Rapid, random eye movements during sleep are probably related to increased temperature in eye-connected parts of the brain, or the speed and randomness of the molecules making it up. — “While for over 50 years, it was thought
that only mammals and birds have these distinct
neurological sleep stages, exciting new research has
shown that reptiles, fish, drosophila, octopus, and other invertebrates also display sleep states with analogous features.”