The effects of ocular artifacts on (lateralized) broadband power in the EEG

Objective: Empirical evidence suggests that blinks and eye movements do not generate substantial activity outside the delta and theta range, and that the propagation of ocular activity to the EEG is rather symmetrical. These observations suggest that an alteration of the alpha and beta asymmetry of the EEG due to ocular artifacts is not likely to occur. The aim of the pres ent study is to examine the effects of ocular artifacts on broadband EEG pa rameters. Methods: EEG and EOG were recorded from 31 participants in a resting condit ion with eyes open and closed, allowing for spontaneous ocular activity. Ge neral effects: of ocular artifacts were examined with mean comparisons, and differential effects were examined with correlation analysis of data porti ons that were selected for a presence or absence of artifacts. Results: At single sites, blinks and eye movements exerted substantial gene ral effects on the whole EEG spectrum, but there were no substantial differ ential effects of artifacts in the alpha and beta bands. except at the fron topolar sites. The distorting effects of ocular artifacts were smaller in m agnitude for asymmetry than for single site measures. Conclusions: The control of ocular artifacts may be dispensable for correla tion analyses of alpha or beta band parameters. (C) 2001 Elsevier Science I reland Ltd. All rights reserved.