An Acoustic Analysis of Rate of Speech Effects on Vowel Production in Aphasia

The present investigation examined the production of tense and lax vowel duration differences at two speaking rates in the speech of 10 nonfluent aphasics, 8 fluent aphasics, and 10 normal control subjects. Subjects produced four repetitions of each of the vowels [i e æ o u I ε υ Λ] at each speaking rate. Acoustic analyses revealed that subjects in all three groups were able to manipulate overall rate of speech. In addition, normal controls and fluent aphasic subjects produced vowels under the fast rate condition which were significantly shorter than those under the slow rate condition. Despite a change in overall speaking rate, the nonfluent aphasics did not exhibit a significant difference in vowel duration at the two rates of speech, suggesting a deficit in the implementation of this temporal parameter. Both normal controls and fluent aphasic patients produced nonoverlapping distributions of tense and lax vowels at both speaking rates. In contrast, the nonfluent aphasics demonstrated a great deal of overlap in the distribution of tense and lax vowel durations at the fast rate. Results are discussed in relation to the nature of the speech production deficits in nonfluent and fluent aphasic patients.     

Compensation for Jaw Fixation by Aphasic Patients

The ability to compensate for fixation of the jaw by a bite block was investigated in 6 nonfluent aphasics, 6 fluent aphasics, and 10 normal control subjects. Acoustic analyses of the vowels [i u a æ] and fricatives [s s] revealed substantial but incomplete compensation for the perturbation in all three subject groups. Perceptual identification scores and quality ratings by naive and phonetically trained listeners indicated poorer identification of the high vowels [i u] under compensatory conditions relative to normal production. Of particular interest was the fact that all three groups of subjects exhibited similar patterns of results. The findings suggest that any deficit in speech motor programming demonstrated by the nonfluent aphasic patients did not affect compensatory abilities. Results are discussed with respect to normal speech adaptation skills and the nature of articulatory breakdown in nonfluent aphasia.     

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.F₀contours 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.     

Speech timing in Parkinson''s and Huntington''s disease

The purpose was to determine the effects of two different basal ganglia diseases on speech planning, initiation, and production. Patients with Parkinson's Disease (PD) and Huntington's Disease (HD) were compared with normal subjects on speech timing tasks. Speech reaction time was unimpaired, while changes in duration at different speech rates were affected differently in the two patient groups. In HD, changes in the duration of syllables, of pauses between phrases, and of sentences were all reduced, while in PD only the control of sentence duration was impaired. The HD patients had reduced syllable repetition rates, but both patient groups maintained their repetition rates over 5 sec. The ratios of word to phrase time, and of phrase to sentence time, remained constant across regular and fast speaking rates and did not differ from normal in either patient group. The results suggest that PD and HD patients are not impaired in speech planning or initiation, but have poor control over the duration of speech events.     

Anticipatory Coarticulation in Aphasia: Effects of Utterance Complexity

The magnitude and extent of anticipatory coarticulation were examined in groups of fluent and nonfluent aphasic patients and normal control subjects. One- and two-syllable target utterances were elicited at slow and fast rates of speech with or without a consonant intervening between the target consonant and vowel, and with or without a preceding schwa, to manipulate utterance complexity. Acoustic analyses (F2 and centroid frequencies) revealed that both groups of aphasic patients exhibited relatively normal patterns of anticipatory coarticulation. However, small but significant differences among the groups emerged in certain conditions. Surprisingly, increased utterance complexity was not found to reduce coarticulatory effects to a greater degree in the nonfluent relative to the fluent aphasic group. Perceptual tests largely confirmed the acoustic analyses.     

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.     

The influence of neighborhood density on phonetic categorization in aphasia

The present study examined the contribution of lexically based sources of information to acoustic-phonetic processing in fluent and nonfluent aphasic subjects and age-matched normals. To this end, two phonetic identification experiments were conducted which required subjects to label syllable-initial bilabial stop consonants varying along a VOT continuum as either /b/ or /p/. Factors that were controlled included the lexical status (word/nonword) and neighborhood density values corresponding to the two possible syllable interpretations in each set of stimuli. Findings indicated that all subject groups were influenced by both lexical status and neighborhood density in making phonetic categorizations. Results are discussed with respect to theories of acoustic-phonetic perception and lexical access in normal and aphasic populations.     

Production of Stress Retraction by Left- and Right-Hemisphere-Damaged Patients

An acoustic-perceptual investigation of a phonological phenomenon in which stress is retracted in double-stressed words (e.g., thirTEEN vs THIRteen MEN) was undertaken to identify the locus of functional impairments in speech prosody. Subjects included left-hemisphere-damaged (LHD) and right-hemisphere-damaged (RHD) patients and nonneurological controls. They were instructed to read sentences containing double-stressed target words in the presence of a clause boundary or its absence. Whereas all three groups of subjects were capable of manipulating the acoustic parameters that signal a shift in stress, there were some differences between the performance of the patient groups and that of the normal controls. Further, stress production deficits were more severe in LHD aphasic patients than in RHD patients. LHD speakers exhibited deficits in the control of both temporal and F0 cues. Their F0 disturbance appears to be secondary to a primary deficit in temporal control at the phase or sentence level, as an increased number of continuation rises found for the LHD patients seemed to arise from lengthy pauses within sentences. Findings are highlighted to address the nature of breakdown in speech prosody and the competing views of prosodic lateralization.     

