Episodic memory: from mind to brain

Why is rumination unhelpful in adolescents? Two studies examining the causal role of abstract processing

Rumination is a common feature of depression in adolescents and adults and it is implicated in the maintenance of depression symptoms. In adults, the maladaptive consequences of rumination have been attributed to the abstract processing mode that characterises this thinking style. The question of whether the same is true in adolescents remains unanswered. Here we describe two experimental studies in which adolescents were trained to think in a mode either characteristic of or inconsistent with the abstract processing style observed in depressive rumination, and the effect on social problem-solving and negative future thinking was examined. The two experiments employed a similar design. 11-14 year olds scoring in the upper and lower quartile on a measure of depression were trained to engage in an abstract or concrete processing style and then carry out a social problem-solving (Study 1) or future thinking (Study 2) task. Adolescents were worse at social problem-solving and had more negative (but not fewer positive) future thoughts when engaging in abstract processing compared to concrete processing, regardless of their current level of depressive symptoms. The finding remained when controlling for state mood. Our findings suggest there may be value in targeting abstract ruminative processing as an early treatment for depression.

Total recall: Detecting autobiographical memory retrieval in the absence of behaviour

Functional neuroimaging has fundamentally changed our understanding of disorders of consciousness (DoC). While many DoC patients exhibit minimal to no behavioural responsiveness, a significant minority show neural evidence of awareness and preserved cognitive functioning. Although several cognitive functions have been explored in DoC patients, autobiographical memory -- the ability to form and retrieve personal memories -- has yet to be investigated. To address this gap, we used functional magnetic resonance imaging (fMRI) to investigate autobiographical memory in one DoC patient. The patient viewed video clips across three conditions: (1) Own - clips recorded from their perspective during a recent mall visit; (2) Other - clips from a healthy control's visit to the same mall; and (3) Bookstore - novel clips from an entirely different store that had not been visited. We trained a linear support vector classifier to associate fMRI activity in canonical autobiographical memory regions with each condition using data from twelve healthy participants. We then applied the trained model to the patient's data to 'decode' which condition their fMRI activity predicted. The model accurately distinguished between Own, Other, and Bookstore conditions in the patient (Balanced Accuracy = 0.448, p = .032), with performance within the control group range (p = .068). Similarly, the model distinguished between the Own and Other conditions above chance (Balanced Accuracy = 0.609, p = .032) and within the control group's distribution (p = .620), suggesting that the patient was still able to differentiate personal experiences from visually similar scenes, despite being behaviourally unable to report that this was the case. These findings provide preliminary evidence that autobiographical memory processes, critical to conscious awareness and identity, remain intact in some DoC patients, shedding further light on their covert capabilities and inner experiences.

Normative data for the 12-item Buschke memory task in the Quebec-French population aged 50 and over

OBJECTIVE

The 12-item Buschke memory test is used to assess verbal episodic memory in adults and older adults. However, there is no normative data for this test adjusted to the older Quebec-French population. The aim of the study was to produce normative data for the 12-item Buschke for the Quebec-French population aged 50 and older.

METHOD

The normative sample consisted of 172 healthy French-speaking participants aged 50-89 years, from the Province of Quebec (Canada). The influence of age, years of formal education, and sex on five 12-item Buschke scores were analyzed. Based on the distribution of scores, normative data were developed as Z-scores equation, regression equation, and percentiles.

RESULTS

Age, years of formal education, and sex were all associated with performance. Equations to calculate Z-scores were provided for the free recall trial 1 and the free recall trials 1-3. Stratified percentiles were provided for the delayed free recall and total recall 1-3.

CONCLUSIONS

The normative data for the 12-item Buschke improve the accuracy of clinicians to detect verbal episodic memory impairments in Quebec's aging population.

An Illusion of Time Caused by Repeated Experience

How do people remember when something occurred? One obvious possibility is that, in the absence of explicit cues, people remember on the basis of memory strength. If a memory is fuzzy, it likely occurred longer ago than a memory that is vivid. Here, we demonstrate a robust illusion of time that stands in stark contrast with this prediction. In six experiments testing adults via an online research platform, we show that experiences that are repeated (and, consequently, better remembered) are counterintuitively remembered as having initially occurred further back in time. This illusion is robust (amounting to as much as a 25% distortion in perceived time), consistent (exhibited by the vast majority of participants tested), and applicable at the scale of ordinary day-to-day experience (occurring even when tested over one full week). We argue that this may be one of the key mechanisms underlying why people's sense of time often deviates from reality.

Shared spectral fingerprints of temporal memory precision and representation of the temporal structure of complex narratives

The ability to date events is fundamental to episodic memory. Separate lines of fMRI research have explored the neurobiological mechanisms underlying temporal precision and the representation of temporal structure in complex events. The present EEG study examined the oscillatory dynamics of both processes in participants performing a timeline positioning task with movie scenes. Multivariate analyses identified a high-beta/low-gamma electrophysiological signature of temporal precision during timeline presentation, involving a right-lateralized network. An independent representation similarity analysis revealed a strong coupling between behavioral and neural distance between pairs of movie parts in the same time-frequency band as the precision effect. Crucially, participants with higher temporal precision showed a stronger correlation between behavioral and neural distance, reinforcing the link between brain signals related to precision and temporal structure representation. These findings support the idea of a systematic temporal organization of experiences, which plays a role in guiding inferential processes.

Picture free and cued selective reminding test (P-FCSRT): A normative study for Chilean middle-aged and older adults

BackgroundThe Picture Free and Cued Selective Reminding Test (P-FCSRT) has proven useful in assessing episodic memory while controlling for interference from attentional processes. In Chile, studies have supported its diagnostic utility in detecting dementia in older adults, however, it lacks both normative data that account for the influence of age and educational level from mid-adulthood onwards, and the quantification of intrusive errors which have significant clinical value.ObjectiveThe aim of this study is to determine normative scores and intrusive errors for the P-FCSRT, controlling for sociodemographic factors (age and educational level) in the Chilean population.MethodsA total sample of 185 healthy participants from the Aging Mets cohort were recruited from three regions in Chile (Antofagasta, Santiago, and Puerto Montt). The P-FCSRT was administered to all participants. A multivariate regression-based normative approach was used to generate normative data, considering the effects of age, years of schooling, and sex.ResultsSignificant effects of age and years of schooling were found on P-FCSRT free recall, total recall, delayed recall, intrusions, and sensitivity to cues. Age had a distinct effect on each P-FCSRT dimension, whereas years of schooling had a consistent effect across them. Sex did not influence any P-FCSRT dimension.ConclusionsThis study is the first to provide normative data for the Chilean version of the P-FCSRT and will be beneficial for clinical neuropsychologists in improving the procedures for a more accurate assessment of episodic memory and related impairments.

