Biomedical subjects

J Gandour

Publications and source records attributed to J Gandour.

At least 19 recordsLinked to original sources

PubMed1999

Effect of sentence length on the production of linguistic stress by left- and right-hemisphere-damaged patients.

An acoustical/perceptual study of phonemic stress (e.g., HOTdog vs. hot DOG) was conducted to evaluate the effect of sentence length on stress production after brain damage. Productions of phonemic stress pairs were elicited in sentence contexts of increasing length from eight left-hemisphere-damaged nonfluent (LHD-NFL), fluent LHD-FL), right-hemisphere-damaged (RHD), and normal speakers (n = 32). Tape recordings of subjects' productions were presented to naïve listeners for perceptual identification of stress placement. Acoustic analysis focused on fundamental frequency, duration, and intensity of the initial and final syllables as well as pause duration between syllables. Perceptual tests indicated that regardless of sentence length, all brain-damaged groups exhibited an impairment in the production of linguistic stress when compared to normals. The LHD-NFL group experienced the greatest difficulty in signaling stress contrasts, followed in order by the LHD-FL and RHD groups. In medium-length sentences, the LHD-FL group's performance was degraded by comparison to short-length sentences. Acoustic analysis showed that pause duration was the strongest predictor of phonemic stress for all groups. Acoustic profiles of the RHD group were similar qualitatively to those of normals, but differed quantitatively in terms of magnitude of effect associated with shifts in stress patterns. Findings are brought to bear on the nature of the stress production deficit after unilateral brain damage, the role of the right hemisphere in linguistic prosody, and the concept of "subtle phonetic deficit" in fluent aphasia.

Acoustics↗

PubMed1998

Locus of functional impairment in the production of speech rhythm after brain damage: a preliminary study.

This acoustic-perceptual, multiple-case study of the Rhythm Rule (RR) in English, a phonological phenomenon whereby adjacent stresses are adjusted to avoid "stress clash" (e.g., thirTEEN vs THIRteen MEN), was undertaken to identify the locus of functional impairments in speech prosody in different aphasic syndromes. Subjects included two left brain-damaged aphasic patients (1 fluent, 1 nonfluent), one right brain-damaged nonaphasic patient, and one nonneurological control. They were instructed to read sentences including experimental (bisyllabic "double-stressed" words) and matching control (bisyllabic "initial-stressed" words) phrases of increasing length. Results of acoustic and perceptual measures indicated that rhythmic disturbances associated with the RR emerged regardless of lesion site. The locus of functional impairment was isolated to phonetic implementation of the RR, as opposed to either loss of word-level stress or loss of the RR. Findings suggest that neural substrates of speech prosody are broadly distributed in the left and right cerebral hemispheres.

Brain Injuries↗

PubMed1998

Pitch processing in the human brain is influenced by language experience.

Positron emission tomography (PET) was used in a cross-linguistic study to compare pitch processing in native speakers of English, a nontone language, with those of Thai, a tone language. When discriminating pitch patterns in Thai words, only the Thai subjects showed activation in the left frontal operculum. Activation of this region near the classically defined Broca's area suggests that the brain recognizes functional properties, rather than simply acoustic properties, of complex auditory cues in accessing language-specific mechanisms in pitch perception.

Acoustic Stimulation↗

PubMed1997

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.

Adult↗

PubMed1997

Contextual variations in trisyllabic sequences of Thai tones.

It is well known that tones assimilate in much the same way as consonants and vowels do. In tonal assimilation, the height and shape of a given tone is altered by adjacent tones. Earlier studies on tonal assimilation in Thai have used two-tone sequences with an intervening obstruent between the two tones of interest. In the present study, three-tone sequences were used with continuously voiced syllables throughout the utterance. Assimilatory effects were expected to be greater between F0 contours of two successive syllables that are continuous in voicing across the syllable boundary. Stimuli consisted of 125 possible three-tone sequences of the five Thai tones, superimposed on monosyllabic words in a carrier sentence. All syllables were stressed in order to eliminate potentially confounding interactions between stress and tonal assimilation. Acoustic analysis revealed that perseverative effects were assimilatory in nature; anticipatory effects, however, were dissimilatory in nature. Perseverative effects appear to be independent of tonal categories, and restricted to contiguous tones. Perseverative effects extend through more than half the duration of the following tone. Both the height and shape of the tones are affected. Anticipatory effects, on the other hand, are limited to the high and rising tones, and extend through less than half the duration of the preceding tone.

