Episodic memory: from mind to brain

Real-world implications of aphantasia: episodic recall of eyewitnesses with aphantasia is less complete but no less accurate than typical imagers

Individuals with aphantasia report an inability to voluntarily visually image and reduced episodic memory, yet episodic accounts provided by witnesses and victims are fundamental for criminal justice. Using the mock-witness paradigm, we investigated eyewitness memory of individuals with aphantasia versus typical imagers. Participants viewed a mock crime and 48 hours later were interviewed about the event, randomly allocated to one of three conditions. Two interview conditions included techniques designed to support episodic retrieval mode, namely (i) Mental Reinstatement of Context (MRC) and (ii) Sketch Reinstatement of Context (Sketch-RC). A third Control condition did not include retrieval support. Aphantasic mock-eyewitnesses recalled 30% less correct information and accounts were less complete, but they made no more errors and were as accurate as typical imagers. Interaction effects revealed reduced correct recall and less complete accounts for aphantasic participants in MRC interviews versus Sketch-RC and Control. Aphantaisic participants in the Control outperformed those in both the Sketch-RC and MRC, although Sketch-RC improved completeness by 15% versus MRC. Our pattern of results indicates reduced mental imagery ability might be compensated for by alternative self-initiated cognitive strategies. Findings offer novel insights into episodic recall performance in information gathering interviews when ability to voluntarily visualize is impoverished.

Openness to Experience is associated with neural and performance measures of memory in older adults

Age-related decline in episodic memory performance is a well-replicated finding across numerous studies. Recent studies focusing on aging and individual differences found that the Big Five personality trait Openness to Experience (hereafter: Openness) is associated with better episodic memory performance in older adults, but the associated neural mechanisms are largely unclear. Here, we investigated the relationship between Openness and memory network function in a sample of 352 participants (143 older adults, 50-80 years; 209 young adults, 18-35 years). Participants underwent functional magnetic resonance imaging (fMRI) during a visual memory encoding task. Functional memory brain-network integrity was assessed using the similarity of activations during memory encoding (SAME) scores, which reflect the similarity of a participant's memory network activity compared to prototypical fMRI activity patterns of young adults. Openness was assessed using the NEO Five-Factor Inventory. Older vs young adults showed lower memory performance and higher deviation of fMRI activity patterns (i.e. lower SAME scores). Specifically in older adults, high Openness was associated with better memory performance, and mediation analysis showed that this relationship was partially mediated by higher SAME scores. Our results suggest that trait Openness may constitute a protective factor in cognitive aging by better preservation of the brain's memory network.

Engram cell connectivity as a mechanism for information encoding and memory function

Information derived from experiences is incorporated into the brain as changes to ensembles of cells, termed engram cells, that allow memory storage and recall. The mechanism by which those changes hold specific information is unclear. Here we test the hypothesis that the specific synaptic wiring between engram cells is the substrate of information storage. First, we monitor how learning modifies the connectivity pattern between engram cells at a monosynaptic connection involving the hippocampal vCA1 region and the amygdala. Then, we assess the functional significance of these connectivity changes by artificially activating or inhibiting its presynaptic and postsynaptic components respectively. Finally, we identify a synaptic plasticity mechanism mediated by PSD-95, which impacts the connectivity pattern among engram cells and contributes to the long-term stability of the memory. These findings impact our theory of learning and memory by helping us explain the translation of specific information into engram cells and how these connections shape brain function.

Conceptual relatedness promotes memory generalization at the cost of detailed recollection

An adaptive memory system is one that allows us to both retrieve detailed memories as well as generalize knowledge about our past, the latter termed memory generalization and is useful for making inferences about new situations. Research has indicated that memory generalization relies on forming knowledge structures by integrating experiences with shared encountered elements. Whether memory generalization occurs more readily when  experiences also have elements that share established (conceptual) information is less clear. It is also unclear if engaging in memory generalization during learning comes at the cost of retrieving detailed memories, the other function of episodic memory. To address these two knowledge gaps, we paired a modified version of the acquired equivalence task with a recognition memory test. Across three experiments, participants first learned a series of overlapping object-scene pairs (A-X, B-X and A-Y) in which half of the overlapping pairs contained conceptually-related objects (e.g., A-pencil; B-scissors; conceptual condition) and the other half contained unrelated objects (neutral condition). Participants ability to generalize to new overlapping object-scene pairs (B-Y) as well as not-learned but semantically-related objects was measured. Finally, participants completed a recognition memory test that included the encoded objects, perceptually similar lures or new foil objects. Across all experiments, we found higher rates of generalization but reduced detailed memory (indexed by increased false alarms to lure objects) for information learned in the conceptual than neutral condition. These results suggest the presence of conceptual knowledge biases an individual towards a generalization function of memory, which comes at the expense of detailed recollection.

The evolutionary origins of the Global Neuronal Workspace in vertebrates

The Global Neuronal Workspace theory of consciousness offers an explicit functional architecture that relates consciousness to cognitive abilities such as perception, attention, memory, and evaluation. We show that the functional architecture of the Global Neuronal Workspace, which is based mainly on human studies, corresponds to the cognitive-affective architecture proposed by the Unlimited Associative Learning theory that describes minimal consciousness. However, we suggest that when applied to basal vertebrates, both models require important modifications to accommodate what has been learned about the evolution of the vertebrate brain. Most importantly, comparative studies suggest that in basal vertebrates, the Global Neuronal Workspace is instantiated by the event memory system found in the hippocampal homolog. This proposal has testable predictions and implications for understanding hippocampal and cortical functions, the evolutionary relations between memory and consciousness, and the evolution of unified perception.

Place and place names: a unified model

The goal of this paper is to offer a unified account of Place as a central theoretical notion across different disciplines. We show that while psychology, geography and other sciences have been converging to a unified view of this notion, linguistics still offers a fragmented perspective. Consequently, place names lack a full-fledged analysis that connects this category to the psychological concept of place. We propose to overcome this impasse by introducing a multi-modal Discourse Representation Theory (DRT) account of place as a conceptual construct and place concepts as specific instances of this construct. We show that current variants of DRT permit us to model place names and their senses, i.e., the meaning(s) that individuals associate with Sydney. We then model non-linguistic place concepts, i.e., the mental representation(s) that individuals can have of the city carrying this name. We present a model of the relation between linguistic meaning and conceptual content via the notion of anchoring relations applied to place. We pair this formal treatment with a morpho-syntactic account of place names building on current generative syntax treatments of proper names. Once we have a morpho-syntactic and semantic model of place names, we use a frame semantics treatment to account for lexical relations among place names. We test the overarching model on a set of recalcitrant problems afflicting current linguistic and multi-disciplinary treatments of place. These are the grammatical complexity and lexical content of place names, place concepts and their networks, and inter-subjective, communicative models of place in discourse. By solving these problems, our account integrates several frameworks (DRT, conceptual analysis, generative syntax, frame semantics) and connects several disciplines (linguistics, psychology, geographic information science, communication models) via a novel, multi-modal account of place. We conclude by discussing the theoretical and empirical import of these results.

