Prefrontal-hippocampal interactions supporting the extinction of emotional memories: the retrieval stopping model

Neuroimaging has revealed robust interactions between the prefrontal cortex and the hippocampus when people stop memory retrieval. Efforts to stop retrieval can arise when people encounter reminders to unpleasant thoughts they prefer not to think about. Retrieval stopping suppresses hippocampal and amygdala activity, especially when cues elicit aversive memory intrusions, via a broad inhibitory control capacity enabling prepotent response suppression. Repeated retrieval stopping reduces intrusions of unpleasant memories and diminishes their affective tone, outcomes resembling those achieved by the extinction of conditioned emotional responses. Despite this resemblance, the role of inhibitory fronto-hippocampal interactions and retrieval stopping broadly in extinction has received little attention. Here we integrate human and animal research on extinction and retrieval stopping. We argue that reconceptualising extinction to integrate mnemonic inhibitory control with learning would yield a greater understanding of extinction’s relevance to mental health. We hypothesize that fear extinction spontaneously engages retrieval stopping across species, and that controlled suppression of hippocampal and amygdala activity by the prefrontal cortex reduces fearful thoughts. Moreover, we argue that retrieval stopping recruits extinction circuitry to achieve affect regulation, linking extinction to how humans cope with intrusive thoughts. We discuss novel hypotheses derived from this theoretical synthesis.

Repeated Retrieval Practice to Foster Students’ Critical Thinking Skills

There is a need for effective methods to teach critical thinking. Many studies on other skills have demonstrated beneficial effects of practice that repeatedly induces retrieval processes (repeated retrieval practice). The present experiment investigated whether repeated retrieval practice is effective for fostering critical thinking skills, focusing on avoiding biased reasoning. Seventy-five students first took a pre-test. Subsequently, they were instructed on critical thinking and avoiding belief-bias in syllogistic reasoning and engaged in retrieval practice with syllogisms. Afterwards, depending on the assigned condition, they (1) did not engage in extra retrieval practice; (2) engaged in retrieval practiced a second time (week later); or (3) engaged in retrieval practiced a second (week later) and a third time (two weeks later). Two/three days after the last practice session, all participants took a post-test consisting of practiced tasks (to measure learning relative to the pre-test) and non-practiced (transfer) tasks. Results revealed no significant difference between the pretest and the posttest learning performance as judged by the mean total performance (MC-answers + justification), although participants were, on average, faster on the post-test than on the pre-test. Exploring performance on MC-answers-only suggested that participants did benefit from instruction/practice but may have been unable to justify their answers. Unfortunately, we were unable to test effects on transfer due to a floor effect, which highlights the difficulty of establishing transfer of critical thinking skills. To the best of our knowledge, this is the first study that addresses repeated retrieval practice effects in the critical thinking domain. Further research should focus on determining the preconditions of repeated retrieval practice effects for this type of tasks.

Specificity of working memory mechanisms in individuals

The research analyzes the capacity of working memory and the mechanisms which determine effectiveness of retrieval in people with long-lasting (from 5 to 20 years) drug use history. The relevance of the research is supported by the fact that the working memory is considered to be a central mechanism of self-control, which, in turn, is considered a leading parameter when an indi-vidual chooses the path to addiction. The research studied 258 people, 151 of whom, 37.1±10.7 years old, have never used substances, and the group of 107, 35.8±7.8 years old, who have long-lasting (from 5 to 20 years) drug use history. The working memory specifics were evaluated by O.Razumnikova’s technique, which allows retrieval of the same set of stimuli presented in different consequence and in three series to be described. The research studied the most discussed mechanisms functioning in the working memory separately: retrieval-induced forgetting and retrieval-based learning. Our data suggest that the structure of the working memory mechanisms does not change along with long-lasting substance use while in case of the RBL effect the difference is threefold: in case of repeated retrieval, the addicts demon-strate insignificant improvement of memorization ability in comparison to the drug-free controls.

Adjective Learning in Young Typically Developing Children and Children With Developmental Language Disorder: A Retrieval-Based Approach

Purpose There are strong retention benefits when learners frequently test themselves during the learning period. This practice of repeated retrieval has recently been applied successfully to children's word learning. In this study, we apply a repeated retrieval procedure to the learning of novel adjectives by preschool-age children with developmental language disorder (DLD) and their typically developing (TD) peers. We ask whether the benefits of retrieval extend to children's ability to apply the novel adjectives to newly introduced objects sharing the same characteristics as the objects used during the learning period. Method Fourteen children with DLD ( M age = 62.64 months) and 13 TD children ( M = 62.54 months) learned novel adjectives in 2 sessions. For each child, half of the adjectives were learned in a repeated spaced retrieval condition, and half were learned in a repeated study–only condition. Recall was assessed immediately after the second learning session and 1 week later. A recognition test was also administered at the 1-week mark. Results On the recall tests, for both groups of children, recall was better for adjectives learned in the repeated spaced retrieval condition. Adjectives learned by the 2nd day were retained 1 week later. Every adjective correctly applied to an object used during the learning period was also extended accurately to new objects with the same characteristics. On these recall tests, the children with DLD did not differ from the TD group in the number of items recalled, though their phonetic accuracy was lower. On the recognition test, the DLD group showed greater accuracy for adjectives that had been learned in the repeated spaced retrieval condition than for those learned in the repeated study condition, whereas the TD group performed at high levels in both conditions. Conclusion Repeated spaced retrieval appears to provide an effective boost to word learning. Because its benefits are seen even when a word must be extended to new objects, the application of this procedure seems well suited for learning new language material rather than being limited to item-specific memorization.

Probing the neural dynamics of mnemonic representations after the initial consolidation

Memories are not stored as static engrams, but as dynamic representations affected by processes occurring after initial encoding. Previous studies revealed changes in activity and mnemonic representations in visual processing areas, parietal lobe, and hippocampus underlying repeated retrieval and suppression. However, these neural changes are usually induced by memory modulation immediately after memory formation. Here, we investigated 27 healthy participants with a two-day functional Magnetic Resonance Imaging design to probe how established memories are dynamically modulated by retrieval and suppression 24 hours after learning. Behaviorally, we demonstrated that established memories can still be strengthened by repeated retrieval. By contrast, repeated suppression had a modest negative effect, and suppression-induced forgetting was associated with individual suppression efficacy. Neurally, we demonstrated item-specific pattern reinstatements in visual processing areas, parietal lobe, and hippocampus. Then, we showed that repeated retrieval reduced activity amplitude in the ventral visual cortex and hippocampus, but enhanced the distinctiveness of activity patterns in the ventral visual cortex and parietal lobe. Critically, reduced activity was associated with enhanced representation of idiosyncratic memory traces in ventral visual cortex and precuneus. In contrast, repeated memory suppression was associated with the reduced lateral prefrontal activity, but relative intact mnemonic representations. Our results replicated most of the neural changes induced by memory retrieval and suppression immediately after learning and extended those findings to established memories after initial consolidation. Active retrieval seems to promote episode-unique mnemonic representations in the neocortex after initial encoding but also consolidation.HighlightsRepeated retrieval strengthened consolidated memories, while repeated suppression had a modest negative effect.Pattern reinstatements of individual memories were detected in the visual area, parietal lobe, and hippocampus after 24 hours.After repeated retrieval, reduced activity amplitude was associated with increased distinctiveness of activity patterns in the ventral visual cortex and right precuneus.Repeated suppression was associated with the reduced lateral prefrontal activity, but unchanged mnemonic representations.