Memory, Novelty and Prior Knowledge

To update or to create? The influence of novelty and prior knowledge on memory networks

Schemas are foundational mental structures shaped by experience. They influence behaviour, guide the encoding of new memories and are shaped by associated information. The adaptability of memory schemas facilitates the integration of new information that aligns with existing knowledge structures. First, we discuss how novel information consistent with an existing schema can be swiftly assimilated when presented. This cognitive updating is facilitated by the interaction between the hippocampus and the prefrontal cortex. Second, when novel information is inconsistent with the schema, it likely engages the hippocampus to encode the information as part of an episodic memory trace. Third, novelty may enhance hippocampal dopamine through either the locus coeruleus or ventral tegmental area pathways, with the pathway involved potentially depending on the type of novelty encountered. We propose a gradient theory of schema and novelty to elucidate the neural processes by which schema updating or novel memory traces are formed. It is likely that experiences vary along a familiarity-novelty continuum, and the degree to which new experiences are increasingly novel will guide whether memory for a new experience either integrates into an existing schema or prompts the creation of a new cognitive framework. This article is part of the theme issue 'Long-term potentiation: 50 years on'.

A theory of hippocampal function: New developments

We develop further here the only quantitative theory of the storage of information in the hippocampal episodic memory system and its recall back to the neocortex. The theory is upgraded to account for a revolution in understanding of spatial representations in the primate, including human, hippocampus, that go beyond the place where the individual is located, to the location being viewed in a scene. This is fundamental to much primate episodic memory and navigation: functions supported in humans by pathways that build 'where' spatial view representations by feature combinations in a ventromedial visual cortical stream, separate from those for 'what' object and face information to the inferior temporal visual cortex, and for reward information from the orbitofrontal cortex. Key new computational developments include the capacity of the CA3 attractor network for storing whole charts of space; how the correlations inherent in self-organizing continuous spatial representations impact the storage capacity; how the CA3 network can combine continuous spatial and discrete object and reward representations; the roles of the rewards that reach the hippocampus in the later consolidation into long-term memory in part via cholinergic pathways from the orbitofrontal cortex; and new ways of analysing neocortical information storage using Potts networks.

Predatory Odor Exposure as a Potential Paradigm for Studying Emotional Modulation of Memory Consolidation-The Role of the Noradrenergic Transmission in the Basolateral Amygdala

The pivotal role of the basolateral amygdala (BLA) in the emotional modulation of hippocampal plasticity and memory consolidation is well-established. Specifically, multiple studies have demonstrated that the activation of the noradrenergic (NA) system within the BLA governs these modulatory effects. However, most current evidence has been obtained by direct infusion of synthetic NA or beta-adrenergic agonists. In the present study, we aimed to investigate the effect of endogenous NA release in the BLA, induced by a natural aversive stimulus (coyote urine), on memory consolidation for a low-arousing, hippocampal-dependent task. Our experiments combined a weak object location task (OLT) version with subsequent mild predator odor exposure (POE). To investigate the role of endogenous NA in the BLA in memory modulation, a subset of the animals (Wistar rats) was treated with the non-selective beta-blocker propranolol at the end of the behavioral procedures. Hippocampal tissue was collected 90 min after drug infusion or after the OLT test, which was performed 24 h later. We used the obtained samples to estimate the levels of phosphorylated CREB (pCREB) and activity-regulated cytoskeleton-associated protein (Arc)-two molecular markers of experience-dependent changes in neuronal activity. The result suggests that POE has the potential to become a valuable behavioral paradigm for studying the interaction between BLA and the hippocampus in memory prioritization and selectivity.

Recognizing ideas generated in a creative task: the roles of the hippocampus and medial prefrontal cortex in facilitating self-generated learning

Creative idea generation plays an important role in promoting successful memory formation. Yet, its underlying neural correlates remain unclear. We investigated the self-generated learning of creative ideas motivated by the schema-linked interactions between medial prefrontal and medial temporal regions framework. This was achieved by having participants generate ideas in the alternative uses task, self-evaluating their ideas based on novelty and source (i.e. new or old), and then later being tested on the recognition performance of the generated ideas. At the behavioral level, our results indicated superior performances in discriminating novel ideas, highlighting the novelty effect on memory. At the neural level, the regions-of-interest analyses revealed that successful recognition of novel ideas was associated with greater activations in the hippocampus (HPC) and medial prefrontal cortex (mPFC) during ideation. However, only activation in the right HPC was positively related to the successful recognition of novel ideas. Importantly, the weaker the connection between the right HPC and left mPFC, the higher the recognition accuracy of novel ideas. Moreover, activations in the right HPC and left mPFC were both effective predictors of successful recognition of novel ideas. These findings uniquely highlight the role of novelty in promoting self-generated learning of creative ideas.

