Reflections on why we need sleep date back from ancient times. While people back then had a lot of absurd theories surrounding the phenomena, modern-day science confirms that it clears our thought, support learning, heightens memory and re-energize our cells. Scientists categorized sleep into two states: Non-REM and REM.
We enter these when our brain waves start going slower, more synchronized AKA Alpha wave and increase in amplitude. This process is what makes us feel drowsy.
The first stage of sleep is the body transitioning from being awake to sleep. This process is characterized by theta waves which are slower in frequency yet more in amplitude compared to alpha waves. Sleep deprived individuals are more likely to experience microsleep where the theta waves replace alpha wave activity quite fast. When this happens people fall asleep without them noticing! On stage 2, the theta wave activities continue while interspersed with the thalamus and the cortex.
The first 2 stages represent the lighter degrees of sleep. In this environment, individuals are easy to wake and some might not know that they were asleep at all. When the delta waves come in, it means that stage 3 and 4 will soon follow. These waves are the highest and slowest in amplitude brain waves. Entering this degree will make it harder for people to wake up since its the deepest kind of sleep. It is also the kind of sleep when talking and walking is more likely to happen.
During NREM sleep, the senses still work the same way when a person is awake. It slowly loses its perceptual activity as sleep grows deeper. Once deep sleep is imminent, the default mode network generates inhibitions that allow thoughts roam free hence, the occurrence of dreams and nightmares.