Have you ever watched someone sleeping? If so, you will have noticed that there is a lot of movement during sleep. Sleep is an active process in which metabolism, memory consolidation, tissue restoration and homeostatic balance is maintained. So, while on the surface, it may appear that the characteristics of sleep are uniform throughout the sleeping period, this is actually far from the truth.
There are three determinants that define the type of sleep – eye movement, brainwave activity and muscle activity.
In 1952, researchers observed that there were phases of sleep where eye movement was very active; with the eyeballs moving from side to side under closed eyelids. This was found to be accompanied by a high level of brain activity.
Similarly, there were phases where the eye movement was almost nil and the brainwave activity was very slow.
The first type of sleep is called REM(rapid eye movement) sleep and the second type is called NREM (non- rapid eye movement) sleep. Both types of sleep alternate with each other in continuous cycles and do different things for the body. Typical sleep duration has several 90-minute segments where the REM and NREM sleep alternate. When you fall off to sleep at your regular hours, in the initial phase of 90 minutes, there is more NREM sleep and less REM. With each phase, the REM type starts increasing and in the last phase before waking up, it is mostly REM sleep.
The NREM sleep acts as a filter of all your memories and experiences in the day. During this phase of sleep, the neural circuits filter out all unnecessary details.
During the REM phase, the neural connections are strengthened; reinforcing thinking patterns and learning. This phase of sleep helps consolidate memories and acts as a restorative for the brain.
If you fail to sleep in time and lose the early part of sleep, then you lose a lot of NREM sleep. Similarly, if you sleep on time but wake up before sleeping for 8 hours or so, you lose a lot of REM sleep. The REM stage is where you dream and your muscles are paralyzed. Researchers believe that REM sleep helps in memory, in managing your moods and emotions better, and helps in creativity.
Reviewed by- Dr. N. Nayak, MBBS, MD
Image Source: Photo by Andrea Piacquadio from Pexels