A vectorial code for semantics in human hippocampus

As we listen to speech, our brains actively compute the meanings of individual words. Inspired by the success of large language models (LLMs), we hypothesized that the brain employs vectorial coding principles, such that meaning is reflected in distributed activity of single neurons. We recorded responses of hundreds of neurons in the human hippocampus, which has a well-established role in semantic coding, while participants listened to narrative speech. We find encoding of contextual word meaning in the simultaneous activity of neurons whose individual selectivities span multiple unrelated semantic categories. Like embedding vectors in semantic models, distance between neural population responses correlates with semantic distance; however, this effect was only observed in contextual embedding models (like BERT) and was reversed in non-contextual embedding models (like Word2Vec), suggesting that the semantic distance effect depends critically on contextualization. Moreover, for the subset of highly semantically similar words, even contextual embedders showed an inverse correlation between semantic and neural distances; we attribute this pattern to the noise-mitigating benefits of contrastive coding. Finally, in further support for the critical role of context, we find that neural response variance increases with lexical polysemy. Ultimately, these results support the hypothesis that semantic coding in the hippocampus follows vectorial principles.

From reactions to reflection: A recursive framework for the evolution of cognition and complexity

This paper presents a comprehensive framework that traces the evolution of consciousness through a continuum of recursive processes spanning reaction, temporogenesis, symbiogenesis, and cognogenesis. By integrating biological cooperation, temporal structuring, and self-referential processing, our model provides a novel perspective on how complexity emerges and scales across evolutionary time. Reaction is established as the foundational mechanism that enables adaptive responses to environmental stimuli, which, through recursive refinement, transitions into temporogenesis-the synchronization of internal processes with external temporal rhythms. Symbiogenesis further enhances this process by fostering cooperative interactions at multiple biological levels, facilitating the emergence of higher-order cognitive functions. Cognogenesis represents the culmination of these recursive processes, where self-awareness and intentionality arise through iterative feedback loops. Our framework offers a biologically grounded pathway to addressing the "hard problem" of consciousness by proposing that subjective experience emerges as a result of progressively complex recursive interactions rather than as a static or isolated phenomenon. In comparing our approach with established theories such as Integrated Information Theory, Global Workspace Theory, and enactive cognition, we highlight its unique contributions in situating consciousness within a broader evolutionary and biological context. This work aims to provide a foundational model that bridges the gap between reaction and reflection, offering empirical avenues for further exploration in neuroscience, evolutionary biology, and artificial intelligence.

Enhanced recognition memory for emotional nonverbal sounds

Emotion often enhances memory for emotional stimuli relative to neutral stimuli. This emotional memory enhancement effect has been studied extensively with visual and verbal stimuli, yet little is known regarding emotion's effects on memory for nonverbal (or environmental) sounds, such as dog snarls and infant cries. Additionally, emotion's enhancing effects on recognition for visual and verbal stimuli are selective to recollection (recognition with contextual retrieval) rather than familiarity (recognition based on memory strength), but whether this is also the case for nonverbal sounds is unknown. We examined recognition memory for negative and neutral nonverbal sounds, predicting that memory would be enhanced for negative sounds and this enhancement would be specific to recollection. Participants incidentally encoded negative and neutral sounds, and memory was tested with a remember-familiar recognition memory task after a 15-minute delay. As predicted, recognition memory was enhanced for negative sounds, was better for higher versus lower arousal negative sounds, and was specific to recollection. These findings suggest that key aspects of the emotional enhancement effect also extend to nonverbal sounds. We discuss how current theories of emotional memory which focus on memory for visual and verbal stimuli can be extended to accommodate findings with nonverbal emotional auditory stimuli.

Consistent neural representation of valence in encoding and recall

Recall is an act of elicitation of emotions similar to those emotions previously experienced. Unlike the past experiences where external sensory stimuli triggered emotions, recall does not require external sensory stimuli. This difference is pertinent to the key debate in affective representation, addressing whether the representation of valence is consistent across modalities (modality-general) or dependent on modalities (modality-specific). This study aimed to verify neural representations of valence between encoding and recall. Using neuroimaging data from movie watching and recall (Chen et al., 2017) and behavioral data for valence ratings (Kim et al., 2020), a searchlight analysis was conducted with cross-participant regression-based decoding between movie watching and recall. Multidimensional scaling was employed as a validation analysis of the results from searchlight analysis. The searchlight analysis revealed the right middle temporal and inferior temporal gyrus as well as the left fusiform gyrus. The validation analysis further exhibited significant consistent neural representations of valence in the inferior temporal gyrus and the left fusiform gyrus. This study identified the brain regions where valence is consistently represented between encoding and recall about real events. These findings contribute to debate in affective representations, by comparing conditions utilized little in prior, suggesting the inferior temporal gyrus relates to representations of valence during encoding and recalling natural events.

Area-specific encoding of temporal information in the neocortex

Episodic memory requires remembering the temporal sequence of events, a process attributed to hippocampal "time cells." However, the distributed nature of brain areas supporting episodic memory suggests that temporal representations may extend beyond the hippocampus. To investigate this possibility, we trained mice to remember the identity of an odor for a specific duration. Using mesoscale two-photon imaging of neuronal activity across the neocortex, we reveal a striking area-specific temporal representation. The retrosplenial cortex (RSC), a hippocampal target area, exhibits time-dependent sequential neuronal firing that encodes both odor identity and elapsed time, with decreasing accuracy over time. By contrast, temporal coding is far less prominent in areas surrounding the RSC, including the posterior parietal cortex and visual, somatosensory, and motor areas, highlighting functional specialization. Our results establish the RSC as a key temporal processing hub for episodic memory, supporting conjunctive "what" and "when" coding models.

Narrative processing primes autobiographical memories: Another instance of semantic-to-autobiographical memory priming

Research has shown that the activation of semantic memories leads to the activation of autobiographical memories. Known as semantic-to-autobiographical memory priming, this form of priming has been demonstrated to prime involuntary and voluntary autobiographical memories with a wide variety of different stimuli (e.g., words, pictures, sentences, sounds, tactile stimuli, etc.). Our goal in the current study was to extend semantic-to-autobiographical memory priming to narrative processing. Participants read a short story that contained multiple prime words, and then they were treated to an involuntary autobiographical memory task (the vigilance task). Instead of the short story, control participants were given a task which required them to make judgments about the alphabetical status of letter strings (e.g., ABC, FGH, XTC), and they were subsequently treated to the vigilance task. The results showed that participants primed with the story produced more involuntary autobiographical memories with primed and unprimed content on the vigilance task than the control participants. The results further support the idea that semantic-to-autobiographical memory primes occurs with a diverse set of stimuli. The results also support the idea that semantic-to-autobiographical memory priming may play a significant role in the production of involuntary autobiographical memories in everyday life.

Collecting initial accounts using ChatCharlie chatbot improves eyewitness memory in later investigative interviews

Initial account interviews (IAi) offer eyewitnesses more immediate opportunities to answer a series of brief questions about their experiences prior to an in-depth, more formal investigative interview. An IAi is typically elicited in-person near/at the scene of a crime using broadly systematic questioning. Retrieval practice can improve subsequent recall in some contexts, but there is a dearth of research centred on the potential costs and benefits of a quick IAi. Furthermore, where an in-person IAi is impossible, no alternative quick provision exists. Given the systematic nature of the IAi protocol, we developed a conversational chatbot as a potential alternative. Using a mock-witness paradigm, we investigated the memory performance of adults from the general population during in-depth in-person interviews one week after having provided an IAi 10 min post event either (1) in person, (2) via the ChatCharlie chatbot, or (3) no IAi (control). IAi conditions leveraged significantly improved event recall during later investigative interviews versus the Control. Accounts were more accurate and complete, and more correct information was remembered without increased errors indicating the potential of digital agents for IAi purposes Findings concur with predictions from theoretical understanding of episodic memory consolidation and the empirical eyewitness literature regarding the benefits of practice in some contexts.