Verbal Memory Performance and Depressive Symptoms in Persons with Treated HIV

The link between memory and comorbid depression in persons with HIV (PWH) is unclear based on evidence from published cohorts. We compared verbal memory in the HVLT-R in a well-characterized HIV cohort (n = 354) with (n = 102) or without (n = 252) comorbid depressive symptoms, and examined memory correlates in both scenarios. Memory fell within unimpaired ranges, but was lower in depressed than non-depressed PWH. Memory was related to quality of life, sociodemographic, and mental health factors, but not to assessed HIV-related or antiretroviral factors. However, longitudinally (n = 52) memory declined with presence and severity of depressive symptoms. In this treated cohort, verbal memory was unrelated to HIV-related variables but to quality of life and depressive symptoms. Greater performance decline over time also related to acute or ongoing depressive symptoms. These findings highlight the importance of addressing comorbid depressive symptoms to improve quality of life in persons with treated HIV.

A computational model of current control mechanism for long-term potentiation (LTP) in human episodic memory based on gene-gene interaction

The establishment of long-term potentiation (LTP) is a prime process for the formation of episodic memory. During the establishment of LTP, activations of various components are required in the signaling cascade of the LTP pathway. Past efforts to determine the activation of components relied extensively on the cellular or molecular level. In this paper, we have proposed a computational model based on gene-level cascading and interaction in LTP signaling for the establishment and control of current signals for achieving the desired level of activation in the formation of episodic memory. This paper also introduces a model for a generalized signaling pathway in episodic memory. A back-propagation feedback mechanism is used for updating the interaction levels in the signaling cascade starting from the last stage and ending at the start stage of the signaling cascade. Simulation of the proposed model has been performed for the LTP signaling pathway in the context of human episodic memory. We found through simulation that the qualifying genes correction factors of all stages are updated to their maximum limit. The article explains the signaling pathway for episodic memory and proves its effectiveness through simulation results.

Neural correlates of autobiographical memory retrieval: An SDM neuroimaging meta-analysis

Autobiographical memory (AM) is a type of episodic memory that involves the recollection and re-experiencing of personal life events. AM retrieval is a complex process requiring the coordination of multiple memory processes across the brain. Important questions remain regarding the degree to which specific brain regions are consistently recruited during AM retrieval and the influence of methodological factors such as type of AM retrieval task and control task. Neuroimaging meta-analyses can summarize the brain regions associated with AM retrieval, addressing these questions by revealing consistent findings across multiple studies. We used a coordinate-based neuroimaging meta-analysis method, seed-based d mapping (SDM), to assess the largest set of neuroimaging studies of AM retrieval to date. An important advantage of SDM over other methods is that it factors in the effect sizes of the activation coordinates from studies, yielding a more representative summary of activations. Studies were selected if they elicited AM retrieval in the scanner, contrasted AM retrieval with a matched control task, and used univariate whole-brain analyses, yielding a set of 50 papers with 963 participants and 891 foci. The findings confirmed the recruitment of many previously identified core AM retrieval regions including the prefrontal cortex (PFC), hippocampus and parahippocampal cortex, retrosplenial cortex and posterior cingulate, and angular gyrus, and revealed additional regions, including bilateral inferior parietal lobule and greater activation extent through the PFC, including lateral PFC activation. Results were robust across different types of AM retrieval tasks (previously rehearsed cues vs. novel cues), and robust across different control tasks (visual/attention vs. semantic retrieval). To maximize the utility of the meta-analysis, all results image files are available online. In summary, the current meta-analysis provides an updated and more representative characterization of the neural correlates of autobiographical memory retrieval and how these neural correlates are affected by important experimental factors.

Cognitive scripts and narrative identity are shaped by structures of power

Constructing a narrative identity involves developing an understanding of oneself as integrated through time and across contexts, a task critical to psychosocial development and functioning. However, research has primarily focused on the individual in isolation or in highly localized contexts. This is problematic because narrative identity is profoundly shaped by structures of power; thus, we cannot understand how individuals understand themselves through time, across contexts, and as a member of a particular community without attention to the structure of society. We propose a structural-psychological framework for the study of autobiographical memory, narrative, and context that examines how structures of power are maintained, and potentially changed, through the narration of autobiographical events, as guided by cognitive scripts, or master narratives.

A map of spatial navigation for neuroscience

Spatial navigation has received much attention from neuroscientists, leading to the identification of key brain areas and the discovery of numerous spatially selective cells. Despite this progress, our understanding of how the pieces fit together to drive behavior is generally lacking. We argue that this is partly caused by insufficient communication between behavioral and neuroscientific researchers. This has led the latter to under-appreciate the relevance and complexity of spatial behavior, and to focus too narrowly on characterizing neural representations of space-disconnected from the computations these representations are meant to enable. We therefore propose a taxonomy of navigation processes in mammals that can serve as a common framework for structuring and facilitating interdisciplinary research in the field. Using the taxonomy as a guide, we review behavioral and neural studies of spatial navigation. In doing so, we validate the taxonomy and showcase its usefulness in identifying potential issues with common experimental approaches, designing experiments that adequately target particular behaviors, correctly interpreting neural activity, and pointing to new avenues of research.

Differential effects of remotely supervised transcranial direct current stimulation on recognition memory depending on task order

Background

Prior work has shown positive effects of High Definition transcranial direct current stimulation (HD-tDCS) over the dorsolateral prefrontal cortex (DLPFC) on semantic memory performance and metamemory monitoring accuracy. However, HD-tDCS requires setup by a trained researcher, which is not always feasible. Few studies have used remotely supervised (rs) tDCS in healthy populations, and remote supervision has strong practical benefits.

Objective/hypothesis

The goal of the current study was to test if previously shown effects of HD-tDCS over the left DLPFC on semantic memory performance and metamemory monitoring accuracy extended to conventional rs-tDCS, which is less focal than HD-tDCS, and to episodic memory and metamemory tasks.

Materials and methods

A total of 36 healthy participants completed 6 weeks of rs-tDCS sessions, with either active left or right anodal DLPFC stimulation, or sham. Participants completed semantic and episodic memory and metamemory tasks, which each lasted for three consecutive sessions, and session order was counterbalanced across participants.

