Georgios Naros1, Alireza Gharabaghi2. 1. Division of Functional and Restorative Neurosurgery, and Centre for Integrative Neuroscience, University of Tuebingen, Germany. Electronic address: georgios.naros@med.uni-tuebingen.de. 2. Division of Functional and Restorative Neurosurgery, and Centre for Integrative Neuroscience, University of Tuebingen, Germany. Electronic address: alireza.gharabaghi@uni-tuebingen.de.
Abstract
BACKGROUND: Unlike in healthy controls, sensorimotor β-desynchronization (β-ERD) is compromised in stroke patients, i.e., the more severe the patient's motor impairment, the less β-ERD. This, in turn, provides a target substrate for therapeutic brain self-regulation and neurofeedback. OBJECTIVE: Transcranial alternating current stimulation (tACS) has been shown to modulate brain oscillations during and after stimulation, and may thus facilitate brain self-regulation during neurofeedback interventions. METHODS: Twenty severely impaired, chronic stroke patients performed kinesthetic motor-imagery while a brain-robot interface transformed β-ERD (17-23 Hz) of the ipsilesional sensorimotor cortex into opening of the paralyzed hand by a robotic orthosis. In a parallel group design, β-tACS (20 Hz, 1.1 mA peak-to-peak amplitude) was applied to the lesioned motor cortex either continuously (c-tACS) before or intermittently (i-tACS) during the intervention. Physiological effects of β-tACS were studied using electroencephalography. The patients' ability for brain self-regulation was captured by neurofeedback performance metrics. RESULTS: i-tACS - but not c-tACS - improved the classification accuracy of the neurofeedback intervention in comparison to baseline. This effect was mediated via the increased specificity of the classification, i.e., reduced variance of resting oscillations. Neither i-tACS nor c-tACS had aftereffects following the stimulation period. CONCLUSION: β-tACS may constitute an adjunct neuromodulation technique during neurofeedback-based interventions for stroke rehabilitation. Copyright Â
BACKGROUND: Unlike in healthy controls, sensorimotor β-desynchronization (β-ERD) is compromised in strokepatients, i.e., the more severe the patient's motor impairment, the less β-ERD. This, in turn, provides a target substrate for therapeutic brain self-regulation and neurofeedback. OBJECTIVE: Transcranial alternating current stimulation (tACS) has been shown to modulate brain oscillations during and after stimulation, and may thus facilitate brain self-regulation during neurofeedback interventions. METHODS: Twenty severely impaired, chronic strokepatients performed kinesthetic motor-imagery while a brain-robot interface transformed β-ERD (17-23 Hz) of the ipsilesional sensorimotor cortex into opening of the paralyzed hand by a robotic orthosis. In a parallel group design, β-tACS (20 Hz, 1.1 mA peak-to-peak amplitude) was applied to the lesioned motor cortex either continuously (c-tACS) before or intermittently (i-tACS) during the intervention. Physiological effects of β-tACS were studied using electroencephalography. The patients' ability for brain self-regulation was captured by neurofeedback performance metrics. RESULTS: i-tACS - but not c-tACS - improved the classification accuracy of the neurofeedback intervention in comparison to baseline. This effect was mediated via the increased specificity of the classification, i.e., reduced variance of resting oscillations. Neither i-tACS nor c-tACS had aftereffects following the stimulation period. CONCLUSION: β-tACS may constitute an adjunct neuromodulation technique during neurofeedback-based interventions for stroke rehabilitation. Copyright Â
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