The physiology of dreaming

This is a critical examination of present evidence concerning the physiological basis of dreaming. First reviewing accumulated knowledge about the rapid eye movement (REM) state, it emphasizes hazards of inference across species from the highly revealing neuro‐physiological observations possible in lower animals to the only available source of information about the subjective experience of dreaming, i.e., human introspection. That gulf might be narrowed if more of the same findings obtained in laboratory cats could be extended to higher primates, where the surface manifestations of REM are almost indistinguishable from those of humans. The discussion next elaborates the complex chain of inference involved in any psychophysiological hypothesis about dreaming even within the realm of human studies. Considering the inherent limitations of applicable methods, physiological understanding of dreaming can only be presumptive. Despite so many uncertainties, the conclusion is drawn that the unique bodily condition of the REM state probably is a necessary physical basis for dreaming while by no means is it sufficient explanation.