Results

Overall, there were no main effects of rs-tDCS on metamemory monitoring accuracy or memory performance for either the semantic or the episodic tasks. However, there were effects of rs-tDCS that depended on the order of completing the episodic and semantic task sessions. When participants completed the semantic task sessions after the episodic task sessions, semantic recognition was greater in the left anodal DLPFC condition. In a parallel effect, when participants completed the episodic task sessions after the semantic task sessions, episodic recognition was greater in the right anodal DLPFC condition.

Conclusion

Prior experience with tDCS is a factor for effects of rs-tDCS on cognition. Additionally, the current experiment provides evidence for the feasibility of fully remotely supervised tDCS in healthy participants.

Altering stimulus timing via fast rhythmic sensory stimulation induces STDP-like recall performance in human episodic memory

Episodic memory provides humans with the ability to mentally travel back to the past,1 where experiences typically involve associations between multimodal information. Forming a memory of the association is thought to be dependent on modification of synaptic connectivity.2,3 Animal studies suggest that the strength of synaptic modification depends on spike timing between pre- and post-synaptic neurons on the order of tens of milliseconds, which is termed "spike-timing-dependent plasticity" (STDP).4 Evidence found in human in vitro studies suggests different temporal scales in long-term potentiation (LTP) and depression (LTD), compared with the critical time window of STDP in animals.5,6 In the healthy human brain, STDP-like effects have been shown in the motor cortex, visual perception, and face identity recognition.7,8,9,10,11,12,13 However, evidence in human episodic memory is lacking. We investigated this using rhythmic sensory stimulation to drive visual and auditory cortices at 37.5 Hz with four phase offsets. Visual relative to auditory cued recall accuracy was significantly enhanced in the 90° condition when the visual stimulus led at the shortest delay (6.67 ms). This pattern was reversed in the 270° condition when the auditory stimulus led at the shortest delay. Within cue modality, recall was enhanced when a stimulus of the corresponding modality led the shortest delay (6.67 ms) compared with the longest delay (20 ms). Our findings provide evidence for STDP in human episodic memory, which builds an important bridge from in vitro studies in animals to human memory behavior.

How to bridge the nurse innovation-diffusion gap? An in-depth case study of Create4Care

Introduction

Nurses frequently innovate in response to operational failures, regulations, procedures, and/or other workflow barriers that prevent them from delivering high-quality patient care. Unfortunately, most nurse innovations do not diffuse to a broader audience, depriving other nurses from taking advantage of solutions that have already been developed elsewhere. This under-diffusion is problematic from a societal and welfare point of view. The goal of this paper is to understand how diffusion shortage of nurse innovations can be reduced.

Methods

We develop a qualitative case study of a medical makerspace at the largest academic hospital in the Netherlands. This medical makerspace reported unusually high rates of nurse innovation diffusion. Our data collection includes on-site observations, archival data, secondary data, and fifteen in-depth interviews with key informants. Qualitative coding procedures and a combination of deductive and inductive reasoning are used to analyze the data.

Results

Our data show that personal, organizational, regulatory, and market barriers prevent nurses from further developing and diffusion their innovations in an anticipatory manner. That is, because nurses expect that transforming an initial solution into an innovation that can be shared with others will be too time consuming and difficult they do not proceed with the further development. The medical makerspace that we investigated adequately addresses this problem by developing an innovation ecosystem that largely takes over the innovation and diffusion process.

Discussion

We provide a concrete example of how a medical makerspace, and innovation support systems in a broader sense, can be designed to more adequately address the nurse innovation-diffusion gap. The two main elements of the practical solution that we identified are: (1) Support systems should facilitate that others may lead the development and diffusion of innovations and (2) The support system should promote that actors integrate their functional specializations within an innovation ecosystem. We make two theoretical contributions. First, we contribute to understanding barriers in the nurse innovation-diffusion process from a psychological point. Second, we identified that an ecosystem perspective is beneficial to develop innovation support systems in which diffusion occurs more often.

Dissociations between directly and generatively retrieved autobiographical memories: evidence from ageing

Autobiographical memory research has largely focused on effortful, generative retrieval processes, particularly in cognitive ageing literature. However, recent evidence has shown that autobiographical memories are often retrieved directly, without effortful retrieval processes. In the present study, we examined the retrieval characteristics and the phenomenological qualities of directly and generatively retrieved memories in younger and older adults. Participants recalled autobiographical memories in response to word-cues and reported whether each of their memories was retrieved directly (i.e., memory popped into mind) or generatively (i.e., they actively searched for it), and provided ratings for several retrieval and phenomenological characteristics. Overall, directly retrieved autobiographical memories were recalled faster and with less effort, were more recent, more frequently rehearsed, more vivid, and more positive in valence than generatively retrieved memories. Importantly, while younger adults recalled a higher number of generatively retrieved autobiographical memories than older adults, there were no age effects on the number of directly retrieved memories. We also established the parallel-form reliability of the word-cue method in eliciting autobiographical memories by comparing two sets of word-cues. The results provide novel insights on the dissociable effects of retrieval type and ageing on autobiographical memories. Theoretical and practical implications of these findings are discussed.

Re-expression of CA1 and entorhinal activity patterns preserves temporal context memory at long timescales

Converging, cross-species evidence indicates that memory for time is supported by hippocampal area CA1 and entorhinal cortex. However, limited evidence characterizes how these regions preserve temporal memories over long timescales (e.g., months). At long timescales, memoranda may be encountered in multiple temporal contexts, potentially creating interference. Here, using 7T fMRI, we measured CA1 and entorhinal activity patterns as human participants viewed thousands of natural scene images distributed, and repeated, across many months. We show that memory for an image's original temporal context was predicted by the degree to which CA1/entorhinal activity patterns from the first encounter with an image were re-expressed during re-encounters occurring minutes to months later. Critically, temporal memory signals were dissociable from predictors of recognition confidence, which were carried by distinct medial temporal lobe expressions. These findings suggest that CA1 and entorhinal cortex preserve temporal memories across long timescales by coding for and reinstating temporal context information.

Cognition from the Body-Brain Partnership: Exaptation of Memory

Examination of cognition has historically been approached from language and introspection. However, human language-dependent definitions ignore the evolutionary roots of brain mechanisms and constrain their study in experimental animals. We promote an alternative view, namely that cognition, including memory, can be explained by exaptation and expansion of the circuits and algorithms serving bodily functions. Regulation and protection of metabolic and energetic processes require time-evolving brain computations enabling the organism to prepare for altered future states. Exaptation of such circuits was likely exploited for exploration of the organism's niche. We illustrate that exploration gives rise to a cognitive map, and in turn, environment-disengaged computation allows for mental travel into the past (memory) and the future (planning). Such brain-body interactions not only occur during waking but also persist during sleep. These exaptation steps are illustrated by the dual, endocrine-homeostatic and memory, contributions of the hippocampal system, particularly during hippocampal sharp-wave ripples.