Adult↗

PubMed1996

Tonal coarticulation in Thai after unilateral brain damage.

The magnitude and temporal extent of anticipatory and perseverative tonal coarticulation was investigated in Thai-speaking normal and brain-damaged adults. A total of 47 speakers (10 young normal, 10 old normal, 13 nonaphasic right-brain-damaged patients, 14 left-brain-damaged aphasic patients, 9 fluent, 5 nonfluent) produced all 25 possible sequences of two tones from the five lexical tones of Thai embedded in a carrier sentence. F0 contours were analyzed in terms of height and slope at 10% intervals throughout the duration of the two syllables. Acoustic analysis revealed that anticipatory and perseverative tonal coarticulation of tones was markedly reduced in left fluent aphasics, totally absent in left nonfluent aphasics, but reasonably intact in right hemisphere patients. Findings are interpreted to highlight the nature of speech disturbances in nonfluent and fluent aphasia, hemispheric specialization for tone, and tonal coarticulation in Thai.

Adult↗

PubMed1996

Acoustic correlates of stress in Thai.

Acoustic correlates of stress [duration, fundamental frequency (Fo), and intensity] were investigated in a language (Thai) in which both duration and Fo are employed to signal lexical contrasts. Stimuli consisted of 25 pairs of segmentally/tonally identical, syntactically ambiguous sentences. The first member of each sentence pair contained a two-syllable noun-verb sequence exhibiting a strong-strong (--) stress pattern, the second member a two-syllable noun compound exhibiting a weak-strong (--) stress pattern. Measures were taken of five prosodic dimensions of the rhyme portion of the target syllable: duration, average Fo, Fo standard deviation, average intensity, and intensity standard deviation. Results of linear regression indicated that duration is the predominant cue in signaling the distinction between stressed and unstressed syllables in Thai. Discriminant analysis showed a stress classification accuracy rate of over 99%. Findings are discussed in relation to the varying roles that Fo, intensity, and duration have in different languages given their phonological structure.

Adult↗

PubMed1995

On the notion of a "subtle phonetic deficit" in fluent/posterior aphasia.

Phonetic investigations in the past decade or so have reported instances of a "subtle phonetic deficit" in the fluent aphasias, thereby challenging the traditional dichotomy of a motoric deficit characterizing the nonfluent aphasias and a selection deficit characterizing the fluent aphasias. This paper critically reviews the acoustic, physiological, and perceptual studies which have attempted to examine this phenomenon. These investigations have been evaluated in terms of differences in subject populations, task demands, subjects' performance, and problematic interpretations. Suggestions are offered for an experimental design which can help us operationalize this term and help us to better understand the speech production deficit in fluent aphasic patients.

Aphasia, Wernicke↗

PubMed1995

Speech prosody in affective contexts in Thai patients with right hemisphere lesions.

The production of speech prosody in emotional contexts was examined in Thai patients with unilateral right hemisphere damage. Twelve right hemisphere patients and nine normals read target sentences embedded in paragraphs that cued either a happy, sad, or neutral affect. Perceptual evaluations of their productions revealed a severe deficit in right hemisphere patients. Acoustic analysis indicated that longterm measures of fundamental frequency, timing, and energy at the sentence level were aberrant in right hemisphere patients. Findings are discussed in relation to nature and extent of prosodic deficits in right hemisphere patients, hemispheric specialization for linguistic and affective prosody, and the effect of language structure on the manifestation of affective prosody.

Adult↗

PubMed1994

Sequences of phonemic approximations in a Thai conduction aphasic.

Sequences of phonemic approximations (SPAs) to a single target word on a picture naming task were investigated in a Thai-speaking conduction aphasic. A corpus of 207 SPAs was analyzed with an adaptation of Valdois, Joanette, and Nespoulous's (1989) methodology to a tone language. Measures included the length of SPAs, overall degree of approximation to the target of the last attempt and each of the preceding attempts, as well as degree of approximation to the target in terms of number of syllables, syllable structure, segments (consonants/vowels), and tones. Results indicated that there was a steady progression toward the target regardless of eventual outcome or length of sequence. Number of syllables of the target word was better preserved than syllable structure, and tones better than segments. In the course of SPAs, tonal information was accessed earlier than segmental, and syllabic length information earlier than syllabic structure. Within SPAs, tonal information was more stable than segmental across successive approximations. Findings are discussed in relation to a functional model of single word production and multidimensional phonological representations.

