Hypothetical role of gravity in Rapid Eye Movements during sleep.

Dream periods during sleep have been observed in most mammals as early in history as antiquity. Sleep researchers at the University of Chicago, discovered the phase of rapid eye movement (REM) during sleep and connected it to the dream period. During this period, called the REM phase (after the American terminology), although the brain shows electrical activity, it is insensitive to external stimulations, including light, sound, contact and, a little unexpectedly, gravity. However, since this discovery was mаde there has been no definitive explanation of the rapid eye movements Many possible explanations have been offered, and yet, the causes and contributing factors of the REM sleep phase are inadequately understood. It has often been proposed that the eyes observe the images produced during dreams, but researchers are not convinced. It is proposed here that the movements of the eyes during REM sleep are due to a feeling of disorientation and a subjective loss of landmarks. During the REM sleep phase, the brain has a reduced sensation of gravity, and the sleeper is in a state similar to weightlessness. The instinctive search for the vertical or horizontal direction triggers movements of the eyes, looking for usual points of reference. This hypothesis is reinforced by an original experiment that was conducted in space. The frequency of the eye movements of astronauts during their first night in space is 10 times more than what is experienced on the ground, and that moment in time is when the feeling or the sensation of weightlessness is certainly the most disturbing. Upon the return to Earth, the frequency of the eye movements increases again the first night after landing. These two moments are when the effects of gravity are felt most drastically. The present assumption needs to be validated experimentally and may necessitate further research.