Comparison of Eye Motion in Wakefulness and REM Sleep

Rapid eye movements (REMs) in sleep have been postulated to represent ocular activity directly related to the visual imagery of dreaming. In accord with this notion, there have been reports that the physiological characteristics of REMs are identical to those of waking saccades which occur in the absence of visual targets. Contradictory evidence is herein presented establishing that REMs are significantly slower than waking saccades of comparable amplitude, and that this slowdown is greater than can be attributed to either eye closure or to eye movements in total darkness. Furthermore, it is shown that in REM sleep, both small (5.5°) and large (11°) saccade‐like movements generate essentially the same maximal force and have the same velocity for the major portion of their trajectories. In sleep, therefore, there is probably a central inhibition of the saccade‐like REMs, especially of the large amplitude movements, thus leading to an uncoupling of the usual amplitude‐velocity relationship observed in the waking state.