The state just before we fall asleep, where we are sort of drifting is called a hypnogogic state. One has a sense of floating or drifting off. A lot of people have a falling sensation just as they drift of to sleep. Sometimes it is so severe that it jerks them awake. This is called a hypnogogic startle.

There are four phases of sleep:

The first phase, is accompanied by alpha waves in the brain. They are spiky and one is relaxed but still awake.

During the next phase, the cycles in your brain become more rhythmic longer theta waves. A light slumber is experienced, this lasts about 10 minutes. Slowly the theta waves are joined by sharp jumps on the ECG, these are called spindles.

About 20 minutes into the sleep cycle the third stage starts and is recognized by large slow waves called delta waves, now no more spindles appear. One is plunged into deep sleep, when one is woken up during this phase disorientation, fuzziness and an extreme desire to go back to sleep is common. Often people describe their mental activity during this deep sleep as ‘thinking.‘

Stage four, is very different from wakefulness and also different from deep sleep, it is called paradoxical sleep. *The Blood Pressure rises *The Pulse quickens *The Brainwaves resemble wakefulness *The eyes, fingers and toes twitch while the rest of the body is virtually paralyzed – it is thought this is protect the sleeper against acting out the contents of the dream and harming themselves. *There is REM (Rapid Eye Movement) visible under the eyelids.

Sometimes a person woken from REM sleep can’t move for a few seconds. This phase of paralyses is controlled by the Neuro-cortex in the primitive Brainstem.

The first cycle of REM sleep lasts about 10 minutes, then one almost wakens, falls back into stage two and then back into deep sleep and REM. One has 4 to 5 REM cycles per night. As each cycle passes REM sleep increases from 10 minutes to almost an hour.

A few facts:

One spends almost 5 years of your life dreaming.
 
Almost 95% of our dreams are lost upon waking.

The brain is more active during sleep than when awake.

Wider spectrums of sight can be ‘seen’ during dreams.