Retrieval induces adaptive forgetting of competing memories via cortical pattern suppression

Abstract

Remembering a past experience can, surprisingly, cause forgetting. Forgetting arises when other competing traces interfere with retrieval, and inhibitory control mechanisms are engaged to suppress the distraction they cause. This form of forgetting is considered adaptive because it reduces future interference. The impact of this proposed inhibition process on competing memories has, however, never been observed both because behavioural methods are “blind” to retrieval dynamics and because neuroimaging methods have not isolated retrieval of individual memories. Here we introduce a canonical template tracking method to quantify the activation state of individual target memories and competitors during retrieval. This method revealed that repeatedly retrieving target memories suppressed cortical patterns unique to competitors. Pattern suppression was related to engagement of prefrontal regions implicated in resolving retrieval competition, and, critically, predicted later forgetting. We thus demonstrate a cortical pattern suppression mechanism through which remembering adaptively shapes which aspects of our past remain accessible.

Neurocognitive mechanisms of the “testing effect”: A review

“…Further in line with this, Karlsson Wirebring et al [31] reported a decrease in activity of the left DLPFC over the course of repeated successful practice-testing which was predictive of better later memory performance. Similarly, in the previously mentioned retrieval-induced forgetting study by Wimber et al [37], activity in the left and right VLPFC decreased over the course of repeated selective retrieval. Moreover, activations predicted how much competing information was suppressed but not how much target information was enhanced: more activation in the left and right VLPFC during the retrieval of specific memories predicted stronger suppression of that memory's competitors.…”

“…More direct investigations of changes in memory representations over time have recently become available from two publications that apply multivariate analysis techniques to the study of repeated retrieval [31,37]. Karlsson Wirebring et al [31] used representational similarity analysis [RSA; 38] to correlate patterns of brain activation between multiple trials to determine under which conditions brain activations are more similar or dissimilar from each other.…”

“…The second report of fMRI measurements during repeated retrieval is available from a study by Wimber et al that focused on retrieval-induced forgetting [37]. The authors employed what they call a canonical template tracking method to determine the activation state of target memories and competing information during testing.…”

“…Abbreviations: T ¼ testing; RS ¼ restudying; T 4RS ¼ contrast between testing trials and restudy trials; LR ¼ later remembered (see Figure 1) have different effects during practice-testing and restudying. Regarding search-set restriction accounts, one study on retrievalinduced forgetting [37] showed that information that directly competes with relevant cue-target associations becomes increasingly suppressed over the course of repeated testing.…”

Consolidation of Complex Events via Reinstatement in Posterior Cingulate Cortex

“…First, rehearsal of a subset of the videos may inhibit consolidation of the nonrehearsed set and this inhibition may result in unrehearsed videos being largely forgotten ("retrievalinduced forgetting") (Anderson et al, 2000;Wimber et al, 2015). Although this explanation does not explain why active rehearsal is such a good method for retention of detail over long periods (Roediger and Karpicke, 2006), it may explain why recall for nonrehearsed videos was so poor.…”