Semantic classification in aphasia: A study of basic, superordinate, and function relations

Nonfluent and fluent aphasics were given classification tasks that required the aphasics to identify three kinds of relations: same basic level category, same superordinate level category, and same function. The subjects received the items in word and picture form. In addition the aphasics were required to name the items they were asked to classify. The results showed that the ability to classify is more disrupted in fluent aphasia than in nonfluent aphasia. Within fluent aphasia, the degree to which classification is disrupted is dependent upon the type of relation being tested. While the overall performance of the fluent aphasics was depressed in comparison to nonfluent aphasics, it was significantly more depressed on function relations. The ability to name an item had a significant effect on the ability to classify only for basic level items.     

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.     

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.     

Nonverbal categorization in fluent and nonfluent anomic aphasics

This study aimed to demonstrate that the naming difficulties of a particular group of aphasics, namely, fluent aphasics, are related to an underlying inability to organize feature set information. In order to test this hypothesis, the performance of fluent aphasics, nonfluent aphasics, and a nonaphasic brain-injured control group, was examined on a nonverbal categorization task, which was carefully structured in terms of instance typicality. Scores of visuoperceptual and naming tests were correlated with categorization task errors. As predicted, fluent aphasics showed a significant deficit in performance on the categorization task in comparison with other subjects. Differences in the nature of the errors the fluent aphasics made suggested that their problems were related to difficulties in abstracting the prototype for each category and in sorting category members with reference to these prototypes. For fluent aphasics, but not other subjects, a significant correlation was found between categorization task performance and naming ability.     

Linguistic and nonlinguistic priming in aphasia

Studies of real-time processing in aphasia suggest that linguistic symptoms may be due to deficits in activation dynamics rather than loss of linguistic knowledge. To investigate the domain specificity of such processing deficits, we compared performance by Italian-speaking fluent aphasics, nonfluent aphasics, and normal controls in a linguistic priming task (grammatical gender) with their performance in a color-priming task that requires no verbal mediation. Normal or larger than normal color-priming effects were demonstrated in both aphasic groups. Gender priming did not reach significance in either group, even though the patients displayed above-chance sensitivity to gender class and gender agreement in their accuracy scores. The demonstration of spared gender knowledge despite impaired gender priming underscores the utility of on-line techniques in the study of aphasia. The demonstration of spared color priming suggests that priming deficits in aphasia are either (1) specific to speech and language or (2) specific only to those sensorimotor and attentional processes that language shares with other nonlinguistic systems.     

Speech-related body movement in aphasia: period analysis of upper arms and head movement.

The effects of aphasia on coverbal body movement have important implications for the understanding of both normal and pathological speech processes. The related findings were often inconsistent, partly due to inherent methodological difficulties which could be reduced by the use of advanced techniques of movement monitoring (Hadar, 1991). The present study employed a new computerized system, CODA-3, which locates small prismatic markers and computes by triangulation their three-dimensional position at 100 Hz. Movement of the head and the upper arms was monitored in 15 aphasic and normal subjects engaged in speech during a naturalistic interview. Movement analysis was based on automatized identification of successive movement extrema ("period analysis") and the computation of amplitude, duration, and velocity of each period. The results showed higher incidence and amplitude of all body movement in the aphasic population. Fluent aphasics showed this particularly with "symbolic," content-bearing movements, while nonfluent aphasics were higher than controls in both symbolic and "motor" (simple and small) movements. No deficit in the internal organization of movement was seen in the aphasic population. These results indicate that aphasics increase their coverbal movement in compensation for their speech impairment: fluent aphasics compensate primarily for a symbolic impairment, while nonfluent aphasics compensate more for a motor impairment.     

Inference revision processing in adults with and without aphasia

Processing abilities in aphasia, and the nature of processing breakdowns, were the focuses of this investigation. Individuals with either fluent or nonfluent aphasia, plus a control group, participated in a cross-modal lexical priming task designed to elicit priming effects when activation of inference interpretations occurred. Comprehension of inferences was measured by responses to four types of questions that related to the inferences. Results indicated that both the control group, as well as the nonfluent aphasia group, activated the intended meaning of the stimuli whereas the fluent aphasics did not. Comprehension of the inferences was best demonstrated by control participants, nonfluent aphasic participants, and fluent aphasic participants, in that order.     

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.     

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.     

Temporal clause comprehension in fluent and nonfluent aphasics

Ten fluent and ten nonfluent aphasics participated in this study. Their ability to comprehend before and after clauses which mirrored the order of occurrence and those which did not mirror the order of events was investigated. Results indicate that type of aphasia was not a significant variable related to comprehension but that sentence type was a significant variable. Aphasics' comprehendbefore clauses better thanafter clauses. Nonfluent aphasics were able to comprehend those temporal clauses that mirror the order of occurrence better than those that do not. Order of mention was not a significant factor related to comprehension in the fluent group.     

