Sleep plays a vital role in our daily lives. We spend more time sleeping than doing any
other single activity. We abandon vigilance in order to sleep, we render ourselves
vulnerable when we sleep. But, what is sleep for? And why do we spend so much time
sleeping? How do the benefits of sleep outweigh the risks? Lets take a look at different
Sleep helps our body save and restore energy by slowing down our
metabolism. By lowering our metabolism, we conserve energy. While we sleep, the brain's
learning processes are turned off. Still another theory predicts that sleep helps
replenish our stores of neurotransmitters. This is because most neurons decrease their
activity during sleep.
Slow wave sleep has restorative effects. It seems like a period of rest for the brain.
Without rest, our brain cannot function properly. Brain areas that are very active during
wakefulness show an increase in slow wave sleep, as if they were resting, restoring
During sleep, we can reorganize and store information. Neurons that are
involved in memory and attentive learning do rest in sleep, specially during REM.[i]Maybe
this is why we feel mentally sharper when we have had a good night of sleep, compared to
how we feel after staying up all night long.
REM sleep plays a role in memory retention and consolidation. Many studies support this
theory, here is one: There are two groups of students, who had learned the same material
the evening before. One group was deprived of REM sleep during one night, the other group
slept normally without interruption. The group with REM sleep deprivation showed that
their retention of material covered was poor compared to the other group that slept
without interruption. Their retention of complex material (stories) was greatly reduced by
REM sleep deprivation. Still, other theories say that sleeping, particularly REM sleep
is designed to remove useless information from memory. This theory suggest that it is of
equal importance to remove unwanted information and to store important data. Memory has to
work two ways: one for storage of important information and one for removal of trivial
Other theories say that sleep plays a role in the development of
the brain. REM sleep is a major component of sleep for babies in utero and infants. REM
sleep is thought to activate visual, motor and sensory areas in the brain. In the baby's
brain, this increases the ability of neurons to make the correct connections and function
properly. For example, observation of lamb fetuses through plexiglass windows implanted on
the uterine walls, has shown that during REM sleep, the fetuses, without having air to
breathe do move their chest as if they were breathing. This suggest that REM plays a
role in preparing, teaching us how to behave, even before we come out to this world.
Another theory proposes that sleep is an adaptive behavior to keep us away from trouble at
night. In a natural environment we are daytime beings; in the darkness of night we cannot
perform the same activities we engage during the day. So by sleeping we simply refrain
from being active at night when our vision is poor and this keeps us away from trouble.
Perhaps sleep has all these functions and more that we do not know about yet. The bottom
line is that sleep is so essential that long periods of sleep depravation eventually
results in stress-related deaths (this has happened with lab animals, the same could
happen with us). Missing even one single night of sleep may affect our mental
performance in decision making on the next day.
Fatal familial insomnia is an inherited disorder characterized by the slow withdrawal of
slow wave sleep until it disappears. There is only small bouts of REM sleep without
paralysis when the patient sleeps. The symptoms include confusion, loss of control over
the endocrine system and autonomic nervous system activities, insomnia, decreased
attention and diminished memory. The disorder is fatal when advanced and it shows how
important sleep really is.