Can sleep affect destination memory? A prospective narrative review

The destination memory is the ability of individuals to remember to whom the information has been delivered. The memory system is an essential and critical piece of social communication and human social cognition. Previously, research has been done on the relationship between source memory and sleep which are critical and fundamental processes influencing our daily lives. However, this present prospective narrative review sheds light on the idea of beginning new research to understand the relationship between destination memory and sleep. Although no such literature exists that can explain this relationship, this review will try to understand prospective future directions by synthesizing available literature on sleep and the source memory. The present narrative review provides an overview of research executed in the fields of source memory, destination memory, and sleep. Destination memory and source memory are the opposite sides of the same coin. They are a part of the episodic memory system. Research suggests that they share similarities, namely their contextual nature, involvement of the pre-frontal cortex (PFC), and role of the medial temporal lobe (MTL). Studies on the effect of sleep on source memory have indicated that it plays a role in consolidation. This consolidation involves binding the item to its context. Due to the shared characteristics of source and destination memory, it can be suggested that sleep may play a role in influencing destination memory. Understanding this relationship will have implications for enhancing social memory/communication efficacy through sleep hygiene.

On the origin of memory neurons in the human hippocampus

The hippocampus is essential for episodic memory, yet its coding mechanism remains debated. In humans, two main theories have been proposed: one suggests that concept neurons represent specific elements of an episode, while another posits a conjunctive code, where index neurons code the entire episode. Here, we integrate new findings of index neurons in humans and other animals with the concept-specific memory framework, proposing that concept neurons evolve from index neurons through overlapping memories. This process is supported by engram literature, which posits that neurons are allocated to a memory trace based on excitability and that reactivation induces excitability. By integrating these insights, we connect two historically disparate fields of neuroscience: engram research and human single neuron episodic memory research.

Psychedelic iatrogenic structural dissociation: an exploratory hypothesis on dissociative risks in psychedelic use

This paper introduces the hypothesis of Psychedelic Iatrogenic Structural Dissociation (PISD), proposing that psychedelics may reactivate dissociated traumatic material, increasing the risk of psychological destabilization in trauma-exposed individuals. Grounded in structural dissociation theory, this framework suggests that psychedelics can disrupt the balance between daily functioning (the Apparently Normal Personality, ANP) and trauma-related responses (the Emotional Personality, EP), leading to the resurfacing of unintegrated memories. A review of recent studies highlights persistent adverse effects associated with psychedelic use, including emotional dysregulation, identity fragmentation, derealization, and perceptual disturbances, particularly among individuals with early trauma histories. To mitigate these risks and facilitate trauma processing, integration practices, body-focused therapies, and structured social support systems are proposed as key interventions. Additionally, emerging neurophysiological models suggest that psychedelics may reconfigure dissociative processes through the modulation of entrenched patterns, potentially facilitating trauma integration or increasing vulnerability to destabilization, depending on individual and contextual factors. These findings underscore the necessity of trauma-informed screening, preparation, and integration protocols to enhance the safety and efficacy of psychedelic therapies, particularly for vulnerable populations.

Validation of a rodent model of episodic memory replay

Vivid episodic memories in humans have been described as the replay of the flow of past events in sequential order. Recently, Panoz-Brown et al. Current Biology, 28, 1628-1634, (2018) developed an olfactory memory task in which rats were presented with a list of trial-unique odors in an encoding context; next, in a distinctive memory assessment context, the rats were rewarded for choosing the second to last item from the list while avoiding other items from the list. In a different memory assessment context, the fourth to last item was rewarded. According to the episodic memory replay hypothesis, the rat remembers the list items and searches these items to find the item at the targeted locations in the list. However, events presented sequentially differ in memory trace strength, allowing a rat to use the relative familiarity of the memory traces, instead of episodic memory replay, to solve the task. Here, we directly manipulated memory trace strength by manipulating the odor intensity of target odors in both the list presentation and memory assessment. The rats relied on episodic memory replay to solve the memory assessment in conditions in which reliance on memory trace strength is ruled out. We conclude that rats are able to replay episodic memories.

Associations Between Episodic Memory and Hippocampal Volume in Late Adulthood

Different tasks of episodic memory (EM) are only moderately correlated with each other. Furthermore, various EM tasks exhibit disproportional relationships with the hippocampus. This study examined the covariance structure of EM tasks and assessed whether this structure relates differently to hippocampal volume (HV) in a sample of 648 cognitively unimpaired older adults (mean age = 69.88). A confirmatory factor analysis (CFA) and linear regression models were used to test the associations between the observed factors of EM and HV. A model with three first-order subfactors (immediate verbal recall, delayed verbal recall, and visuospatial) derived from a second-order EM domain factor satisfied model fit (χ2 p value ≥ 0.05, CFI > 0.90, RMSEA < 0.08, SRMR < 0.08). Total, left, and right HV explained a similar amount of variance in all EM subfactors. CA1, CA3, subiculum, and entorhinal cortex volume were associated with all subfactors, while CA2 and dentate gyrus volume were not associated with EM. These results suggest that EM tasks are measuring the same construct, but different complex processes contribute to EM. Furthermore, HV accounted for a small portion of the variance in EM, suggesting that HV might not be a useful marker of EM in cognitively unimpaired older adults. Finally, this study provides evidence that various hippocampal subfield volumes may not be purely associated with any one aspect of EM processing.

Movement boosts memory: Investigating the effects of acute exercise on episodic long-term memory

Long-term memory is important for cognitive health across the lifespan. Previously research has indicated that a bout of exercise improves memory retention for approximately one week; however, its prolonged effects are unknown. This study investigated the effects of acute moderate-intensity exercise on long-term memory for 11 months. Participants engaged in the exercise intervention and seated rest control condition, followed by a word encoding memory task. Word retention in the exercise intervention was better than in the control condition at 6- and 8-weeks post-encoding. These findings suggest that exercise before encoding enhances long-term episodic memory recall for at least eight weeks.

To know or not to know? Curiosity and the value of prospective information in animals

Humans and other animals often seek instrumental information to strategically improve their decisions in the present. Our curiosity also leads us to acquire non-instrumental information that is not immediately useful but can be encoded in memory and stored for use in the future by means of episodic recall. Despite its adaptive benefits and central role in human cognition, questions remain about the cognitive mechanisms and evolutionary origins that underpin curiosity. Here, we comparatively review recent empirical studies that some authors have suggested reflects curiosity in nonhuman animals. We focus on findings from laboratory tasks in which individuals can choose to gain advanced information about uncertain future outcomes, even though the information cannot be used to increase future rewards and is often costly. We explore the prevalence of preferences in these tasks across animals, discuss the theoretical advances that they have promoted, and outline some limitations in contemporary research. We also discuss several features of human curiosity that can guide future empirical research aimed at characterising and understanding curiosity in animals. Though the prevalence of curiosity in animals is actively debated, we surmise that investigating behavioural candidates for curiosity-motivated behaviour in a broader range of species and contexts, should help promote theoretical advances in our understanding of cognitive principles and evolutionary pressures that support curiosity-driven behaviour.

