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

Das revidierte Kölner Apraxie-Screening (KAS-R) als diagnostisches Verfahren für Patienten mit rechtshemisphärischem Schlaganfall

Das Kölner Apraxie-Screening (KAS) erfasst apraktische Defizite nach linkshemisphärischen Schlaganfällen. Ziel dieser Studie ist es, durch Anpassungen des Testmaterials des KAS und psychometrische Analysen ein diagnostisches Verfahren für Patienten mit rechtshemisphärischem Schlaganfall zu entwickeln. Mittels Itemanalysen von Daten 77 gesunder Probanden und 100 rechtshemisphärischer Schlaganfallpatienten wurden 8 KAS-Items ausgeschlossen. Das somit noch aus 12 Items bestehende KAS-R weist eine gute interne Konsistenz (α = 0,795) sowie eine hohe Sensitivität (79,4 %) und Spezifität (84,4 %) auf. Bei einem Cut-off-Wert von ≤ 46 (von 48) Punkten zeigen 39 der 100 Schlaganfallpatienten eine Apraxie. Dabei korreliert das KAS-R – im Sinne einer guten Konstruktvalidität – signifikant mit den externen Validierungsverfahren. Die Ergebnisse zeigen, dass das KAS-R ein reliables und valides diagnostisches Verfahren für apraktische Defizite nach rechtshemisphärischem Schlaganfall ist

Preserved performance monitoring and error detection in left hemisphere stroke

Depending on the lesion site, a stroke typically affects various aspects of cognitive control. While executing a task, the performance monitoring system constantly compares an intended action plan with the executed action and thereby registers inaccurate actions in case of any mismatch. When errors occur, the performance monitoring system signals the need for more cognitive control, which is most efficient when the subject notices errors rather than processing them subconsciously. The current study aimed to investigate performance monitoring and error detection in a large sample of patients with left hemisphere (LH) stroke.In addition to clinical and neuropsychological tests, 24 LH stroke patients and 32 healthy age-matched controls performed a Go/Nogo task with simultaneous electroencephalography (EEG) measurements. This set-up enabled us to compare performance monitoring at the behavioral and the neural level. EEG data were analyzed using event-related potentials [ERPs; e.g., the error-related negativity (Ne/ERN) and error positivity (Pe)] and additionally more sensitive whole-brain multivariate pattern classification analyses (MVPA). We hypothesized that LH stroke patients would show behavioural deficits in error detection when compared to healthy controls, mirrored by differences in neural signals, in particular reflected in the Pe component.Interestingly, despite clinically relevant cognitive deficits (e.g., aphasia and apraxia) including executive dysfunction (trail making test), we did not observe any behavioral impairments related to performance monitoring and error processing in the current LH stroke patients. Patients also showed similar results for Ne/ERN and Pe components, compared to the control group, and a highly similar prediction of errors from multivariate signals. ERP abnormalities during stimulus processing (i.e., N2 and P3) demonstrated the specificity of these findings in the current LH stroke patients. In contrast to previous studies, by employing a relatively large patient sample, a well-controlled experimental paradigm with a standardized error signaling procedure, and advanced data analysis, we were able to show that performance monitoring (of simple actions) is a preserved cognitive control function in LH stroke patients that might constitute a useful resource in rehabilitative therapies for re-learning impeded functions

Prävalenz und Charakteristika apraktischer Defizite bei links- und rechtshemisphärischen Schlaganfällen

Investigations of apraxia typically focus on the role of the left hemisphere (LH), although apraxic deficits can also be observed after a right hemispheric (RH) stroke. We directly compared the prevalence and severity of apraxic deficits in patients with LH (n = 66) and RH (n = 73) stroke, after controlling for the effects of age and language performance. Apraxic deficits were assessed using the KAS (Cologne Apraxia Screening, including subscales for pantomiming and the imitation of bucco-facial and hand/arm gestures) as well as the Goldenberg Hand and Finger Imitation Test. Subsequently, we evaluated the effect of age, language performance, and hemisphere on the prevalence and characteristics of apraxic deficits by regression analyses and mixed design ANOVAS. For the imitation of hand positions, no significant difference was found between LH and RH stroke patients, when controlling for age and language performance. Consistent with the literature, RH stroke patients showed a poorer performance when imitating finger configurations. RH stroke patients also performed worse in the bucco-facial items of the KAS, particularly due to lower scores in upper-face gestures. For both patient groups, the language performance was related more to the pantomime than to the imitation subscales of the KAS. Data suggest that a comparable prevalence and severity of apraxic deficits can be found after LH and RH stroke when controlling for age and language abilities. As a consequence, an apraxic work-up should be included in the assessment of both LH and RH stroke patients prior to neurorehabilitation

Recovery from apraxic deficits and its neural correlate

Background and Objective: Apraxia is a deficit of motor cognition leading to difficulties in actual tool use, imitation of gestures, and pantomiming object use. To date, little data exist regarding the recovery from apraxic deficits after stroke, and no statistical lesion mapping study investigated the neural correlate of recovery from apraxia. Accordingly, we here examined recovery from apraxic deficits, differential associations of apraxia task (imitation vs. pantomime) and effector (bucco-facial vs. limb apraxia) with recovery, and the underlying neural correlates. Methods: We assessed apraxia in 39 patients with left hemisphere (LH) stroke both at admission and approximately 11 days later. Furthermore, we collected clinical imaging data to identify brain regions associated with recovery from apraxic deficits using voxel-based lesion-symptom mapping (VLSM). Results: Between the two assessments, a significant recovery from apraxic deficits was observed with a tendency of enhanced recovery of limb compared to bucco-facial apraxia. VLSM analyses revealed that within the lesion pattern initially associated with apraxia, lesions of the left insula were associated with remission of apraxic deficits, whereas lesions to the (inferior) parietal lobe (IPL; supramarginal and angular gyrus) and the superior longitudinal fasciculus (SLF) were associated with persistent apraxic deficits. Conclusions: Data suggest that lesions affecting the core regions (and white matter) of the fronto-parietal praxis network cause more persistent apraxic deficits than lesions affecting other regions (here: the left insula) that also contribute to motor cognition and apraxic deficits

Correlation between capacitance and porosity in microporous carbon monoliths

Specific capacitance of carbons in aqueous KOH electrolyte seems to have two contributions, a double-layer capacitance and a pseudocapacitance. Moreover, the specific capacitance increases as the specific surface area does. Here, we report that the pseudocapacitance is associated with the K+ ion and the double-layer capacitance with both K+ and OH- ions. The former ion dominates the capacitance of a real two-electrode supercapacitor. Two microporous carbon monoliths with surface areas similar for micropores below 0.63 nm but different for larger micropores are chosen. There is a correlation between the double-layer capacitance due to those ions and the surface areas due to micropores with sizes above a certain value. It provides information on the size of those ions as they are electroadsorbed at the double layer. The dielectric permittivity associated with the K+ and OH - ion is discussed in relation to the confinement of these electroadsorbed ions in the micropores. © 2014 American Chemical Society.Financial support through the projects MAT2011-25198 and MP 1004 is gratefully acknowledged. V.B. thanks MINECO for R&C contract.Peer Reviewe