Types of Sleep

What happens during sleep? Your brain waves change.

When we sleep, the type of electroencephalographic (EEG) waves that the brain produces differs from when we’re awake.

• When you’re awake and active, the brain makes small, fast and random waves called beta waves.
• When you’re relaxing, the brain produces slower alpha waves.
• When you’re asleep, the brain produces slower and bigger delta and theta waves.

EEG states of being;

Why is this?

It’s because when you’re awake, the nerve cells in your brain tend to work on their own. This shows up as small, fast waves on the EEG. When you’re asleep, more of the nerve cells work together, giving large, slow waves.

The two types of sleep

Sleep is vital for life, yet research has not yet identified precisely what sleep does. We do know that sleep is divided into two distinct states, Rapid Eye Movement (REM) and Non-REM (NREM) sleep, both of which are as different from one another as each is from being awake.

1. Rapid Eye Movement (REM)

REM normally occurs in 90 minute intervals. It’s during these periods that we experience 'story-like' dreams. The first period of REM may last only five minutes, while later periods get progressively longer, concluding with a final REM sleep lasting anywhere from 30 minutes to a full hour.

The significance and purpose of dreams has prompted a multitude of theories, including that their significance is little more than diversionary; a nightly ‘cinema of the mind’.

During REM sleep, the eyes move quickly behind the eyelids and muscles can twitch.

We’re almost completely paralysed during REM sleep. Only the heart, diaphragm, eye muscles, and the muscles of the intestines and blood vessels continue business as usual.

2. Non-REM sleep (NREM)

NREM sleep is traditionally divided into 4 further stages, based on the size and speed of the brainwaves generated by the sleeper.

• Stage 1 sleep - this is the transition between wakefulness and sleep.
• Stage 2 sleep - this will make up the largest part of human sleep.
• Stages 3-4 sleep - considered to be 'deep sleep'; the phase during which the most stimulation is required to awaken a sleeper. Otherwise known as 'delta sleep' or 'slow wave sleep', these are the deepest stages of sleep during which big, slow brain waves, called 'delta waves', are generated.

Deep sleep is important because during stages 3-4, large quantities of growth hormone are released into the body. That’s why these stages of sleep are thought to restore the body from the wear and tear of waking activity.