Sensory encoding and memory in the mushroom body: signals, noise, and variability

To survive in changing environments, animals need to learn to associate specific sensory stimuli with positive or negative valence. How do they form stimulus-specific memories to distinguish between positively/negatively associated stimuli and other irrelevant stimuli? Solving this task is one of the functions of the mushroom body, the associative memory center in insect brains. Here we summarize recent work on sensory encoding and memory in the Drosophila mushroom body, highlighting general principles such as pattern separation, sparse coding, noise and variability, coincidence detection, and spatially localized neuromodulation, and placing the mushroom body in comparative perspective with mammalian memory systems.

Remembering what we imagine: the role of event schemas in shaping how imagined autobiographical events are recalled

Much like recalling autobiographical memories, constructing imagined autobiographical events depends on episodic memory processes. The ability to imagine events contributes to several future-oriented behaviors (e.g., decision-making, problem solving), which relies, in part, on the ability to remember the imagined events. A factor affecting the memorability of such events is their adherence to event schemas-conceptualizations of how events generally unfold. In the current study, we examined how two aspects of event schemas-event expectancy and familiarity-affect the ability to recall imagined events. Participants first imagined and described in detail autobiographical events that either aligned with or deviated from an event, expected to occur in a context (e.g., a kitchen) that was either familiar or unfamiliar. This resulted in imaginations ranging from maximally schema-congruent (expected events in a familiar context) to maximally novel (unexpected events in an unfamiliar context). Twenty-four hours later, participants recalled these imagined events. Recollections were scored for the number of reinstated details from the imaginations and the number of newly added details. We found greater reinstatement of details for both the maximally congruent and maximally novel events, while maximally novel events were recalled more precisely than other events (i.e., fewer added details). Our results indicate a complementary benefit to remembering schematic and novel imagined events, which may guide equally important but distinct future-oriented behaviors.

On the frequency and nature of the cues that elicit déjà vu and involuntary autobiographical memories

Barzykowski and Moulin suggest that déjà vu and involuntary autobiographical memories recruit similar retrieval processes. Here, we invite the authors to clarify three issues: (1) What mechanism prevents déjà vu to happen more frequently? (2) What is the role of semantic cues in involuntary autobiographical retrieval? and (3) How déjà vu relates to non-believed memories?

Activating M1 muscarinic cholinergic receptors induces destabilization of resistant contextual fear memories in rats

Destabilization of previously consolidated memories places them in a labile state in which they are open to modification. However, strongly encoded fear memories tend to be destabilization-resistant and the conditions required to destabilize such memories remain poorly understood. Our lab has previously shown that exposure to salient novel contextual cues during memory reactivation can destabilize strongly encoded object location memories and that activity at muscarinic cholinergic receptors is critical for this effect. In the current study, we similarly targeted destabilization-resistant fear memories, hypothesizing that exposure to salient novelty at the time of reactivation would induce destabilization of strongly encoded fear memories in a muscarinic receptor-dependent manner. First, we show that contextual fear memories induced by 3 context-shock pairings readily destabilize upon memory reactivation, and that this destabilization is blocked by systemic (ip) administration of the muscarinic receptor antagonist scopolamine (0.3 mg/kg) in male rats. Following that, we confirm that this effect is dorsal hippocampus (dHPC)-dependent by targeting M1 receptors in the CA1 region with pirenzepine. Next, we show that more strongly encoded fear memories (induced with 5 context-shock pairings) resist destabilization. Consistent with our previous work, however, we report that salient novelty (a change in floor texture) presented during the reactivation session promotes destabilization of resistant contextual fear memories in a muscarinic receptor-dependent manner. Finally, the effect of salient novelty on memory destabilization was mimicked by stimulating muscarinic receptors with the selective M1 agonist CDD-0102A (ip, 0.3 mg/kg). These findings reveal further generalizability of our previous results implicating novel cues and M1 muscarinic signaling in promoting destabilization of resistant memories and suggest possible therapeutic options for disorders characterized by persistent, maladaptive fear memories such as PTSD and phobias.

