Rapid motor cortical reorganization following subacute spinal cord dysfunction.

OBJECTIVE: Damage to the spinal cord is known to be associated with a posterior shift of the motor cortical upper limb representation, i.e. towards the somatosensory cortex. Due to missing pre-traumatic data, knowledge resulted from comparing findings between patients and healthy subjects. Here, we present a case of transient spinal cord injury resulting in a left-sided hemiparesis for 4 weeks. By chance, this patient had a pre-lesional navigated transcranial magnetic stimulation (nTMS) motor mapping 2 years before. Hence, nTMS mapping was repeated during the acute (after 1 day), sub-acute (after 10 days) and chronic (after 2 years) phase to trace the cortical reorganization following this incident. METHODS: Acute clinical work-up included magnetic resonance imaging and navigated transcranial magnetic stimulation (nTMS). Motor mapping was performed with 110% of the abductor pollicis brevis muscle (APB) resting motor threshold (rMT). Amplitudes and latencies of the motor-evoked potential (MEPs) were recorded and analyzed. In addition, motor function was evaluated by the Medical Research Council (MRC) scale, a standard Purdue Pegboard test and by a reaction time (RT) task. RESULTS: MRI revealed no aberrant findings. nTMS mapping, however, showed a posterior shift of the APB representation from the anatomical hand knob towards the somatosensory cortex in the acute in comparison to the pre-lesional phase. Concomitantly, there was an increase of rMT (6%). Within 10 days, there was an incomplete reversal of the posterior shift in parallel with improvement of the clinical motor function. Long-term follow-up revealed a complete restitution of nTMS cortical mapping and motor function. CONCLUSION: The present case report thoroughly documents a rapid cortical reorganization within a few days after a transient spinal shock. Our data adds further evidence to the literature suggesting a posterior shift of motor cortical representation following spinal cord injury. For the first time, 52 cortical reorganization was shown idiosyncratically in a single patient arising from the fortuitous fact of having a pre - lesional nTMS map.

Reinforcement learning of self-regulated sensorimotor ß-oscillations improves motor performance.

Self-regulation of sensorimotor oscillations is currently researched in neurorehabilitation, e.g. for priming subsequent physiotherapy in stroke patients, and may be modulated by neurofeedback or transcranial brain stimulation. It has still to be demonstrated, however, whether and under which training conditions such brain self-regulation could also result in motor gains. Thirty-two right-handed, healthy subjects participated in a three-day intervention during which they performed 462 trials of kinesthetic motor-imagery while a brain-robot interface (BRI) turned event-related ß-band desynchronization of the left sensorimotor cortex into the opening of the right hand by a robotic orthosis. Different training conditions were compared in a parallel-group design: (i) adaptive classifier thresholding and contingent feedback, (ii) adaptive classifier thresholding and non-contingent feedback, (iii) non-adaptive classifier thresholding and contingent feedback, and (iv) non-adaptive classifier thresholding and non-contingent feedback. We studied the task-related cortical physiology with electroencephalography and the behavioral performance in a subsequent isometric motor task. Contingent neurofeedback and adaptive classifier thresholding were critical for learning brain self-regulation which, in turn, led to behavioral gains after the intervention. The acquired skill for sustained sensorimotor ß-desynchronization correlated significantly with subsequent motor improvement. Operant learning of brain self-regulation with a BRI may offer a therapeutic perspective for severely affected stroke patients lacking residual hand function.

Decoding of motor intentions from epidural ECoG recordings in severely paralyzed chronic stroke patients.

OBJECTIVE: Recently, there have been several approaches to utilize a brain-computer interface (BCI) for rehabilitation with stroke patients or as an assistive device for the paralyzed. In this study we investigated whether up to seven different hand movement intentions can be decoded from epidural electrocorticography (ECoG) in chronic stroke patients. APPROACH: In a screening session we recorded epidural ECoG data over the ipsilesional motor cortex from four chronic stroke patients who had no residual hand movement. Data was analyzed offline using a support vector machine (SVM) to decode different movement intentions. MAIN RESULTS: We showed that up to seven hand movement intentions can be decoded with an average accuracy of 61% (chance level 15.6%). When reducing the number of classes, average accuracies up to 88% can be achieved for decoding three different movement intentions. SIGNIFICANCE: The findings suggest that ipsilesional epidural ECoG can be used as a viable control signal for BCI-driven neuroprosthesis. Although patients showed no sign of residual hand movement, brain activity at the ipsilesional motor cortex still shows enough intention-related activity to decode different movement intentions with sufficient accuracy.