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C C Mitchum

Publications and source records attributed to C C Mitchum.

9 recordsLinked to original sources
PubMed1997

Patterns of sentence comprehension in aphasia: a consideration of three hypotheses.

Three hypotheses concerning the functional source of aphasic patients' difficulty comprehending semantically reversible sentences were tested using declarative sentences in active and passive voice and sentences with center-embedded relative clauses. Each of the three hypotheses is predicated on relative patterns of impairment and sparing of patient performance on these (and other) sentence types, yet the three hypotheses make somewhat different predictions about performance patterns across these types. Results from 5 Broca's aphasic patients were not consistent with the predictions of the linguistically motivated Trace Deletion Hypothesis or of a hypothesis based on an impairment involving grammatical morphemes. The hypothesis that aphasic comprehension impairments reflect a general limitation of working memory capacity was given partial support by the ordinal pattern of difficulty for a mixed group of 10 patients, but failed to account for patterns obtained from individual patients. Results are interpreted as having relevance for methodological as well as theoretical aspects of research on aphasic sentence comprehension.

Adult↗
PubMed1997

Verb retrieval in aphasia. 1. Characterizing single word impairments.

The ability of aphasic patients to produce words from the grammatical classes of nouns and verbs was investigated in tasks that elicited these types of words in isolation. Eleven chronic aphasic patients produced nouns and verbs in picture naming, videotaped scene naming, sentence completion, naming from definition, and oral reading. Comprehension of the meanings of nouns and verbs was tested in word/picture and word/video scene matching, and appreciation of noun/verb grammatical class differences was tested with two metalinguistic tasks. Five patients demonstrated significantly more difficulty producing verbs than nouns, two patients were significantly more impaired producing nouns than verbs, and the remaining four patients showed no difference between the two classes. There was no improvement in verb production when naming actions presented on videotape, suggesting that selective verb impairments are not attributable to conceptual difficulty in identifying actions in static pictures. Selective noun impairments occurred in the context of severe anomia, as reported in previous studies. Selective verb impairments were demonstrated for both agrammatic and fluent (Wernicke) patients, indicating that such deficits are not necessarily associated with the nonfluent and morphologically impoverished production that is characteristic of agrammatism. There was no indication that single word comprehension was affected in these patients in a manner consonant with their production impairments. Results are interpreted in light of current models of lexical organization and processing.

Adult↗
PubMed1997

Verb retrieval in aphasia. 2. Relationship to sentence processing.

Sentence comprehension and production were evaluated for 10 chronic aphasic patients who have been shown to demonstrate one of three patterns in the relative case of retrieval of nouns and verbs. Although these patterns of noun/verb production were not entirely predictable from patients' clinical classifications, they were found here to be significantly correlated with several structural indices of sentence production and with failure to comprehend semantically reversible sentences. Noun/ verb retrieval patterns were not strongly correlated with speech fluency nor with morphological characteristics of sentence production. Patients with relative impairment in the production of verbs were found to rely on high frequency, semantically empty, "light" verbs when producing sentences and to favor simple syntactic structures in which verbs do not require inflections. When forced to produce substantive verbs (in picture and scene descriptions), verb retrieval continued to undermine the production of well-formed sentences for the verb-impaired patients. In addition, two of five such patients also showed some evidence of poor realization of noun arguments for verbs they could not produce. Results are interpreted as indicating multiple contribution to patients' sentence processing impairments, one of which may be selective difficulty retrieving verbs.

Adult↗
PubMed1997

Lexical-semantic organization: evidence from aphasia.

The emerging field of clinical neuroscience requires the combination of diverse theoretical and methodological approaches to the study of brain function. The study of neurogenic language disorders has played a central role in the development of models of language/brain relationships. These contributions are reviewed with regard to the study of word processing impairments in aphasia, where data from brain-damaged patients has been used to guide the development of models of lexical/semantic organization. It is argued that the study of aphasic patients will continue to occupy a central role in both neuroscience and clinical research as new technologies are developed for functional brain imaging and as theoretically driven treatments for aphasia are designed and tested.

