Today we know that both deep sleep and REM sleep play important roles in how memories change over time. The sleeping brain reshapes memory by increasing the imprint of emotionally relevant information while helping irrelevant material fade away.

In stark contrast to this misperception, neuroscientists have recently discovered that parts of the brain can fall asleep for a few moments or longer without our realizing it. At any given moment, some circuits in the brain may be off-line, slumbering,

Stickgold proved that during sleep, on a very deep level we process the experiences and information that we gather while we are awake. When we sleep, and in particular when we dream, the brain goes through the countless things we were exposed to throughout the day—the cars we saw in a parking lot, the story arc of the TV show we watched, the ideas