Electroencephalographic spectral power and lateralized motor activities.

The powers of the theta (3.5-7 Hz), alpha (7.4-12.3 Hz) and beta 1 (12.9-14.8 Hz) rhythms were analysed in symmetrical derivations. Sixteen right-handed young male adults were observed: at rest, with eyes closed (EC) (4 sequences) and eyes open (EO) (4 sequences); during right then left tonic alternate or sequential movements of the hand and while gazing to the right then to the left. At rest there exists a clear and significant spectral dominance to the right which does not appear in all the rhythms or in all the derivations. As far as the alpha rhythm EC is concerned, individual analysis of the sequences shows that of those which are significantly lateralized, three-quarters are lateralized towards the right. Right motor activity exaggerates, left motor activity diminishes, this right electrical dominance. Lateral gaze is the most powerful activity in this respect. At each derivation, comparison of intensities during right and left activities shows that the contralateral movements diminish the spectral power in the 3 bands studied. This effect seems to be obtained most frequently at the centro-parietal level. The spectral power at rest compared with that during motor activity is higher constantly for theta rhythm, in almost half the cases for the alpha and occasionally for the beta 1.