Constructive episodic retrieval processes underlying memory distortion contribute to creative thinking and everyday problem solving

Constructive episodic retrieval processes play an adaptive role in supporting divergent thinking (i.e., creatively combining diverse bits of information) and means-end problem solving (i.e., generating steps to solve a social problem). However, the constructive nature of episodic memory that supports these adaptive functions also leads to memory error. In three experiments we aimed to identify a direct link between divergent thinking and means-end problem solving - as assessed in the Alternative Uses Task (AUT) and Means-End Problem Solving (MEPS) task - with the generation of false memories in the Deese-Roediger-McDermott paradigm. In Experiment 1, we replicated prior findings where false memory was positively correlated with performance on the AUT, and also showed for the first time that increased performance in the MEPS task is associated with increased false recall. In Experiment 2, we demonstrated that the link between false recall and performance on the MEPS task did not extend to other forms of problem solving, as assessed with the Everyday Descriptions Task (EDT). In Experiment 3, we showed that when the EDT was preceded by the MEPS task in an attempt to influence participants to engage in a similar episodic-problem solving strategy, performance in both tasks was correlated with false memory. These findings provide evidence for a direct link between the adaptive benefits of constructive episodic processes, in the form of enhanced divergent creative thinking and problem solving, and costs, in the form of increased memory error.

The past and future of uncertainty in advanced illness: a systematic scoping review of underlying cognitive processes

BACKGROUND

To explain what cognitive capacity shapes uncertainty in advanced illness by identifying the types of evidence, mapping underlying cognitive processes to uncertainty, and outlining future directions for research and interventions.

DESIGN

A systematic scoping review of mixed study designs was carried out following the methodological framework of Arksey and O'Malley (2005) and using qualitative content analysis.

METHODS

PubMed, CINAHL, Embase, and PsycINFO were searched for original studies published in full and in English through December 2021 that reported on uncertainty in illness and related cognitions, cognitive science, or cognitive functions.

RESULTS

After screening 978, 18 articles met the inclusion criteria for review. We found the cognitive capacity of mental time travel - to relive the past or foresee life in the future - interacted with episodic memory retrieval to inform decision-making, and prospection to imagine, predict or prepare for future outcomes to determine lesser or greater uncertainty in advanced illness.

CONCLUSIONS

Mental time travel is a fundamental cognitive function when the future is limited by an advanced illness, to review life as a meaningful narrative. The role of mental time travel to construct or make sense of uncertain futures inherent in advanced illness can inform theory and targets for intervention.

Cognitive activity at work and the risk of dementia

Dementia prevalence is projected to rise steeply in coming decades, producing tremendous burdens on families, and health and social services. Motivated by the need for further robust evidence on modifiable risk factors, we investigate the relationship between cognitive activity at work and later-life dementia. Using data from the US Health and Retirement Study matched to the O*NET occupational database, we find that a one standard deviation increase in the cognitive activity associated with one's longest held occupation is associated with a 0.9 percentage point reduction in (predicted) dementia, or a 24% reduction relative to the mean. This relationship is consistently found across model specifications and robustness tests. When controlling for individual fixed-effects we find that the association between dementia and work cognitive activity increases with age. Overall, our results provide some evidence in support of the inclusion of cognitive activity at work as a recognized modifiable risk factor for dementia.

The acute effects of psychoactive drugs on emotional episodic memory encoding, consolidation, and retrieval: A comprehensive review

Psychoactive drugs modulate learning and emotional processes in ways that could impact their recreational and medical use. Recent work has revealed how drugs impact different stages of processing emotional episodic memories, specifically encoding (forming memories), consolidation (stabilizing memories), and retrieval (accessing memories). Drugs administered before encoding may preferentially impair (e.g., GABAA sedatives including alcohol and benzodiazepines, Δ9-tetrahydrocannabinol or THC, ketamine), enhance (e.g., dextroamphetamine and dextromethamphetamine), or both impair and enhance (i.e., ± 3,4-methylenedioxymethylamphetamine or MDMA) emotionally negative and positive compared to neutral memories. GABAA sedatives administered immediately post-encoding (during consolidation) can preferentially enhance emotional memories, though this selectivity may decline or even reverse (i.e., preferential enhancement of neutral memories) as the delay between encoding and retrieval increases. Finally, retrieving memories under the effects of THC, dextroamphetamine, MDMA, and perhaps GABAA sedatives distorts memory, with potentially greater selectively for emotional (especially positive) memories. We review these effects, propose neural mechanisms, discuss methodological considerations for future work, and speculate how drug effects on emotional episodic memory may contribute to drug use and abuse.

Incidental temporal binding in rats: A novel behavioral task

We designed a behavioral task called One-Trial Trace Escape Reaction (OTTER), in which rats incidentally associate two temporally discontinuous stimuli: a neutral acoustic cue (CS) with an aversive stimulus (US) which occurs two seconds later (CS-2s-US sequence). Rats are first habituated to two similar environmental contexts (A and B), each consisting of an interconnected dark and light chamber. Next, rats experience the CS-2s-US sequence in the dark chamber of one of the contexts (either A or B); the US is terminated immediately after a rat escapes into the light chamber. The CS-2s-US sequence is presented only once to ensure the incidental acquisition of the association. The recall is tested 24 h later when rats are presented with only the CS in the alternate context (B or A), and their behavioral response is observed. Our results show that 59% of the rats responded to the CS by escaping to the light chamber, although they experienced only one CS-2s-US pairing. The OTTER task offers a flexible high throughput tool to study memory acquired incidentally after a single experience. Incidental one-trial acquisition of association between temporally discontinuous events may be one of the essential components of episodic memory formation.

