Changes in direct current potentials during sleep deprivation.
Previous research reported changes in steady-state brain electrical activity during sleep. However, due to the quasi-linear nature of the Direct Current (DC) changes, artifact contamination was a potential confound. The present study was performed to further explore DC potentials and to help establish its validity. Twenty-five male university students (13 control and 12 sleep-deprived; mean age 19 y (range 17-27 y) served as subjects. During wakefulness, subjects were tested every hour while standard EEG activity recordings were made, as well as DC measurement. Split plot analyses of variance (ANOVAs) revealed that changes in DC activity levels differed between the two groups. The control subjects showed the same pattern of decreasing DC observed previously with a return to baseline levels during waking hours. The sleep-deprived subjects showed a smaller decrease in DC level through the night, followed by a rise in DC level that continued until the end of the 24 h study. It was concluded that DC measurement reflects changes in brain state associated with fatigue that are not attributable to artifactual processes.