The direction of spread of alpha activity over the scalp

The direction of spread of alpha activity over the scalp was studied using the modified 'entropy analysis' method which distinguishes the direction of time differences between two correlated signals in the alpha band. The resting EEG was recorded from F3, F4, C3, C4, P3, P4, O1 and O2, each referenced to linked ears in 10 subjects. The directed measure of correlation of alpha activity in two directions (e.g., from O1 and O2 and from O2 to O1) was obtained from all possible pairs of electrodes. The dominant longitudinal direction of alpha activity was found to be anterior to posterior within as well as across hemispheres. No dominant transverse direction was found. This suggests that the spread of alpha activity over the scalp is in the dominant anterior-posterior direction.