Fluent versus nonfluent primary progressive aphasia: a comparison of clinical and functional neuroimaging features

To better characterize fluent and nonfluent variants of primary progressive aphasia (PPA). Although investigators have recognized both fluent and nonfluent patients with PPA, the clinical and neuroimaging features of these variants have not been fully defined. We present clinical and neuropsychological data on 47 PPA patients comparing the fluent (n=21) and nonfluent (n=26) subjects. We further compared language features with PET/SPECT data available on 39 of these patients. Compared to the nonfluent PPA patients, those with fluent PPA had greater impairment of confrontational naming and loss of single word comprehension. They also exhibited semantic paraphasic errors and loss of single word comprehension. Patients with nonfluent PPA were more likely to be female, were more often dysarthric, and exhibited phonological speech errors in the absence of semantic errors. No significant differences were seen with regard to left hemisphere abnormalities, suggesting that both variants result from mechanisms that overlap frontal, temporal, and parietal regions. Of the language measures, only semantic paraphasias were strongly localized, in this case to the left temporal lobe. Fluent and nonfluent forms of PPA are clinically distinguishable by letter fluency, single word comprehension, object naming, and types of paraphasic errors. Nevertheless, there is a large amount of overlap between dysfunctional anatomic regions associated with these syndromes.     

Contextual influences in aphasia: effects of predictive versus nonpredictive narratives

The influence of prior linguistic predictive and nonpredictive context on the comprehension of reversible passive sentences was investigated in 16 adults with aphasia. Eight subjects were classified as fluent and 8 as nonfluent. Subjects were presented with the sentences in isolation and preceded by nonpredictive and predictive contextual paragraphs. The overall results indicated that the subjects benefited significantly from the prior contextual narratives regardless of whether the paragraphs were predictive or nonpredictive. There were no significant differences between the two subject groups. The significant facilitation generated by the nonpredictive context suggests that redundancy of information may play a role in comprehension.     

Sensitivity to local sentence context information in lexical ambiguity resolution: evidence from left- and right-hemisphere-damaged individuals

Using a cross-modal semantic priming paradigm, the present study investigated the ability of left-hemisphere-damaged (LHD) nonfluent aphasic, right-hemisphere-damaged (RHD) and non-brain-damaged (NBD) control subjects to use local sentence context information to resolve lexically ambiguous words. Critical sentences were manipulated such that they were either unbiased, or biased toward one of two meanings of sentence-final equibiased ambiguous words. Sentence primes were presented auditorily, followed after a short (0 ms) or long (750 ms) interstimulus interval (ISI) by the presentation of a first- or second-meaning related visual target, on which subjects made a lexical decision. At the short ISI, neither patient group appeared to be influenced by context, in sharp contrast to the performance of the NBD control subjects. LHD nonfluent aphasic subjects activated both meanings of ambiguous words regardless of context, whereas RHD subjects activated only the first meaning in unbiased and second-meaning biased contexts. At the long ISI, LHD nonfluent aphasic subjects failed to show evidence of activation of either meaning, while RHD individuals activated first meanings in unbiased contexts and contextually appropriate meanings in second-meaning biased contexts. These findings suggest that both left (LH) and right hemisphere (RH) damage lead to deficits in using local contextual information to complete the process of ambiguity resolution. LH damage seems to spare initial access to word meanings, but initially impairs the ability to use context and results in a faster than normal decay of lexical activation. RH damage appears to initially disrupt access to context, resulting in an over-reliance on frequency in the activation of ambiguous word meanings.     

The Interpretation of Sentence Ambiguity in Patients with Unilateral Focal Brain Surgery

Interpretations of ambiguous sentences were studied in patients with unilateral anterior temporal lobectomy or selective amygdalo-hippocampectomy. The sentences represented lexical and syntactic ambiguities. In both left- and right-sided groups, regardless of type of surgery, total mean score on the test was below normal. Left-sided cases, regardless of type of surgery, provided significantly fewer alternative interpretations than right-sided cases. The results suggest greater left than right hemisphere specialization in both lexical and syntactic processing, but also suggest right hemisphere involvement in resolution of lexical ambiguity.     

Depression in aphasic patients: Frequency, severity, and clinical-pathological correlations

Twenty-five hospitalized nonfluent, fluent, and global aphasic patients who were several months past the onset of their illness were compared for presence and severity of depression based on four psychopathological measures. The nonfluent aphasic patients had both greater frequency and severity of depression than the other two groups. CT scans showed that the global aphasic patients had the largest lesion size (volumetric) and showed a strong correlation between lesion size and degree of depression. In contrast, patients with fluent aphasias showed an inverse correlation between severity of depression and lesion size; among the nonfluent aphasic patients there was no significant correlation. Depression appears to be common in this population of hospitalized aphasic patients with chronic illness and nonfluent patients are the most depressed group within this population. The increased frequency and severity of depression in the nonfluent patients did not appear to be related to their overall physical or cognitive impairment; two possible mechanisms are discussed.     

