Ipsilesional Mu Sensorimotor Rhythms Track With Hand Function Recovery In Stroke Survivors

This research seeks to identify source localization of neuromechanical changes associated with gains in hand grip function following BCI intervention sessions for upper extremity motor recovery. Mu rhythm desynchronization (ERD) of contralateral brain motor areas is thought to occur during movement and changes in brain motor area ERD relate to changes in behavioral measures, hand grip function, with BCI intervention. N=16 right hemisphere survivors participated in 9-15 sessions with BCI. Participants executed hand movements in response to visual cues on a computer screen with the corresponding audio instructions (e.g., Left, Right, Rest). The sessions (i.e. pre and post BCI intervention) contained two runs, each consisting of 15 trials for rest, left hand, and right hand movements (i.e., 5 trials for each of the three conditions) presented in random order. Data from the pre and post conditions were then grand averaged. sLORETA estimates were calculated as follows: 1) Clean EEG data segmented (LEFT hand attempted movements and REST) separately for PRE and POST conditions. 2) Cross-spectra (MU[8-12 Hz]) were computed then averaged (i.e. 1 average per each subject separately for left, right and rest trials. 3) sLORETA of MU power estimates at 6239 cortical locations/voxels were obtained, normalized across subjects. In the sLORETA implementation, computations made in realistic head model using the MNI152 template, with 3D solution space restricted to cortical gray matter, as determined by the probabilistic Talairach atlas. The specific frequency band cross-spectra (frequency-domain) obtained from the average-reference potential data, were the inputs for source localization. 4) sLORETA estimates between the 2 conditions [Movement - Rest] were then calculated in cortical space. Pearson correlation of voxel-wise Mu ERD with the change in Hand Grip were calculated. A stronger Mu ERD in the ipsilesional primary motor cortical area (BA 4) at ‘post’ intervention (i.e., more negative values compared to ‘pre’) was associated with a greater change in hand grip (r=-0.435, p=0.046 [1-tailed]). Increases in functional recovery of the impaired upper extremity (Hand Grip) have a direct correlation with greater changes in Mu ERD of ipsilesional motor brain areas.