Hippocampo-cortical coupling mediates memory consolidation during sleep

Abstract

Memory consolidation is thought to involve a hippocampo-cortical dialog during sleep to stabilize labile memory traces for long-term storage. However, direct evidence supporting this hypothesis is lacking. We dynamically manipulated the temporal coordination between the two structures during sleep following training on a spatial memory task specifically designed to trigger encoding, but not memory consolidation. Reinforcing the endogenous coordination between hippocampal sharp wave-ripples, cortical delta waves and spindles by timed electrical stimulation resulted in a reorganization of prefrontal cortical networks, along with subsequent increased prefrontal responsivity to the task and high recall performance on the next day, contrary to control rats, which performed at chance levels. Our results provide, to the best of our knowledge, the first direct evidence for a causal role of a hippocampo-cortical dialog during sleep in memory consolidation, and indicate that the underlying mechanism involves a fine-tuned coordination between sharp wave-ripples, delta waves and spindles.

Chronic nicotine attenuates behavioral and synaptic plasticity impairments in a streptozotocin model of Alzheimer’s disease

“…Particularly, the hippocampus and prefrontal cortex act in synchrony during spatial working memory tasks and are reactivated during rest or non-REM sleep, supporting episodic memory consolidation (Maingret et al, 2016;Jadhav et al, 2016;Barker et al, 2017). Thus, synaptic plasticity in the CA1-mPFC pathway is a possible substrate for episodic memory storage (Laroche et al, 2000).…”

“…Limbic-cortical synaptic plasticity can be dysfunctional in prodromal Alzheimer's disease, which could explain its mild cognitive alterations (Scheff et al, 2006;Arendt, 2009). In this context, the hippocampal CA1-medial prefrontal cortex (mPFC) communication is prone to long-term plasticity (Lopes-Aguiar et al, 2008Takita et al, 2013), is implicated in working memory (Spellman et al, 2015;Blot et al, 2015) and memory consolidation (Laroche et al, 2000;Taylor et al, 2016;Maingret et al, 2016;Jadhav et al, 2016;Barker et al, 2017). Thus, synaptic plasticity in this circuit could be increasingly altered as Alzheimer's disease develops, which can be experimentally studied using the icv-STZ model of sAD.…”

The effect of sex and menstrual phase on memory formation during a nap

“…Furthermore, several pieces of evidence converge to suggest that improved memory retention is directly related to specific events during sleep including sleep spindles (bursts of fast, 12-15Hz thalamic activity) and slow oscillations (SO, high voltage up and down states <1Hz that reflect periods of neuronal spiking and neuronal silence, respectively). Specifically, in rats hippocampal ripples were found to occur in temporal proximity to cortical sleep spindles, suggesting an information transfer between the hippocampus and neocortex, which is supposed to underlie the consolidation of declarative memories during sleep (Maingret et al, 2016;Girardeau et al, 2009;Ji & Wilson, 2007). In particular, spindles and SOs have independent features that correlate with improvements in declarative memory formation (Mednick et al, 2013;Oyanedel et al 2014, Gais et al, 2002, Schabus et al, 2004Clemens et al, 2005).…”

Coordination of Slow Waves With Sleep Spindles Predicts Sleep-Dependent Memory Consolidation in Schizophrenia

“…Merely having enough spindles may not be sufficient -intact sleep-dependent memory consolidation is also thought to rely on the precise temporal coordination of spindles with neocortical slow waves (SW) and hippocampal sharp-wave ripples [13][14][15][16][17] .…”