Hot topic - To sleep, perchance to learn
04 November 2004 - written by Bupa's Health information team
Tasks that we learn during the day may be processed by our brains during deep sleep, so that we perform them better the following day, according to a new study published in the 28 October 2004 edition of Neuron.1
What did the study show?
The study showed that the same part of the brain that is involved in learning new tasks during the day is still busy working during sleep. This may strengthen what we have learned during the day, and enable us to perform better the next day.
In addition, the study showed that the more active the brain is during sleep, the better we perform the next day.1
How was the study carried out?
The researchers asked volunteers to learn the layout of a virtual town that was adapted from a computer game. While some of the volunteers were given training, others were just left to learn the layout by themselves. They tested the volunteers by asking them to find routes through the town to specific locations as quickly as possible. This was a test of spatial memory.1
What is spatial memory?
Spatial memory is the part of memory that is responsible for recording information about your surroundings and it's orientation.
For example, if you walked into a darkened room in your own home, you would have a good idea of where all the individual items were in the room, so you would be unlikely to walk into them. To be able to do this, you need to be able to remember what is in the room and where it is in relation to where you are standing - this uses your spatial memory.
How was spatial memory tested?
The researchers used a machine that scanned the volunteers' brains at various points throughout the study - when they were awake and when they were asleep.
The flow of the blood through parts of the brain is a measure of the activity in those parts. In this study, they measured changes in brain activity due to spatial processing in a part of the brain called the hippocampus.1
What is the hippocampus?
The hippocampus is a part of the brain that appears to be one of the most important structures for normal memory function. It is vital for making new memories, so if you didn't have it you would be stuck in the past of old memories.2
What activity was seen in the hippocampus during sleep?
When the trained volunteers were asleep, their activity in the hippocampus was greater compared with those who weren't trained.
The greater the activity in the hippocampus during sleep, the better the volunteers did in the tests the next day.1
Is the brain more active all night?
No. The greater activity in the hippocampus was only seen during the periods of sleep known as slow wave sleep and not during rapid eye movement (REM) sleep.1
What is slow wave sleep?
Slow wave sleep is a period of sleep during which your brain waves are slow, your muscles are relaxed and your heart beat and breathing is slow and regular. In a normal adult, after falling asleep there is a period of about 20 to 30 minutes before you enter slow wave sleep.
During slow wave sleep, your body is refreshed and you do not dream. Slow wave sleep is switched with periods of REM sleep throughout the night.3
What is rapid eye movement (REM) sleep?
During REM sleep, your eyes dart about, your brain is very active and you dream. Throughout the night, the periods of slow wave sleep get shorter and the periods of REM sleep get longer.3
Why does sleep help memory?
It is thought that while you are asleep, the information that you have learned during the day is altered, re-structured and strengthened in the hippocampus. Sleep allows your brain to store this strengthened information in your memory for future use.
Why does spatial processing appear to take place during slow wave sleep only?
Although it is not yet fully understood one explanation may be that the active or waking brain is too 'noisy' and interferes with the learning process. More research is needed to find the answer.4
Will a good night's sleep improve my memory?
It is not guaranteed that a good night's sleep will improve your memory. However, this study suggests that during sleep your brain processes tasks that you have learned during the day, enabling you to perform those tasks better the following day.1
How much sleep do I need?
The amount of sleep you need depends mainly on your age. As you get older you need less sleep. A baby needs about 17 hours of sleep a day while older children need about nine or ten hours. Most adults need between seven and eight hours of sleep a day, although some need more and some can manage on less.5
Further information
Bupa resources:
- Article: Yawn - sleep well!
http://www.bupa.co.uk/health_information/html/healthy_living/general/yawn/ - Factsheet: Insomnia
http://hcd2.bupa.co.uk/fact_sheets/html/Insomnia.html
References
- Peigneux P, Laureys S, Fuchs S et al. Are spatial memories strengthened in the human hippocampus during slow wave sleep? Neuron 2004;44(3):535-545.
- Bray JJ, Cragg PA, Macknight ADC et al. Lecture Notes on Human Physiology, 4th edition: Chapter 9, pp. 230-231. Blackwell Science Ltd, 1999.
- GPnotebook: Sleep.
http://www.gpnotebook.co.uk/cache/1234829326.htm - Nelson L. While you were sleeping. Published online 25 August 2004.
http://www.nature.com/news/2004/040823/pf/430962a_pf.html - The Royal College of Psychiatrists: Sleeping well.
http://www.rcpsych.ac.uk/info/help/sleep/sleep.pdf