Solving the elusiveness of word meanings: two arguments for a continuous meaning space for language

I explore the hypothesis that the experience of meaning discreteness when we think about the "meaning" of a word is a "communicative" illusion. The illusion is created by processing-contextual constraints that impose disambiguation on the semantic input making salient a specific interpretation within a conceptual space that is otherwise continuous. It is this salience that we experience as discreteness. The understanding of word meaning as non-discrete raises the question of what is context; what are the mechanisms of constraint that it imposes and what is the nature of the conceptual space with which pronunciations (i.e., visual/oral signs) associate themselves. I address these questions by leveraging an algebraic continuous system for word meaning that is itself constrained by two fundamental parameters: control-asymmetry and connectedness. I evaluate this model by meeting two challenges to word meaning discreteness (1) cases where the same pronunciation is associated with multiple senses that are nonetheless interdependent, e.g., English "smoke," and (2) cases where the same pronunciation is associated with a family of meanings, minimally distinct from each other organized as a "cline," e.g., English "have." These cases are not marginal-they are ubiquitous in languages across the world. Any model that captures them is accounting for the meaning system for language. At the heart of the argumentation is the demonstration of how the parameterized space naturally organizes these kinds of cases without appeal for further categorization or segmentation of any kind. From this, I conclude that discreteness in word meaning is epiphenomenal: it is the experience of salience produced by contextual constraints. And that this is possible because, by and large, every time that we become consciously aware of the conceptual structure associated with a pronunciation, i.e., its meaning, we do so under real-time processing conditions which are biased toward producing a specific interpretation in reference to a specific situation in the world. Supporting it is a parameterized space that gives rise to lexico-conceptual representations: generalized algebraic structures necessary for the identification, processing, and encoding of an individual's understanding of the world.

Imagery in the entropic associative memory

The Entropic Associative Memory is a novel declarative and distributed computational model of associative memory. The model is general, conceptually simple, and offers an alternative to models developed within the artificial neural networks paradigm. The memory uses a standard table as its medium, where the information is stored in an indeterminate form, and the entropy plays a functional and operation role. The memory register operation abstracts the input cue with the current memory content and is productive; memory recognition is performed through a logical test; and memory retrieval is constructive. The three operations can be performed in parallel using very few computing resources. In our previous work we explored the auto-associative properties of the memory and performed experiments to store, recognize and retrieve manuscript digits and letters with complete and incomplete cues, and also to recognize and learn phones, with satisfactory results. In such experiments a designated memory register was used to store all the objects of the same class, whereas in the present study we remove such restriction and use a single memory register to store all the objects in the domain. In this novel setting we explore the production of emerging objects and relations, such that cues are used not only to retrieve remembered objects, but also related and imaged objects, and to produce association chains. The present model supports the view that memory and classification are independent functions both conceptually and architecturally. The memory system can store images of the different modalities of perception and action, possibly multimodal, and offers a novel perspective on the imagery debate and computational models of declarative memory.

Sequential involvements of the perirhinal cortex and hippocampus in the recall of item-location associative memory in macaques

The standard consolidation theory suggests that the hippocampus (HPC) is critically involved in acquiring new memory, while storage and recall gradually become independent of it. Converging studies have shown separate involvements of the perirhinal cortex (PRC) and parahippocampal cortex (PHC) in item and spatial processes, whereas HPC relates the item to a spatial context. These 2 strands of literature raise the following question; which brain region is involved in the recall process of item-location associative memory? To solve this question, this study applied an item-location associative (ILA) paradigm in a single-unit study of nonhuman primates. We trained 2 macaques to associate 4 visual item pairs with 4 locations on a background map in an allocentric manner before the recording sessions. In each trial, 1 visual item and the map image at a tilt (-90° to 90°) were sequentially presented as the item-cue and the context-cue, respectively. The macaques chose the item-cue location relative to the context-cue by positioning their gaze. Neurons in the PRC, PHC, and HPC, but not area TE, exhibited item-cue responses which signaled retrieval of item-location associative memory. This retrieval signal first appeared in the PRC, followed by the HPC and PHC. We examined whether neural representations of the retrieved locations were related to the external space that the macaques viewed. A positive representation similarity was found in the HPC and PHC, but not in the PRC, thus suggesting a contribution of the HPC to relate the retrieved location from the PRC with a first-person perspective of the subjects and provide the self-referenced retrieved location to the PHC. These results imply distinct but complementary contributions of the PRC and HPC to recall of item-location associative memory that can be used across multiple spatial contexts.

Evaluating the effects of episodic and semantic memory induction procedures on divergent thinking in younger and older adults

Evidence suggesting that episodic specificity induction improves divergent thinking performance in younger and older adults has been taken as indicative of the role of declarative memory processes in creativity. A series of studies were carried out to verify the specificity of such findings by investigating the effects of several novel episodic and semantic memory induction procedures on a widely employed measure of divergent creative thinking (the Alternate Uses Task), in comparison to a control induction and a no-induction baseline in both younger and older adults. There was no clear evidence for a specific role played by the induction of episodic or semantic memory processes in facilitating creative thinking across the three experiments, and the effects of the induction procedures (episodic, semantic and control) on divergent thinking were not comparable across age groups. On the other hand, higher levels of creativity were generally associated with older adults (60-80 years). In Experiments 2 and 3, older adults generated a greater number of responses (fluency), more unique responses (average originality, peak originality, creativity ratings) and more varied responses (flexibility) than younger adults (18-30 years). The findings are discussed in relation to the specificity of declarative memory operations and their impact on creative thinking, especially within the context of healthy ageing.

Lifelong impairment in episodic re-experiencing: Neuropsychological and neuroimaging examination of a new case of Severely Deficient Autobiographical Memory

Autobiographical memory (AM) represents a complex and multimodal cognitive function, that allows an individual to collect and retrieve personal events and facts, enabling to develop and maintain the continuity of the self over time. Here we describe the case of DR (acronym of the fictional name Doriana Rossi), a 53-year-old woman, who complains of a specific and lifelong deficit in recalling autobiographical episodes. Along with an extensive neuropsychological assessment, DR underwent a structural and functional MRI examination to further define this impairment. The neuropsychological assessment revealed a deficit in episodic re-experiencing of her own personal life events. DR showed reduced cortical thickness in the Retrosplenial Complex in the left hemisphere, and in the Lateral Occipital Cortex, in the Prostriate Cortex and the Angular Gyrus in the right hemisphere. An altered pattern of activity in the calcarine cortex was detected during ordering of autobiographical events according to her own personal timeline. The present study provides further evidence about the existence of a severely deficient autobiographical memory condition in neurologically healthy people, with otherwise preserved cognitive functioning. Furthermore, the present data provide new important insights into neurocognitive mechanisms underpinning such a developmental condition.

Memory and Consciousness-Usually in Tandem but Sometimes Apart

Episodic memory, the ability to remember specific events from one's personal past, has been the subject of research for several decades, with a particular emphasis on its relationship with consciousness. In the December 2022 issue of Cognitive and Behavioral Neurology , Budson, Richman, and Kensinger shed new light on this complex topic with a comprehensive exploration of consciousness. In this commentary, I present three propositions about the relationship between episodic memory and consciousness: (1) Episodic memory is usually associated with conscious retrieval; (2) it is possible to have consciousness without episodic memory; and (3) episodic memory can be accessed without conscious retrieval. Drawing from studies conducted with nonhuman animals, I provide evidence to support each of these propositions and discuss how they relate to the theory presented by Budson et al (2000). Although some of my propositions differ from their views, their work has been valuable in stimulating ongoing discussions to advance our understanding of memory.

