NREM sleep is divided into 4 stages of increasing depth.

Respiratory or heart rhythm becomes irregular (unlike NREM sleep).

NREM sleep: Across these four stages we move from very light sleep during Stage 1 down to very deep sleep in Stage 4.

NREM sleep is non-rapid eye movement sleep, 75–80% of total sleep time in normal human adults.

These sleep spindles last about one second and can occur 1,000 times per night during NREM sleep.

The invention relates to the use of 5-HT2 receptor antagonists for producing a medicament which extends non-REM sleep and REM sleep.

Non-REM sleep is divided into four stages that range from light sleep to deep sleep.

Stage 3 non-REM sleep marks the passage from moderately to truly deep sleep.

During non-REM sleep, it is occasional and involuntary.

Non-REM sleep has four stages of increasingly deep sleep.

Slow sleep is composed of three phases, the third of which is called “slow-deep sleep”.

Slow sleep is composed of three phases, the third of which is called “slow-deep sleep”.

Slow sleep is composed of three phases, the third of which is called “slow-deep sleep”.

Slow sleep, as you will have understood, is the third phase of sleep.

Once the slow sleep period is over, you fall into a deep sleep.