Читать книгу Sleep: The secret to sleeping well and waking refreshed - Prof. Idzikowski Chris - Страница 27

In an electro-encephalogram (EEG), electrodes are glued to a person’s scalp and then connected to powerful amplifiers that measure brain activity. Their output used to be printed on paper, but can now be seen on a computer monitor in the form of a graph called a hypnogram, or polysomnograph, which shows the brainwaves emitted during sleep. Eye activity and muscle tone are also recorded.

Using the EEG in this way has shown that people have two different kinds of sleep: non-REM (Rapid Eye Movement) sleep and REM, or dreaming, sleep, and that they go through five different stages within these two main types: Stage 1 (drowsiness), Stage 2 (light sleep), Stages 3 and 4 (deep sleep, sometimes called delta or slow-wave sleep) and Stage 5 (also known as REM sleep).