The Experts below are selected from a list of 237 Experts worldwide ranked by ideXlab platform
Nages Nagaratnam - One of the best experts on this subject based on the ideXlab platform.
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Language Dysfunction in White Matter: Lesions Without Significant Hemiparesis
Neurorehabilitation and Neural Repair, 1996Co-Authors: Nages Nagaratnam, Robyn BarnesAbstract:Subcortical lesions associated with aphasia are usually associated with concomitant neurologic deficits. Five patients with subcortical aphasia with purely white matter involvement and without significant hemiparesis were studied in relation to the sever ity of the aphasia, size..and site of the cerebral lesion, and outcome of the aphasia. The severity of the aphasia was determined by the Boston Diagnostic Aphasia Exam ination (BDAE). All patients had CCT. In four patients the lesions were located in the superior and/or anterior superior periventricular white matter (PVWM) and in the remaining one in the extra-anterior PVWM and posterior extension of PVWM. Three patients had characteristics of global aphasia, one had mixed transcortical aphasia, and one had Wernicke's aphasia. Coexistent disorders were dysarthria and dysgraphia in four patients and hypophonia in one. Language recovery was good in two patients with mixed transcortical and fluent aphasia and moderate to poor in the remaining three, two of w...
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Speech Recovery Following Global Aphasia Without Hemiparesis
Neurorehabilitation and Neural Repair, 1996Co-Authors: Nages Nagaratnam, Robyn Barnes, S. NagaratnamAbstract:Twelve patients with global aphasia without hemiparesis were studied to determine site of infarction and relate this to severity of aphasia and recovery from it. All patients were studied with CT scans without contrast and the site of the lesion or lesions deter mined by tracing the lesion from standard horizontal slices taken 10 mm apart. Lan guage impairment was determined by the Boston Diagnostic Aphasia Examination and the Aphasia Language Performance Scales, done within four to eight days after onset and at three months following the stroke. All patients had deficits in all language modalities with reduced verbal output, impaired comprehension, impaired reading, writing, and repetition.The CT scans showed that four patients had lesions in language areas located ante riorly, four had lesions posteriorly, and in four the lesions were both anterior and posterior.Recovery was correlated with lesion location and aphasia severity. Those with initially severe aphasia had less good recovery than those with m...
Robyn Barnes - One of the best experts on this subject based on the ideXlab platform.
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Language Dysfunction in White Matter: Lesions Without Significant Hemiparesis
Neurorehabilitation and Neural Repair, 1996Co-Authors: Nages Nagaratnam, Robyn BarnesAbstract:Subcortical lesions associated with aphasia are usually associated with concomitant neurologic deficits. Five patients with subcortical aphasia with purely white matter involvement and without significant hemiparesis were studied in relation to the sever ity of the aphasia, size..and site of the cerebral lesion, and outcome of the aphasia. The severity of the aphasia was determined by the Boston Diagnostic Aphasia Exam ination (BDAE). All patients had CCT. In four patients the lesions were located in the superior and/or anterior superior periventricular white matter (PVWM) and in the remaining one in the extra-anterior PVWM and posterior extension of PVWM. Three patients had characteristics of global aphasia, one had mixed transcortical aphasia, and one had Wernicke's aphasia. Coexistent disorders were dysarthria and dysgraphia in four patients and hypophonia in one. Language recovery was good in two patients with mixed transcortical and fluent aphasia and moderate to poor in the remaining three, two of w...
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Speech Recovery Following Global Aphasia Without Hemiparesis
Neurorehabilitation and Neural Repair, 1996Co-Authors: Nages Nagaratnam, Robyn Barnes, S. NagaratnamAbstract:Twelve patients with global aphasia without hemiparesis were studied to determine site of infarction and relate this to severity of aphasia and recovery from it. All patients were studied with CT scans without contrast and the site of the lesion or lesions deter mined by tracing the lesion from standard horizontal slices taken 10 mm apart. Lan guage impairment was determined by the Boston Diagnostic Aphasia Examination and the Aphasia Language Performance Scales, done within four to eight days after onset and at three months following the stroke. All patients had deficits in all language modalities with reduced verbal output, impaired comprehension, impaired reading, writing, and repetition.The CT scans showed that four patients had lesions in language areas located ante riorly, four had lesions posteriorly, and in four the lesions were both anterior and posterior.Recovery was correlated with lesion location and aphasia severity. Those with initially severe aphasia had less good recovery than those with m...
Hellmuth Obrig - One of the best experts on this subject based on the ideXlab platform.
