A daytime nap with REM sleep is linked to enhanced generalization of emotional stimuli.

How memory representations are shaped during and after their encoding is a central question in the study of human memory. Recognition responses to stimuli that are similar to those observed previously can hint at the fidelity of the memories or point to processes of generalization at the expense of precise memory representations. Experimental studies utilizing this approach showed that emotions and sleep both influence these responses. Sleep, and more specifically rapid eye movement sleep, is assumed to facilitate the generalization of emotional memories. We studied mnemonic discrimination by the emotional variant of the Mnemonic Separation Task in participants (N = 113) who spent a daytime nap between learning and testing compared with another group that spent an equivalent time awake between the two sessions. Our findings indicate that the discrimination of similar but previously not seen items from previously seen ones is enhanced in case of negative compared with neutral and positive stimuli. Moreover, whereas the sleep and the wake groups did not differ in memory performance, participants entering rapid eye movement sleep exhibited increased generalization of emotional memories. Our findings indicate that entering into rapid eye movement sleep during a daytime nap shapes emotional memories in a way that enhances recognition at the expense of detailed memory representations.

Study protocol of the Hungarian Longitudinal Study of Healthy Brain Aging (HuBA).

Background and purpose:

Neuro­cog­nitive aging and the associated brain diseases impose a major social and economic burden. Therefore, substantial efforts have been put into revealing the lifestyle, the neurobiological and the genetic underpinnings of healthy neurocognitive aging. However, these studies take place almost exclusively in a limited number of highly-developed countries. Thus, it is an important open question to what extent their findings may generalize to neurocognitive aging in other, not yet investigated regions. The purpose of the Hungarian Longitudinal Study of Healthy Brain Aging (HuBA) is to collect multi-modal longitudinal data on healthy neurocognitive aging to address the data gap in this field in Central and Eastern Europe.

We adapted the Australian Ima­ging, Biomarkers and Lifestyle (AIBL) study of aging study protocol to local circumstances and collected demographic, lifestyle, men­tal and physical health, medication and medical history related information as well as re­cor­ded a series of magnetic resonance imaging (MRI) data. In addition, participants were al­so offered to participate in the collection of blood samples to assess circulating in­flam­matory biomarkers as well as a sleep study aimed at evaluating the general sleep quality based on multi-day collection of subjective sleep questionnaires and whole-night elec­troencephalographic (EEG) data.

Baseline data collection has al­ready been accomplished for more than a hundred participants and data collection in the se­cond
session is on the way. The collected data might reveal specific local trends or could also indicate the generalizability of previous findings. Moreover, as the HuBA protocol al­so offers a sleep study designed for tho­rough characterization of participants’ sleep quality and related factors, our extended multi-modal dataset might provide a base for incorporating these measures into healthy and clinical aging research. 

Besides its straightforward na­tional benefits in terms of health ex­pen­di­ture, we hope that this Hungarian initiative could provide results valid for the whole Cent­ral and Eastern European region and could also promote aging and Alzheimer’s disease research in these countries.

Positive schizotypy is associated with amplified mnemonic discrimination and attenuated generalization.

Tendency to experience inaccurate beliefs alongside perceptual anomalies constitutes positive schizotypal traits in the general population and shows continuity with the positive symptoms of schizophrenia. It has been hypothesized that the positive symptomatology of schizophrenia, and by extension, the odd beliefs and unusual perceptual experiences in the general population, are associated with specific alterations in memory functions. An imbalance between memory generalization and episodic memory specificity has been proposed on several counts; however, the direction of the imbalance is currently unclear. Here, we evaluated the association between positive schizotypy, and memory alterations related to hippocampal computations in a general population sample enriched for positive schizotypy. We found that memory generalization is attenuated while memory specificity is elevated in participants with more pronounced positive schizotypal traits. Our findings show that people who are prone to irrational beliefs and unusual experiences also show measurable alterations in memory and likely have difficulty grasping the global picture and rather be overpowered by fragments of information.

