REM sleep stands for rapid eye movement sleep and is defined as the light portion of the sleep cycle where the eyes move back and forth rapidly. (sfnewborncare.com)
The e-book readers experienced less rapid eye movement sleep than their printed - book - reading counterparts, and were less alert the mornings after. (latimes.com)
They occur during non-rapid eye movement sleep stages two and three. (sciencedaily.com)