EEG Electrode Positions Outside the Hairline to Monitor Sleep in Man

This study investigated the use of electroencephalographic (EEG) electrode placements outside the hairline to monitor sleep. Six subjects slept for 1 night during which the EEG was recorded from "standard" electrode placements and simultaneously from the "test" placements outside the hairline where adhesive pregelled electrodes could be used. Each subject's EEG record was scored independently by two observers. The standard and test electrode placements were assessed separately. Cohen's kappa (kappa) was used to quantify the agreement in the sleep scores (a) between observers when both scored the standard placements and (b) between the test and standard placements when scored by the same observer. The agreement for all stages between observers (a) was excellent (kappa = 0.82); and the agreement within observers, between placements (b) was even better [kappa = 0.86 for the six sleep stages considered separately; when stages awake/1 and 3/4 were combined (a) kappa = 0.88 and (b) kappa = 0.09]. It is concluded that EEG electrode placements outside the hairline can be used effectively to record sleep EEGs. The adoption of these electrode placements would simplify the monitoring procedure for many applied physiological studies especially when usual laboratory techniques for EEG are precluded.