Contextual influences on phonetic identification in aphasia: the effects of speaking rate and semantic bias

Two experiments examined the influence of context on stop-consonant voicing identification in fluent and nonfluent aphasic patients and normal controls. Listeners were required to label the initial stop in a target word varying along a voice onset time (VOT) continuum as either voiced or voiceless ([b]/[p] or [d]/[t]). Target stimuli were presented in sentence contexts in which the rate of speech of the sentence context (Experiment 1) or the semantic bias of the context (Experiment 2) was manipulated. The results revealed that all subject groups were sensitive to the contextual influences, although the extent of the context effects varied somewhat across groups and across experiments. In addition, a number of patients in both the fluent and nonfluent aphasic groups could not consistently identify even endpoint stimuli, confirming phonetic categorization impairments previously shown in such individuals. Results are discussed with respect to the potential reliance by aphasic patients on higher level context to compensate for phonetic perception deficits.     

The quantitative analysis of agrammatic production: procedure and data

Despite the long-standing interest in structural aspects of aphasic production, no method has emerged for the systematic analysis of aphasic speech. This paper attempts to address that need by outlining a procedure for the quantitative assessment of narrative speech which yields measures for both morphological and structural characteristics of aphasic production. In addition to complete instructions for carrying out this analysis, data for three groups of subjects are presented: agrammatic aphasics, aphasics who are similarly nonfluent but not clinically judged as agrammatic, and normal controls. While the agrammatics were distinguishable from the nonagrammatic patients on most measures, both nonfluent groups showed comparable reductions in the structural complexity of their propositional utterances. Other findings include indications from individual patient data that aspects of grammatical morphology may dissociate in agrammatism.     

The conceptual structure of aphasic and schizophrenic patients in a nonverbal sorting task

Hierarchical and overlapping cluster methods were applied to the sortings of aphasic, nonaphasic brain-damaged, schizophrenic, and normal subjects presented with 30 pictures of animals. The hierarchical structure solutions were most diffuse for the groups of the schizophrenics and the fluent aphasics. The structure for the nonfluent aphasics showed more clarity, but was also deviant from the structures of the normals and the brain-damaged without aphasia. Fluent aphasics but not nonfluent aphasics tended to sort pictures which they could not name into smaller groups. For the nonfluent aphasics, there was a significant correlation between the commonality of the sortings and the severity of aphasic disturbances as measured by the Token Test. The relationship between conceptual disorganization and language impairment seems to be functionally different for fluent and nonfluent aphasics.This research was supported by a research grant from the Deutsche Forschungsgemeinschaft.     

Comparison for aphasic and control subjects of eye movements hypothesized in neurolinguistic programming

Neurolinguistic programming's hypothesized eye movements were measured independently using videotapes of 10 nonfluent aphasic and 10 control subjects matched for age and sex. Chi-squared analysis indicated that eye-position responses were significantly different for the groups. Although earlier research has not supported the hypothesized eye positions for normal subjects, the present findings support the contention that eye-position responses may differ between neurologically normal and aphasic individuals.     

Developmental changes in units of processing in reading

A visual search task was used to investigate the development of word processing skills used in reading meaningful prose. Children from the second and fourth grades and college students were asked to locate a prespecified letter, syllable, word, or category exemplar as they read through sentences. Target detection time, sentence reading time, and sentence comprehension were measured. The results provide converging evidence that whole words were the preferred units of processing during reading for all three grade levels. Reading rates for sentences in the word search condition were comparable to normal reading rates. The search for smaller units required additional processing time, but word and category search times differed only for the youngest subjects.     

Auditory feedback control in adults who stutter during metronome-paced speech I. Timing Perturbation

PurposeThis study determined whether adults who stutter (AWS) exhibit deficits in responding to an auditory feedback timing perturbation, and whether external timing cues, which increase fluency, attenuate any disruptions due to altered temporal auditory feedback.MethodsFifteen AWS and sixteen adults who do not stutter (ANS) read aloud a multisyllabic sentence either with normal pacing or with each syllable paced at the rate of a metronome. On random trials, an auditory feedback timing perturbation was applied, and timing responses were compared between groups and pacing conditions.ResultsBoth groups responded to the timing perturbation by delaying subsequent syllable boundaries, and there were no significant differences between groups in either pacing condition. Furthermore, no response differences were found between normally paced and metronome-paced conditions.ConclusionThese findings are interpreted as showing that 1) AWS respond normally to pure timing perturbations, and 2) metronome-paced speech has no effect on online speech timing control as assessed in the present experiment.     

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 na?ve 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.