Researchers at Massachusetts Institute of Technology (MIT) have identified a brain circuit that can trigger small regions of the brain to fall asleep even while the rest of the brain remains awake, which explains why we sometimes 'zone out'.
Using "optogenetics, a technique that allows scientists to stimulate or silence neurons with light," on test mice, researchers found "a brain circuit that can trigger small regions of the brain to fall asleep or become less alert, while the rest of the brain remains awake."
A brain structure known as the thalamic reticular nucleus (TRN), which relays signals to the thalamus and then the brain's cortex, inducing pockets of the slow, oscillating brain waves characteristic of deep sleep.
"During sleep, maybe specific brain regions have slow waves at the same time because they need to exchange information with each other, whereas other ones don't," said one of the lead authors Laura Lewis, from Massachusetts Institute of Technology.
The TRN may also be responsible for what happens in the brain when sleep-deprived people experience brief sensations of "zoning out" while struggling to stay awake.
And if you find that you become spacey when you're exhausted, sleep-deprived, or just generally out of it, Lewis believes that this may be "because the brain begins to transition into sleep, and some local brain regions become drowsy even if you force yourself to stay awake."
This research may be key in developing sleep drugs and anesthetics that work with the TRN to induce these slow wave patterns, thereby reducing the potential for harmful side effects.