Defects in immune response to Toxoplasma gondii are associated with enhanced HIV-1-related neurocognitive impairment in co-infected patients

Human immunodeficiency virus-1 (HIV-1) and Toxoplasma gondii can invade the central nervous system and affect its functionality. Advanced HIV-1 infection has been associated with defects in immune response to T. gondii, leading to reactivation of latent infections and development of toxoplasmic encephalitis. This study evaluates relationship between changes in immune response to T. gondii and neurocognitive impairment in HIV-1/T. gondii co-infected patients, across different stages of HIV-1 infection. The study assessed the immune response to T. gondii by measuring cytokine production in response to parasite antigens, and also neurocognitive functions by performing auditory and visual P300 cognitive evoked potentials, short term memory (Sternberg) and executive function tasks (Wisconsin Card Sorting Test-WCST) in 4 groups of individuals: HIV-1/T. gondii co-infected (P2), HIV-1-infected/T. gondii-non-infected (P1), HIV-1-non-infected/T. gondii-infected (C2) and HIV-1-non-infected/T. gondii-non-infected (C1). Patients (P1 and P2) were grouped in early/asymptomatic (P1A and P2A) or late/symptomatic (P1B/C and P2B/C) according to peripheral blood CD4+ T lymphocyte counts (>350 or <350/μL, respectively). Groups were compared using T-student or U-Mann-Whitney tests as appropriate, p<0.05 was considered as significantly. For P300 waves, HIV-1-infected patients (P1) had significantly longer latencies and significantly smaller amplitudes than uninfected controls, but HIV-1/T. gondii co-infected patients (P2) had significantly longer latencies and smaller amplitude than P1. P1 patients had significantly poorer results than uninfected controls in Sternberg and WCST, but P2 had significantly worse results than P1. HIV-1 infection was associated with significantly lower production of IL-2, TNF-α and IFN-γ in response to T. gondii from early/asymptomatic stages, when comparing P2 patients to C2 controls. These findings may indicate impairment in anti-parasitic response in co-infected patients, facilitating early limited reactivation of the parasitic latent infection, therefore creating cumulative damage in the brain and affecting neurocognitive functions from asymptomatic stages of HIV-1 infection, as suggested by defects in co-infected patients in this study.

Behavioral, neurological, and psychiatric frailty of autobiographical memory

Autobiographical-episodic memory is considered to be the most complex of the five long-term memory systems. It is autonoetic, which means, self-reflective, relies on emotional colorization, and needs the features of place and time; it allows mental time traveling. Compared to the other four long-term memory systems-procedural memory, priming, perceptual, and semantic memory-it develops the latest in phylogeny and ontogeny, and is the most vulnerable of the five systems, being easily impaired by brain damage and psychiatric disorders. Furthermore, it is characterized by its fragility and proneness to distortion due to environmental influences and subsequent information. On the brain level, a distinction has to be made between memory encoding and consolidating, memory storage, and memory retrieval. For encoding, structures of the limbic system, with the hippocampus in its center, are crucial, for storage of widespread cortical networks, and for retrieval again a distributed recollection network, in which the prefrontal cortex plays a crucial role, is engaged. Brain damage and psychiatric diseases can lead to what is called "focal retrograde amnesia." In this context, the clinical picture of dissociative or functional or psychogenic amnesia is central, as it may result in autobiographical-emotional amnesia of the total past with the consequence of an impairment of the self as well. The social environment therefore can have a major impact on the brain and on autobiographical-episodic memory processing. This article is categorized under: Psychology > Memory.

Inhibitory control of sharp-wave ripple duration during learning in hippocampal recurrent networks

Recurrent excitatory connections in hippocampal regions CA3 and CA2 are thought to play a key role in the generation of sharp-wave ripples (SWRs), electrophysiological oscillations tightly linked with learning and memory consolidation. However, it remains unknown how defined populations of inhibitory interneurons regulate these events during behavior. Here, we use large-scale, three-dimensional calcium imaging and retrospective molecular identification in the mouse hippocampus to characterize molecularly identified CA3 and CA2 interneuron activity during SWR-associated memory consolidation and spatial navigation. We describe subtype- and region-specific responses during behaviorally distinct brain states and find that SWRs are preceded by decreased cholecystokinin-expressing interneuron activity and followed by increased parvalbumin-expressing basket cell activity. The magnitude of these dynamics correlates with both SWR duration and behavior during hippocampal-dependent learning. Together these results assign subtype- and region-specific roles for inhibitory circuits in coordinating operations and learning-related plasticity in hippocampal recurrent circuits.

The influence of music liking on episodic memory for rich spatiotemporal contexts

It is thought that the presence of music influences episodic memory encoding. However, no studies have isolated the influence of music liking - the hedonic value listeners attribute to a musical stimulus - from that of the core affect induced by the presence of that music. In an online survey, participants rated musical excerpts in terms of how much they liked them, as well as in terms of felt valence, felt arousal and familiarity. These ratings were then used to inform the stimuli presented in an online episodic memory task which, across different scenarios, involved dragging cued objects to cued locations and then recalling details of what was moved, where they were moved to and the order of movements made. Our results showed an influence of liking and music-reward sensitivity on memory for what was moved, as well as a detrimental effect of arousing musical stimuli on memory for un-cued scenario details. Taken together, our study showcases the importance of episodic memory paradigms that involve rich spatiotemporal contexts and provides insights into how different aspects of episodic memory may be influenced by the presence of music.

Developments in the functions of autobiographical memory: An advanced review

In this advanced review, the development of the three most commonly used functions of autobiographical memory-directing behavior, social bonding, and self-continuity-and the support they have received in the literature are discussed. Support for this tripartite model often comes from correlational studies that use self-report measures, but participants in these studies may not be aware that they retrieved autobiographical memories to fulfill certain goals. Not only is more experimental research needed to confirm the findings from correlational studies, this kind of research needs to be more rigorous. Moreover, the functions of the tripartite model may not be the only autobiographical memory functions that can be distinguished. For example, there is already substantial support for the emotion-regulation function. Although memories can be used for multiple functions, patterns between aspects of the event (e.g., emotional valence) or memory (e.g., specificity) and their functionality have been found. In addition, individual differences (e.g., cultural background, depression symptoms) and situational factors (e.g., is there a goal that needs to be fulfilled) may regulate the functional deployment of autobiographical memories. Future research should therefore extend its focus on the conditions in which these functions can be observed. This article is categorized under: Psychology > Memory.