The key to superior memory encoding under stress: the relationship between cortisol response and mnemonic discrimination.

Some previous studies have shown that increased stress hormone levels have beneficial effects on memory encoding; however, there is no clear consensus on which encoding-related processes are affected by stress hormones. In the present study, we investigated the relationship between interindividual differences in neuroendocrine response to acute stress and interference resolution (i.e., mnemonic discrimination). Participants were healthy young adults who were exposed to physical and psychological stressors (Socially Evaluated Cold Pressor Test). Then participants completed the modified version of the Mnemonic Similarity Task. Specifically, they were presented with photographs of emotionally arousing (negative and positive) and nonarousing (neutral) scenes followed by a recognition memory test where they saw a mixture of old and new stimuli. Crucially, participants were also presented with critical lure items, that is, visually similar stimuli to ones presented at encoding. We found that participants who had higher cortisol response to the stressors were better in discriminating between the studied items and their visually similar lures. This effect was present for the arousing and nonarousing materials as well. These findings suggest that increased hormonal response to acute stress has a beneficial impact on the formation of distinct, nonoverlapping, unique memory representations, and consequently, on episodic memory encoding processes.

[Verbal Episodic Memory Test]. / A Verbális Epizodikus Memória Teszt.

Background and purpose:

The decline of episodic memory is one of the earliest cognitive markers of mild cognitive impairment and various types of dementia. Until today, however, there is no standardized Hun­garian episodic memory test that takes into account the characteristics of the Hungarian language. The study presents the structure and standardized use of a new memory test (Verbal Episodic Memory Test, VEMT) as well as normative data in Hungary. 

The VEMT is suitable for the comprehensive examination of verbal learning abilities in a broader sense, and more specifically, for the neuropsychological measurement of verbal list learning abilities. In the present study, we constructed a normative database consisting of data from 385 participants.

We showed that the VEMT is sensitive to demographic factors (e.g., age) which are linked to differences in episodic memory performance. Open access to the test is provided, and the normative scores are presented as well. 

The indicators of the test are suitable for drawing a learning curve, for showing the interaction of new and previously learned information (interference effects), and for measuring differences between free recall and cued recall. Furthermore, the test scores are appropriate for distinguishing the effects of different types of memory encoding forms (phonological, semantic, and episodic), for measuring the ability to reconstruct the presentation of a sequence (memory order information), for detecting the rate of forgetting, for measuring recognition abilities, and for detecting hippocampus-related mnemonic pattern separation and completion functions. 

Learning to distinguish: shared perceptual features and discrimination practice tune behavioural pattern separation.

Pattern separation is a computational mechanism performed by the hippocampus allowing the reduction of overlap between sensory inputs with similar perceptual features. Our first aim was to develop a new paradigm sensitive to the behavioural consequences of pattern separation (mnemonic discrimination). For this purpose, we constructed morphed face stimuli with parametrically changing levels of similarity. After encoding participants saw studied items and similar lure faces. Perceptual similarity affected false recognition and there was a gradual reduction in discrimination accuracy with the increment of similarity between the stimuli. However, confidence ratings were sensitive to smaller changes (Experiment 1) than the other test type with "old"/"similar"/"new" response options (Experiment 2). Mnemonic discrimination relies strongly on retrieving details of the original stimulus. Therefore, we investigated whether pattern separation can be tuned by retrieval in the form of a discrimination task (Experiment 3). Our findings suggest that repeatedly encountering the stimuli within a two-alternative forced-choice task (in comparison with the repeated presentation of the material) increased both the correct identification and the false recognition of similar stimuli two days after encoding. We conclude that basic computational mechanisms of the hippocampus can be tuned by a task that requires discrimination between studied and new stimuli.

Enhanced mnemonic discrimination for emotional memories: the role of arousal in interference resolution.

