Electrophysiological manifestations of open- and closed-class words in patients with Broca's aphasia with agrammatic comprehension. An event-related brain potential study.
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This paper presents electrophysiological data on the on-line processing of open- and closed-class words in patients with Broca's aphasia with agrammatic comprehension. Event-related brain potentials were recorded from the scalp when Broca patients and non-aphasic control subjects were visually presented with a story in which the words appeared one at a time on the screen. Separate waveforms were computed for open- and closed-class words. The non-aphasic control subjects showed clear differences between the processing of open- and closed-class words in an early (210-375 ms) and a late (400-700 ms) time-window. The early electrophysiological differences reflect the first manifestation of the availability of word-category information from the mental lexicon. The late differences presumably relate to post-lexical semantic and syntactic processing. In contrast to the control subjects, the Broca patients showed no early vocabulary class effect and only a limited late effect. The results suggest that an important factor in the agrammatic comprehension deficit of Broca's aphasics is a delayed and/or incomplete availability of word-class information. (+info)
Cross-modal generalization effects of training noncanonical sentence comprehension and production in agrammatic aphasia.
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The cross-modal generalization effects of training complex sentence comprehension and complex sentence production were examined in 4 individuals with agrammatic Broca's aphasia who showed difficulty comprehending and producing complex, noncanonical sentences. Object-cleft and passive sentences were selected for treatment because the two are linguistically distinct, relying on wh-and NP movement, respectively (Chomsky, 1986). Two participants received comprehension training, and 2 received production training using linguistic specific treatment (LST). LST takes participants through a series of steps that emphasize the verb and verb argument structure, as well as the linguistic movement required to derive target sentences. A single-subject multiple-baseline design across behaviors was used to measure acquisition and generalization within and across sentence types, as well as cross-modal generalization (i.e., from comprehension to production and vice versa) and generalization to discourse. Results indicated that both treatment methods were effective for training comprehension and production of target sentences and that comprehension treatment resulted in generalization to spoken and written sentence production. Sentence production treatment generalized to written sentence production only; generalization to comprehension did not occur. Across sentence types generalization also did not occur, as predicted, and the effects of treatment on discourse were inconsistent across participants. These data are discussed with regard to models of normal sentence comprehension and production. (+info)
Vascular aphasias: main characteristics of patients hospitalized in acute stroke units.
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BACKGROUND AND PURPOSE: Aphasia is frequent in stroke patients and is associated with poor prognosis. However, characteristics and determinants of vascular aphasias remain controversial. The aim of this study was to evaluate aphasia characteristics at the acute stage in patients admitted to a stroke unit. METHODS: The study was performed in 308 patients consecutively assessed with a standardized aphasia battery. RESULTS: Aphasia was observed in 207 patients; global and nonclassified aphasias accounted for 50% of aphasic syndromes at the acute stage, whereas classic aphasias (Wernicke's, Broca's, transcortical, and subcortical aphasias) were less frequent. Age differed across aphasic syndromes in ischemic stroke patients only; patients with conduction aphasia were younger, and patients with subcortical aphasia were older. Sex did not significantly differ across aphasic syndromes. The presence of a previous stroke was more frequent in nonclassified aphasia. CONCLUSIONS: This study shows (1) that vascular aphasias are frequently severe or nonclassic at the acute stage, a finding explained in part by the presence of a previous stroke; (2) that the age effect is due mainly to its influence on infarct location; and (3) that the main determinant of aphasia characteristics is lesion location. (+info)
West Nile virus meningoencephalitis complicated by motor aphasia in Hodgkin's lymphoma.
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A 4 year old boy with Hodgkin's lymphoma was admitted to the paediatric ward with meningoencephalitis dominated by generalised seizures and motor aphasia. Serum IgM specific antibodies to West Nile virus were positive. In view of ongoing neurological deterioration and immunocompromised state he was treated with oral ribavirin for 14 days. A gradual improvement was noted within two weeks of therapy initiation, and with intensive supportive care he recovered completely after four months. (+info)
Postictal mixed transcortical aphasia.
