Reconsolidation of episodic memories:a subtle reminder triggers integration of new information

Recent demonstrations of “reconsolidation” suggest that memories can be modified when they are reactivated. Reconsolidation has been observed in human procedural memory and in implicit memory in infants. This study asks whether episodic memory undergoes reconsolidation. College students learned a list of objects on Day 1. On Day 2, they received a reminder or not, and then learned a second list. Memory for List 1 was tested immediately on Day 2 (Experiment 2) or on Day 3 (Experiment 1). Although the reminder did not moderate the number of items recalled from List 1 on either day, subjects who received a reminder incorrectly intermixed items from the second list when recalling List 1 on Day 3. Experiment 2 showed that this effect does not occur immediately and thus is time-dependent. The reminder did not affect memory for List 2 on Day 3 (Experiment 3), demonstrating that modification occurred only for the original memory (List 1). The study demonstrates the crucial role of reminders for the modification of episodic memory, that reconsolidation of episodic memory is time-dependent, and, in contrast to previous reconsolidation findings, that reconsolidation is also a constructive process, one that supports the incorporation of new information in memory

Stress-Induced Increase in Cortisol Negatively Affects the Consolidation of Contextual Elements of Episodic Memories

Stress can modulate episodic memory in various ways. The present study asks how post-encoding stress affects visual context memory. Participants encoded object images centrally positioned on background scenes. After encoding, they were either exposed to cold pressure stress (CPS) or a warm water control procedure. Forty-right hours later, participants were cued with object images, and for each image, they were asked to select the background scene with which it was paired during study among three highly similar options. Only male but not female participants reacted with a significant increase in salivary cortisol to CPS, and the stress and control group did not differ in recognition performance. Comparing recognition performance between stress responders and non-responders, however, revealed a significant impairment in context memory in responders. Additionally, proportional increase in cortisol was negatively correlated with the number of correctly recognized scenes in responders. Due to the small number of responders, these findings need to be interpreted with caution but provide preliminary evidence that stress-induced cortisol increase negatively affects the consolidation of contextual elements of episodic memories

Moderate stress enhances immediate and delayed retrieval of educationally relevant material in healthy young men.

Retrieval practice is a powerful memory enhancer. However, in educational settings, test taking is often experienced as a stressful event. While it is known that stress can impair retrieval processes, little is known about the delayed consequences of testing memory for educationally relevant material under stressful conditions, which is the focus of the present study. Participants (38 women, 37 men) memorized a scientific text passage on Day 1. On Day 2, they were either exposed to a stressor (cold pressor test; CPS) or a warm water control, and immediately afterward, they were asked to recall the text passage (i.e., retrieval under stress vs. control). Salivary cortisol was measured as an index of the stress response before, and 20 min after the CPS versus control treatment. The delayed effects of testing under stress were assessed with a final recall test on Day 3. In comparison to the control condition, CPS caused significant increases in salivary cortisol, and, surprisingly resulted in enhanced memory in men. Importantly, this enhancement was not only observed in the test that immediately followed the stressor, but also in the delayed test. In women, CPS caused only marginal increases in cortisol concentrations, and retrieval remained unaffected. Our study suggests that moderate stress can improve memory performance for educationally relevant material in a long-lasting manner in healthy young men

How reactivation strength affects memory updating

Memory reactivation induces plasticity, rendering reactivated memories susceptible to interference. The currentstudy examined whether the method and strength of reactivation modulates retroactive interference effects. Two days afterlearning AB word pairs, memory for these pairs was either not reactivated, moderately reactivated (presentation of A cues in anunrelated task), or strongly reactivated (restudy of AB pairs or cued recall of B targets). Immediately afterwards, participantseither learned AC word pairs, DE word pairs, or performed an unrelated distractor task. Cued recall of target words wastested two days later. Strong reactivation before learning new material protected memory from retroactive interference andintrusions, whereas moderate reactivation resulted in both. This finding suggests that strong reactivation enhances event-baseddistinctiveness, counteracting memory modification. Results are discussed in reference to the testing effect literature and thereconsolidation account, and implications for educational practice are outlined

The mere exposure effect is sensitive to color information: Evidence for color effects in a perceptual implicit memory test

Abstract. Priming effects in perceptual tests of implicit memory are assumed to be perceptually specific. Surprisingly, changing object colors from study to test did not diminish priming in most previous studies. However, these studies used implicit tests that are based on object identification, which mainly depends on the analysis of the object shape and therefore operates color-independently. The present study shows that color effects can be found in perceptual implicit tests when the test task requires the processing of color information. In Experiment 1, reliable color priming was found in a mere exposure design (preference test). In Experiment 2, the preference test was contrasted with a conceptually driven color-choice test. Altering the shape of object from study to test resulted in significant priming in the color-choice test but eliminated priming in the preference test. Preference judgments thus largely depend on perceptual processes. In Experiment 3, the preference and the color-choice test were studied under explicit test instructions. Differences in reaction times between the implicit and the explicit test suggest that the implicit test results were not an artifact of explicit retrieval attempts. In contrast with previous assumptions, it is therefore concluded that color is part of the representation that mediates perceptual priming

Differential effects of unipolar versus bipolar depression on episodic memory updating

Episodic memories, when reactivated, can be modified or updated by new learning. Since such dynamic memory processes remain largely unexplored in psychiatric disorders, we examined the impact of depression on episodic memory updating. Unipolar and bipolar depression patients, and age/education matched controls, first learned a set of objects (List-1). Two days later, participants in all three groups were either reminded of the first learning session or not followed by the learning of a new set of objects (List-2). Forty-eight hours later, List-1 recall was impaired in unipolar and bipolar patients compared to control participants. Further, as expected, control participants who received a reminder spontaneously recalled items from List-2 during recall of List-1, indicative of an updated List-1 memory. Such spontaneous intrusions were also seen in the unipolar and bipolar patients that received the reminder, suggesting that memory updating was unaffected in these two patient groups despite impaired recall of List 1. Unexpectedly, we observed a trend towards higher intrusions, albeit statistically insignificant, not only in the reminder but also in the no-reminder subgroups of bipolar patients. We probed this further in a second cohort by testing recall of List-2, which was also impaired in both depression groups. Again bipolar patients showed intrusions, but this time in the reverse order from List-1 into List-2, independent of a reminder. Taken together, despite impaired recall, updating of episodic memories was intact and unidirectional in unipolar depression. In contrast, indiscriminate updating, as evidenced by bidirectional interference between episodic memories, was seen in bipolar depression. These findings reveal a novel distinction between unipolar versus bipolar depression using a reactivation-dependent memory updating paradigm.Department of Biotechnology Research Associateship; Madan and Usha Sethi Fellowship12 month embargo; available online 17 April 2019This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]