In the present study we investigated the long-standing question whether and why emotionally arousing memories are more distinct as compared to neutral experiences. We assumed that memory benefits from the distinctiveness of emotional information, and that emotions affect encoding by reducing interference among overlapping memory representations. Since pattern separation is the process which minimizes interference between memory representations with similar features, we examined the behavioral manifestation of putative neural mechanisms enabling pattern separation (i.e. mnemonic discrimination) for emotionally arousing materials using the Mnemonic Similarity Task with negative, positive, and neutral images as stimuli. Immediately after incidental encoding, subjects were presented with stimuli they had seen at encoding and also with new items. Crucially, participants were also presented with lure images that were visually similar to ones they had seen before. Response options were old, new, and similar. Our results showed that individuals were better in discriminating between similar, emotionally arousing memories, when compared to the neutral stimuli. Moreover, this so-called lure discrimination performance was better for the negative images, than it was for the positive stimuli. Finally, we showed that the high arousing negative stimuli were better separated than the low arousing negative stimuli, and a similar pattern of results was found for the positive items. Altogether, these findings suggest that lure discrimination is modulated by arousal and not by valence. We argue that noradrenergic activity might facilitate interference resolution among memory representations with similar features, and that superior pattern separation might play a key role in memory enhancement for emotional experiences.

Reversing the testing effect by feedback is a matter of performance criterion at practice.

Retrieval practice is generally considered to be one of the most effective long-term learning strategies and is presumed to be more favorable than repeated study. However, a few recent studies have demonstrated that repetitive feedback at final recall can reverse the long-term advantage of testing over restudy. The result that feedback at long-term tests can dramatically decrease the relative effectiveness of retrieval-based learning could be important for both theoretical and practical reasons. Considering that these earlier studies administered low retrieval success at retrieval practice, we investigated whether the effect of feedback on the testing effect is modulated by the level of retrieval success during practice. In three experiments the level of success at retrieval practice was manipulated by multiple pre-practice learning trials, and multiple tests with feedback were applied after a 1-week retention interval at final recall. Our results have demonstrated that a feedback-induced reversed testing effect was present only at low retrieval success during practice (Experiment 1), whereas with moderate (Experiment 2) and high retrieval success (Experiment 3) during practice a significant testing effect emerged and no reversed testing effect was found even after repeated cycles of feedback. These results point to the conclusion that the level of retrieval success was the key factor in reversing the testing effect in earlier studies. Application of high retrieval success during practice can produce long-lasting accessible memories even in learning settings applying multiple tests with feedback.

Behavioural pattern separation is strongly associated with familiarity-based decisions.

Pattern separation is the process that minimises interference between memory representations with similar features and is suggested to be associated with hippocampus-related recollection. We tested this hypothesis using the incidental Mnemonic Similarity Task with old (target), similar (lure), and new (foil) items presented on a recognition test, which is widely used for detecting individual differences in behavioural pattern separation performance. In Experiment 1, participants made old/similar/new decisions and rated decision confidence on a scale ranging from "not at all sure" to "very sure". In Experiment 2, participants made recognition confidence judgments on a scale ranging between "sure it was new" and "sure it was old". In Experiment 3, subjects gave old/similar/new decisions and made a secondary Remember/Know/Guess judgment. In Experiment 1, confidence ratings were higher for targets compared to lures when we analysed correct responses (old for targets and similar for lures). Additionally, we found a symmetrical ROC curve and a linear zROC curve for target-lure discrimination in Experiment 2. Finally, we found a bias toward Know responses when we analysed behavioural pattern separation performance (i.e., the rate of similar responses given to the lures). These findings suggest that familiarity, rather than recollection, contributes to behavioural pattern separation performance.

Successful list-method directed forgetting without retroactive interference of post-instruction learning.

