Everyone sleeps, but there is a great mystery involving sleep; why do we do this? In ancient and prehistoric times, when animals roamed wild, sleeping didn't seem like the ideal solution. The Greek philosopher Aristotle formulated the first scientific theory about why we sleep. He believed that a person wakes up from sleep once digestion of food is completed (2013). This theory has been proven wrong, but research shows that sleep has effects on the brain and body. Humans sleep for about a third of their lives, and there are dozens of different theories as to why it is actually a necessity (TED, 2013). There are three theories that stand out. They include: restoration, energy conservation, brain processing, and memory consolidation. Restoration theory predicts that we replace and rebuild while we sleep. Energy consolidation is similar to simply losing calories while we sleep. Brain processing and memory consolidation is the theory that scientists believe the brain processes information and builds memory. This theory is the one that many scientists are leaning towards more than others. Sleeping is more beneficial to the brain than the body, but sleep is beneficial to a person's health. A sleep-deprived person is more susceptible to disease, including cardiovascular disease and cancer (Cox, 2002). In the 1950s, the average person slept 8 hours. The average hours of sleep for people today is 6.5 hours (TED, 2013). It is important that people continue to sleep to ensure brain plasticity. Brain plasticity is the natural way the brain changes. The brain works constantly, even during sleep. Rapid eye movement (REM) sleep... middle of paper... Scientists can give an electrical impulse to a pair of neurons and they will communicate more easily in the future. This action is known as long-term potentiation (LTP). This effect will last long enough to create a memory. LTP is prevalent in the hippocampus. The hippocampus is a subcortical structure that plays a role in allowing the storage of new information in the brain's memory banks. In the awake brain, information about the external world reaches the hippocampus via the entorhinal cortex (Buzsák, 1998). During sleep, the direction of information flow is reversed: population bursts initiated in the hippocampus invade the neocortex. We suggest that neocortico-hippocampal information transfer and the process of modification in neocortical circuits by hippocampal output occur in a temporally discontinuous manner associated with the wake-sleep cycle.