Specialization for different memory dimensions in brain activity evoked by cued recollection

Cued recollection involves the retrieval of different features of the encoded event. Previous research has shown that the recollection of complex events jointly recruits the Default Mode and the Frontoparietal Control networks, but the degree to which activity within these networks varies as a function of the particular memory dimension (e.g., the "when-what-where" information) remains largely unknown. In the present functional Magnetic Resonance Imaging (fMRI) study, human participants retrieved specific information about a previously encoded TV show to assess the veracity of detailed sentences along four memory dimensions (i.e., object and character details, spatial layouts, temporal sequences, verbal dialogues). A common activity for all dimensions was observed in a left-lateralized network of regions that largely overlaps with the Frontoparietal Control Network (FPCN), including the lateral prefrontal, lateral superior parietal, and lateral temporal cortex. Instead, a larger degree of specialization for different memory dimensions was observed within the Default Mode Network (DMN), particularly in its posterior nodes. Dimension-related specificity in both networks was associated with memory performance across subjects. Finally, a clear leftward asymmetry was observed in the DMN for all dimensions except for the temporal one, whereas the FPCN showed a bilateral activation across dimensions. The present results generally support the view that specific memory information is processed by a mosaic of regions within large portions of the associative cortex involved in higher-order mnemonic functions.

Emotional past and future events after pulvinar damage: A neuropsychological case series

The pulvinar nucleus represents a key neural structure involved in signalling emotional content in the domain of visual perception, whereas its role in the processing of simulated emotional events is less clear. fMRI research has hinted at a role for the pulvinar in imagined emotional scenarios, but the evidence is mixed and this proposal has yet to be tested using the lesion study method. In this study, 3 patients with unilateral lesions to the pulvinar, and 10 matched control participants, completed a set of well-established tasks that required them to think about emotional past and future events. This procedure allowed for a comprehensive evaluation of emotional past and future thinking, using both subjective and objective measures. The results indicate that, relative to controls, processing of emotional past and future events is not impaired in patients with unilateral pulvinar nucleus lesions. However, outcomes of this study should be interpreted in the context of the volume, lateralisation and location of pulvinar lesions in these cases. These data have implications for understanding of the processing of emotionally-salient stimuli in the context of pulvinar damage.

A fragile effect: The influence of episodic memory on delay discounting

Delay discounting occurs when a reward loses value as a function of delay. Episodic future thinking (EFT) reliably decreases delay discounting. EFT may share cognitive features with recalling episodic memories such as constructive episodic simulation. We therefore explored whether recalling episodic memories also reduces delay discounting. In Experiment 1, participants wrote about episodic memories and recalled those memories before completing a delay discounting task. Episodic memories reduced delay discounting according to one commonly used delay discounting measure (area under the curve) but not another (using the hyperbolic model). Experiment 2 compared the effects of general and episodic memories. Neither general nor episodic memories significantly decreased delay discounting compared with a control "counting" condition, but episodic memories reduced delay discounting compared with general memories under some conditions. In Experiment 3, episodic memories did not decrease delay discounting compared with three other control conditions while EFT did. Experiment 3 therefore found that thinking must be both episodic and future orientated to reduce delay discounting. Together, these results suggest that episodic thinking is not sufficient to reliably decrease delay discounting, rather, features unique to episodic future thinking are required. Episodic memory might reduce delay discounting in some contexts, but this effect is small and fragile.

Schemas, reinforcement learning and the medial prefrontal cortex

Schemas are rich and complex knowledge structures about the typical unfolding of events in a context; for example, a schema of a dinner at a restaurant. In this Perspective, we suggest that reinforcement learning (RL), a computational theory of learning the structure of the world and relevant goal-oriented behaviour, underlies schema learning. We synthesize literature about schemas and RL to offer that three RL principles might govern the learning of schemas: learning via prediction errors, constructing hierarchical knowledge using hierarchical RL, and dimensionality reduction through learning a simplified and abstract representation of the world. We then suggest that the orbitomedial prefrontal cortex is involved in both schemas and RL due to its involvement in dimensionality reduction and in guiding memory reactivation through interactions with posterior brain regions. Last, we hypothesize that the amount of dimensionality reduction might underlie gradients of involvement along the ventral-dorsal and posterior-anterior axes of the orbitomedial prefrontal cortex. More specific and detailed representations might engage the ventral and posterior parts, whereas abstraction might shift representations towards the dorsal and anterior parts of the medial prefrontal cortex.

Reinstatement and transformation of memory traces for recognition

Episodic memory relies on the formation and retrieval of content-specific memory traces. In addition to their veridical reactivation, previous studies have indicated that traces may undergo substantial transformations. However, the exact time course and regional distribution of reinstatement and transformation during recognition memory have remained unclear. We applied representational similarity analysis to human intracranial electroencephalography to track the spatiotemporal dynamics underlying the reinstatement and transformation of memory traces. Specifically, we examined how reinstatement and transformation of item-specific representations across occipital, ventral visual, and lateral parietal cortices contribute to successful memory formation and recognition. Our findings suggest that reinstatement in temporal cortex and transformation in parietal cortex coexist and provide complementary strategies for recognition. Further, we find that generalization and differentiation of neural representations contribute to memory and probe memory-specific correspondence with deep neural network (DNN) model features. Our results suggest that memory formation is particularly supported by generalized and mnemonic representational formats beyond the visual features of a DNN.

Crossmodal semantic congruence and rarity improve episodic memory

Semantic congruence across sensory modalities at encoding of information has been shown to improve memory performance over a short time span. However, the beneficial effect of crossmodal congruence is less well established when it comes to episodic memories over longer retention periods. This gap in knowledge is particularly wide for cross-modal semantic congruence under incidental encoding conditions, a process that is especially relevant in everyday life. Here, we present the results of a series of four experiments (total N = 232) using the dual-process signal detection model to examine crossmodal semantic effects on recollection and familiarity. In Experiment 1, we established the beneficial effects of crossmodal semantics in younger adults: hearing congruent compared with incongruent object sounds during the incidental encoding of object images increased recollection and familiarity after 48 h. In Experiment 2 we reproduced and extended the finding to a sample of older participants (50-65 years old): older people displayed a commensurable crossmodal congruence effect, despite a selective decline in recollection compared with younger adults. In Experiment 3, we showed that crossmodal facilitation is resilient to large imbalances between the frequency of congruent versus incongruent events (from 10 to 90%): Albeit rare events are more memorable than frequent ones overall, the impact of this rarity effect on the crossmodal benefit was small, and only affected familiarity. Collectively, these findings reveal a robust crossmodal semantic congruence effect for incidentally encoded visual stimuli over a long retention span, bearing the hallmarks of episodic memory enhancement.

