Topography of visual EEG reactivity in school-age children.

In order to quantify the visual reactivity of EEG to opening the eyes, the topography of EEG power spectra for a sample of 72 healthy subjects of age ranging from 7 to 15 years was investigated. The EEGs were recorded from 16 scalp sites with eyes open (EOP) and eyes closed (ECL). Ln-transformed absolute EEG powers, acquired under these two states, were tested with Wilcoxon's paired test for differences between the powers. The absolute powers in alpha band and in total, were significantly higher in all derivations, under the ECL, as compared with the EOP, condition. Absolute powers in theta band under the ECL condition were also significantly higher than those under the EOP condition, except for frontal derivations. Changes in delta power were insignificant. Beta 1 band activity, when eyes were closed, was maximal in posterior and minimal in anterior derivations. When the eyes were open, the greatest beta 1 power was found in the frontal derivations. Beta 2 was the only band in which a frequent increase in power took place with eyes opening. Eyes opening appeared to decrease significantly, the beta 1 and beta 2 powers only in posterior derivations. The results showed that the visual blocking of EEG was mostly due to a higher degree of EEG desynchronization for the subjects aged 7-5 years.