A hippocampal 'sharp-wave sleep' state that is dissociable from cortical sleep.

Summary: Did you know parts of your brain can sleep while you are awake? Scientists studied rats and found that a deep part of the brain called the hippocampus has its own kind of sleep. It uses special brain waves called "sharp waves." These waves happen when the rat is sleeping, but also when it is just resting quietly awake. This means the hippocampus can take a quick nap and recharge even if the rest of the brain is awake!