The High Energy Cost of Theta-Gamma Activity during REM Sleep

The occurrence of wake-like electroencephalography (EEG) traces during rapid-eye movement sleep (REM) has intrigued scientists for decades. A recent study by Bergel et al. (Nat. Commun. 2018;9;5364) imaged brain-wide hemodynamics in rats during wakefulness and sleep. The findings suggest that brain energy expenditure is highest during REM because of heightened theta and gamma activity.