Changes in the spectral power and coherence of the EEG alpha rhythm in humans performing grasp efforts by the right and left arm

We compared changes in the EEG indices in healthy dextral volunteers performing static force grasps by the arm. Three test modes were used: (i) performance of two successive grasps by the dominant (right) arm (test A), (ii) performance of two successive grasps by the subdominant (left) arm (test B), and (iii) performance of the grasps first by the right arm and then by the left arm (test C). Fourteen, six, and nine persons took part in tests A–C, respectively. In the course of grasps performed by the right and left arms, bilateral increases in synchronization within the alpha 1 and alpha 2 ranges were frequently observed in occipital regions in both the first and repeated grasps (P < 0.05). Consecutive grasps by the right arm were accompanied by clear desynchronization in a few anterior and central leads. Alpha 2 desynchronization was observed in both realizations of the left-arm grasps (test B) performed by some subjects, but intragroup modifications were not significant in this case. The coherence coefficients of the alpha 2 rhythm in most cases increased for symmetric leads from the right and left hemispheres in the course of grasps by both the right and left hands. The effect of intensification of interhemisphere links was manifested in the anterior and central cortical regions; this fact showed that interhemisphere interaction increases in the course of the static effort. Changes in the coherence coefficients for the alpha 2 range in the performance of the grasp efforts by the right arm and the left arm were most clear in the posterotemporal (P = 0.02), parietal (P = 0.05), and anterofrontal (P = 0.06) lead pairs. Thus, we demonstrated the dependence between the side of performance of the muscle effort in the mode close to isometric and lateralization of the EEG modifications. Neirofiziologiya/Neurophysiology, Vol. 38, No. 3, pp. 235–238, May–June, 2006.