The latest research suggests that while you are asleep, your brain is busily processing the day's information. It combs through recently formed memories, stabilizing, copying, filing, and making them more useful for the next day.
A night of sleep can make memories resistant to interference from other information and allow you to recall them more effectively. It also lets your brain sift through newly formed memories, possibly even identifying what is worth keeping and what to let go of.
During sleep, your mind analyzes collections of memories, helping you discover hidden relations between seemingly random pieces of information, and helps you find the meaning in what you have learned.
It's been discovered that you need a minimum of six hours of sleep to see an improvement in your performance over the 24 hours following a learning session.
Memories are created by altering the strengths of connections among hundreds, thousands or perhaps even millions of neurons, making certain patterns of activity more likely to recur. These patterns of activity, when reactivated, lead to the recall of a memory whether that memory is where you left your car keys or something you're trying to memorize.
These changes in synaptic strength are thought to arise from a molecular process known as long-term potentiation, which strengthens the connections between pairs of neurons that fire at the same time.
Thus, cells that fire together wire together, locking the pattern in place for future recall.
During sleep, your brain reactivates the patterns of neural activity that it performed during the day, thus strengthening your memories by long-term potentiation.
As this unconscious rehearsing strengthens memory, something more complex is happening as well your brain may be selectively rehearsing the more difficult aspects of a task. It seems your brain needs time to process or rehearse new information, connecting the dots, so to speakand sleep provides the maximum benefit.
As exciting new findings about sleep come in more and more rapidly, it becomes more and more clear that your brain is anything but inactive during sleep.
It is now clear that sleep can consolidate memories by enhancing and stabilizing them, and by finding patterns within studied material even when you don't know that patterns might be there. It's also clear that skimping on sleep can interfere with crucial cognitive processes. Miss a night of sleep, and the day's memories might be compromised.
Source: Scientific American August 7, 2008