What is putting part of your brain to sleep, while the rest is awake?

In Brain Science, Sleep by Brainy Days Ahead

MIT neuroscientists have discovered 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. This circuit originates in 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. Read on.