Sleeping & dreaming……
People spend about a third of their lives asleep, and a quarter of that time dreaming. During sleep, the metabolism slows, the immune systems concentrate on fighting infections and the production of growth hormone increases, not only for growth but also for repair of body tissue. On a mental level, sleep deprivation leads to poor concentration, memory failure and irritability.
The sleep cycle is broken up into several distinct phases. The first is a period of “slow-wave” sleep, when brain activity, breathing and heart rate all slow down. Slow-wave sleep goes through four stages, the last of which is the deepest, when the brain waves are slowest. This is the time when it is most difficult to rouse someone.
After about 90 minutes, Rapid Eye Movement (REM) sleep begins, when the most vivid dreams occur. Phases of REM sleep recur four or five times during the night, between periods of slow-wave sleep. Each REM phase is longer and more intense, from 15 minutes for the first up to 45 minutes for the last, which is often in the final hour of sleep before you wake up.
Why You Dream
Studies have shown that if people are deprived of REM sleep they become irritable and lack concentration. They try to catch up on dreams as soon as they are allowed to sleep again by dreaming more than usual, even if this means having less non-REM sleep.
This suggests that dreams are in some way necessary for mental and emotional health. They may be a sign that the brain is “ticking over”, continuing to interpret signals from the outside world.
They maybe a form of wish-fulfilment or a way of expressing and resolving emotional crises. Dreams may also be a way for the brain to sort information it has received during the day, as well as considering ideas and grappling with problems.
When You Dream
It was once thought that dreams occurred only during REM sleep, but research has found that dreams occur throughout the night during periods of non-REM sleep, although they are less vivid and are usually forgotten. In the lighter phases of sleep (stages one and two), dreams resemble the fleeting images and thoughts you may experience if you simply allow your mind to drift while awake. Dreams from deeper sleep (stages three and four) are often fragmentary sensations, feelings and thoughts rather than images.
When people are stirred from these deeper stages of slow-wave sleep they are often groggy, confused and unable to remember what they have dreamed. In contrast, dreams during REM sleep have characters and story-lines played out in a series of vivid images. You will usually wake from REM sleep fully conscious and with clear memories of your dreams.
The body also responds to different types of dream experience. During slow-wave sleep you may twitch, talk or even sleep-walk, but during REM sleep you are virtually still. Although the brain remains active, muscle tone is lost, resulting in virtual paralysis. This means there is no danger of physically acting out a dream, and also explains the sense of paralysis often experienced during a nightmare.
Why You Forget Your Dreams
Even though everyone has periods of REM sleep, some people claim never to dream. This is simply because they don’t remember them. But if dreams are important, why is this?
About a quarter of sleeping time is taken up with dreaming, approximately two hours a night. That is a lot to remember, especially if you recall your dreams only when you wake up during them or immediately afterwards. Most people lead busy lives, and wake up ready to get on with the day. Taking the time to think about what you were dreaming of during the night would seem a luxury.
Dreams are also difficult to remember — frequently chaotic and confusing, they flash incoherently from one image to the next. Memories of them tend to be partial and imprecise, and it is always easier to remember dreams that are dramatic and colourful or those that have some personal significance.