Decoupling of large-scale brain networks supports the consolidation of durable episodic memories

Abstract

At a large scale, the human brain is organized into modules of interconnected regions, some of which play opposing roles in supporting cognition. In particular, the Default-Mode Network (DMN) has been linked to operations on internal representations, while task-positive networks are recruited during interactions with the external world. Here, we test the hypothesis that the generation of durable long-term memories depends on optimal recruitment of such antagonistic large-scale networks. As long-term memory consolidation is a process ongoing for days and weeks after an experience, we propose that individuals characterized by strong decoupling of the DMN and task-positive networks at rest operate in a mode beneficial for the long-term stabilization of episodic memories. To capture network connectivity unaffected by transient task demands and representative of brain behavior outside an experimental setting, 87 participants were scanned during rest before performing an associative encoding task. To link individual resting-state functional connectivity patterns to time-dependent memory consolidation processes, participants were given an unannounced memory test, either after a brief interval or after a retention period of ~6 weeks. We found that participants with a resting state characterized by high synchronicity in a DMN-centered network system and low synchronicity between task-positive networks showed superior recollection weeks after encoding. These relationships were not observed for information probed only hours after encoding. Furthermore, the two network systems were found to be anticorrelated. Our results suggest that this memory-relevant antagonism between DMN and task-positive networks is maintained through complex regulatory interactions between the systems.

Differential Regional Brain Spontaneous Activity in Subgroups of Mild Cognitive Impairment

“…The inferior parietal lobe is a central node within the posterior DMN, which is highly active at rest but inhibited during goal-directed cognitive tasks (Andrews-Hanna, 2012). The DMN, particularly for the posterior division, plays a key role in highly integrated tasks such as episodic memory (Yi et al, 2015;Sneve et al, 2017). The DMN is among the earliest to show abnormal amyloid deposition and has been the focus of AD and MCI researches (Koch et al, 2015).…”

Functional network interactions at rest underlie individual differences in memory ability

“…Differences in memory performance may therefore also reflect differences in memory encoding, consolidation or related attentional or memory search processes. A recent study of Sneve et al (2017) targeted memory consolidation specifically. The authors showed that individuals with enhanced intrinsic connectivity between the hippocampus, DMN and FPN subnetworks, parietal and limbic subnetworks, had better memory performance 6.5 wk after encoding.…”

Neural Signatures of Memory Encoding in Schizophrenia Are Modulated by Antipsychotic Treatment

“…Perrone-Bertolotti et al [93] used ROI analysis using a priori ROI masks for 3 DMN regions as proposed by [92]. Sneve et al [94] used the Yeo et al [95] cortical parcellation to define 17 bilateral networks. The only study that used independent components analysis to highlight large-scale brain networks is the study of Santangelo et al [96].…”