Comparative Study Between Cognitive Phenotypes of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome and Multiple Sclerosis

Objective: Cognitive impairments are one of the most common and disabling symptoms associated with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). Here, we address the possibility of a specific cognitive profile inherent to ME/CFS. Due to the occurrence of cognitive deficits, fatigue, and pain in both pathologies, multiple sclerosis (MS) is a relevant comparison model. For this purpose, we carried out a comparative study between cognitive profiles of patients with ME/CFS and patients suffering from MS. Methods: In total, 40 ME/CFS and 40 MS patients were included. A complete screening of all cognitive functions was carried out through an extensive battery of tests routinely used in clinical practice. Results: ME/CFS and MS patients showed deficits in episodic memory retrieval, visual selective attention and reading speed. ME/CFS patients also elicited a lower level of performance than MS patients regarding consolidation. For both groups, levels of performance on these cognitive tests did not correlate with levels of fatigue, pain, and depression. Conclusions: This study highlighted both similarities and differences in the cognitive profiles of ME/CFS and MS patients. While both groups exhibited deficits in episodic memory retrieval, visual selective attention, and reading speed, ME/CFS patients showed distinct impairment in consolidation processes. These cognitive deficits were not correlated with fatigue, pain, or depression, reinforcing the hypothesis of intrinsic cognitive dysfunction in ME/CFS. These findings define a specific cognitive phenotype for ME/CFS, which could improve diagnostic accuracy and therapeutic strategies. Future research, particularly in functional imaging, may elucidate the neurobiological mechanisms underlying these impairments.

A systematic review of eye movements during autobiographical recall: Does the mind's eye look at pictures of personal memories?

Retrieving personal memories is usually accompanied by eye movements. Although the functional significance of eye movements during retrieval is relatively well established in the case of episodic memory, their role in autobiographical memory is not clearly delineated in the literature. This systematic review critically examines existing studies in the field to summarize the current understanding of eye movements during autobiographical recall, leading to three conclusions. First, eye movements can be taken to reflect the retrieval of mental visual images in autobiographical memory. Second, eye movements may serve a functional role and support recall by helping retrieve visual details of the memory. Third, eye movements appear to be modulated by various aspects of the retrieval process, suggesting that they could meaningfully reflect aspects of the cognitive processes at play. The discussion highlights the major limitations of current research and proposes suggestions for future studies that will allow developing a more robust theoretical framework.

The Implementation of Infant Anoesis and Adult Autonoesis in the Retrogenesis and Staging System of the Neurocognitive Disorders: A Proposal for a Multidimensional Person-Centered Model

Background: Retrogenesis is the process by which the degenerative and vascular mechanisms of dementia reverse the order of acquisition in the normal development. Objective: The development of memory/knowledge after birth may help to know the biopsychosocial and functional characteristics (biosphere) of the retrogenesis. Methods: A literature review was performed in the PubMed, Google Scholar, and Scopus databases using 43 keywords related to retrogenesis: 234 eligible records were selected. Results: The infantile amnesia, characterized from anoesis, was described along the infant/child's biosphere in which the limbic system progressively develops the acquisition of the body knowledge (Anoetic Body Consciousness, AnBC). Anoesis is the infant memory state characterized by the absence of long-term memories of the many stressful/painful experiences that accompany the acquisition under the long-life voluntary control of the long-term memories fundamental for the body growth and survival (mainly chewing/swallowing and walking). At the age of 3-4 years, usually, the AnBC evolves, as a continuum, into the adulthood autonoesis with the emergence, in the child/adolescent, of the consciousness of "self" trough the development of the Episodic Autobiographic Memory (EAM) and the Autonoetic Mind Consciousness (AuMC). The development of cognition and knowledge is due to the progressive maturation of the whole limbic system and not only of the hippocampus. In the biopsychosocial retrogenesis, the EAM/AuMC vanishes progressively along the mild, moderate, and severe stages of dementia when the infant AnBC resurfaces, losing progressively the basic activities of daily living in a retrogenetic order of acquisition where the last functions to disappear are chewing/swallowing. Conclusion: The transition from the adult EAM-AuMC to the infant AnBC, as a continuum in the individual biosphere, adds a contribution to the assessment of the retrogenesis in dementia from a multidimensional person-centered model.

Neural mechanisms of non-pharmacological interventions in patients with mild cognitive impairment and Alzheimer's disease: An ALE meta-analysis

Non-pharmacologic interventions are effective for persons showing mild cognitive impairment (MCI) and Alzheimer's disease (AD). We used activation likelihood estimation (ALE) meta-analysis to systematically quantify the results of 19 neuroimaging studies in order to identify brain regions in which patients showed stable increases or decreases in activation after interventions. We also tested the moderating effects of disease stage (MCI vs. AD) and intervention modality (cognitive training vs. exercise intervention). The results showed increased activation in the cuneus, precuneus and medial frontal gyrus in the combined groups after treatment, whereas the anterior cingulate gyrus showed decreased activation. Secondly, in the MCI group there was increased activation in the precuneus and precentral gyrus after treatment, whereas there was decreased activation in the anterior cingulate gyrus; in the AD group there was only increased activation after treatment, including in the lingual gyrus and bilateral superior temporal gyrus. Finally, the bilateral cuneus and precentral gyrus showed increased activation after cognitive training, while bilateral insula, among others, showed decreased activation. This suggests that there are brain activation changes after non-pharmacological treatments for MCI and AD patients, but that the treatment mechanisms are moderated by stage and intervention modality. Future studies could continue to explore specific neural mechanisms involved in different intervention conditions for these patients.

Temporal recall in the shadow of emotion: separate emotional contexts during encoding enhance the temporal source memory retrieval

Episodic memory, with its emphasis on temporal-spatial contexts, has been a longstanding focus in memory research. While previous studies have investigated the role of emotion in temporal source memory using emotionally charged stimuli, such as emotional words or images, the influence of a separated emotional context remains less explored. This study sought to understand the impact of separate emotional contexts on temporal source memory. Participants were shown Chinese characters alongside separate emotional contexts (i.e. a neutral or negative picture) and then engaged in either a retrieval practice or a control condition. Finally, they were tested for recognition, temporal source memory, and emotional source memory for all the learned characters. Results revealed that a negative emotional context, unlike a neutral setting, enhanced the accuracy of temporal memory for adjacent neutral characters. However, this negative context reduced the accuracy of recalling the associated emotion. Importantly, the boost in temporal memory due to the emotional context remained even when participants were unsure or mistaken about the associated emotion. This study demonstrates the complex interplay between emotion and temporal memory, underscoring the enhancement effect of separated emotional contexts on temporal recall, irrespective of explicit emotional memory retrieval.

Does sleep benefit source memory? Investigating 12-h retention intervals with a multinomial modeling approach

For retention intervals of up to 12 h, the active systems consolidation hypothesis predicts that sleep compared to wakefulness strengthens the context binding of memories previously established during encoding. Sleep should thus improve source memory. By comparing retention intervals filled with natural night sleep versus daytime wakefulness, we tested this prediction in two online source-monitoring experiments using intentionally learned pictures as items and incidentally learned screen positions and frame colors as source dimensions. In Experiment 1, we examined source memory by varying the spatial position of pictures on the computer screen. Multinomial modeling analyses revealed a significant sleep benefit in source memory. In Experiment 2, we manipulated both the spatial position and the frame color of pictures orthogonally to investigate source memory for two different source dimensions at the same time, also allowing exploration of bound memory for both source dimensions. The sleep benefit on spatial source memory replicated. In contrast, no source memory sleep benefit was observed for either frame color or bound memory of both source dimensions, probably as a consequence of a floor effect in incidental encoding of color associations. In sum, the results of both experiments show that sleep within a 12-h retention interval improves source memory for spatial positions, supporting the prediction of the active systems consolidation hypothesis. However, additional research is required to clarify the impact of sleep on source memory for other context features and bound memories of multiple source dimensions.

