ABSTRACT
Ponto–geniculo–occipital (PGO) spikes may be the most critical phasic physiological event associated with REM sleep. PGO spikes have been studied extensively in animals with depth electrodes, but cannot be recorded directly in humans. Phasic integrated potentials (PIPs) recorded from the eye muscles may be one correlate of PGO activity in humans (Rechtschaffen, Molinari, Watson, & Wincor, 1970). Like PGO spikes, most PIPs are concentrated within REM sleep, although some are scattered in NREM sleep. PIPs, and PGO spikes, always accompany rapid eye movements during REM, but may also occur without rapid eye movements. The amount of NREM PIP activity is an individual characteristic; that is, someone who has many NREM PIPS on one night will have many on the next, whereas someone who has relatively few NREM PIPs on one night will have few on the next. A number of studies have been carried out on the relationship between PIPs and mental activity during sleep, PIPs and psychosis, and PIPs and individual differences in personality.
