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

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