Dichotic listening in the recovery of aphasia after stroke

Three different dichotic listening tests were given to a group of aphasic patients at various stages of the recovery process. Results were different for each test and in the course of time fluent aphasics demonstrated a tendency to increase right ear preference while nonfluent aphasics showed an increase of left ear preference in the test of dichotic words. The importance of these findings to the understanding of recovery of function is discussed in terms of the role played by the right hemisphere.     

Comparison of the performances of a fluent and a nonfluent aphasic on a pantomimic referential task

The pantomimic performances of a typical Broca's (nonfluent) and Wernicke's (fluent) aphasic were compared with each other and with four normal control subjects on a simple task of nonverbal referential communication. Both aphasic subjects demonstrated only about 50% accuracy in their pantomimic communication. Also, measures were obtained of the motoric fluency of the pantomimes of all subjects and comparisons were made between the fluent and nonfluent aphasics. These measures demonstrated distinct differences in the fluency patterns of the pantomimes of the two aphasic subjects similar to the differences in speech fluency which distinguish and characterize these two types of aphasia; that is, the fluent aphasic pantomimed fluently and like the control subjects and the nonfluent aphasic pantomimed nonfluently. The quantitative and qualitative similarities in the fluency patterns of the speech and the pantomimic behaviors of the aphasic subjects are discussed in terms of their implications for a definition of aphasia.     

Anatomoclinical correlations of the aphasias as defined through computerized tomography: Exceptions

We have studied the frequency of exceptions to classical aphasia localizations in right-handed, literate, adult, native speakers of Italian with focal vascular left-hemisphere lesions, correlating clinical and computerized tomography data. Two hundred sixty-seven subjects were given computerized tomography (CT) examinations; lesions were mapped onto lateral diagrams and the sites of the lesions were defined. Patients were then classified as nonfluent aphasics, fluent aphasics, and nonaphasics. Patients with negative CT scans (n = 10) or only "deep" lesions (n = 50) were not studied for anatomoclinical correlations. Of the remaining 207 patients, 36 presented unexpected findings. There were seven cases of fluent aphasia and "anterior" CT lesions and six cases with nonfluent aphasia and "posterior" CT lesions among them. The significance of these findings is discussed.     

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.     

The neurological substrates for prosodic aspects of speech

The ability to comprehend and produce the stress contrast between noun compounds and noun phrases (e.g., greenhouse vs. green house) was examined for 8 nonfluent aphasics, 7 fluent aphasics, 7 right hemisphere damaged (RHD) patients, and 22 normal controls. The aphasics performed worse than normal controls on the comprehension task, and the RHD group performed as well as normals. The ability to produce stress contrasts was tested with a sentence-reading task; acoustic measurements revealed that no nonfluent aphasic used pitch to distinguish noun compounds from phrases, but two used duration. All but one of the RHD patients and all but one of the normals produced pitch and/or duration cues. These results suggest that linguistic prosody is processed by the left hemisphere and that with brain damage the ability to produce pitch and duration cues may be dissociated at the lexical level.     

Accessibility of case and gender contrasts for agent--object assignment in Broca's aphasics and fluent anomics

Yugoslav agrammatic Broca's aphasics, fluent anomics, and control subjects were tested for comprehension of agent-object relations in a series of simple Serbo-Croatian sentences in the conversational past tense, consisting of two nouns and a transitive action verb. The availability of two closed class cues--case contrasts and gender contrasts--as well as the availability of an open class lexical cue--animacy contrasts--was varied across sentences. An analysis of subjects' agent-object assignments yielded the following results: Both Broca's aphasics and fluent anomics showed a selective impairment in sensitivity to closed class morphology, although anomics were considerably less impaired than Broca's aphasics. This finding was interpreted as evidence for a non-syndrome-dependent vulnerability of abilities to process closed class morphology for comprehension. In addition, the pattern of agent-object assignments for Broca's aphasics revealed that the degree to which they were able to access the two closed class cues depended on a convergence of the various cues to agent-object relations. In particular, a convergence of case and gender contrasts had an interactive effect on Broca's responses: Gender agreement cues were accessed only in the presence of convergent case contrasts. Conversely, sensitivity to case contrasts was dramatically heightened in the presence of convergent gender contrasts. These results were consistent with a view that the two cues function as intrasentential "primes" or "retrieval cues" for one another.     

