Eye closure causes widespread low-frequency power increase and focal gamma attenuation in the human electrocorticogram

Objective: We sought to characterize the effects of eye closure on EEG power using electrocorticography (ECoG). Specifically, we sought to elucidate the anatomical areas demonstrating an eye closure effect, and at which frequencies this effect occurs. Methods: ECoG was recorded from 32 patients undergoing invasive monitoring for seizure focus localization. Patients were instructed to close and open their eyes repeatedly. ECoG power was compared in the epochs following eye closure and opening, for various frequency bands and brain regions. Results: We found that at low frequencies, eye closure causes widespread power increases involving all lobes of the brain. This effect was significant not only in the alpha (8-12 Hz) band but in the delta (2-4 Hz), theta (4-8 Hz), and beta (15-30 Hz) bands as well. At high frequencies, eye closure causes comparatively focal power decreases over occipital cortex and frontal Brodmann areas 8 and 9. Conclusions: Eye closure (1) affects a broad range of frequencies outside the a band and (2) involves a distributed network of neural activity in anatomical areas outside visual cortex. Significance: This study constitutes the first large-scale, systematic application of ECoG to study eye closure, which is shown to influence a broad range of frequencies and brain regions. (C) 2014 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.