The focus of the study is the role of interference in list-method directed forgetting. More specifically, our question was whether retroactive interference of the to-be-remembered information is a necessary prerequisite for the directed forgetting effect. In Experiment 1 we used a directed forgetting procedure with one learning list without the interference of any to-be-remembered information. In line with previous results, we did not find a significant directed forgetting effect. Experiment 2 applied a directed forgetting procedure with two study lists, however, the forget instruction was given following the second list. So, List 2 items were designated as to-be-forgotten items, without further learning, whereas List 1 items were to-be-remembered items. The forget instruction selectively decreased the recall of List 2 items, without decreasing the recall performance for List 1. In Experiment 3, using the same procedure with different items, smaller learning lists and reversed output order, we replicated the results of Experiment 2. Altogether, these results point to a flexible, goal-related nature of the directed forgetting phenomenon, showing that some form of interference is a necessary requirement for successful directed forgetting. However, proactive interference of to-be-remembered information in interaction with a forget instruction is suitable for forgetting of subsequently encoded information.

Testing promotes long-term learning via stabilizing activation patterns in a large network of brain areas.

The testing effect refers to the phenomenon that repeated retrieval of memories promotes better long-term retention than repeated study. To investigate the neural correlates of the testing effect, we used event-related functional magnetic resonance imaging methods while participants performed a cued recall task. Prior to the neuroimaging experiment, participants learned Swahili-German word pairs, then half of the word pairs were repeatedly studied, whereas the other half were repeatedly tested. For half of the participants, the neuroimaging experiment was performed immediately after the learning phase; a 1-week retention interval was inserted for the other half of the participants. We found that a large network of areas identified in a separate 2-back functional localizer scan were active during the final recall of the word pair associations. Importantly, the learning strategy (retest or restudy) of the word pairs determined the manner in which the retention interval affected the activations within this network. Recall of previously restudied memories was accompanied by reduced activation within this network at long retention intervals, but no reduction was observed for previously retested memories. We suggest that retrieval promotes learning via stabilizing cue-related activation patterns in a network of areas usually associated with cognitive and attentional control functions.

Interference resolution in retrieval-induced forgetting: behavioral evidence for a nonmonotonic relationship between interference and forgetting.

Retrieving memories renders related memories less accessible. This phenomenon, termed retrieval-induced forgetting (RIF), is thought to be the result of processes that resolve interference during competitive retrieval. In several studies, researchers have manipulated the level of interference to test different theoretical accounts of RIF (e.g., inhibitory vs. noninhibitory). However, the nature of how interference and RIF are related has not been systematically investigated. Here, we introduce a design that allows for assessing interference during competitive retrieval by measuring the recall RTs associated with target recall. Using such a design, we found that RIF occurred only when interference during competitive retrieval reached moderate levels, but not when it was too low or too high. This finding might indicate that low levels of interference do not trigger interference resolution, whereas interference resolution might fail when the interference reaches extremely high levels.

Intact short-term memory and impaired executive functions in obsessive compulsive disorder.

BACKGROUND AND PURPOSE: Previous neuropsychological studies produced inconsistent results with tasks tapping short-term verbal and visual-spatial memory and executive functions in obsessive compulsive disorder (OCD). The aim of this study was to investigate the presence of deficits in these cognitive domains. A further goal was to describe the distribution of patients in different impairment ranges for all functions, and clarify the relationship between symptom severity and cognitive impairments. METHODS: Thirty patients with OCD (DSM-IV) and 30 healthy volunteers were compared using well-known neuropsychological tasks. We assessed short-term verbal memory with the Digit Span Forward and Digit Span Backward Tasks, short-term visual-spatial memory with the Corsi Block Tapping Task, while we measured the level of executive functions with the StroopTask and the Wisconsin Card Sorting Test (WCST). RESULTS: Compared with a matched healthy control group, the performance of OCD patients was in the impaired range only in the two executive tasks. We find a significant positive correlations between the Y-BOCS (Yale-Brown Obsessive Compulsive Scale) total scores and the number of perseverative responses (r(28) = 0.409, p < 0.05) and perseverative errors (r(28) = 0.385, p < 0.05) in the WCST. CONCLUSION: Our results gave evidence that executive functions are impaired while short-term memory is intact in OCD. This is in line with neuropsychological model of OCD that the deficit of cognitive and behavioral inhibition are responsible for the main cognitive findings of this disorder, most prevalently the deficit in set shifting and prepotent response inhibition.

