Language dominance in neurologically normal and epilepsy subjects: a functional MRI study.
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Language dominance and factors that influence language lateralization were investigated in right-handed, neurologically normal subjects (n = 100) and right-handed epilepsy patients (n = 50) using functional MRI. Increases in blood oxygenation-dependent signal during a semantic language activation task relative to a non-linguistic, auditory discrimination task provided an index of language system lateralization. As expected, the majority of both groups showed left hemisphere dominance, although a continuum of activation asymmetry was evident, with nearly all subjects showing some degree of right hemisphere activation. Using a categorical dominance classification, 94% of the normal subjects were considered left hemisphere dominant and 6% had bilateral, roughly symmetric language representation. None of the normal subjects had rightward dominance. There was greater variability of language dominance in the epilepsy group, with 78% showing left hemisphere dominance, 16% showing a symmetric pattern and 6% showing right hemisphere dominance. Atypical language dominance in the epilepsy group was associated with an earlier age of brain injury and with weaker right hand dominance. Language lateralization in the normal group was weakly related to age, but was not significantly related to sex, education, task performance or familial left-handedness. (+info)
Cortical language activation in stroke patients recovering from aphasia with functional MRI.
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BACKGROUND AND PURPOSE: Two mechanisms for recovery from aphasia, repair of damaged language networks and activation of compensatory areas, have been proposed. In this study, we investigated whether both mechanisms or one instead of the other take place in the brain of recovered aphasic patients. METHODS: Using blood oxygenation level-dependent functional MRI (fMRI), we studied cortical language networks during lexical-semantic processing tasks in 7 right-handed aphasic patients at least 5 months after the onset of left-hemisphere stroke and had regained substantial language functions since then. RESULTS: We found that in the recovered aphasic patient group, functional language activity significantly increased in the right hemisphere and nonsignificantly decreased in the left hemisphere compared with that in the normal group. Bilateral language networks resulted from partial restitution of damaged functions in the left hemisphere and activation of compensated (or recruited) areas in the right hemisphere. Failure to restore any language function in the left hemisphere led to predominantly right hemispheric networks in some individuals. However, better language recovery, at least for lexical-semantic processing, was observed in individuals who had bilateral rather than right hemisphere-predominant networks. CONCLUSIONS: The results indicate that the restoration of left-hemisphere language networks is associated with better recovery and inversely related to activity in the compensated or recruited areas of the right hemisphere. (+info)
Does the National Institutes of Health Stroke Scale favor left hemisphere strokes? NINDS t-PA Stroke Study Group.
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BACKGROUND AND PURPOSE: The National Institutes of Health Stroke Scale (NIHSS) is a valid, reproducible scale that measures neurological deficit. Of 42 possible points, 7 points are directly related to measurement of language compared with only 2 points related to neglect. METHODS: We examined the placebo arm of the NINDS t-PA stroke trial to test the hypothesis that the total volume of cerebral infarction in patients with right hemisphere strokes would be greater than the volume of cerebral infarction in patients with left hemisphere strokes who have similar NIHSS scores. The volume of stroke was determined by computerized image analysis of CT films and CT images stored on computer tape and optical disks. Cube-root transformation of lesion volume was performed for each CT. Transformed lesion volume was analyzed in a logistic regression model to predict volume of stroke by NIHSS score for each hemisphere. Spearman rank correlation was used to determine the relation between the NIHSS score and lesion volume. RESULTS: The volume for right hemisphere stroke was statistically greater than the volume for left hemisphere strokes, adjusting for the baseline NIHSS (P<0. 001). For each 5-point category of the NIHSS score <20, the median volume of right hemisphere strokes was approximately double the median volume of left hemisphere strokes. For example, for patients with a left hemisphere stroke and a 24-hour NIHSS score of 16 to 20, the median volume of cerebral infarction was 48 mL (interquartile range 14 to 111 mL) as compared with 133 mL (interquartile range 81 to 208 mL) for patients with a right hemisphere stroke (P<0.001). The median volume of a right hemisphere stroke was roughly equal to the median volume of a left hemisphere stroke in the next highest 5-point category of the NIHSS. The Spearman rank correlation between the 24-hour NIHSS score and 3-month lesion volume was 0.72 for patients with left hemisphere stroke and 0.71 for patients with right hemisphere stroke. CONCLUSIONS: For a given NIHSS score, the median volume of right hemisphere strokes is consistently larger than the median volume of left hemisphere strokes. The clinical implications of our finding need further exploration. (+info)
Language barriers and bibliographic retrieval effectiveness: use of MEDLINE by French-speaking end users.
