Читать книгу The Element Encyclopedia of 20,000 Dreams: The Ultimate A–Z to Interpret the Secrets of Your Dreams - Theresa Cheung, Theresa Cheung - Страница 8

‘Yet it is in our idleness, in our dreams, that the submerged truth sometimes comes to the top.’ Virginia Woolf

Perhaps the best way to understand sleep and dreams is to understand the brain. At the very start of the twentieth century it was found that the brain gave off electrical impulses, and by the 1920s scientists could measure brain waves. To obtain these readings, electrodes were attached to various parts of the head, the impulses being transformed onto electroencephalograms (EECs) on computer screens.

It seems that once you settle down to bed, your brain and body undergo radical changes from their waking state. The difference between being asleep and being awake is loss of conscious awareness, and once you start to doze, dream researchers believe you progress through four stages of sleep. These form the basis of a cycle that repeats up to four or five times every eight hours of sleep.

During the first stage, your body and mind become relaxed. Heart and breathing rate slow down, blood pressure lowers, body temperature drops slightly and eyes roll from side to side. You are neither fully conscious, nor fully unconscious, and could easily awake if disturbed. This stage of gradually falling asleep is also called the hypnagogic state (the hypnopompic state is a similar state when you are just waking up) and you may experience hallucinations that float before your eyes.

In stage two, breathing and heart rate become even slower, eyes continue to roll and you become more and more unaware of the noises of the outside world. It isn’t until the third stage of sleep, however, that you are sleeping soundly and it would be difficult to wake you. Finally, you enter a deep sleep state known as non-rapid eye movement (NREM) when your brain is released from the demands of the conscious mind. It will now be quite hard to wake you and, although you may sleepwalk or have night terrors, you will rarely be able to remember them. This slow-wave sleep cycle lasts about ninety minutes. At the end of stage four, you move back through stages three and two and one, at which point you enter a phase called rapid eye movement, or REM, sleep.