A massive but short lasting forebrain deafferentation during sleep in the rat and cat

The rat and cat show just prior and sometimes after paradoxical sleep a short-lasting behavioral stage characterized by: i) frontal cortex high amplitude spindle bursts and low frequency theta activity in the dorsal hippocampus, and ii) the lowest ventrobasal complex transmission level of all sleep-waking stages. The duration of this "intermediate" stage is increased at the expense of paradoxical sleep by low doses of barbiturate. The intercollicular "cerveau isolé" preparation shows for hours the electrophysiological patterns of the intermediate stage. It is concluded that the intermediate stage of sleep corresponds to a forebrain massive deafferentation process leading to a functional disconnecting from the brainstem. For the survival of the species it is understandable that this behavioral stage is necessarily short lasting.