Towards a pluralistic neurobiological understanding of consciousness

Theories of consciousness are often based on the assumption that a single, unified neurobiological account will explain different types of conscious awareness. However, recent findings show that, even within a single modality such as conscious visual perception, the anatomical location, timing, and information flow of neural activity related to conscious awareness vary depending on both external and internal factors. This suggests that the search for generic neural correlates of consciousness may not be fruitful. I argue that consciousness science requires a more pluralistic approach and propose a new framework: joint determinant theory (JDT). This theory may be capable of accommodating different brain circuit mechanisms for conscious contents as varied as percepts, wills, memories, emotions, and thoughts, as well as their integrated experience.

Metabolic Disturbance of High-Saturated Fatty Acid Diet in Cognitive Preservation

Aging continues to be the main cause of the development of Alzheimer's, although it has been described that certain chronic inflammatory pathologies can negatively influence the progress of dementia, including obesity and hyperlipidemia. In this sense, previous studies have shown a relationship between low-density lipoprotein receptor (LDLR) and the amyloid-beta (Aβ) binding activity, one of the main neuropathological features of Alzheimer's disease (AD). LDLR is involved in several processes, including lipid transport, regulation of inflammatory response and lipid metabolism. From this perspective, LDLR^-/- mice are a widely accepted animal model for the study of pathologies associated with alterations in lipid metabolism, such as familial hypercholesterolemia, cardiovascular diseases, metabolic syndrome, or early cognitive decline. In this context, we induced hyperlipidemia in LDLR^-/- mice after feeding with a high-saturated fatty acid diet (HFD) for 44 weeks. LDLR^-/--HFD mice exhibited obesity, hypertriglyceridemia, higher glucose levels, and early hepatic steatosis. In addition, HFD increased plasmatic APOE and ubiquitin 60S levels. These proteins are related to neuronal integrity and health maintenance. In agreement, we detected mild cognitive dysfunctions in mice fed with HFD, whereas LDLR^-/--HFD mice showed a more severe and evident affectation. Our data suggest central nervous system dysfunction is associated with a well-established metabolic syndrome. As a late consequence, metabolic syndrome boots many behavioral and pathological alterations recognized in dementia, supporting that the control of metabolic parameters could improve cognitive preservation and prognosis.

Lack of source memory as a potential marker of early assimilation of novel items into current knowledge

In daily life, humans process a plethora of new information that can be either consistent (familiar) or inconsistent (novel) with prior knowledge. Over time, both types of information can integrate into our accumulated knowledge base via distinct pathways. However, the mnemonic processes supporting the integration of information that is inconsistent with prior knowledge remain under-characterized. In the current study, we used functional magnetic resonance imaging (fMRI) to examine the initial assimilation of novel items into the semantic network. Participants saw three repetitions of adjective-noun word pairs that were either consistent or inconsistent with prior knowledge. Twenty-four hours later, they were presented with the same stimuli again while undergoing fMRI scans. Outside the scanner, participants completed a surprise recognition test. We found that when the episodic context associated with initially inconsistent items was irretrievable, the neural signature of these items was indistinguishable from that of consistent items. In contrast, initially inconsistent items with accessible episodic contexts showed neural signatures that differed from those associated with consistent items. We suggest that, at least one day post encoding, items inconsistent with prior knowledge can show early assimilation into the semantic network only when their episodic contexts become inaccessible during retrieval, thus evoking a sense of familiarity.

Episodic Memory formation: A review of complex Hippocampus input pathways

Memories of everyday experiences involve the encoding of a rich and dynamic representation of present objects and their contextual features. Traditionally, the resulting mnemonic trace is referred to as Episodic Memory, i.e. the "what", "where" and "when" of a lived episode. The journey for such memory trace encoding begins with the perceptual data of an experienced episode handled in sensory brain regions. The information is then streamed to cortical areas located in the ventral Medio Temporal Lobe, which produces multi-modal representations concerning either the objects (in the Perirhinal cortex) or the spatial and contextual features (in the parahippocampal region) of the episode. Then, this high-level data is gated through the Entorhinal Cortex and forwarded to the Hippocampal Formation, where all the pieces get bound together. Eventually, the resulting encoded neural pattern is relayed back to the Neocortex for a stable consolidation. This review will detail these different stages and provide a systematic overview of the major cortical streams toward the Hippocampus relevant for Episodic Memory encoding.

Me, Myself and My Insula: An Oasis in the Forefront of Self-Consciousness

The insula is a multiconnected brain region that centralizes a wide range of information, from the most internal bodily states, such as interoception, to high-order processes, such as knowledge about oneself. Therefore, the insula would be a core region involved in the self networks. Over the past decades, the question of the self has been extensively explored, highlighting differences in the descriptions of the various components but also similarities in the global structure of the self. Indeed, most of the researchers consider that the self comprises a phenomenological part and a conceptual part, in the present moment or extending over time. However, the anatomical substrates of the self, and more specifically the link between the insula and the self, remain unclear. We conducted a narrative review to better understand the relationship between the insula and the self and how anatomical and functional damages to the insular cortex can impact the self in various conditions. Our work revealed that the insula is involved in the most primitive levels of the present self and could consequently impact the self extended in time, namely autobiographical memory. Across different pathologies, we propose that insular damage could engender a global collapse of the self.

Episodic and Semantic Autobiographical Memory in Mild Cognitive Impairment (MCI): A Systematic Review

INTRODUCTION

Mild cognitive impairment (MCI) is a syndrome defined as a decline in cognitive performance greater than expected for an individual according to age and education level, not interfering notably with daily life activities. Many studies have focused on the memory domain in the analysis of MCI and more severe cases of dementia. One specific memory system is represented by autobiographical memory (AM), which has been largely studied in Alzheimer's disease and its effect on AM; however, the impairment of AM in moderate forms of decline, such as MCI, is still controversial.

OBJECTIVE

The main aim of this systematic review is to analyze the functioning of autobiographical memory in patients with MCI, considering both the semantic and the episodic components.

MATERIALS

The review process was conducted according to the PRISMA statement. The search was conducted until 20 February 2023 in the following bibliographical databases: PubMed, Web of Science, Scopus, and PsycInfo, and twenty-one articles were included.

RESULTS

The results highlight controversial findings concerning the semantic component of AM since only seven studies have found a worse semantic AM performance in patients with MCI compared to the HC group. The results of impaired episodic AM in individuals with MCI are more consistent than those concerning semantic AM.