Tell me why: the missing w in episodic memory's what, where, and when

Endel Tulving defined episodic memory as consisting of a spatiotemporal context. It enables us to recollect personal experiences of people, things, places, and situations. In other words, it is made up of what, where, and when components. However, this definition does not include arguably the most important aspect of episodic memory: the why. Understanding why we remember has important implications to better understand how our memory system works and as a potential target of intervention for memory impairment. The intrinsic and extrinsic factors related to why some experiences are better remembered than others have been widely investigated but largely independently studied. How these factors interact with one another to drive an event to become a lasting memory is still unknown. This review summarizes research examining the why of episodic memory, where we aim to uncover the factors that drive core features of our memory. We discuss the concept of episodic memory examining the what, where, and when, and how the why is essential to each of these key components of episodic memory. Furthermore, we discuss the neural mechanisms known to support our rich episodic memories and how a why signal may provide critical modulatory impact on neural activity and communication. Finally, we discuss the individual differences that may further drive why we remember certain experiences over others. A better understanding of these elements, and how we experience memory in daily life, can elucidate why we remember what we remember, providing important insight into the overarching goal of our memory system.

Complex memories induced by intracranial electrical brain stimulation are related to complex networks

The precise and fleeting moment of rich recollection triggered by an environmental cue is difficult to reproduce in the lab. However, epilepsy patients can experience sudden reminiscences after intracranial electrical brain stimulation (EBS). In these cases, the transient brain state related to the activation of the engram and its conscious perception can be recorded using intracerebral EEG (iEEG). We collected various EBS-induced reminiscences for iEEG analysis, classifying them as follows: no or weak details (familiarity); moderate details and context (semantic and personal semantic memories); high details and context (episodic). Nine brain areas were selected within the temporal lobes (including the hippocampus and temporal neocortex, ipsi- and contralateral) and the insula, defining a network (each area as a node). Functional connectivity was measured by estimating pair-wise non-linear correlations between signals recorded from these brain regions during different memory events. Seventeen reminiscences in six patients (2 episodic, 10 personal semantic, 2 semantic memories, 5 familiar objects, 1 déjà-rêvé) were compared to 18 control experiential phenomena (unrelated to reminiscence), 18 negative EBS (which failed to elicit memories or other phenomena) in the same locations, and pre-EBS baseline activity. The global functional connectivity in the network was higher following EBS-induced reminiscences than during baseline activity, control phenomena, or negative EBS. The degree of connectivity increased with the complexity of memories; it was higher for detailed and contextualized memories like episodic memories. More significant links compared to baseline (edges with higher non-linear correlation relative to baseline) were observed for episodic memories than for less contextualized memories. These increases in connectivity occurred in all frequency bands, except the delta band. Our results support understanding declarative memory retrieval as having a multiplexed organization. They also show that richer memories activated by intracranial EBS are related to more complex connectivity patterns across medial and neocortical temporal lobe structures.

Domain-Specific Memory Impairments in Bipolar Mania: Insights from a Tertiary Care Hospital

Background

Cognitive deficits in bipolar affective disorder (BPAD), particularly during manic episodes, are well-documented. However, research on domain-specific memory impairments in bipolar mania is limited, especially in the Indian subcontinent. This study aimed to assess memory impairments in individuals with bipolar disorder using the Postgraduate Institute Memory (PGI-Memory) scale and to highlight domain-specific deficits compared to healthy controls.

Methods

This cross-sectional study was conducted at a tertiary care center in North India. Twenty subjects diagnosed with bipolar mania and 20 age, sex, and education-matched healthy controls between the ages of 18 and 40 were recruited. Memory functions were assessed using the PGI-Memory scale. Mental control and working memory were also evaluated.

Results

Both groups were matched in terms of age, sex, and education. Individuals with bipolar disorder demonstrated significant deficits in various memory domains, including immediate (d = 1.47), recent (d = 0.93), remote (d = 1.58), long-term (d = 2.37), and associative memory (similar pairs: d = 1.4, dissimilar pairs: d = 1.84,), as well as in visual reproduction (d = 2.3) and recognition tasks (d = 1.54). In contrast, their working memory performance was comparable to that of the control group. The largest deficits were observed in long-term memory, visual reproduction, and associative memory.

Conclusions

Bipolar mania is associated with widespread memory impairments, particularly in long-term and associative memory, which may contribute to difficulties in emotional regulation and daily functioning. These findings emphasize the importance of considering memory impairments in the diagnosis and management of BPAD. Further studies are required to investigate the neurobiological foundations of these impairments and to develop specific interventions.

Looking to the past to see the future: mother-child future talk following memory sharing in three cultural communities

The present study examined mother-child spontaneous future talk following memory sharing in three cultural communities. Seventy-one European American, 60 Chinese American, and 58 mainland Chinese mothers and their 3-year-old children discussed two past events at home, one positive and one negative. Chinese and Chinese American mothers and children were more likely than European American mothers and children to spontaneously engage in future talk following memory sharing. After discussing negative past events, Chinese and Chinese American mothers and children were more likely than European American mothers and children to engage in didactic talk that emphasized children's adherence to moral standards, social norms, and behavioral expectations in the future. Conversely, European American mothers were more likely than the two groups of Chinese mothers to engage in autonomous talk that emphasized children's preferences and opinions regarding the future. Findings are discussed in light of the influence of mother-child conversations as a cultural context on the development of mental time travel and a temporally extended self.

Emotional future simulations: neural and cognitive perspectives

LeDoux's work on the emotional brain has had broad impact in neuroscience and psychology. Here, we discuss an aspect of the emotional brain that we have examined in our laboratory during the past two decades: emotional future simulations or constructed mental representations of positive and negative future experiences. Specifically, we consider research concerning (i) neural correlates of emotional future simulations, (ii) how emotional future simulations impact subsequent cognition and memory, (iii) the role of emotional future simulations in worry and anxiety, and (iv) individual differences in emotional future simulation related to narcissistic grandiosity. The intersection of emotion and future simulation is closely linked to some of LeDoux's primary scientific concerns.

Optimising episodic encoding within segmented virtual contexts

The encoding of episodic memories depends on segmentation; memory performance improves when segmentation is available and performance is impaired when segmentation is absent. Indeed, for episodic memories to be created, the encoding of information into long-term memory requires the experience of event boundaries (i.e., context-shifts defined by salient moments of change between packets of to-be-learned stimuli). According to this view episodic encoding, and therefore learning, is critically dependent on the nature of working memory. Motived by this theoretical framework, here we explore the effects of segmentation on long-term memory performance, investigating the possibility of optimising learning by aligning the presentation of stimuli to the capacity of working memory. Across two experiments, we examined whether manipulating the boundaries between events influences memory. Participants travelled within a virtual environment, with spatial-temporal gaps between virtual locations providing context-shifts to segment sequentially presented lists of words. Both accurate recall and memory for temporal order improve and the number of falsely recalled words reduces when reducing the quantity of information presented between boundaries. Taken together, the present results suggest that closely matching the quantity of information between boundaries to working memory capacity optimises long-term memory performance.

