THE AMPLITUDE OF ELICITED PGO WAVES - A CORRELATE OF ORIENTING

Ponto-geniculo-occipital (PGO) waves spontaneously occur in the pons, lateral geniculate body (LGB), and occipital cortex during rapid eye m ovement sleep (REM), and PGO-like waves (PGO(E)) may be elicited in LG B during sleep and waking. Because REM has been hypothesized to be a s tate of continual ''orienting'' or ''hyper-alertness,'' we tested whet her the amplitudes of PGO(E) in ''alerting'' situations(the abrupt ons et 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) accompany ing OR to PGOE 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 wer e not significantly different from those of the highest amplitude spon taneous PGO waves. We propose that the presence of PGO(E) signals regi stration of stimuli and that stimuli of sufficient significance to ind uce behavioral OR in waking also elicit PGO(E) of significantly greate r amplitudes in all behavioral states. These findings support the hypo thesis that the presence of high-amplitude PGO waves in REM indicates that the brain is in a state of more-or-less continual orienting.