The Science of Dreaming
Here's a little info on how Sleep Cycles work, and how they effect your dreaming...
Five Stages of your Sleep Cycle
Each night you pass through four stages of sleep (Non-REM sleep), before entering into the fifth and final stage called REM sleep.
(REM = "rapid eye movement.") Each stage takes 90-120 minutes to complete, and completing all 5 stages marks one full sleep cycle. Once you pass through the REM stage, the 5 stages start over again and a new sleep cycle begins. On average, if you sleep for eight or more hours per night, you are completing a total of five full sleep cycles.
NREM (non-REM) Stage 1 is a light sleep where you are easily awoken, and if aroused you may feel as if you have not slept. During this stage you lose self-awareness, may have the feeling of falling, and begin to loose muscle tone, muscle tone? Are you sure that’s the right phrase? which results in twitches and jerks (causing you to suddenly wake up). This stage typically lasts for 5-15 minutes.
NREM Stage 2 is marked by a loss of nearly all muscle control, so your physical body won't act out your dreams while sleeping. The heart rate slows and the body temperature decreases. This is a light dreamless sleep, and at this point, the body prepares to enter deep sleep.
NREM Stage 3 (and 4) Another dreamless state, these stages, are known as slow-wave, or delta, sleep. If aroused from sleep during these stages, a person may feel disoriented for a few minutes. These are deep sleep stages, with stage 4 being more intense word usage than Stage 3. In these stages you are also less responsive to your environment, although oddly enough this is the time that sleepwalking can occur.
REM (rapid eye movement) is the final stage in a sleep cycle, occurring 90 minutes after sleep onset. This stage marks the onset of dreaming, where your brainwaves become more active than before. (Similar to that of wakefulness, which is why you see REM sleep located in "stage 1" in the above graph). It is harder to awaken during this stage, however if you are awoken from REM sleep, you are more likely to jump right back in when you fall asleep again. Intense dreaming occurs during REM sleep as a result of this heightened brain activity, but paralysis occurs simultaneously in the major voluntary muscle groups.
In the first sleep cycle, the REM stage typically only lasts about 10 minutes. However, with each recurring sleep cycle, REM stage lengthens, and the final REM stage may last up to an hour. Adults spend about 20% of their sleep in the REM stage, and although REM is not fully understood, we do know that REM deprivation impairs our ability to learn complex tasks and hinders the formation of long term memories.
Best Time For Dreaming?
Your longest, most intense, and most memorable dreams will usually occur in the fourth and fifth sleep cycles (after about six hours of sleep) during the longer periods of REM. This means that it is essential to get sufficient rest in order to not miss out on REM sleep! Sleeping in or going to bed early will allow extended REM time in the morning or at the end of your 4th and 5th sleep cycle. (Studies have shown that it is actually healthier to complete 4-5 sleep cycles, which means the average adult needs between 7-8 hours of sleep).
As for dreaming, completing the final sleep cycles and the final REM stages will allow you to experience more vivid dreams, and your over-all dream recall.