Aphasia↗
PubMed1996

Assessing the elements contributing to a "mapping" deficit: a targeted treatment study.

Aphasic patients with excellent comprehension of word meanings frequently fail to understand simple declarative sentences in which either of two nouns could reasonably serve as agent of a transitive action. This study employed targeted treatment of this comprehension problem in a chronic aphasic patient (E.A.) in an attempt to isolate the source or sources of his comprehension failure. Treatment exercises that relied on error feedback in sentence-picture matching or verification initially were not effective. Comprehension of active and passive sentences improved only after both structures were explicitly compared and linked to a picture. Subsequently E.A. maintained consistently accurate interpretation of both sentence types in the treatment exercises as long as the full sentence was available to him. E.A. learned to assign thematic roles using a limited set of cues in the surface structure. Although improvement was reported in untreated sentences, the degree of generalization and the level of performance differed across tasks and appeared to be attributable to cognitive impairments that were not addressed by the treatment. Results are interpreted as evidence suggesting that multiple impairments contribute to failure of sentence comprehension tasks.

Aphasia↗
PubMed1996

Comprehension of reversible sentences in "agrammatism": a meta-analysis.

The functional source(s) of agrammatic aphasic patients' difficulty comprehending semantically reversible active and passive sentences was investigated in a meta-analysis of published sentence/picture matching data from patients with agrammatic production. The analysis revealed approximately equal distributions of three distinct patterns of performance on active and passive voice sentences relative to what would be expected by chance: both structures comprehended better than chance; both structures comprehended no better than chance; active voice sentences comprehended better than chance, while passive voice sentences were comprehended at levels no better than (or worse than) chance. These results are in conflict with explanations of aphasic sentence comprehension failure in which a single pattern of relative performance on active and passive voice structures is asserted to be characteristic of the comprehension of all agrammatic speakers. They also highlight the difficulty of identifying any single causal factor to account for sentence comprehension failure in patients with "agrammatic" sentence production. Results are interpreted with regard to the role of data from aphasic patients in the testing of hypotheses about the organization of normal language processes.

Aphasia, Broca↗
PubMed1991

Short-term memory and sentence comprehension. An investigation of a patient with crossed aphasia.

The relationship between short-term memory impairment and sentence comprehension is explored in a right-handed patient with a focal temporoparietal lesion of the right hemisphere. The general clinical profile, as well as characteristics of the patient's immediate memory for word lists, suggests the occurrence of a 'mirror image' crossed aphasia. Detailed analysis of the patient's ability to repeat and to comprehend sentences, however, indicates some important differences between this case and previously reported patients with short-term memory impairment. It is suggested that these differences, which may be related to an unusual pattern of neuroanatomical organization of cognitive functions, involve symptom dissociations with implications for models of normal language/memory interactions.

Brain↗
PubMed1988

The role of intonation cues in aphasic patients' performance of the grammaticality judgment task.

This study investigated the possibility that the reported success of agrammatic aphasic patients in performing auditory grammaticality judgments results from their use of intonational cues to sentence well-formedness. Two agrammatic aphasics, two anomic aphasics, and two nonagrammatic patients with comprehension deficits for semantically reversible sentences were asked to judge grammatical well-formedness in three conditions. Results in a "natural" listening condition replicated the finding of M.C. Linebarger, M.F. Schwartz, and E. M. Saffran (1983, Cognition, 13, 361-392) that agrammatic patients are sensitive to grammaticality despite poor ability to use syntatic cues in comprehension tasks. Two additional listening conditions employed signal-processed auditory stimuli in which the fundamental frequency was normal or was set at a constant level. Right-hemisphere-damaged and normal controls showed no performance deficit for judgments of monotone sentences. The aphasic patients' performance was slightly worse for both signal-processed conditions, but there was little apparent effect of removing sentence intonation on their ability to judge sentence grammaticality. These results indicate that the high levels of performance on grammaticality judgement tasks have not resulted from patients' detection of intonational cues in ungrammatical sentences.

Adult↗