Why Getting a Good Night’s Sleep Helps You Learn Better Back in 1994, researchers at the Weizmann Institute in Israel showed that a night of sleep improved the ability to rapidly discriminate between two objects. But the sleep had to be the ‘REM’ (rapid eye movement; our sleep follows 90-minute cycles, moving in and out of REM sleep, whose brainwaves look similar to those of when we are awake; in the picture ‘awake’ is on the left, REM in the middle and slow-wave on the right). When the volunteers were deprived of REM sleep, this improvement disappeared. Because an improvement happened with sleep, this led the scientists to realise that sleep actually does something to memory. A similar study conducted in 2000 by Stickgold added more information to these findings: performance only improved after 6 hours of sleep, and that sleep in all its phases (REM and slow-wave) was necessary, not just the REM phase. When we encode information in our brain, the newly acquired memory begins a journey in which it is stabilised, enhanced and even altered, until it bears only a faint resemblance to its original form. Over the first few hours, a memory can become more stable and become ‘resistant’ to interference from competing memories. In 2006 a lovely experiment (Stickgold & Ellenbogen) demonstrated that sleep actually helps to make memories more robust. Volunteers were were trained to memorise pairs of words in an A-B pattern, for example, ‘blanket-window’. Some of the participants were then allowed to sleep. Later they all learned pairs in an A-C patter, for example, ‘blanket-sneaker’ which were supposed to interfere with their memories of the A-B pairs.  The volunteers who had been allowed to sleep could remember more of the A-B pairs than the people who had stayed awake. When the researchers tried to interfere more with the A-C pairs, it became even more obvious that those who had slept had a stronger, more stable memory for the A-B sets. So it seems from this that sleep does something to improve memory that being awake does not. But sleep does not only stabilise memory. Very recent studies have shown that the brain is doing even more sophisticated thing It seems to be dissecting our memories and only retaining the most important details….In one study, a series of pictures was used which included either an unpleasant or a neutral object on a neutral background. Volunteers were asked to view the pictures one after another. 12 hours later their memories were tested for the objects and for the backgrounds. The results were surprising: whether the person had stayed awake or had slept, the accuracy of their memories dropped by 10% for everything except for the memory of the more emotionally-evocative objects. The memory of these actually improved after a night’s sleep, showing 15% improvement relative to the backgrounds. During our sleep time, our brain also reactivates the patterns of brain activity that have taken place during the day. This was shown for the first time by Wilson & McNaughton in 1994. Rats were fitted with implants that monitored their brain activity. The rats were taught to circle a track to find food, and the neuronal firing patterns were constantly recorded. Cells in the hippocampus – an area in the brain that is critical for memory of spaces – created a map of the track, with different ‘place cells’ firing as the rats crossed each region of the track. These ‘place cells’ corresponded so closely to exact physical locations that the researchers could monitor the rats’ progress around the track by simply watching which place cells were firing at any given time. But the story gets even more fascinating, because the researchers continued to record from these place cells whilst the rats still slept. They saw that the cells were continuing to fire in the same order. It is as if the rats were practicing running around the track in their sleep!! The brain is really amazing. In 2005, a researcher (Walker) at Harvard discovered that the brain even rehearses more difficult aspects of a task. When volunteers learned to type complicated sequences such as 4-1-3-2-4 on a keyboard, then sleeping between practice sessions led to faster and more coordinated finger movements. He found, on more closer examination, that people were not simply getting faster in general on this type of task, but that they were getting faster on those particular keystroke sequences at which he or she was the worst. The brain does this by moving the memory for these sequences overnight. Walker used functional magnetic resonance imaging (fMRI) to show that the subjects used different brain regions to control their typing after they had slept. The following day, typing used more activity in brain areas responsible for faster and more precise key-press movements, and less activity in areas associated with conscious and emotional effort. The entire memory got strengthened – especially the parts that needed it most. Sleep does this work by using different parts of the brain than were used to learn the task. Studies carried out in 2004 by Wagner &Born in Lubeck (Germany) elegantly demonstrated how powerful sleep can be in processing memories.  Participants were taught how to solve a mathematical problem by using a very long procedure. They were then asked to practice it 100 times. Following this they were sent away and told to come back 12 hours later, when they were instructed to try it another 200 times. What the researchers did not tell their subjects is that there was a much simpler way to solve the problem. The researchers could tell if and when the subjects gained that insight because their speed would suddenly increase. Many of the volunteers did discover the ‘secret’ in that second session. But when they got a night’s sleep in between the 2 sessions, they were more than 2.5 times as likely to figure it out: 59% of the people who slept found the trick, compared to 23% who stayed awake between sessions. Somehow the sleeping brain was solving this problem without even knowing that there was a problem to solve! What a marvellous thing sleep is! The brain not only strengthens memories, sifting out the aspects it wants to keep, but it also finds patterns between things that we may not even know are there. This means that when we get too little sleep - less than 6 hours sleep a night - certain processes like these do not get enough opportunity to be completed. In our current fast-paced lives this is quite a thought for concern… And remember that many famous people – and not so famous ones too – have had major insights whilst sleeping. The brain does its best to try and find connections to bring seemingly unconnected data together. And I think that on that note, it is time for me to go and crawl under the duvet….and sleep on it! Of course, you all know now that really I will not be sleeping but working. See you all in January, and have a wonderful Christmas & New Year. References A. Karni, D. Tanne, B. S. Rubenstein, J. J. M. Askenasy & D. Sagi. Dependence on REM Sleep of Overnight Improvement of a Perceptual Skill. Science, 1994, volume 265, pages 679-682. R. Stickgold, L. James & J. A. Hobson. Visual Discrimination Learning Requires Sleep after Training. Nature Neuroscience, 2000, volume 3, number 12, pages 1237-1238. R. Stickgold. Neuroscience: A Memory Boost While You Sleep. Nature, 2006, volume 444, pages 559-560. M. A. Wilson & B. L. McNaughton. Reactivation of Hippocampal Ensemble Memories During Sleep. Science, 1994, volume 265, pages 676-679. M. P. Walker, R. Stickgold. D. Alsop, N. Gaab, G. Schlaug. Sleep-Dependent Motor Memory Plasticity in the Human Brain. Neuroscience, 2005, volume 133, pages 911-917. U. Wagner, S. Gals, H. Haider, R. Verleger & J. Born. Sleep Inspires Insight. Nature, 2004, volume 427, pages 352-355. R. Stickgold. Sleep-Dependent Memory Consolidation. Nature, 2005, volume 437, pages 1272-1278. D. Ji & M. Wilson. Coordinated Memory Replay in the Visual Cortex and Hippocampus. Nature Neuroscience, 2007, volume 10, number 1, pages 100-107. J. M. Ellenbogen, P. Hu, J. D. Payne, D. Titone & M. P. Walker. Human Relational Memory Requires Time and Sleep. Proceedings of the National Academy of Sciences USA, 2007, volume 104, number 18, pages 7723-7728.