People sometimes remember to forget: Strategic retrieval from the list before last enables directed forgetting of the most recent information.

List-method directed forgetting usually involves asking people to study a list, followed by a cue to forget it, and then studying a second list. Prior work suggests that List 2 encoding is necessary for directed forgetting to occur, but recent studies have found that moving the forget cue from List 1 to List 2 allows people to selectively forget List 2. These results were attributed to an inhibitory mechanism. In four experiments, we aimed to replicate these findings and provide an alternative explanation based on the list-before-the-last paradigm. We propose that in the forget condition, participants may strategically retrieve List 1 in response to the forget cue, contributing to selective forgetting. Previous research suggests that explicit retrieval of earlier-leaned information causes a contextual shift, resulting in forgetting of target information. Verbal reports from Experiments 1 and 2 indicated that participants often covertly select a retrieval strategy to forget the most recent list. In Experiment 3, explicit instructions to retrieve resulted in significant forgetting. Directly manipulating forgetting strategy between participants in Experiment 4 suggested that retrieval may be one of several effective mechanisms to forget recently-encountered information. In the retrieval conditions, the data support our claim that in the absence of explicit postcue encoding, people can strategically retrieve earlier-learned information to forget. This novel forgetting mechanism is probably also used outside of the laboratory to "roll back" memory for incorrect information. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Litmus test of rich episodic representations: Context-induced false recognition.

Context-dependent episodic memory is typically investigated using tasks in which retrieval occurs either in the reinstated context of encoding or in a completely new context. A fundamental question of episodic memory models is the level of detail in episodic memory representations containing contextual information about the encoded event. The present study examined whether memory is affected when the contexts of encoding and retrieval are highly similar but not exactly the same. At encoding, participants saw unique object images presented on the background of unique context scene images. On a surprise recognition test, the objects were either old or visually similar to ones seen at encoding (lure stimuli). The objects were presented on either the old or a lure context image; the lure context image was visually similar to the corresponding object's encoding context. Context reinstatement increased the hit rate for the old objects, but also increased the false alarm for the lure objects. This latter finding indicates that the presence of the encoding context at test does not always aid recognition memory decisions. These results suggest that slight visual differences between the contexts of encoding and retrieval matter, as context reinstatement leads to a tendency to respond Old even in case of small differences in the old and lure contexts.

Inhibition and interference in the think/no-think task.

Five experiments using the think/no-think (TNT) procedure investigated the effect of the no-think and substitute instructions on cued recall. In Experiment 1, when unrelated A-B paired associates were studied and cued for recall with A items, recall rates were reliably enhanced in the think condition and reliably impaired below baseline in the no-think condition. In Experiments 2 and 5, final recall was cued with B items, leading to reliably higher recall rates, as compared with baseline, in both the think and no-think conditions. This pattern indicates backward priming of no-think items. In Experiments 3 and 4, the no-think instruction was replaced with a thought substitution instruction, and participants were asked to think of another word instead of the studied one when they saw the no-think cued items. As in Experiments 1 and 2, the same amount of forgetting of B items was observed when A items were the cues, but in contrast to Experiment 2, there was no increase in the recall performance of A items when B items were the cues. These results suggest that not thinking of studied items or, alternatively, thinking of a substitute item to avoid a target item may involve different processes: the former featuring inhibition and the latter interference.

The validation of the Hungarian version of the dimensional Yale-Brown obsessive-compulsive scale.

