A hierarchical cascade of sleep rhythms drive memory consolidation in humans and are disrupted in epilepsy.

Abstract

The cross-regional interplay of slow oscillations, sleep spindles, and ripples during sleep is believed to support systems memory consolidation but is understudied in humans. Using a validated behavioral task and intracranial neural recordings from orbitofrontal cortex, thalamus, and hippocampus in 19 epilepsy patients, we examined the cross-regional interplay of sleep-oscillations and their role in memory consolidation. Orbitofrontal slow oscillations robustly modulate sleep rhythms both within and across regions. Most combinations of oscillation rates predict overnight memory consolidation, but hippocampal ripple rate and coupled hippocampal-orbitofrontal ripples were the strongest positive predictors of memory consolidation. In contrast, epileptic spikes coupled to sleep oscillations strongly predicted reduced memory consolidation, with the strongest negative effect observed when epileptic spikes were coupled to slow oscillations. These findings provide direct evidence of the hierarchical cascade of sleep oscillations in human memory processing and reveal how epileptic spikes disrupt this process in patients with epilepsy.