Stimulate to Remember? The Effects of Short Burst of Transcutaneous Vagus Nerve Stimulation (taVNS) on Memory Performance and Pupil Dilation

The decline in noradrenergic (NE) locus coeruleus (LC) function in aging is thought to be implicated in episodic memory decline. Transcutaneous auricular vagus nerve stimulation (taVNS), which supports LC function, might serve to preserve or improve memory function in aging. However, taVNS effects are generally very heterogeneous, and it is currently unclear whether taVNS has an effect on memory. In this study, an emotional memory task with negative events involving the LC-NE system was combined with the short burst of event-related taVNS (3 s) in younger adults (N = 24). The aim was to investigate taVNS-induced changes in pupil dilation during encoding and possible taVNS-induced improvements in (emotional) memory performance for early and delayed (24 h) recognition. Negative events were associated with increased pupil dilation and better memory performance. Additionally, real as compared to sham or no stimulation selectively increased memory for negative events. Short bursts of stimulation, whether real or sham, led to an increase in pupil dilation and an improvement in memory performance over time, likely due to the attention-inducing sensory modulation of electrical stimulation.

Dissociations between musical semantic memory and verbal memory in a patient with behavioral variant frontotemporal dementia

OBJECTIVES

Patients with dementia show dissociations between musical semantic memory (i.e., spared musical lexicon) and other memory modalities, except in some severe cases. We aim to study, from a neuropsychological point of view, the dissociation between musical semantic memory compared to language and verbal memory in a patient with severe Behavioral Variant Frontotemporal Dementia (bvFTD). We hypothesize a single dissociation between these domains will be found, with sparing of musical semantic memory.

METHODS

LC, a patient with severe bvFTD, and three matched controls were assessed through language, semantic, and episodic memory, and musical semantic memory tasks. The control group had similar music taste as LC: to participate as controls, tango must be one of their favorite musical genres.

RESULTS

LC showed impairment in all Verbal Memory tasks, but not in musical tasks. There was a dissociation between musical semantic memory, and language and verbal semantic memory.

CONCLUSIONS

The musical lexicon can be preserved in advanced stages of dementia, which supports the idea that music can be a therapeutic tool in patients with severe dementia.

Shift happens: aging alters the content but not the organization of memory for complex events

While cognitive aging research has compared episodic memory accuracy between younger and older adults, less work has described differences in how memories are encoded and recalled. This is important for memories of real-world experiences, since there is immense variability in which details can be accessed and organized into narratives. We investigated age effects on the organization and content of memory for complex events. In two independent samples (N = 45; 60), young and older adults encoded and recalled the same short-movie. We applied a novel scoring on the recollections to quantify recall accuracy, temporal organization (temporal contiguity, forward asymmetry), and content (perceptual, conceptual). No age-effects on recall accuracy nor on metrics of temporal organization emerged. Older adults provided more conceptual and non-episodic content, whereas younger adults reported a higher proportion of event-specific information. Our results indicate that age-related differences in episodic recall reflect distinctions in what details are assembled from the past.

Hemispheric asymmetries in episodic memory

The term "episodic memory" refers to our ability to remember past personal experiences. This ability is severely disrupted following bilateral damage to a dedicated neural substrate located symmetrically in the mesial temporal lobes. Milder deficits are also observed following unilateral damage to the same structures. In this chapter, we contrast memory deficits after left and right mesiotemporal damage and review some of the hypotheses proposed to account for the observed differences. As proposed by other authors (e.g., Binder et al., 2010), the observed lesion side effects in memory profiles after unilateral brain damage do not directly reflect specialization across the two symmetric memory substrates. Rather, they depend on the different kinds of information each of the two mesiotemporal structures receives from the ipsilateral hemisphere where other non-memory-specific cognitive systems are asymmetrically housed. In particular, this chapter outlines the role of language, working memory, and visuospatial processes in accounting for side effects in memory profiles. This is because all these systems greatly contribute to the functioning of episodic memory and also show a variable extent of lateralization in the human brain.

Mental Time Travel: A Retrospective

Because imagination activates the same neural circuits used in understanding the present, one can access that imagination even in non-linguistic animals through decoding techniques applied to large neural ensembles. This personal retrospective traces the history of the initial discovery that hippocampal theta sequences sweep forward to goals during moments of deliberation and discusses the history that was necessary to put ourselves in the position to recognize this signal. It also discusses how that discovery fits into the larger picture of hippocampal function and the concept of cognition as computation.

Forgetting is comparable between healthy young and old people

Aging is typically associated with declines in episodic memory, executive functions, and sleep quality. Therefore, the sleep-dependent stabilization of episodic memory is suspected to decline during aging. This might reflect in accelerated long-term forgetting, which refers to normal learning and retention over hours, yet an abnormal retention over nights and days. Accelerated long-term forgetting has been observed in dementia, mild cognitive impairment, and in people with memory complaints. Here, we explored whether accelerated long-term forgetting also manifests in healthy aging. We investigated verbal episodic memory in 236 healthy men and women between 18 and 77 years of age. All participants were mentally intact in terms of executive functions, working memory, episodic memory, verbal intelligence, and mood. We related their forgetting rates over one week following learning to their subjective sleep quality and executive functions. Fifteen words were freely recalled and then recognized among 30 distractor words at 30 min and again at one week following learning. Although the healthy older adults compared to the healthy younger adults reported a diminished sleep efficiency and learned fewer words, they exhibited no disproportionate forgetting over days. Hence, accelerated long-term forgetting is not present in healthy aging but might be a first sign of memory dysfunction due to neuropathology.

Cardiorespiratory fitness, hippocampal subfield morphology, and episodic memory in older adults

Objective

Age-related hippocampal atrophy is associated with memory loss in older adults, and certain hippocampal subfields are more vulnerable to age-related atrophy than others. Cardiorespiratory fitness (CRF) may be an important protective factor for preserving hippocampal volume, but little is known about how CRF relates to the volume of specific hippocampal subfields, and whether associations between CRF and hippocampal subfield volumes are related to episodic memory performance. To address these gaps, the current study evaluates the associations among baseline CRF, hippocampal subfield volumes, and episodic memory performance in cognitively unimpaired older adults from the Investigating Gains in Neurocognition Trial of Exercise (IGNITE) (NCT02875301).

Methods

Participants (N = 601, ages 65-80, 72% female) completed assessments including a graded exercise test measuring peak oxygen comsumption (VO2peak) to assess CRF, cognitive testing, and high-resolution magnetic resonance imaging of the hippocampus processed with Automated Segmentation of Hippocampal Subfields (ASHS). Separate linear regression models examined whether CRF was associated with hippocampal subfield volumes and whether those assocations were moderated by age or sex. Mediation models examined whether hippocampal volumes statistically mediated the relationship between CRF and episodic memory performance. Covariates included age, sex, years of education, body mass index, estimated intracranial volume, and study site.

