certain memory processes can happen only when we are asleep

We dream to remember.To increase performance on certain mental tasks,sleep is good,but dreaming while sleeping is better.
In 2010, researchers found that subjects were much better
at getting through a complex 3-D maze if they had napped and dreamed of the maze prior to their second attempt.
In fact, they were up to ten times better at it than those who only thought of the maze while awake between attempts,
and those who napped but did not dream about the maze.
Researchers theorize that certain memory processes
can happen only when we are asleep,and our dreams are a signal
that these processes are taking place.