Yet thanks to new research coming out of the University of Maryland School of Medicine, scientists were able to identify the key neural mechanisms regulating our transitions between wakefulness and sleep, shedding some light on this elusive phenomenon.

As the Maryland team detailed in a recent paper in Nature Communications, in order to determine the neural process regulating transitions between sleep and wakefulness, it focused on the suprachiasmatic nucleus in the hypothalamus, a small group of brain cells long known to be responsible for regulating the body's circadian cycles. These cycles refer to the physiological or behavioral changes in a plant or animal that occur in roughly 24-hour cycles. Circadian rhythms are primarily modulated by the day-night cycle, and inform an organism when to do things like eat, sleep, or migrate, as the case may be. 

The Maryland team examined a group of neuronal ion channels (proteins which allow ions, or electrically charged atoms, to move across a cell), known as BK potassium channels, within the suprachiasmatic nuclei of a number of mice. These BK potassium channels are particularly active in the suprachiasmatic nucleus, and in mice, which have sleep schedules opposite of humans, these channels are most active at night while the mice are awake.