Characterization of motor and somatosensory function for stroke patients.

In a pilot study, stroke patients with a lesion related to the motor system were studied using magnetoencephalography (MEG) and electromyography (EMG). The patients performed sustained finger movements for 30 s followed by 30 s of rest and 20 repetitions of this sequence in total. Task-related cortical signals derived from MEG were observed here at very different frequency scales. Slow signals below 0.1 Hz were extracted by independent component analysis and are associated with the sustained activation of the motor cortex, the dcMEG motor activation. MEG-EMG coupling phenomena in the 10-30 Hz range were analyzed using the imaginary part of coherency and are attributed to cortico-muscular coupling driving the muscles. Additionally a signal from the somatosensory cortex due to an electrical stimulation at the wrist, the N20m, was recorded as a physiological marker. Field maps and time series associated with the three types of signals are presented for one patient and one control subject as the signal quality of the patient data was not sufficient to achieve a group result. The feasibility of a comprehensive electrophysiological measuring and analysis procedure of the motor function for stroke research is demonstrated by the results.