Rochana Dardarananda

Voice onset time in aphasia: Thai II. Production☆

The aim of this study was to investigate voice onset time (VOT) production in homorganic word-initial stops in Thai in order to explore the nature of speech production deficits across clinical varieties of aphasia. Thai exhibits a three-category distinction in bilabial (/b,p,ph/) and alveolar (/d,t,t,h/) stops, and a two-category distinction in velar (/k,kh/) stops. Subjects included three Broca asphasics, one transcortical motor asphasic, two global asphasics, one conduction aphasic, one Wernicke aphasic, one nonaphasic dysarthric patient, one right-brain-damaged patient, and five normal controls. Test stimuli consisted of eight monosyllabic real words. The results of VOT measurements indicated that Broca and global asphasics exhibited a more severe production disorder than Wernicke, conduction, or transcortical motor asphasics. The right-brain-damaged patient showed no impairment in VOT production. Comparisons are drawn to earlier studies of VOT production in aphasia in two-category languages. Issues concerning the underlying basis of the production deficit for nonfluent aphasics, fluent aphasics, and nonaphasic dysarthrics as well as the relation between perception and production of VOT are discussed.

Dysprosody in Broca's aphasia: a case study.

A detailed acoustic analysis of timing, intensity, and fundamental frequency (F0) at different levels of linguistic structure was conducted on the speech output of a Brocas aphasic who was a native speaker of Thai. Timing was measured with respect to syllables, phrases, and sentences in connected speech. Intensity variation at the sentence level was measured in connected speech. F0 variation associated with the five Thai tones was measured in both isolated words and connected speech. Results indicated that timing was differentially impaired depending upon complexity of articulatory gesture and size of the linguistic structure. Timing, as well as intensity, was aberrant at the sentence level. In contrast, F0 contours of the five tones were spared at all levels of linguistic structure. Findings are interpreted to support the view that dysprosody in Brocas aphasia is more applicable to speech timing than to F0.

Prosodic disturbance in aphasia: Vowel length in Thai ☆

The aim of this study is to determine to what extent a phonologically contrastive function of the prosodic feature of length is resistant to impairment in aphasia. The language chosen for investigation is Thai, a language which contrasts short and long vowels. Subjects included two Broca aphasics, one transcortical motor aphasic, one Wernicke aphasic, one conduction aphasic, one nonaphasic right-brain-damaged patient, one nonaphasic cerebellar dysarthric patient, and five normal controls. The subjects read a list of words containing short and long vowels. Vowel durations were measured from spectrograms. The results showed that the timing of vowel duration for signaling the contrast between short and long vowels remains relatively intact in nonfluent as well as fluent aphasic patients. These data are brought to bear on issues concerning the specialization of the left hemisphere for temporal processing, the contribution of the right hemisphere to the processing of nonaffective components of prosody, the nature of prosodic disturbance in Brocas aphasia and cerebellar dysarthria, and the separate disruption of prosodic features.

Case study of a Thai conduction aphasic

Abstract A case study of a 55-year-old nonfamilial left-handed monolingual Thai patient with clinical and pathoanatomic evidence of major infarction in the left temporoparietal region is presented. He was studied at 9 years poststroke with a Thai adaptation of the Boston Diagnostic Aphasia Exam and supplementary tests. His language characteristics included fluent spontaneous speech, near-normal auditory language comprehension, and poor repetition, leading to a diagnosis of conduction aphasia. In regard to this aphasic syndrome, issues concerning classification, neuroanatomic correlates, and underlying neuropsychological mechanisms are addressed. The nature of his grammatical disturbance is examined critically in light of the notion of “information load.”

Tonal disturbances in Thai after brain damage

Abstract An acoustic-perceptual investigation of the five lexical tones of Thai was conducted to evaluate the nature of tonal disruption in aphasia. Subjects included two Broca aphasics, one transcortical motor, one global, one left subcortical aphasic, one language-delayed adult, and five normals. The five Thai tones (mid, low, falling, high, rising) were produced in isolated monosyllables and presented to native listeners for identification. Measures of F0 were extracted using a cepstral method of analysis. Results from tonal identification tests indicated that the mid and high tones were especially vulnerable to disruption. All significant tonal substitutions resulted in a mid, low, or falling tone. Acoustic analysis revealed that aberrant tones were characterized by falling or rising-falling F0 contours. Findings are discussed from both perceptual and articulatory perspectives on the tone space.

Nature of spelling errors in a Thai conduction aphasic

A Thai conduction aphasics performance on a written confrontation naming task is reported. Analysis of his spelling errors indicated that errors rarely violated Thai phonotactic constraints; consonant substitutions were phonologically similar to the target stimuli; longer stimuli were more likely to be in error; distribution of errors was the same across consonants, vowels, and tones; and distribution of error types varied between segmentals (consonants, vowels) and suprasegmentals (tones). Error patterns were similar to those observed in oral reading and repetition. The pattern of impaired writing performance is discussed in relation to a functional model of the spelling process, and it is hypothesized to reflect primarily a functional lesion to the phonological buffer.

Timing disturbances in the speech of a language-delayed Thai adult.

An acoustic-perceptual investigation was performed on various aspects of timing in the speech of a 21-year-old adult speaker of Thai who reportedly did not start speaking until the age of 7. Selected aspects of timing included: ( I ) the voicing contrast in Thai homorganic word-initial stops; (2) the duration contrast in Thai short and long vowels; and (3) the duration patterns of phrases and sentences in Thai connected speech. Measures of stop consonant voicing and vowel length were taken from monosyllabic citation forms; measures of syllables, phrases and sentences from an oral reading of a paragraph-sized passage. Findings indicated that speech timing skills relatcd to stop consonant voicing, vowel length, and rhythm can be differentially impaired, and moreover, that the pattern of impairment appears to be related to the size of the temporal planning unit.