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OBJECTIVE: A study was conducted to determine if bibliographic retrieval performed by French-speaking end users is impaired by English language interfaces. The American database MEDLINE on CD-ROM was used as a model. METHODS: A survey of self-administered questionnaires was performed at two libraries of Victor Segalen Bordeaux 2 University, during a two-month period in 1997. Three study groups were constituted: MEDLINE / Ovid end users, MEDLINE / Ovid librarian-mediated users, and Pascal, a French bibliographic database, end users. RESULTS: Among 191 respondents, only 22% thought English was an obstacle to their bibliographic retrieval. However, the research software was generally underused and the quality of the retrieval weak. The differences were statistically significant between users trained by librarians and the self-trained group, the former performing better. CONCLUSION: Special efforts need to be made to develop curriculum training programs for computerized bibliographic retrieval in medical schools, regardless of the native language of the student. (+info)
Language boundaries and biological differentiation of Bougainville: multivariate analysis of variance.
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Blood genetic and antropometric data on Melanesians from Bougainville, Papus New Guinea, are analyzed by random-effects analysis of variance to partition the observed variation into components for the individuals, village, and language group level. Both clinial and unpatterned group differences exist. The differences between language groups appear to be substantial, even when the results are corrected for clinal effects. The amounts of variation of each level correspond roughly to a similar analysis of heterozygosity in blood polymorphisms. Observed current migration figures suggest that language and village constitute a 2-fold hierarchical subdivision of the breeding system, and this analysis shows probable random drift effects between groups at both the village and language level. Both language and genetic constitution of these villages are the result of differentiation in place. (+info)
The power and limits of a rule-based morpho-semantic parser.
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The venue of Electronic Patient Record (EPR) implies an increasing amount of medical texts readily available for processing, as soon as convenient tools are made available. The chief application is text analysis, from which one can drive other disciplines like indexing for retrieval, knowledge representation, translation and inferencing for medical intelligent systems. Prerequisites for a convenient analyzer of medical texts are: building the lexicon, developing semantic representation of the domain, having a large corpus of texts available for statistical analysis, and finally mastering robust and powerful parsing techniques in order to satisfy the constraints of the medical domain. This article aims at presenting an easy-to-use parser ready to be adapted in different settings. It describes its power together with its practical limitations as experienced by the authors. (+info)
Language-independent automatic acquisition of morphological knowledge from synonym pairs.
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Medical words exhibit a rich and productive morphology. Beyond simple inflection, derivation and composition are a common way to form new words. Morphological knowledge is therefore very important for any medical language processing application. Whereas rich morphological resources are available for the English medical language with the UMLS Specialist Lexicon, no such resources are publicly available for French or most other languages. We propose a simple and powerful method to help acquire automatically such knowledge. This method takes advantage of the synonym terms present in medical terminologies. In a bootstrapping step, it detects morphologically related words from which it learns "derivation rules". In an expansion step, it then applies these rules to the whole vocabulary available. Our goal is to acquire data for French and other languages for which they are not available. However, to evaluate the efficiency of the method, we tested it on English in a setting which is close to that prevailing for French, and we confronted its results to those obtained with the Specialist lexical variant generation tool. (+info)
Integration and visualization of multimodality brain data for language mapping.
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A goal of the University of Washington Brain Project is to develop software tools for processing, integrating and visualizing multimodality language data obtained at the time of neurosurgery, both for surgical planning and for the study of language organization in the brain. Data from a single patient consist of four magnetic resonance-based image volumes, showing anatomy, veins, arteries and functional activation (fMRI). The data also include the location, on the exposed cortical surface, of sites that were electrically stimulated for the presence of language. These five sources are mapped to a common MR-based neuroanatomical model, then visualized to gain a qualitative appreciation of their relationships, prior to quantitative analysis. These procedures are described and illustrated, with emphasis on the visualization of fMRI activation, which may be deep in the brain, with respect to surface-based stimulation sites. (+info)