A bird is a bird is a bird: Making reference within and without superordinate categories

Adults with localized cerebral insult often err in their use of a word to refer to an object or an idea. It is important to assess, then, the patients' appreciation of what a word can refer to, and the way in which they may violate the borders around a referential field. Nonfluent aphasics, fluent aphasics, and nonaphasic patients with insult to the right hemisphere were asked to provide names of items which could be referred to by familiar superordinate terms like “bird.” The principal results revealed that the nonfluent aphasics are anchored to the central portions of a superordinate's referential field (naming items like “robin” and “sparrow,” for instance). While fluent aphasics often violate the borders around a referential field (e.g., providing “beaver” in response to “birds”), it was nevertheless possible to characterize some limits to their choice of a superordinate's referents. These findings were independent both of the absolute number of responses provided and the frequency of occurrence of the response. Further, the patients with insult to the left hemisphere produce few consecutive items whose referents hold attributes in common. When these clusters are produced by aphasics, they consist primarily of subordinates whose referents exhibit many overlapping features (e.g., “bald eagle, black eagle, golden eagle” in response to “bird”). The right-hemisphere-damaged subjects, in contrast, produce many clusters of related items. These consist of less central, basic object level words whose referents hold less obvious features in common (e.g., “albatross, crane, gull” in response to “bird”). Aphasics, then, may be limited in their ability to analyze referents for critical features. Taken together, these data contribute to a more precise characterization of the nonfluent aphasics' and the fluent aphasics' referential deficits, and lend support specifically to the notion that neither group of aphasics relies on definition-like features to determine what a word can refer to.     

Selective word-learning deficits in aphasia

The purpose of this study was to determine whether patients with focal brain damage can learn anything about a new word, and if so, whether selected aspects of the new word are acquired depending on the nature of the patient's language processing deficit. In the context of drawing pictures with a number of felt pens identical in all respects except color, agrammatic Broca's aphasics and fluent aphasics were exposed to the new word "bice," an adjective referring to the dark green portion of the color spectrum. Our findings revealed that brain-damaged patients can engage in lexical acquisition, but Broca's aphasics and fluent aphasics apparently learn about different aspects of the new word. Specifically, on successive exposures to "bice," both Broca's aphasics and fluent aphasics exhibit progressively more accurate hypotheses for identifying a bice-colored object. During subsequent assessments, agrammatic aphasics reveal on a metalinguistic judgment task their significant difficulty appreciating the grammatical form class of "bice"; on an object classification task, fluent aphasics are significantly impaired in their classification of bice-colored objects as "bice." Taken together, these unique word-learning profiles reinforce earlier observation on the selective nature of language processing deficits after focal left-hemisphere insult, and support the claim that separate language processing devices may be selectively compromised in different groups of aphasics. The relationship between syntactic and lexical semantic processing is discussed.     

Temporal dimensions of consonant and vowel production: an acoustic and CT scan analysis of aphasic speech

This study explored a number of temporal (durational) parameters of consonant and vowel production in order to determine whether the speech production impairments of aphasics are the result of the same or different underlying mechanisms and in particular whether they implicate deficits that are primarily phonetic or phonological in nature. Detailed analyses of CT scan lesion data were also conducted to explore whether more specific neuroanatomical correlations could be made with speech production deficits. A series of acoustic analyses were conducted including voice-onset time, intrinsic and contrastive fricative duration, and intrinsic and contrastive vowel duration as produced by Broca's aphasics with anterior lesions (A patients), nonfluent aphasics with anterior and posterior lesions (AP patients), and fluent aphasics with posterior lesions (P patients). The constellation of impairments for the anterior aphasics including both the A and AP patients suggests that their disorder primarily reflects an inability to implement particular types of articulatory gestures or articulatory parameters rather than an inability to implement particular phonetic features. They display impairments in the implementation of laryngeal gestures for both consonant and vowel production. These patterns seem to relate to particular anatomical sites involving Broca's area, the anterior limb of the internal capsule, and the lowest motor cortex areas for larynx and tongue. The posterior patients also show evidence of subtle phonetic impairments suggesting that the neural instantiation of speech may require more extensive involvement, including the perisylvian area, than previously suggested.     

Speech timing subsequent to brain damage: effects of utterance length and complexity

Acoustic analyses of syllable durations were conducted in order to address several hypotheses concerning deficits in the control of speech timing subsequent to focal brain damage. Groups of nonfluent and fluent aphasics, right-hemisphere-damaged patients, and normal controls produced monosyllabic root syllables in medial and final position in the context of short and long sentences and syntactically simple and complex sentences. Durations of the target syllable as a proportion of the utterance were compared across contexts and groups. Somewhat surprisingly, the results revealed relatively normal temporal patterns in all subject groups, with the main exception emerging for the nonfluent aphasic patients who failed to demonstrate normal phrase-final lengthening effects. Implications of the findings for theories of temporal control in brain-damaged patients are considered.