Increasing PGO spike density by auditory stimulation increases the duration and decreases the latency of rapid eye movement (REM) sleep.

The purpose of this study was to determine whether ponto-geniculo-occipital (PGO) spikes play a role in triggering or maintaining sleep. During the recording of the sleep cycle of cats, the appearance of the first PGO spike automatically triggered an auditory stimulus through a speaker placed in the cat's recording cage. The effect of this procedure was compared to similar period when no such stimulus was given. The results showed that the auditory stimulus increased PGO spike density during REM sleep. It also produced a spectacular increase in the duration of REM, while decreasing the latency of its appearance from the first PGO spike. It is suggested that the auditory stimulus reinforces the 'PGO system', which in turn may function as a pace-setter for priming and maintaining REM sleep.