Using EEG Microstates to Examine Post-Encoding Quiet Rest and Subsequent Word-Pair Memory

Abstract

Evidence suggests that the brain preferentially consolidates memories during "offline" periods, in which an individual is not performing a task and their attention is otherwise undirected, including spans of quiet, resting wakefulness. Moreover, research has demonstrated that factors such as the initial encoding strength of information influence which memories receive the greatest benefit. Recent studies have begun to investigate these periods of post-learning quiet rest using EEG microstate analysis to observe the electrical dynamics of the brain during these stretches of memory consolidation, specifically finding an increase in the amount of the canonical microstate D during a post-encoding rest period.Here, we implement an exploratory analysis to probe the activity of EEG microstates during post-encoding sessions of quiet rest in order to scrutinize the impact of learning on microstate dynamics and to further understand the role these microstates play in the consolidation of memories. In two different studies, we examined a combined 74 subjects (55 female) as they completed a word-pair memory task designed to use repetition and presentation-time to vary the initial encoding strength of the word-pair memories. In both studies, we were able to replicate previous research in which there was a significant increase (both p's < .05) in the amount of microstate D (often associated with the dorsal attention network) during post-encoding rest. This change was accompanied, in both studies, by a significant decrease (both p's < .05) in the amount of microstate C (often associated with the default mode network). We also found preliminary evidence indicating a positive relationship between the amount of microstate D and improved memory for weakly encoded memories, which merits further exploration.3

EEG microstate features according to performance on a mental arithmetic task

“…In the semantic memory task, pre-stimulus EEG microstates showed correlation with known electrophysiological markers, which means they can reflect cortical activation 18 . When performing a word-pair memory task, it was observed that the network dynamics of the memory consolidation process changed EEG microstates 19 . There are also studies that have revealed the association between EEG microstates and the changes in cortical activity induced by brain stimulation.…”

“…Several studies have supported that cognitive manipulation of EEG microstates is possible [17][18][19][20][21] . It was reported that stress response was estimated using EEG microstate sequences in psychosocial stress paradigm 17 .…”

An online experiment that presents challenges for translating rest-related gains in visual detail memory from the laboratory to naturalistic settings

“…It is possible that the degree of task engagement, performance (e.g., finding two differences before the end of a trial), and other factors may have resulted in participants experiencing at least brief entry into rest-like states that were conducive to consolidation. This possibility is supported by recent neuroimaging evidence demonstrating that the brief experiencing of certain EEG microstates during post-encoding activity positively predicts subsequent memory [ 64 ]. This possibility may account for individual differences in memory performance following the filled delay though it is unlikely to account for comparable memory between our filled and unfilled delay conditions given that interference effects have been reported in related laboratory-based research [ 25 ].…”

Repetition accelerates neural markers of memory consolidation

“…Post-encoding resting state activity has been suggested to support the consolidation of memories which has, in turn, been associated with their behavioral accessibility (Tambini et al, 2010; Deuker et al, 2013; Staresina et al, 2013; Tambini & Davachi, 2013, 2019; Schlichting & Preston, 2014; Tompary et al, 2015; Gruber et al, 2016; Murty et al, 2017; Poskanzer et al, 2021). Here, we asked if post-encoding neural replay was related to memory behavior for weakly and strongly encoded memories.…”