CONCLUSIONS

Starting from the evidence of this systematic review, further studies should detect and investigate the cognitive and emotional mechanisms that undermine AM performance, allowing the development of specific interventions targeting these mechanisms.

Effects of bilingualism on autobiographical memory: variation in idea density and retrieval speed

Prior work on bilingual memory has largely focused on working memory and less on autobiographical memory. In the present study, we tested the effect of bilingualism on autobiographical memory and examined whether an effect would be moderated or mediated by working memory. Spanish-English bilingual and English-only monolingual adults completed an autobiographical cued-recall task, as well as a working memory measure. Memories were coded for retrieval speed and propositional idea density. Bilingual status was associated with faster memory retrieval but did not affect propositional idea density. Better working memory was associated with slower memory retrieval but did not affect propositional idea density, nor did working memory moderate or mediate the effect of bilingualism. Together, these results indicate an effect of bilingualism on the speed of autobiographical memory retrieval that does not extend to autobiographical memory content and suggest that the effect of bilingualism is independent of the effect of working memory.

Standardized extract of Ginkgo biloba treatment and novelty on the weak encoding of spatial recognition memory in rats

Long-term memory (LTM) formation is dependent on neurochemical changes that guarantee that a recently formed memory (short-term memory [STM]) remains in the specific neural circuitry via the consolidation process. The persistence of recognition memory has been evidenced by using behavioral tagging in young adult rats, but it has not been effective on aging. Here, we investigated the effects of treatment with a standardized extract of Ginkgo biloba (EGb) associated with novelty on the consolidation of object location memory (OLM) and its persistence after weak training of spatial object preference in young adult and aged rats. The object location task used in this study included two habituation sessions, training sessions associated or not associated with EGb treatment and contextual novelty, and short-term or long-term retention testing sessions. Altogether, our data showed that treatment with EGb associated with novelty close to the time of encoding resulted in STM that lasted for 1 h and persisted for 24 h for both young adult and aged rats. In aged rats, the cooperative mechanisms induced robust long-term OLM. Our findings support and extend our knowledge about recognition memory in aged rats and the modulating effects of EGb treatment and contextual novelty on the persistence of memory.

Social memory characteristics of non-clinical college students with social anxiety

According to the cognitive theory of social anxiety, the cognitive schema of people with social anxiety makes them easily attracted by threatening information and memory processing. Two experiments explored the social memory characteristics of college students with social anxiety. In Experiment 1, the study investigated the social memory bias of college students with social anxiety. In Experiment 2, cue word technology was used to investigate the social autobiographical memory amount and generalization degree of college students with social anxiety using cue words. The results showed that: (1) Compared with low social anxiety college students, college students with high social anxiety had a memory bias for negative social information, but did not have a negative memory bias for irrelevant social information; (2) Compared with low social anxiety college students, college students with high social anxiety had more negative social autobiographical memory; (3) Compared with low social anxiety college students, college students with high social anxiety have a higher degree of social autobiographical memory generalization. This study revealed that college students with high social anxiety had a negative memory bias toward social information, the amount of negative social autobiographical memory was larger and the degree of social autobiographical memory generalization was higher, providing new perspectives for future interventions in this population.

Episodic Memory Retrieval Affects the Onset and Dynamics of Evidence Accumulation during Value-based Decisions

In neuroeconomics, there is much interest in understanding simple value-based choices where agents choose between visually presented goods, comparable to a shopping scenario in a supermarket. However, many everyday decisions are made in the physical absence of the considered goods, requiring agents to recall information about the goods from memory. Here, we asked whether and how this reliance on an internal memory representation affects the temporal dynamics of decision making on a cognitive and neural level. Participants performed a remember-and-decide task in which they made simple purchasing decisions between money offers and snack items while undergoing EEG. Snack identity was presented either visually (value trials) or had to be recalled from memory (memory trials). Behavioral data indicated comparable choice consistency across both trial types, but considerably longer RTs in memory trials. Drift-diffusion modeling suggested that this RT difference was because of longer nondecision time of decision processes as well as altered evidence accumulation dynamics (lower accumulation rate and higher decision threshold). The nondecision time effect was supported by a delayed onset of the lateralized readiness potential. These results show that both decision and nondecision processes are prolonged when participants need to resort to internal memory representations during value-based decisions.

Time is of the essence: past selves are not prioritized even when selective discrimination costs are controlled for

The perceptual Self-Prioritization effect (SPE) refers to an advantage in attending to stimuli associated with the self relative to those associated with another individual. In the perceptual matching task, arbitrary pairings between oneself and other persons, and a geometric shape need to be learned. Apart from the SPE, this task also produces high matching performance for a close other. While cognitive representations of past selves are sometimes viewed as resembling that of an intimate other, and while there is some evidence that other types of psychological closeness modulate the SPE, it remains unclear whether such prioritization effects extend to past selves. Previous experiments on this topic required participants to distinguish between different points in time within the same task, raising the possibility that potential past self-prioritization was masked by task difficulty. In our experiment, we addressed this potential confound by presenting N = 118 participants with a simpler version of the matching task. We re-investigated self-prioritization in perceptual matching under conditions of mental time travel to the past. In line with previous evidence, we found clear prioritization of present selves, which was evident in response times, accuracies and the efficiency of practice. Performance was consistently poorest for the past self, indicating not only a lack of privileged processing, but rather a relative de-prioritization. Performance was not improved by either increased proximity of the time period in question, nor by experimenter-induced re-imagining of the self. Our results do not support a perceptual prioritization of past selves.

Distinct brain networks for remote episodic memory depending on content and emotional experience

Memories of life episodes are the heart of individual stories. However, modelling episodic memory is a major challenge in both humans and animals when considering all its characteristics. As a consequence, the mechanisms that underlie the storage of old nontraumatic episodic memories remain enigmatic. Here, using a new task in rodents that models human episodic memory including odour/place/context components and applying advances behavioural and computational analyses, we show that rats form and recollect integrated remote episodic memories of two occasionally encountered complex episodes occurring in their daily life. Similar to humans, the information content and accuracy of memories vary across individuals and depend on the emotional relationship with odours experienced during the very first episode. We used cellular brain imaging and functional connectivity analyses, to find out the engrams of remote episodic memories for the first time. Activated brain networks completely reflect the nature and content of episodic memories, with a larger cortico-hippocampal network when the recollection is complete and with an emotional brain network related to odours that is critical in maintaining accurate and vivid memories. The engrams of remote episodic memories remain highly dynamic since synaptic plasticity processes occur during recall related to memory updates and reinforcement.