Spatiotemporal patterns of movement-related fields in stroke patients

In this study, brain functions in stroke patients and normal subjects were analyzed by observing neuromagnetic fields during button pressing tasks. The measurements included force measurement, visual stimuli presentation and magnetoencephalography (MEG). A 122-channel whole-head MEG system (Neuromag 122) was used. A total of 18 subjects (11 post-stroke and 7 control subjects) participated in the study; adequate MEG data were obtained from 3 of the patients. Equivalent current dipoles for MRFs were estimated with the following parameters: goodness of fit (> 75%), confidence volume (< 6000 mm3), and the duration of dipole (> 10 msec). In addition to the single dipole analysis, Minimum Current Estimates were applied for source estimation since neural activities for stroke patients were observed at the motor cortex of the contralateral side as well as other areas of the brain. Contralateral motor cortex was activated for the normal subjects at 50 ms prior to the force onset, whereas ipsilateral motor cortex was activated for some stroke patients and patients' dipole moments differed not only in their locations but also in their latencies, ranging from -150 to 50 ms to the force onset. The results were in agreement with the findings by PET and fMRI studies; therefore, it was implied that the compensating motor functions were shifted to neighboring areas of the brain due to the recovering motor function after stroke.