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lesion correlates of patholinguistic profiles in chronic aphasia comparisons of syndrome modality and symptom level assessment
Brain, 2014Co-Authors: Ilona Henseler, Frank Regenbrecht, Hellmuth ObrigAbstract:One way to investigate the neuronal underpinnings of language competence is to correlate patholinguistic profiles of aphasic patients to corresponding lesion sites. Constituting the beginnings of aphasiology and neurolinguistics over a century ago, this approach has been revived and refined in the past decade by statistical approaches mapping continuous variables (providing metrics that are not simply categorical) on voxel-wise lesion information (voxel-based lesion–symptom mapping). Here we investigate whether and how voxel-based lesion–symptom mapping allows us to delineate specific lesion patterns for differentially fine-grained clinical classifications. The latter encompass ‘classical’ syndrome-based approaches (e.g. Broca’s aphasia), more symptom-oriented descriptions (e.g. agrammatism) and further refinement to linguistic sub-functions (e.g. lexico-semantic deficits for inanimate versus animate items). From a large database of patients treated for aphasia of different aetiologies ( n = 1167) a carefully selected group of 102 first ever ischaemic stroke patients with chronic aphasia (∅ 12 months) were included in a VLSM analysis. Specifically, we investigated how performance in the Aachen Aphasia Test—the standard clinical test battery for chronic aphasia in German—relates to distinct brain lesions. The Aachen Aphasia Test evaluates aphasia on different levels: a non-parametric discriminant procedure yields probabilities for the allocation to one of the four ‘standard’ syndromes (Broca, Wernicke, global and amnestic aphasia), whereas standardized subtests target linguistic modalities (e.g. repetition), or even more specific symptoms (e.g. phoneme repetition). Because some subtests of the Aachen Aphasia Test (e.g. for the linguistic level of lexico-semantics) rely on rather coarse and heterogeneous test items we complemented the analysis with a number of more detailed clinically used tests in selected mostly mildly affected subgroups of patients. Our results indicate that: (i) Aachen Aphasia Test-based syndrome allocation allows for an unexpectedly concise differentiation between ‘Broca’s’ and ‘Wernicke’s’ aphasia corresponding to non-overlapping anterior and posterior lesion sites; whereas (ii) analyses for modalities and specific symptoms yielded more circumscribed but partially overlapping lesion foci, often cutting across the above syndrome territories; and (iii) especially for lexico-semantic capacities more specialized clinical test-batteries are required to delineate precise lesion patterns at this linguistic level. In sum this is the first report on a successful lesion-delineation of syndrome-based aphasia classification highlighting the relevance of vascular distribution for the syndrome level while confirming and extending a number of more linguistically motivated differentiations, based on clinically used tests. We consider such a comprehensive view reaching from the syndrome to a fine-grained symptom-oriented assessment mandatory to converge neurolinguistic, patholinguistic and clinical-therapeutic knowledge on language-competence and impairment. * Abbreviations : AAT : Aachen Aphasia Test RWT : Regensburger Wortflussigkeits Test VLSM : voxel-based lesion–symptom mapping WMS-R : Wechsler Memory Scale-Revised
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Lesion correlates of patholinguistic profiles in chronic aphasia: comparisons of syndrome-, modality- and symptom-level assessment.
