Anticipatory Tonal Coarticulation in Thai Noun Compounds after Unilateral Brain Damage

Abstract

The time course and extent of anticipatory coarticulation between tones was investigated in normal and brain-damaged Thai-speaking subjects. Subjects were classified into five groups including 11 young normal, 9 old normal, 12 right hemisphere, 9 left hemisphere fluent, and 6 left hemisphere nonfluent. Stimuli consisted of five bisyllabic noun compounds with a falling tone on the initial syllable and each of the five Thai tones (mid, low, falling, high, rising) on the final syllable. Height and slope of F 0 was measured at 10% intervals throughout the duration of the initial syllable. Results indicated anticipatory effects on both height and slope of the falling tone. Height effects extended throughout from the beginning. The falling tone was generally higher when occurring before the low/rising tones than when occurring before the mid/falling/high tones. Slope effects were restricted to the terminal portion. The falling tone before the low/rising tones exhibited a steeper slope than before falling/high tones. In magnitude of effect, patients with left and right hemisphere lesions were statistically indistinguishable from those of normal subjects. No differences were noted in coarticulatory patterns as a function of aphasia type. All brain-damaged speakers were more variable in F 0 production than normals. Findings are interpreted to highlight properties of nonfluent aphasic speech and neurological bases of speech production.