The transfer of EOG activity into the EEG for eyes open and closed.

The transfer of EOG activity into the EEG is investigated for eyes open (EO) eyes closed (EC), relying on spontaneously produced EOG activity. Blinks were prominent with EO and eye movements with EC. A frequency domain approach is more appropriate compared to treating the EOG influence as constant over frequency (i.e., assuming that a fraction of the EOG amplitude is present at EEG derivations). A major problem is to take into account the coherent EEG activity present at the EOG derivations, and this holds true in particular for the higher frequency bands were EOG power is relatively low. Blinks and eye movements have different spectral patterns and are also transferred differently to the locations on the skull. Eye movements are transferred best at low frequencies. The gains of blinks peak in the theta band. Due to high random variability in the individual gain functions, sample average gain functions ('grand means') rather than individual ones were studied.