It is so named because the eyes move rapidly back and forth during this period. The second component is cataplexy, which is a sudden and temporary loss of muscle tone while conscious. Cataplexy is one of the most baffling aspects. In humans, an attack might be triggered by sudden surges of emotion, especially laughter, anger, or surprise, causing victims to buckle at the knees and collapse. After a few moments, they can stand again.
Sleep paralysis is the third component, and perhaps the most frightening for victims.
During sleep paralysis, a narcoleptic might awaken during the night and find that he or she is totally paralyzed. The paralysis usually lasts no longer than a minute but might seem to last for hours to the victim. As horses are unable to tell us whether they dream, hallucinate, or experience sleep paralysis, we will never know if the other two components play a part or not. Typically, the horse will drop his head quite low and spread his front legs for balance while the hindquarters sag. Most horses remain standing during attacks, but some, particularly ponies, sit down on their haunches and might roll onto their sides.