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Postictal aphasia has been described in left temporal lobe seizures. It may be of fluent, non-fluent or global type. We present here a patient who displayed signs of mixed transcortical aphasia (MTCA). The patient was a 67 year old man who underwent excision of a left frontal parasagittal meningioma in 1987. Since then he has been treated with phenytoin for generalized tonic-clonic seizures (GTCS). He was admitted in status epilepticus. On awakening, the patient was non-fluent with palilalia and echolalia. His repetition was relatively preserved but all the other language functions were impaired. This picture faded away within a few hours. Brain CT, performed during this postictal state, was normal except for signs related to frontal craniotomy. SPECT, which was performed after language functions returned to normal, displayed left frontal, cingular and insular hypoperfusion. The postictal language dysfunction of the patient corresponded to MTCA. Although our case has frontal, he had no other structural lesion that could explain either diffuse ischemia of the left hemisphere or watershed areas secondary to the generalized seizures. The uniqueness of this case is the combination of postictal MTCA with good prognosis. (+info)
Speech production: Wernicke, Broca and beyond.
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We investigated the brain systems engaged during propositional speech (PrSp) and two forms of non- propositional speech (NPrSp): counting and reciting overlearned nursery rhymes. Bilateral cerebral and cerebellar regions were involved in the motor act of articulation, irrespective of the type of speech. Three additional, left-lateralized regions, adjacent to the Sylvian sulcus, were activated in common: the most posterior part of the supratemporal plane, the lateral part of the pars opercularis in the posterior inferior frontal gyrus and the anterior insula. Therefore, both NPrSp and PrSp were dependent on the same discrete subregions of the anatomically ill-defined areas of Wernicke and Broca. PrSp was also dependent on a predominantly left-lateralized neural system distributed between multi-modal and amodal regions in posterior inferior parietal, anterolateral and medial temporal and medial prefrontal cortex. The lateral prefrontal and paracingulate cortical activity observed in previous studies of cued word retrieval was not seen with either NPrSp or PrSp, demonstrating that normal brain- language representations cannot be inferred from explicit metalinguistic tasks. The evidence from this study indicates that normal communicative speech is dependent on a number of left hemisphere regions remote from the classic language areas of Wernicke and Broca. Destruction or disconnection of discrete left extrasylvian and perisylvian cortical regions, rather than the total extent of damage to perisylvian cortex, will account for the qualitative and quantitative differences in the impaired speech production observed in aphasic stroke patients. (+info)
Selective priming of syntactic processing by event-related transcranial magnetic stimulation of Broca's area.
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It remains controversial whether Broca's aphasia is an articulatory deficit, a lexical-access problem, or agrammatism. In spite of recent neuroimaging studies, the causal link between cortical activity and linguistic subcomponents has not been elucidated. Here we report an experiment with event-related transcranial magnetic stimulation (TMS) to clarify the role of Broca's area, more specifically, the left inferior frontal gyrus (F3op/F3t), in syntactic processing. An experimental paradigm contrasted sentences requiring syntactic decisions with those requiring semantic decisions. We found selective priming effects on syntactic decisions when TMS was administered to the left F3op/F3t at a specific timing, but not to the left middle frontal gyrus (F2). Our results provide direct evidence of the involvement of the left F3op/F3t in syntactic processing. (+info)
Word retrieval learning modulates right frontal cortex in patients with left frontal damage.
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Previous studies have suggested that recovery or compensation of language function after a lesion in the left hemisphere may depend on mechanisms in the right hemisphere. However, a direct relationship between performance and right hemisphere activity has not been established. Here, we show that patients with left frontal lesions and partially recovered aphasia learn, at a normal rate, a novel word retrieval task that requires the damaged cortex. Verbal learning is accompanied by specific response decrements in right frontal and right occipital cortex, strongly supporting the compensatory role of the right hemisphere. Furthermore, responses in left occipital cortex are abnormal and not modulated by practice. These findings indicate that frontal cortex is a source of top-down signals during learning. (+info)