lesions. Subjects (n = 41) included 9 young and 10 old normal adults, 12 right hemisphere patients, and 10 left hemisphere aphasic patients (7 fluent and 3 nonfluent). Sentences were comprised of six words, three of which were keywords occurring in sentence-initial, -medial, and -final positions. All 125 possible sequences of three of the five Thai tones (mid, low, falling, high, rising) were superimposed on monosyllabic keywords. Utterances were produced at a conversational speaking rate. Average F(0) of keywords was analyzed as a function of sentence position, tone, and group. For both normal and brain-damaged speakers, results indicated that tones in sentence-final position were significantly lower in F(0) than in either sentence-initial or -medial position; falling and high tones were significantly higher in F(0) than mid, low, and rising tones. Findings are discussed in relation to issues pertaining to hemispheric specialization and the nature of F(0) deficits in nonfluent and fluent aphasic patients.