A proposed regional hierarchy in recovery of post-stroke aphasia

Brain and Language, v.98, 118-123 (2006)
Source: OAI
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    ABSTRACT: Despite ongoing improvements in the acute treatment of cerebrovascular diseases and organization of stroke services, many stroke survivors are in need of neurorehabilitation, as more than two-thirds show persisting neurologic deficits. While early elements of neurorehabilitation are already taking place on the stroke unit, after the acute treatment, the patient with relevant neurologic deficits usually takes part in an organized inpatient multidisciplinary rehabilitation program and eventually continues with therapies in an ambulatory setting afterwards. A specialized multidisciplinary neurorehabilitation team with structured organization and processes provides a multimodal, intense treatment program for stroke patients which is adapted in detail to the individual goals of rehabilitation. There are many parallels between postlesional neuroplasticity (relearning) and learning in the development of individuals as well as task learning of healthy persons. One key principle of neurorehabilitation is the repetitive creation of specific learning situations to promote mechanisms of neural plasticity in stroke recovery. There is evidence of achieving a better outcome of neurorehabilitation with early initiation of treatment, high intensity, with specific goals and active therapies, and the coordinated work and multimodality of a specialized team. In this context, interdisciplinary goal-setting and regular assessments of the patient are important. Furthermore, several further potential enhancers of neural plasticity, e.g., peripheral and brain stimulation techniques, pharmacological augmentation, and use of robotics, are under evaluation.
    Journal of Neurology 10/2011; 259(5):817-32. · 3.58 Impact Factor
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    ABSTRACT: Aphasia is a common symptom after left hemispheric stroke. Neuroimaging techniques over the last 10-15 years have described two general trends: Patients with small left hemisphere strokes tend to recruit perilesional areas, while patients with large left hemisphere lesions recruit mainly homotopic regions in the right hemisphere. Non-invasive brain stimulation techniques such as transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) have been employed to facilitate recovery by stimulating lesional and contralesional regions. The majority of these brain stimulation studies have attempted to block homotopic regions in the right posterior inferior frontal gyrus (IFG) to affect a presumed disinhibited right IFG (triangular portion). Other studies have used anodal or excitatory tDCS to stimulate the contralesional (right) fronto-temporal region or parts of the intact left IFG and perilesional regions to improve speech-motor output. It remains unclear whether the interhemispheric disinhibition model, which is the basis for motor cortex stimulation studies, also applies to the language system. Future studies could address a number of issues, including: the effect of lesion location on current density distribution, timing of the intervention with regard to stroke onset, whether brain stimulation should be combined with behavioral therapy, and whether multiple brain sites should be stimulated. A better understanding of the predictors of recovery from natural outcome studies would also help to inform study design, and the selection of clinically meaningful outcome measures in future studies.
    Neuropsychology Review 09/2011; 21(3):288-301. · 6.42 Impact Factor
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    ABSTRACT: During normal semantic processing, the left hemisphere (LH) is suggested to restrict right hemisphere (RH) performance via interhemispheric suppression. However, a lesion in the LH or the use of concurrent tasks to overload the LH's attentional resource balance has been reported to result in RH disinhibition with subsequent improvements in RH performance. The current study examines variations in RH semantic processing in the context of unilateral LH lesions and the manipulation of the interhemispheric processing resource balance, in order to explore the relevance of RH disinhibition to hemispheric contributions to semantic processing following a unilateral LH lesion. RH disinhibition was examined for nine participants with a single LH lesion and 13 matched controls using the dual task paradigm. Hemispheric performance on a divided visual field lexical decision semantic priming task was compared over three verbal memory load conditions, of zero-, two- and six-words. Related stimuli consisted of categorically related, associatively related, and categorically and associatively related prime-target pairs. Response time and accuracy data were recorded and analyzed using linear mixed model analysis, and planned contrasts were performed to compare priming effects in both visual fields, for each of the memory load conditions. Control participants exhibited significant bilateral visual field priming for all related conditions (p < .05), and a LH advantage over all three memory load conditions. Participants with LH lesions exhibited an improvement in RH priming performance as memory load increased, with priming for the categorically related condition occurring only in the 2- and 6-word memory conditions. RH disinhibition was also reflected for the LH damage (LHD) group by the removal of the LH performance advantage following the introduction of the memory load conditions. The results from the control group are consistent with suggestions of an age related hemispheric asymmetry reduction and indicate that in healthy aging compensatory bilateral activation may reduce the impact of inhibition. In comparison, the results for the LHD group indicate that following a LH lesion RH semantic processing can be manipulated and enhanced by the introduction of a verbal memory task designed to engage LH resources and allow disinhibition of RH processing.
    Behavioral and Brain Functions 03/2012; 8:14. · 2.79 Impact Factor