The amplitude of elicited PGO waves: a correlate of orienting

Abstract

Ponto-geniculo-occipital (PGO) waves spontaneously occur in the pons, lateral geniculate body (LGB), and occipital cortex during rapid eye movement sleep (REM), and PGO-like waves (PGO E) may be elicited in LGB during sleep and waking. Because REM has been hypothesized to be a state of continual “orienting” or “hyper-alertness,” we tested whether the amplitudes of PGO E in “alerting” situations (the abrupt onset of a loud sound or presentation of a novel stimulus within a series of stimuli) that evoke orienting responses (OR) would be greater than those following stimuli without OR. We also compared PGO E accompanying OR to PGO E during REM and NREM when OR are absent. The amplitudes of PGO E in W were greatest when OR were observed, and the amplitudes of PGO E accompanying OR were not significantly different from PGO E amplitudes in REM. Likewise, the amplitudes of PGO E during REM were not significantly different from those of the highest amplitude spontaneous PGO waves. We propose that the presence of PGO E signals registration of stimuli and that stimuli of sufficient significance to induce behavioral OR in waking also elicit PGO E of significantly greater amplitudes in all behavioral states. These findings support the hypothesis that the presence of high-amplitude PGO waves in REM indicates that the brain is in a state of more-or-less continual orienting.