24-h profiles of direct current brain potential fluctuation in rats

The long-term profile of direct current (DC) brain potential fluctuation has not yet been clarified. In this study, DC potentials were recorded in the frontal area of the cerebral cortex, referenced to the cerebellum, for 24 h in freely moving rats under light control (dark period: 20:00–8:00 h). Significant diurnal variation was observed, and the DC potential at the frontal area during the light period was more positive to the cerebellum than during the dark period. Amplitudes of DC potentials were negatively correlated with muscular activity. In addition, phasic negative shifts with durations of less than an hour were observed and were accompanied by muscular activation and delta wave suppression. These results suggest that the DC brain potentials fluctuate during the day and are related to changes in arousal level.