Results

Higher CRF was significantly associated with greater total left (B = 5.82, p = 0.039) and total right (B = 7.64, p = 0.006) hippocampal volume, as well as greater left CA2 (B = 0.14, p = 0.022) and dentate gyrus (DG; B = 2.34, p = 0.031) volume, and greater right CA1 (B = 3.99, p = 0.011), CA2 (B = 0.15, p = 0.002), and subiculum (B = 1.56, p = 0.004) volume. Sex significantly moderated left DG volume (B = -4.26, p = 0.017), such that the association was positive and significant only for males. Total left hippocampal volume [indirect effect = 0.002, 95% CI (0.0002, 0.00), p = 0.027] and right subiculum volume [indirect effect = 0.002, 95% CI (0.0007, 0.01), p = 0.006] statistically mediated the relationship between CRF and episodic memory performance.

Discussion

While higher CRF was significantly associated with greater total hippocampal volume, CRF was not associated with all underlying subfield volumes. Our results further demonstrate the relevance of the associations between CRF and hippocampal volume for episodic memory performance. Finally, our results suggest that the regionally-specific effects of aging and Alzheimer's disease on hippocampal subfields could be mitigated by maintaining higher CRF in older adulthood.

Neuropsychological profile of French adults with early-treated phenylketonuria: a multicenter study

BACKGROUND AND OBJECTIVE

Adult patients with early-treated phenylketonuria (AwET-PKU) may present some subtle neurocognitive deficits. The aim of the study was to investigate 1) neurocognitive functions in a large group of AwET-PKU 2) the influence of plasma phenylalanine (Phe).

METHODS

Participants: 187 AwET-PKU (classic PKU [cPKU] 81%, mild PKU [mPKU] 14%, and mild persistent hyperphenylalaninemia [MPH] 5%). Cognitive assessments: tests included the Wechsler Adult Intelligence Scale-IV, California Verbal Learning Test-II, Trail Making Test, and verbal fluency tests. Biochemical data: plasma Phe was measured concurrently with cognitive assessments.

RESULTS

Episodic memory: cPKU patients had lower performance in immediate recall compared to mPKU patients. There was a negative correlation between Phe levels and immediate recall indices, but no correlation with delayed memory. Processing speed: cPKU patients performed worse than mPKU patients in processing speed tests. Negative correlations were observed between Phe levels and processing speed measures, with more pronounced effects in cPKU patients. Executive functioning: No differences were found between cPKU and mPKU patients on executive functioning tests. No correlation was found between executive function and Phe levels. Working memory: cPKU patients had poorer working memory performance compared to mPKU patients, though no correlation was found between working memory performance and Phe levels.

CONCLUSIONS

The study reveals neurocognitive deficits in adults with PKU, particularly in episodic memory and processing speed. Higher plasma Phe levels are associated with poorer performance in these areas, especially in cPKU patients. Working memory and executive functioning did not show significant correlations with Phe levels.

Physical activity indexed using table tennis skills modulates the neural dynamics of involuntary retrieval of negative memories

Memory intrusion is a characteristic of posttraumatic stress disorder manifesting as involuntary flashbacks of negative events. Interference of memory reconsolidation using cognitive tasks has been employed as a noninvasive therapy to prevent subsequent intrusive retrieval. The present study aims to test whether physical activity, with its cognitive demands and unique physiological effects, may provide a novel practice to reduce later involuntary retrieval via the reconsolidation mechanism. In addition, the study investigates the EEG representation of neural function in interpreting the interplay of intrusion and recognition. Eighty-seven participants were tested on successive sessions comprised encoding (Day 0), reconsolidation (24-hr) and priming retrieval (Day 7) in a between-subject design with random assignment to 3 different groups: whole-body exercise, sensorimotor engagement and sitting groups. Of the key results, when involuntary retrieval was subsequently triggered by relevant stimuli, reduced subjective recognition was observed, and working memory maintenance was shortened, indicated by shorter Negative Slow Wave duration. The study implicates the potential neurophysiological mechanism of cognitive and behavioral interventions, specifically those aimed at reducing intrusion frequency through the reconsolidation mechanism; these are proposed to facilitate accelerated recovery from involuntary memories.

The future, before, and after: Bayesian and multivariate analyses reveal shared and unique neural mechanisms of imagining and remembering the same unique event

Research shows that the brain regions that subserve our ability to remember the past are also involved in imagining the future. Given this similarity in brain activity, it remains unclear how brain activity distinguishes imagination from memory. In the current work, we scanned participants using functional magnetic resonance imaging before and after they performed a highly unique and elaborate activity wherein they went skydiving for the first time in their lives. Multivariate pattern analysis, Bayesian inference, and a tightly controlled experimental design were used to identify the neural activity that differentiates between memory and imagination of the same events. The results showed that large swaths of the default mode network exhibited identical patterns of activity in recollection and imagination; several frontal areas were involved in imagination (but not in recollection). Representational similarity analysis revealed that the left ventral precuneus exhibited different patterns of memory and imagination. Further examination revealed that this subarea may be especially important for recollection of specific episodes. These results advance our understanding of how the critical distinction between the past and future might be manifested in the brain.

Context in memory is reconstructed, not encoded

Context has long been regarded as an important element of long-term memory, and episodic memory in particular. The ability to remember not only the object or focus of a memory but also contextual details allow us to reconstruct integrated representations of events. However, despite its prevalence in the memory literature, context remains difficult to define and identify, with different studies using context to refer to different sets of stimuli or concepts. These varying definitions of context have not prevented it from being a key element of many models of memory. Within these models, context is usually explicitly encoded as an element of an event and processed through different neural pathways to other elements of the event, such as objects. Here we challenge the notion that context in memory is encoded. We offer an alternative where context in memory takes a variety of forms depending on the question being asked. We propose events are simply encoded, but the focus of retrieval (object) and context are not defined until recall.

Pattern separation during encoding and Subsequent Memory Effect

Memory retrieval has been extensively studied in relation to the encoding processes that precede access to stored information. Event related potentials (ERP) research has compared brain potentials elicited during the study phase of successful and unsuccessful retrieval, finding greater activation for the subsequent retrieval information. In this work we were interested in exploring the neural markers associated to subsequent recognition when similar memories are subsequently encoded. We used a Subsequent Memory paradigm in which we manipulated the number of similar items within a category (2 or 6) that participants encoded. Manipulating the number of similar encoded items within a category allowed us to test whether encoding markers of subsequent recognition depend solely on memory trace strength or, on the contrary, successful recognition is influenced by subsequently presented similar memories, and consequently may not be reflected in higher activation in such cases. After a 20-minute period, participants performed a recognition task providing one of a three-option judgement: "old", "similar" and "new", which allowed us to test if the amplitude of ERP waveforms varied based on the similarity judgement of the unrecognized encoded item. We did not observe a significant parietal subsequent memory effect, however, old hits and similar false alarms were both significantly different from similar correct rejections and old false alarms in ERP retrieval. These findings suggest that differences in brain responses between conditions are specifically related to the retrieval process and not the encoding process, indicating potential differential effects on memory during retrieval. Moreover, it is also possible that differences in brain responses develop or change over the rest time between phases, influencing how these conditions manifest across different stages of information processing.