[Changes of spectral EEG parameters in normals at two week follow-up]

Computer EEG is commonly used in longitudinal clinical studies though physiological changes of electrical brain activity during repeated EEG recordings are poorly known. Resting eyes-closed EEG was recorded twice in two weeks in 14 healthy subjects (13 women, aged 25-69 years). At follow-up, the significant decrease of alpha and theta-2 power, along with changes of alpha-1 and alpha-2 mean frequencies in the right hemisphere, was observed. In addition, the increase of delta-2, theta and beta power was prominent in the left temporal region in the combination with slowing of delta-1 mean frequency in the left hemisphere and theta-2 frequency in the temporal regions. The present results reveal that physiological changes of brain electrical activity at repeated recordings are prominent and this fact should be correctly treated during longitudinal clinical studies using EEG.