When you fall asleep at night, there are number of changes that occur in your brain and body despite our apparent unawareness. The frequency of brain electrical activity ( as seen by an EEG machine )gradually slows down over periods of deep sleep (Non -REM) and picks up again during periods of REM (rapid eye movement) sleep.
During deep sleep , our brains are resting and recharging for the awake state. During REM sleep the body is paralyzed completely, while the brain is more or less active. Typically 5 NREM/REM cycles occur per night with the duration of REM sleep increasing as the night progresses.
Dreams occur through out the night as our memories and thoughts are slowly consolidated and encoded. New neuronal connections are made and old ones reinforced. We remember those dreams that occur during REM sleep but not those which occur during deep sleep.
Beyond a cognitive level, the hormones that repair and restore the body are released during NREM sleep making it very important in maintaining a healthy body.
A variety of interesting phenomena occur during the different stages of sleep . . .
During deep sleep, phenomena such as sleepwalking, sleep-talking and night terrors can occur.
Whilst sleep walking, the sleeper may walk around or wander around at night and wake up next morning with no memory of such an event occurring. Other complex behavior such as dressing and eating can also occur. There have been rare reports of self harm, violence or hurt during such states. Injury may occur when someone walk out of windows or falls down stairs. Eyes are sometimes open and glassy, communication is impossible. If you are faced with someone who is sleep walking, do not try to wake them up, gently guide them back to bed.
Awakening one who is sleep walking will leave them in a disoriented state and at greater risk of causing harm to themselves or others. Like we said, during deep sleep, the body is more or less awake while the brain sleeps.
Night terrors are commoner among children. They wake up screaming and terrified in the middle of the night and are unable to recall why. This is often accompanied by symptoms of arousal such as palpitations, tachycardia and sweating. They also trigger panic attacks (episodes of intense anxiety associated with a fear of dying or loosing control).
Sleep related eating disorder was reported first in the 1950s wherein a number of women aged 20-30 were reported to wake up , eat and drink at night with minimal awareness of the same!
REM sleep – Dreams and nightmares occur during NREM sleep, despite several attempts by several researchers, there are no definite ways to interpret dreams. Read some common dream interpretations here.
Sleep paralysis –
Occurs during REM sleep when the body is paralyzed, but you can still see ! Often confused for possessions and demons. This deserves a separate post , will write about it sometime !
Fun fact – REM sleep plays a role in the reorganization, restoration of brain processes that mediate the structure and storage of information. . About 50% of the sleep cycle of a newborn human is REM or quasi-REM kinds of sleep. Newborns sleep 16 to 20 hours a day.