Visual extinction in relation to visuospatial neglect after right-hemispheric stroke: quantitative assessment and statistical lesion-symptom mapping

Visual neglect and extinction are two common neurological syndromes in patients with right-hemispheric brain damage. Whether and how these two syndromes are associated or share common neural substrates is still a matter of debate.To address these issues, the authors investigated 56 patients with right-hemispheric stroke with a novel diagnostic test to detect extinction and neglect. In this computerised task, subjects had to respond to target stimuli in uni- and bilateral stimulation conditions with detection probabilities being assessed. A cluster-analytical approach identified 18 patients with neglect and 13 patients with extinction. Statistical lesion-symptom mapping analyses with measures for extinction and neglect were performed.Extinction and neglect co-occurred in a subset of patients but were also observed independently from each other, thereby constituting a double dissociation. Lesions within the right inferior parietal cortex were significantly associated with the severity of visual extinction. Visuospatial neglect was related to damage of fronto-parietal brain regions, with parieto-occipital areas affecting line bisection and dorsal fronto-parietal areas affecting cancellation task performance, respectively.Quantifying lesion-induced symptoms with this novel paradigm shows that extinction and neglect are dissociable syndromes in patients with right-hemispheric stroke. Furthermore, extinction and neglect can be related to differential neural substrates, with extinction being related to focal brain damage within the right inferior parietal cortex

High surface area carbon aerogels for supercapacitors

Applications of carbon aerogels as electrodes in supercapacitors require high surface area and simple production method. Carbon aerogels are derived via the pyrolysis of resorcinol-formaldehyde (RF) aerogels. In order to simplify production, subcritical drying of the RF gels is favoured, which is possible for gels prepared with high molar resorcinol to catalyst (R/C) ratios, i.e. very low catalyst concentrations. Resulting carbon aerogels consist of big microporous particles. The micropore surface area can account for more than 90% of the total surface area. The effect of thermal and chemical activation of such aerogels was investigated as a means to increase accessible surface and double-layer capacities. Aerogel structure was studied by small angle X-ray scattering (SAXS) and nitrogen – and CO2 – sorption. Accessibility of pores and aerogel performance as electrodes in supercapacitors was electrochemically investigated

Praevention von Aggression und Gewalt an Schulen. Ein Konzept fuer die Schule als System und fuer den Unterricht. Interventionskonzept zur primaeren und sekundaeren Gewaltpraevention. Konzeption, Durchfuehrung, Evaluation Schlussbericht und Evaluation

SIGLEAvailable from TIB Hannover: F03B456 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Testing for neglect in right-hemispheric stroke patients using a new assessment battery based upon standardized activities of daily living

Spatial neglect is most frequently observed after right-hemispheric stroke and is characterized by a failure to report, to respond, or to orient to stimuli presented to the contralesional side. Although many neglect patients show difficulties in accomplishing activities of daily living (ADL), to date the clinical assessment of neglect is based upon neuropsychological paper-and-pencil tests. Thus, essential information about the patient's functional status may be missed out. Accordingly, we aimed at developing a new neglect test battery that incorporates standardized ADL. Six conventional paper-and-pencil neglect tests and eight standardized ADL with newly developed neglect-specific scoring criteria and cut-off scores were administered to 68 right-hemispheric stroke patients. According to the neuropsychological tests 22 patients showed symptoms suggesting neglect, whereas 17 patients showed symptoms suggesting neglect according to the newly developed neglect test based upon ADL. Neglect-specific impairments in the neuropsychological tests were significantly associated with those in the ADL-based tests, although dissociations were observed in seven patients. Neglect severity (as reflected in the percentage of positive subtests) was comparable for both test batteries and both test instruments showed high interrater reliability. Voxel-based lesion-symptom mapping revealed that the severity of neglect according to the neuropsychological and ADL-based tests was significantly associated with lesions within right fronto-parietal networks. We conclude that the newly developed ADL-based neglect battery provides an economic and ecologically valid tool for the assessment of neglect. The test can be used to assess and quantify neglect in everyday activities, and thus to monitor realistically rehabilitative needs of neglect patients

Reduced Awareness for Apraxic Deficits in Left Hemisphere Stroke

Objective: Reduced awareness for motor or cognitive impairments has mainly been studied in relation to right-hemispheric deficits such as left-sided hemiparesis. However, recent studies suggest that also left hemisphere (LH) stroke can lead to reduced awareness for neurological/neuropsychological deficits, for example, aphasia. The aim of the current study was to characterize reduced awareness for apraxic as well as aphasic deficits in patients suffering from LH stroke. Method: After the assessment of apraxia and aphasia, patients (n = 32) were asked to rate their performance on a 1-to 5-point rating scale. An unawareness score (UAS) was computed as the difference between the examiners' ratings and self-ratings, resulting in negative scores for patients who overestimated their performance in a given assessment, that is, exhibited reduced awareness for their stroke-related deficits. Results: Patients with apraxia (n = 14) and aphasia (n = 16) significantly overestimated their performance in the respective assessment. However, the level of awareness was not generally related to the severity of apraxia, and there were no group differences in other variables between patients with full (n = 7) and reduced awareness (n = 7) for apraxic deficits. The reduction of awareness for apraxic deficits did not differ significantly for buccofacial versus limb gestures. Conclusion: Data show that LH stroke can lead to reduced awareness not only for aphasic deficits but also for buccofacial and limb apraxia

Timing Matters? Learning of Complex Spatiotemporal Sequences in Left-hemisphere Stroke Patients

During rehabilitation after stroke motor sequence learning is of particular importance because considerable effort is devoted to (re)acquiring lost motor skills. Previous studies suggest that implicit motor sequence learning is preserved in stroke patients but were restricted to the spatial dimension, although the timing of single action components is as important as their spatial order. As the left parietal cortex is known to play a critical role in implicit timing and spatiotemporal integration, in this study we applied an adapted version of the SRT task designed to assess both spatial (different stimulus locations) and temporal (different response–stimulus intervals) aspects of motor learning to 24 right-handed patients with a single left-hemisphere (LH) stroke and 24 age-matched healthy controls. Implicit retrieval of sequence knowledge was tested both at Day 1 and after 24 hr (Day 2). Additionally, voxel-based lesion symptom mapping was used to investigate the neurobiological substrates of the behavioral effects. Although LH stroke patients showed a combined spatiotemporal learning effect that was comparable to that observed in controls, LH stroke patients did not show learning effects for the learning probes in which only one type of sequence information was maintained whereas the other one was randomized. Particularly on Day 2, patients showed significantly smaller learning scores for these two learning probes than controls. Voxel-based lesion symptom mapping analyses revealed for all learning probes that diminished learning scores on Day 2 were associated with lesions of the striatum. This might be attributed to its role in motor chunking and offline consolidation as group differences occurred on Day 2 only. The current results suggest that LH stroke patients rely on multimodal information (here: temporal and spatial information) when retrieving motor sequence knowledge and are very sensitive to any disruption of the learnt sequence information as they seem to build very rigid chunks preventing them from forming independent spatial and temporal sequence representations