Abstract
SummaryReminders of the past can trigger the recollection of events that one would rather forget. Here, using fMRI, we demonstrate two distinct neural mechanisms that foster the intentional forgetting of such unwanted memories. Both mechanisms impair long-term retention by limiting momentary awareness of the memories, yet they operate in opposite ways. One mechanism, direct suppression, disengages episodic retrieval through the systemic inhibition of hippocampal processing that originates from right dorsolateral prefrontal cortex (PFC). The opposite mechanism, thought substitution, instead engages retrieval processes to occupy the limited focus of awareness with a substitute memory. It is mediated by interactions between left caudal and midventrolateral PFC that support the selective retrieval of substitutes in the context of prepotent, unwanted memories. These findings suggest that we are not at the mercy of passive forgetting; rather, our memories can be shaped by two opposite mechanisms of mnemonic control.
Highlights
The ability to remember one’s past is a two-sided coin
Neuroimaging Results Distinct Regions Contribute to Direct Suppression versus Thought Substitution To examine whether the two groups exhibited selective activation patterns consistent with the hypothesized mechanisms, we report average contrast estimates from a priori regions of interest (ROIs; see Experimental Procedures; Tables S1–S4 for exploratory whole-brain analyses)
We first concentrate on right dorsolateral prefrontal cortex (DLPFC) and HC, the brain areas hypothesized to mediate direct suppression, before turning to left caudal PFC (cPFC) and mid-VLPFC, the regions hypothesized to be involved in thought substitution
Summary
The ability to remember one’s past is a two-sided coin. It allows us to relive cherished episodes and confronts us with past events that we would rather forget. When people confront an unwelcome reminder of a past event, they can exclude the unwanted memory from awareness. This process, in turn, impairs retention of the suppressed memory (Anderson and Green, 2001; Hertel and Calcaterra, 2005; Anderson and Huddleston, 2011). The present fMRI experiment scrutinized the existence of two possible routes to forgetting unwanted memories. Both of these putative mechanisms are hypothesized to induce forgetting by limiting momentary awareness of an unwanted memory, yet they achieve this function in fundamentally opposite ways that are mediated by different neural networks
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