Spontaneous saccadic eye movements are slower than saccades to other imagined stimuli – and even slower than REMs

There is a controversial debate whether rapid eye movements in sleep (REMs) are meaningful (functional) saccades or are due to spontaneous eye muscle contractions. We therefore compared saccadic eye movements with closed eyes to previously seen visual stimuli (dots, static images, videos), auditory stimuli, during math calculations and spontaneous saccades to REMs. In trials with visual stimuli subjects were asked to remember and imagine them. In trials with auditory stimuli short audio tapes were played, in trials with math calculations subjects had to count back. Additionally one trial was without detailed ins…