Modulating brain plasticity in rehabilitation of stroke and other brain lesions

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Background: Disability resulting from stroke and traumatic brain injury represent the main causes of long-term complications in adults. There are no universally accepted treatments available to treat these conditions and the financial, personal, familial and social cost of these disabilities cannot be underestimated. Preliminary data from different laboratories have shown that it is possible to modulate plastic processes in the lesioned brain by pharmacological, brain stimulation and somatosensory stimulation techniques. The purpose of this project is to identify mechanisms of stroke motor disability and characterize the most promising techniques to improve cortical plasticity in these patients to enhance functional recovery. Findings this year: We studied neurophysiological mechanisms of motor performance In poorly recovered patients unable to move their hand. We evaluated interhemispheric and intracortical inhibition in paretic arm muscles of patients with no recovery of hand movement. We recorded silent periods (contralateral and ipsilateral) induced by transcranial magnetic stimulation during voluntary isometric contraction of the paretic biceps and triceps brachii muscles (correlates of intracortical and interhemispheric inhibition, respectively) and investigated links between the silent periods and motor recovery, an issue that has not been previously explored. We found that interhemispheric inhibition, stronger in the paretic triceps than biceps brachii muscles, significantly correlated with the magnitude of residual impairment (lower Fugl-Meyer scores). In contrast, intracortical inhibition in the paretic biceps brachii, but not in the triceps, correlated positively with motor recovery (Fugl-Meyer scores) and negatively with spasticity (lower Modified Ashworth scores). Our results suggest that interhemispheric inhibition and intracortical inhibition of paretic upper arm muscles relate to motor recovery in different ways. While interhemispheric inhibition may contribute to poorer recovery, muscle-specific intracortical inhibition may relate to successful motor recovery and lesser spasticity. In a collaborative study primarily performed at the University of Tubingen, we evaluated efficacy of daily brain-machine interface (BMI) training to increase the hypothesized beneficial effects of physiotherapy alone in patients with severe paresis in a double-blind sham-controlled design proof of concept study. Thirty-two chronic stroke patients with severe hand weakness were randomly assigned to 2 matched groups and participated In training rewarding desynchronization of ipsilesional oscillatory sensorimotor rhythms with contingent online movements of hand and arm orthoses. In the control group, movements of the orthoses occurred randomly. Both groups received identical behavioral physiotherapy immediately following BMI training or the control intervention. Upper limb motor function scores, electromyography from arm and hand muscles, placebo-expectancy effects, and functional magnetic resonance imaging (fMRI) blood oxygenation level-dependent activity were assessed before and after intervention. We found a significant group time interaction in upper limb (combined hand and modified arm) Fugl-Meyer assessment (cFMA) motor scores. cFMA scores improved more in the experimental than in the control group, presenting a significant improvement of cFMA scores reflecting a clinically meaningful change from no activity to some in paretic muscles. cFMA improvements in the experimental group correlated with changes in fMRI laterality index and with paretic hand electromyography activity. Placebo-expectancy scores were comparable for both groups. Thus, the addition of BMI training to behaviorally oriented physiotherapy can be used to induce functional improvements in motor function in chronic stroke patients without residual finger movements and may open a new door in stroke neurorehabilitation.