EEG correlates of subcortical optokinetic nystagmus

Objective Our aim was to reveal the changes of concomitant scalp EEG activity during subcortical (stare-) optokinetic nystagmus (OKN). Methods Stare-OKN of 10 subjects was evoked and recorded simultaneously with the EEG. Frequency distribution of OKN-beats was determined in each subject. Power changes of alpha and beta frequency bands of the EEG during OKN stimulation were statistically analysed. Results During continuous subcortical OKN–the EEG alpha power decreased significantly while beta power increase was not significant. A significant transient alpha power enhancement around the onset of subcortical OKN-clusters was detected. Conclusions We found significant changes in the parieto-occipital alpha EEG activity during subcortical OKN. The transient alpha synchronisation at the beginning of each OKN-cluster is a paradox phenomenon which might indicate increased visual attention. Significance The present study is the first report investigating EEG changes related to subcortical OKN. Our findings suggest the involvement of cortical mechanisms in the generation of stare-OKN. The results might help in the elucidation of cortico-genicular mechanisms of ocular movements under physiological and pathological conditions.