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 present study is to examine the effects of ocular artifacts on broadband EEG parameters. Methods: EEG and EOG were recorded from 31 participants in a resting condition with eyes open and closed, allowing for spontaneous ocular activity. General effects: of ocular artifacts were examined with mean comparisons, and differential effects were examined with correlation analysis of data portions that were selected for a presence or absence of artifacts. Results: At single sites, blinks and eye movements exerted substantial general effects on the whole EEG spectrum, but there were no substantial differential effects of artifacts in the alpha and beta bands. except at the frontopolar sites. The distorting effects of ocular artifacts were smaller in magnitude for asymmetry than for single site measures. Conclusions: The control of ocular artifacts may be dispensable for correlation analyses of alpha or beta band parameters. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.