Elicited ponto-geniculo-occipital waves by auditory stimuli are synchronized with hippocampal theta-waves.

The study demonstrated that ponto-geniculo-occipital (PGO) waves are phase-locked with hippocampal theta-waves during rapid eye movement (REM) sleep. A possible mechanism for influencing a PGO wave generator by hippocampal theta-waves was hypothesized. The generator is known to receive afferent inputs such as auditory input. To test this hypothesis, the temporal relationship between hippocampal theta-waves and elicited PGO waves (PGO(E)) by auditory stimuli was analysed. The analysis showed that PGO(E) were synchronized with theta-waves, but did not reset the phase of a theta-wave. Because the occurrence of PGO(E) and spontaneous PGO waves shared the same phase-dependency on theta-waves, the results strongly suggest that the PGO wave generator was driven by theta-waves, as originally hypothesized.