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.