Suppression weakens unwanted memories via a sustained reduction of neural reactivation

Abstract

Aversive events sometimes turn into intrusive memories. However, prior evidence indicates that such memories can be controlled via a mechanism of retrieval suppression. Here, we test the hypothesis that suppression exerts a sustained influence on memories by deteriorating their neural representations. This deterioration, in turn, would hinder their subsequent reactivation and thus impoverish the vividness with which they can be recalled. In an fMRI study, participants repeatedly suppressed memories of aversive scenes. As predicted, this process rendered the memories less vivid. Using a pattern classifier, we observed that suppression diminished the neural reactivation of scene information both globally across the brain and locally in the parahippocampal cortices. Moreover, the decline in vividness was associated with reduced reinstatement of unique memory representations in right parahippocampal cortex. These results support the hypothesis that suppression weakens memories by causing a sustained reduction in the potential to reactivate their neural representations.

Concurrent representations of reinstated and transformed memories and their modulation by reward

“…When participants correctly recalled a scene, the activation pattern in the PHC was more similar to the activation pattern during encoding of that scene. This is in line with previous research showing scene-specific pattern reinstatement in the PHC (Meyer & Benoit, 2022; Schultz et al, 2019; Schultz, Sommer, et al, 2022; Staresina et al, 2012) and scene-specific memory processing in general (Liang & Preston, 2017; Schultz et al, 2012; Schultz, Yoo, et al, 2022; Staresina et al, 2013). Anatomically, the PHC is a connecting hub between the dorsal visual stream and downstream regions in the MTL, including the entorhinal cortex and HC (Lavenex & Amaral, 2000; Suzuki & Amaral, 1994b, 1994a), and thus well-positioned to support spatial, scene-specific, or contextual memory (Eichenbaum et al, 2007).…”

Emotional learning retroactively promotes memory integration through rapid neural reactivation and reorganization

“…The sample sizes across three studies were estimated by a power analysis using G*Power 3.1, which yielded the power of around 85–90% (i.e. from 26 to 30 participants) for a moderate repeated-measures ANOVA, consistent with many memory studies ( Gruber et al, 2016 ; Liu et al, 2016 ; Meyer and Benoit, 2022 ; Schlichting and Preston, 2014 ; Wimmer and Shohamy, 2012 ). In Study 3, the sample size of 28 valid participants could give us power more than 70% for a moderate correlation (i.e.…”

Attentional capture mediates the emergence and suppression of intrusive memories

“…Evidence indicates that suppression harms most active memory features via targeted inhibition. 13 , 37 Partial reactivation of the memory trace associated with prediction error seems essential to trigger memory disruption, 89 in line with the non-monotonic plasticity hypothesis whereby during memory reactivation, long-term depression of synaptic connections follows moderate postsynaptic depolarization. 12 , 90 By reactively targeting intrusive reactivation, suppression may therefore maintain the activation of the memory trace at a moderate level of activity eligible for disruption.…”

“…Up to now, the decoding of fMRI signals has consisted in tracking memory reactivation using perceptual templates of memory activity, in order to explore how memory inhibition relates to forgetting. 12 , 13 , 14 In the present study, we decoded recordings of the brain’s electrical activity in order to study the temporal dynamics of the emergence of unwanted visual images in participants’ minds. Importantly, the classification of memories as intrusive was not based solely on the perceptual similarity between encoding and retrieval.…”