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1/8. Crossed nonaphasia in a dextral with left hemispheric lesions: a functional magnetic resonance imaging study of mirrored brain organization.

    BACKGROUND: General conclusions concerning mechanisms of cerebral lateralization may be learned from the investigation of functional brain organization in patients with anomalous lateralization. CASE DESCRIPTION: The functional organization of language, attention, and motor performance was investigated in a 42-year-old patient with crossed nonaphasia by means of functional MRI. The strongly right-handed man experienced a left middle cerebral artery infarction documented by MRI without exhibition of aphasia. However, the left hemispheric stroke was accompanied by visuospatial impairment, right-sided slight sensory and motor paresis, and right homonymous hemianopia. No history of familial sinistrality or prior neurological illness was present. Functional MR language mapping revealed strong right hemispheric activation in inferior frontal and superior temporal cortices. Finger tapping with the right hand recruited ipsilateral premotor and motor areas as well as supplementary motor cortex. A Stroop task, usually strongly associated with left-sided inferior frontal activation in dextrals, resulted in strong right hemispheric frontal activation. CONCLUSIONS: From our data there is clear evidence that different modalities, such as language perception and production, attention, and motor performance, are processed exclusively by 1 hemisphere when atypical cerebral dominance is present.
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2/8. Hyperintense MCA branch sign on FLAIR-MRI.

    We report three patients with cardioembolic stroke or transient ischaemic attack. Fluid-attenuated inversion recovery (FLAIR) MRI within hours of symptom onset, demonstrated linear hyperintensities on the surface of the cortex corresponding to neurologic deficits. This unusual finding was indicative of MCA branch occlusion that was confirmed or suggested with angiography. Ultra-early evaluation with FLAIR- and diffusion-MRI may help establish the diagnosis of acute ischaemic stroke particularly due to embolic MCA branch occlusion.
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keywords = cortex
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3/8. Modelling rhythmic function in a musician post-stroke.

    The aim of this study was to model the components of rhythmic function in a case (H.J.) of acquired rhythmic disturbance. H.J. is a right-handed, amateur male musician who acquired arrhythmia in the context of a global amusia after sustaining a right temporoparietal infarct. His rhythmic disturbance was analysed in relation to three independent components using an autoregressive extension of wing and Kristofferson's model of rhythmic timing. This revealed preserved error-correction and motor implementation capacities, but a gross disturbance of H.J.'s central timing system ("cognitive clock"). It rendered him unable to generate a steady pulse, prevented adequate discrimination and reproduction of novel metrical rhythms, and partly contributed to bi-manual co-ordination difficulties in his instrumental performance. The findings are considered in relation to the essential components of the cognitive architecture of rhythmic function, and their respective cerebral lateralisation and localisation. overall, the data suggested that the functioning of the right temporal auditory cortex is fundamental to 'keeping the beat' in music. The approach is presented as a new paradigm for future neuropsychological research examining rhythmic disturbances.
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keywords = cortex
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4/8. Recovery of semantic word processing in transcortical sensory aphasia: a functional magnetic resonance imaging study.

    In a previous functional magnetic resonance imaging (fMRI) study with normal subjects, we demonstrated regions related to conceptual-semantic word processing around the first frontal sulcus (BA 9) and the posterior parietal lobe (BA 7/40) in agreement with several previous reports. We had the possibility, using the same fMRI paradigm, to study two consecutive cases with left middle cerebral artery (MCA) infarction (RC and HP) and lesions affecting either solely the pre-frontal (HP) or both the pre-frontal and posterior parietal part of the network activated in normal subjects (RC). Both patients showed transcortical sensory aphasia (TSA) on acute assessment. This contradicts classical disconnection accounts of the syndrome stating intact conceptual representations in TSA. Their recovery of language comprehension was associated with activation of a left hemispheric network. Mainly activations of left perilesional pre-frontal regions (RC), left Wernicke's area (RC and HP) or the left posterior middle and inferior temporal cortex (HP) were demonstrated in the TSA patients. The latter findings suggest that in our cases of TSA functional take-over has occurred in regions with related functions ('redundancy recovery') rather than in previously unrelated areas ('vicarious functioning'). Our data support distributed models of conceptual-semantic word processing and multiple left hemispheric representations of closely related functions.
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keywords = cortex
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5/8. middle cerebral artery territory infarction sparing the precentral gyrus: report of three cases.

    We report three patients with large middle cerebral artery infarctions in the non-dominant hemisphere, with striking recovery of motor function. In each case this excellent functional outcome correlated with selective sparing of the motor cortex in the precentral gyrus. We discuss some of the possible circulatory variants that might underlie this pattern of infarction.
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6/8. Spatial-temporal anisometries following right parietal damage.

    patients with right parietal damage often have a lateralized deficit of spatial attention. In addition to a spatial deficit, such patients have also been reported to have a non-spatial deficit in temporal processing. Here, we tested the hypothesis that these spatial and temporal deficits might be linked if the right temporal-parietal cortex is important in integrating spatial and temporal attention. In AF, a patient with an acute right temporal-parietal stroke, we replicated previous observations showing that he was biased to judge ipsilesional stimuli as occurring before contralesional stimuli. More importantly, for vertically aligned stimuli, AF more accurately judged the temporal order of successive ipsilesional than contralesional stimuli. Furthermore, his contralesional performance improved with stimuli with larger vertical separations. Taken together, these findings provide additional evidence that right temporal-parietal damage produces a processing refractory period for stimuli in contralesional space that extends in both space and time. These findings are in agreement with other studies that suggest that the right temporal-parietal cortex is important in integrating the where and when of stimuli.
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keywords = cortex
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7/8. Assessing recovery in middle cerebral artery stroke using functional MRI.

    PRIMARY OBJECTIVE: To understand the temporal evolution of brain reorganization during recovery from stroke. research design: A patient who suffered left middle cerebral artery stroke 9 months earlier was studied on three occasions, approximately 1 month apart. methods AND PROCEDURES: brain activation was studied using functional magnetic resonance imaging (fMRI). During each session, the patient performed a finger-to-thumb opposition task, which involved one bimanual and two unimanual conditions. Each condition consisted of overt movement of fingers and imagery of the same task. RESULTS: With recovery, greater recruitment was observed of the affected primary motor cortex (M1) and a decrease in activation of the unaffected M1 and supplementary motor area. In addition, the widespread activation of brain areas seen during the initial session changed to a more focused pattern of activation as the patient recovered. Imagery tasks resulted in similar brain activity as overt execution pointing to imagery as a potential tool for rehabilitation.
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keywords = cortex
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8/8. No indication of brain reorganization after unilateral ischemic lesions of the auditory cortex.

    We used magnetoencephalography to study contralesional auditory reorganization in three men with chronic unilateral ischemic lesions of the auditory cortex. Although no response was found over the lesioned hemisphere, processing in the unaffected hemisphere was indistinguishable vs healthy controls. In contrast to sensorimotor and language systems, the auditory system seems to lack contralateral reorganization, presumably because patients are typically not aware of hearing deficits and thus do not perform training.
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keywords = cortex
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