Heterogeneous profiles of coupled sleep oscillations in human hippocampus

Abstract

Cross-frequency coupling of sleep oscillations is thought to mediate memory consolidation. While the hippocampus is deemed central to this process, detailed knowledge of which oscillatory rhythms interact in the human hippocampus is lacking. Combining intracranial hippocampal and non-invasive electroencephalography from twelve neurosurgical patients, we characterized spectral power and coupling during non-rapid eye movement (NREM) and rapid eye movement (REM) sleep. Hippocampal coupling was extensive, with the majority of channels expressing spectral interactions. NREM consistently showed delta-ripple coupling, but ripples were also modulated by slow oscillations (SOs) and sleep spindles. SO-delta and SO-theta coupling, as well as interactions between delta/theta and spindle/beta frequencies also occurred. During REM, limited interactions between delta/theta and beta frequencies emerged. Moreover, oscillatory organization differed substantially between i) hippocampus and scalp, ii) sites along the anterior-posterior hippocampal axis, and iii) individuals. Overall, these results extend and refine our understanding of hippocampal sleep oscillations.

Changes in cross-frequency coupling following closed-loop auditory stimulation in non-rapid eye movement sleep

“…Similar to phase-amplitude coupling between slow waves and sigma, modulation of theta band activity (5)(6)(7)(8) by the phase of slow waves has been described in several studies. Both in surface EEG and in intracranial (iEEG) recordings, theta power was increased during the transition to the down phase of slow waves, with the last trough of theta-burst coinciding with the slowwave down-phase (Cox et al, 2014a(Cox et al, , 2019Gonzalez et al, 2018;Klinzing et al, 2016).…”