Promotion and suppression of autobiographical thinking differentially affect episodic memory consolidation.

Samarth Varma,Roy P C Kessels,Atsuko Takashima,Sander M Daselaar,Nadine Ravel

doi:10.1371/journal.pone.0201780

Samarth Varma, Roy P C Kessels + Show 3 more

Open Access

https://doi.org/10.1371/journal.pone.0201780

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Abstract

During a post-encoding delay period, the ongoing consolidation of recently acquired memories can suffer interference if the delay period involves encoding of new memories, or sensory stimulation tasks. Interestingly, two recent independent studies suggest that (i) autobiographical thinking also interferes markedly with ongoing consolidation of recently learned wordlist material, while (ii) a 2-Back task might not interfere with ongoing consolidation, possibly due to the suppression of autobiographical thinking. In this study, we directly compare these conditions against a quiet wakeful rest baseline to test whether the promotion (via familiar sound-cues) or suppression (via a 2-Back task) of autobiographical thinking during the post-encoding delay period can affect consolidation of studied wordlists in a negative or a positive way, respectively. Our results successfully replicate previous studies and show a significant interference effect (as compared to the rest condition) when learning is followed by familiar sound-cues that promote autobiographical thinking, whereas no interference effect is observed when learning is followed by the 2-Back task. Results from a post-experimental experience-sampling questionnaire further show significant differences in the degree of autobiographical thinking reported during the three post-encoding periods: highest in the presence of sound-cues and lowest during the 2-Back task. In conclusion, our results suggest that varying levels of autobiographical thought during the post-encoding period may modulate episodic memory consolidation.

Highlights

In the recent testing-effect/retrieval practice literature, the retrieval of recently learned items from memory has been shown to strengthen memory traces
As predicted, planned t-tests showed that memory performance was higher when learning was followed by the 2-Back condition, than by the rest+sounds condition, t(35) = 2.82, p = 0.008, 95% confidence intervals (CI) = [0.03, 0.18]
We found a trend towards statistical significance in the interaction between delay condition type and delay condition order, on the proportional retention scores associated with the delay conditions (F(10, 60) = 1.94, p = 0.06, ηp2 = 0.25)

Summary

Introduction

In the recent testing-effect/retrieval practice literature, the retrieval of recently learned items from memory has been shown to strengthen memory traces (see reviews by [1, 2]). Even in the absence of conscious rehearsal, interference-free post-encoding environments like sleep or quiet wakeful rest can lead to significant improvements in the retention of recently acquired memories through a process of memory consolidation [3,4,5]. Autobiographical thinking interferes, 2-Back task benefits consolidation periods, the hippocampus triggers repeated reactivation of neural activity patterns, which code the prior learning experience [6, 7], gradually strengthening the associated memory trace [8, 9]. Behavioral reports further indicate that such environmental cues could trigger retrieval of cue-associated memories from one’s personal past and/or imagination of a future scenario, even in the absence of explicit instructions to do so [14, 18]

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