According to the American Academy of Sleep Medicine there are 4 stages of sleep. This is composed of 3 stages of Non-REM sleep (N1, N2, N3) and REM.
The previous model of the sleep involved 5 stages of sleep (Stage 1, Stage 2, Stage 3, Stage 4, and REM). However, in recent times the American Academy of Sleep Medicine has combined stage 3 and 4 to become N3.
Here is an overview of the various stages of sleep:
N1 – (drowsy sleep)
• Transitioning from wakefulness to sleep
• Brain waves transition from alpha to theta waves
• Our muscle activity begins to slow down
N2 – (Light sleep)
• Heart rate slows down
• Body temperature decreases
• We experience sleep spindles (bursts of brain activity that help with restful sleep and the consolidation of information)
N3 – (Deep Sleep)
• Very restorative part of sleep
• Characterized by delta wave sleep
• Difficult to wake someone up
REM – (Rapid Eye Movement Sleep)
• Entire body is paralyzed except for the eyes.
• Increased heart rate, blood pressure, and sexual arousal
• About 20-25% of total sleep
• Where vast majority of dreaming occurs
Sleep Cycle Patterns
Our sleep cycles occur every 70-110 minutes, but there are variations throughout the night.
In the first half of sleep (usually the first 4-5 hours), our sleep is dominated by the N3 (deep sleep) stage with short REM periods. The sleep cycle moves through like this:
N1 --> N2 --> N3 --> N2 --> N1 --> REM
As the night progresses REM sleep periods increase.
In the second half of sleep our brains stop going into N3 and cycle through:
N1 (Drowsy Sleep) --> N2 (Light Sleep) --> N1 (Drowsy Sleep) --> REM (Rapid Eye Movement Sleep)
It is during the REM stage that the majority of our dreaming occurs.
Therefore lucid dreams are far more likely to occur during the latter half of sleep. It is also why a lot of the lucid dream induction techniques we cover in our online video training, occur in the latter half of sleep.