BACKGROUND: The Obsessive-Compulsive disorder (OCD) has a complex phenotype, which can be summarized by using a few consistent and temporally stable symptom dimensions. The dimensional approach derived from the systematic factor analytic studies of OCD symptoms. In 2006, a new psychometric scale was created by M.C. Rosario-Campos and her colleague, the Dimensional Yale-Brown Obsessive-Compulsive Scale (DY-BOCS). This scale measures the presence and severity of obsessive-compulsive (OC) symptoms within six distinct dimensions. The Hungarian translation of the test and preliminary results were published in 2009. PURPOSE: The objective of this recent study was two folded: on one hand, our goal was to validate the Hungarian version of the DY-BOCS on a larger sample size. On the other hand, we wanted to publish our results gained by the Hungarian version of the test in English. METHODS: We assessed 30 Hungarian patients diagnosed with OCD by DSM-IV. Reliability and validity of the expert and of the self-report were estimated. RESULTS: Self-report and expert ratings were highly correlated. The global DY-BOCS score was well correlated with the total Yale-Brown Obsessive-Compulsive Scale score. The internal validity of the symptom dimensions and the global severity score were high. Divergent validity was also good. CONCLUSION: These results indicate that the Hungarian version of the DY-BOCS is a reliable and valid clinical tool.

An event-related potential study of the testing effect: Electrophysiological evidence for context-dependent processes changing throughout repeated practice.

The testing effect refers to a special form of performance improvement following practice. Specifically, repeated retrieval attempts improve long-term memory. In the present study we examined the underlying mechanisms of the testing effect as a function of time by investigating the electrophysiological correlates of repeated retrieval practice. We additionally investigated the ERP waveforms of the repeated practice phase as a function of the accuracy on the final test in a "difference due to memory" (Dm) analysis. We found a parietally distributed, increased positive amplitude between 500 and 700 ms, and a more positive parietal wave between 700 and 1000 ms in the later relative to the early phases of retrieval practice. We found parietal Dm effects in the same two time windows in the retrieval practice condition with a more positive amplitude predicting retrieval success on the final test. We interpret the earlier waveform as a component associated with episodic recollection and the later ERP as a component related to post-retrieval evaluation processes. Our results demonstrate the important role of these retrieval-related processes in the facilitating effect of retrieval practice on later retrieval, and show that the involvement of these processes changes throughout practice.

Irrelevant background context decreases mnemonic discrimination and increases false memory.

One of the greatest commonplaces in memory research is that context improves recall and enhances or leaves recognition intact. Here we present results which draw attention to the fact that the reappearance of irrelevant and unattended background contexts of encoding significantly impairs memory discrimination functions. This manuscript presents the results of two experiments in which participants made indoor/outdoor judgements for a large number of object images presented together with individual, irrelevant and presumably unattended background scenes. On a subsequent unexpected recognition test participants saw the incidentally encoded target objects, visually similar lures or new foil objects on the same or new background scenes. Our results showed that although the reappearance of the background scene raised the hit rate for target objects, it decreased mnemonic discrimination, a behavioral score for pattern separation, a hippocampal function that is affected in early dementia. Furthermore, the presence of the encoded background scene at the recognition test increased the false recognition of lure objects, even when participants were explicitly instructed to neglect the context scene. Altogether these results gave evidence that if context increases recognition hits for target memories, it does so at the cost of increasing false recognition and diminished discriminability for similar information.

Consolidation of episodic memories during sleep: long-term effects of retrieval practice.

Two experiments investigated the long-term effects of retrieval practice. In the retrieval-practice procedure, selected items from a previously studied list are repeatedly recalled. The typical retrieval-practice effects are considerably enhanced memory for practiced items accompanied by low levels of recall, relative to baseline, for previously studied items that are associated with the practiced items but were not themselves practiced. The two experiments demonstrated that the former effect persisted over 12 hr; the latter effect also persisted over 12 hr, but only if a period of nocturnal sleep occurred during the retention interval. We propose that consolidation processes occurring during sleep, and possibly featuring some form of off-line rehearsal, mediate these long-term effects of retrieval practice.