Smooth tracking of visual targets distinguishes lucid REM sleep dreaming and waking perception from imagination.
Nature Communications August 17, 2018 Stephen LaBerge, Benjamin Baird, Philip G Zimbardo
People typically cannot smoothly track imagined objects with their eyes, but during REM sleep dreams, smooth pursuit eye movements occur when tracking a slow-moving visual target in a lucid dream. These movements closely resemble those during actual perception, unlike the jerky, saccadic tracking seen during waking imagination. The findings indicate that visual imagery in REM sleep is more like perception than imagination, showing that the brain's smooth pursuit circuitry can be activated by a visual experience without retinal input. Voluntary gaze shifts within dreams also correspond to physical eye rotations.