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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.

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.

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.

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.

Studies aimed at characterizing the operation of cognitive functions in normal individuals have examined data from patients with focal cerebral insult. These studies assume that brain damage impairs functions of the cognitive processes along lines that honour the 'normal' pre-morbid organization of the cognitive system. For example, detailed study of individual brain-damaged patients has revealed apparently selective disruption of cognitive functions such as auditory/verbal working memory, phonological processing ability, grapheme-to-phoneme translation procedures and semantic processing. Warrington et al. have studied patients with even more fine-grained selective disturbances of the semantic system. The most selective deficits have been reported for four patients who were significantly better at identifying inanimate objects than they were at identifying living things and foods. These patterns of selective deficit after localized brain damage provide important information about the normal organization of the lexicon, and ultimately about how components of the lexical system are related to particular neural substrates. Here, we report a case study of a patient demonstrating a very selective disturbance of the ability to name items from two related semantic categories. Despite normal performance on a large battery of lexical/semantic tasks, the patient shows a consistent and striking disability in naming members of the semantic categories of 'fruits' and 'vegetables'. The selectivity of this deficit supports a category-specific organization of the mental lexicon, and suggests independence of the processing routes involving naming and name recognition.

Using heuristically guided state space search, a prototype program has been developed to simulate and classify phonemic errors occurring in the speech of neurologically impaired patients. Simulations are based on an interchangeable rule/operator set of elementary errors which represent a theory of phonemic processing faults. This work is significant because it introduces and evaluates a novel approach to error simulation and classification, provides a prototype simulation tool for neurolinguistic research, and forms the initial phase of a larger research effort involving computer modelling of neurolinguistic processes.

A case study is reported of an aphasic patient with fluent speech and markedly superior comprehension of written vs. spoken words. Results of extensive testing supported the hypothesis that the patient suffers from a phonological processing deficit that affects performance in all tasks that require the generation of a phonological code. This selective deficit is interpreted as the underlying cause of diverse symptoms such as asyntactic comprehension of written sentences, the commission of spelling errors in writing, and the production of literal paraphasias and neologisms in spontaneous speech. Alternative possibilities for the classification of this patient are discussed.

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.

Four aphasic patients were tested in several tasks to determine their ability to use syntactic information. Two patients classified as Broca's aphasics and presenting markedly different levels of severity of aphasia were deficient in their ability to use syntactic information in sentence comprehension and construction. It is argued that the syndrome of Broca's aphasia undermines patients' ability to perform the syntactic analyses that are necessary to understand and to produce sentences in both language modalities. A third patient was a conduction aphasic who presented a pattern of sentence comprehension similar to the Broca patient, but produced no other evidence of syntactic impairment. The argument is advanced that the conduction patient's apparently selective impairment of syntactic processing in comprehension is actually a reflection of a severe auditory-verbal short-term memory deficit. The fourth patient was classified as a mildly-impaired Wernicke's aphasic, who presented no evidence of a selective disturbance of syntactic processing abilities. These results are interpreted as support for the hypothesis that the syndrome of Broca's aphasia results from an impairment to the syntactic component of the language processing system.

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.