Recordings of the evoked auditory wave P1 from the pons during natural and drug-induced REM.

A positive component of the middle latency auditory evoked response recorded from the vertex, the P1 wave, was found to be sensitive to changes in the wakefulness-sleep states. We report here that this wave can be recorded from the pons of chronically prepared cats. During natural REM sleep and REM induced by micro-injections of carbachol and neostigmine into the pons the pontine P1 had amplitudes much higher than during slow wave sleep (SWS). The increase in amplitude was dose dependent. Scopolamine had a profound and long-lasting weakening effect on the wave. These results indicate a relation between the P1 wave and the cholinergic generator mechanism for REM sleep. Also, our results support the role of an increased recruitment of the pontine neurones in the generation of REM sleep.