Aphasia↗

PubMed1994

Speech timing at the sentence level in Thai after unilateral brain damage.

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.

Adult↗

PubMed1993

Anticipatory tonal coarticulation in Thai noun compounds after unilateral brain damage.

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 F0 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 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 F0 production than normals. Findings are interpreted to highlight properties of nonfluent aphasic speech and neurological bases of speech production.

Acoustic Stimulation↗

PubMed1993

Intraword timing relations in Thai after unilateral brain damage.

The present study examined temporal characteristics of monosyllabic, bisyallabic, and trisyllabic words in Thai to evaluate timing control at the word level in brain-damaged patients. Subjects included young and old normal adults, right hemisphere patients, and left hemisphere nonfluent and fluent aphasic patients. Utterances were produced at a conversational speaking rate. Results indicated that, on an absolute or relative measurement scale, magnitude of the shortening effect on nonfinal syllables in polysyllabic words was significantly smaller in left nonfluent aphasics than in other groups. In trisyllabic words, duration of the penultimate syllable for left fluent aphasics was also significantly longer than that of normals. Left nonfluent and fluent aphasics were significantly more variable than other speakers in their production of bisyllabic and trisyllabic words. Findings are discussed in relation to issues pertaining to the nature of timing deficits in nonfluent and fluent aphasic patients.

Adult↗

PubMed1992

Timing characteristics of speech after brain damage: vowel length in Thai.

This paper explores the extent of timing deficits in vowels produced by brain-damaged speakers of a language with a phonological contrast in vowel length. Short and long vowels in Thai were produced in isolated monosyllabic words by 20 normal adults, 14 right hemisphere patients, and 17 left hemisphere aphasics. Vowel durations were measured spectrographically. Although the phonological contrast was relatively preserved, as indicated by average duration, a subtle timing deficit in vowels produced by nonfluent aphasics was indicated by a compressed duration continuum and increased variability in vowel production.

Adult↗

PubMed1992

Lexical tones in Thai after unilateral brain damage.

An acoustic perceptual investigation of the five lexical tones of Thai was conducted to evaluate the nature of tonal disruption in patients with unilateral lesions in the left and right hemisphere. Subjects (n = 48) included 10 young normal adults, 10 old normal adults, 11 right hemisphere nonaphasics, 9 left hemisphere fluent aphasics, and 8 left hemisphere nonfluent aphasics. The five Thai tones (mid, low, falling, high, rising) were produced in isolated monosyllables, presented for tonal identification judgments, and measured for fundamental frequency (Fo) and duration. Results of an analysis of variance indicated that left hemisphere nonfluent speakers signaled and tonal contrasts at a lower level of proficiency. The extent of their impairment varied depending on severity level of aphasia. When compared to normal speakers, tonal identification for less severe nonfluent aphasics differed more in degree than in kind, and for more severe nonfluent aphasics differed both in kind and in degree. Acoustic analysis revealed that with the exception of one left nonfluent, average Fo contours were comparable in shape across speaker groups. Variability in Fo production, however, was greater in left nonfluent speakers than in any of the other four groups of speakers. Issues are discussed regarding the extent and nature of tonal disruption in aphasia and hemispheric specialization for tone production.

Adult↗

PubMed1992

Vowel duration in mothers' speech to young children.

The purpose of this investigation was to determine whether content words are selectively highlighted through increased vowel duration in mothers' speech to young children. Fifteen mother-child dyads served as subjects. All children (ages 1:6-2:4) were female and had a mean length of utterance between 1.00 and 1.40 morphemes. Each mother was asked to read five experimental stories aloud to her child and to an adult. The vowel durations of both content words and function words in these stories were examined. Vowels in content words--but not function words--were significantly longer in child-directed than in adult-directed speech. It is suggested that this characteristic of child-directed speech might heighten young children's attention to content words and contribute to the exclusion of function words during the early stages of English language development.

Female↗

PubMed1991

Nature of spelling errors in a Thai conduction aphasic.

A Thai conduction aphasic's 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.

Agraphia↗

PubMed1989

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 Broca's 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 Broca's aphasia is more applicable to speech timing than to F0.

Aphasia↗