Brain : a journal of neurology, 2014Co-Authors: Ilona Henseler, Frank Regenbrecht, Hellmuth ObrigAbstract:One way to investigate the neuronal underpinnings of language competence is to correlate patholinguistic profiles of aphasic patients to corresponding lesion sites. Constituting the beginnings of aphasiology and neurolinguistics over a century ago, this approach has been revived and refined in the past decade by statistical approaches mapping continuous variables (providing metrics that are not simply categorical) on voxel-wise lesion information (voxel-based lesion-symptom mapping). Here we investigate whether and how voxel-based lesion-symptom mapping allows us to delineate specific lesion patterns for differentially fine-grained clinical classifications. The latter encompass 'classical' syndrome-based approaches (e.g. Broca's aphasia), more symptom-oriented descriptions (e.g. agrammatism) and further refinement to linguistic sub-functions (e.g. lexico-semantic deficits for inanimate versus animate items). From a large database of patients treated for aphasia of different aetiologies (n = 1167) a carefully selected group of 102 first ever ischaemic stroke patients with chronic aphasia (∅ 12 months) were included in a VLSM analysis. Specifically, we investigated how performance in the Aachen Aphasia Test-the standard clinical test battery for chronic aphasia in German-relates to distinct brain lesions. The Aachen Aphasia Test evaluates aphasia on different levels: a non-parametric discriminant procedure yields probabilities for the allocation to one of the four 'standard' syndromes (Broca, Wernicke, global and amnestic aphasia), whereas standardized subtests target linguistic modalities (e.g. repetition), or even more specific symptoms (e.g. phoneme repetition). Because some subtests of the Aachen Aphasia Test (e.g. for the linguistic level of lexico-semantics) rely on rather coarse and heterogeneous test items we complemented the analysis with a number of more detailed clinically used tests in selected mostly mildly affected subgroups of patients. Our results indicate that: (i) Aachen Aphasia Test-based syndrome allocation allows for an unexpectedly concise differentiation between 'Broca's' and 'Wernicke's' aphasia corresponding to non-overlapping anterior and posterior lesion sites; whereas (ii) analyses for modalities and specific symptoms yielded more circumscribed but partially overlapping lesion foci, often cutting across the above syndrome territories; and (iii) especially for lexico-semantic capacities more specialized clinical test-batteries are required to delineate precise lesion patterns at this linguistic level. In sum this is the first report on a successful lesion-delineation of syndrome-based aphasia classification highlighting the relevance of vascular distribution for the syndrome level while confirming and extending a number of more linguistically motivated differentiations, based on clinically used tests. We consider such a comprehensive view reaching from the syndrome to a fine-grained symptom-oriented assessment mandatory to converge neurolinguistic, patholinguistic and clinical-therapeutic knowledge on language-competence and impairment.
Richard D Palmiter - One of the best experts on this subject based on the ideXlab platform.
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dopamine is required for hyperphagia in lep ob ob mice
Nature Genetics, 2000Co-Authors: Mark S Szczypka, Mark A Rainey, Richard D PalmiterAbstract:Feeding is a complex process responsive to sensory information related to sight and smell of food, previous feeding experiences, satiety signals elicited by ingestion and hormonal signals related to energy balance. Dopamine released in specific brain regions is associated with pleasurable and rewarding events and may reinforce positive aspects of feeding. Dopamine also influences initiation and coordination of motor activity and is required for sensorimotor functions. Thus, dopamine may facilitate integration of sensory cues related to hunger, initiating the search for food and its consumption. Dopaminergic neurons in the substantia nigra and ventral tegmental area project to the caudate putamen and nucleus accumbens, where they modulate movement and reward. There are projections from the nucleus accumbens to the lateral hypothalamus that regulate feeding. Dopamine-deficient mice (Dbh(Th/+), Th-/-; hereafter DD mice) cannot synthesize dopamine in dopaminergic neurons. They gradually become aphagic and die of starvation. Daily treatment of DD mice with L-3,4-dihydroxyphenylalanine (L-DOPA) transiently restores brain dopamine, locomotion and feeding. Leptin-null (Lep(ob/ob)) mice exhibit obesity, decreased energy expenditure and hyperphagia. As the hypothalamic leptin-melanocortin pathway appears to regulate appetite and metabolism, we generated mice lacking both dopamine and leptin (DD x Lep(ob/ob)) to determine if leptin deficiency overcomes the Aphagia of DD mice. DD x Lep(ob/ob) mice became obese when treated daily with L-DOPA, but when L-DOPA treatment was terminated the double mutants were capable of movement, but did not feed. Our data show that dopamine is required for feeding in leptin-null mice.
S. Nagaratnam - One of the best experts on this subject based on the ideXlab platform.
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Speech Recovery Following Global Aphasia Without Hemiparesis
Neurorehabilitation and Neural Repair, 1996Co-Authors: Nages Nagaratnam, Robyn Barnes, S. NagaratnamAbstract:Twelve patients with global aphasia without hemiparesis were studied to determine site of infarction and relate this to severity of aphasia and recovery from it. All patients were studied with CT scans without contrast and the site of the lesion or lesions deter mined by tracing the lesion from standard horizontal slices taken 10 mm apart. Lan guage impairment was determined by the Boston Diagnostic Aphasia Examination and the Aphasia Language Performance Scales, done within four to eight days after onset and at three months following the stroke. All patients had deficits in all language modalities with reduced verbal output, impaired comprehension, impaired reading, writing, and repetition.The CT scans showed that four patients had lesions in language areas located ante riorly, four had lesions posteriorly, and in four the lesions were both anterior and posterior.Recovery was correlated with lesion location and aphasia severity. Those with initially severe aphasia had less good recovery than those with m...