NMDA Receptor-Arc Signaling Is Required for Memory Updating and Is Disrupted in Alzheimer's Disease

BACKGROUND

Memory deficits are central to many neuropsychiatric diseases. During acquisition of new information, memories can become vulnerable to interference, yet mechanisms that underlie interference are unknown.

METHODS

We describe a novel transduction pathway that links the NMDA receptor (NMDAR) to AKT signaling via the immediate early gene Arc and evaluate its role in memory. The signaling pathway is validated using biochemical tools and transgenic mice, and function is evaluated in assays of synaptic plasticity and behavior. The translational relevance is evaluated in human postmortem brain.

RESULTS

Arc is dynamically phosphorylated by CaMKII (calcium/calmodulin-dependent protein kinase II) and binds the NMDAR subunits NR2A/NR2B and a previously unstudied PI3K (phosphoinositide 3-kinase) adapter p55PIK (PIK3R3) in vivo in response to novelty or tetanic stimulation in acute slices. NMDAR-Arc-p55PIK recruits p110α PI3K and mTORC2 (mechanistic target of rapamycin complex 2) to activate AKT. NMDAR-Arc-p55PIK-PI3K-mTORC2-AKT assembly occurs within minutes of exploratory behavior and localizes to sparse synapses throughout hippocampal and cortical regions. Studies using conditional (Nestin-Cre) p55PIK deletion mice indicate that NMDAR-Arc-p55PIK-PI3K-mTORC2-AKT functions to inhibit GSK3 and mediates input-specific metaplasticity that protects potentiated synapses from subsequent depotentiation. p55PIK conditional knockout mice perform normally in multiple behaviors including working memory and long-term memory tasks but exhibit deficits indicative of increased vulnerability to interference in both short-term and long-term paradigms. The NMDAR-AKT transduction complex is reduced in postmortem brain of individuals with early Alzheimer's disease.

CONCLUSIONS

A novel function of Arc mediates synapse-specific NMDAR-AKT signaling and metaplasticity that contributes to memory updating and is disrupted in human cognitive disease.

Predictions transform memories: How expected versus unexpected events are integrated or separated in memory

Our brains constantly generate predictions about the environment based on prior knowledge. Many of the events we experience are consistent with these predictions, while others might be inconsistent with prior knowledge and thus violate our predictions. To guide future behavior, the memory system must be able to strengthen, transform, or add to existing knowledge based on the accuracy of our predictions. We synthesize recent evidence suggesting that when an event is consistent with our predictions, it leads to neural integration between related memories, which is associated with enhanced associative memory, as well as memory biases. Prediction errors, in turn, can promote both neural integration and separation, and lead to multiple mnemonic outcomes. We review these findings and how they interact with factors such as memory reactivation, prediction error strength, and task goals, to offer insight into what determines memory for events that violate our predictions. In doing so, this review brings together recent neural and behavioral research to advance our understanding of how predictions shape memory, and why.

Effects of schema on the relationship between post-encoding brain connectivity and subsequent durable memory

Schemas can facilitate memory consolidation. Studies have suggested that interactions between the hippocampus and the ventromedial prefrontal cortex (vmPFC) are important for schema-related memory consolidation. However, in humans, how schema accelerates the consolidation of new information and relates to durable memory remains unclear. To address these knowledge gaps, we used a human analogue of the rodent spatial schema task and resting-state fMRI to investigate how post-encoding brain networks can predict long-term memory performance in different schema conditions. After participants were trained to obtain schema-consistent or schema-inconsistent object-location associations, they learned new object-location associations. The new associations were tested after the post-encoding rest in the scanner and 24 h later outside the scanner. The Bayesian multilevel modelling was applied to analyse the post-encoding brain networks. The results showed that during the post-encoding, stronger vmPFC- anterior hippocampal connectivity was associated with durable memory in the schema-consistent condition, whereas stronger object-selective lateral occipital cortex (LOC)-ventromedial prefrontal connectivity and weaker connectivity inside the default mode network were associated with durable memory in the schema inconsistent condition. In addition, stronger LOC-anterior hippocampal connectivity was associated with memory in both schema conditions. These results shed light on how schemas reconfigure early brain networks, especially the prefrontal-hippocampal and stimuli-relevant cortical networks and influence long-term memory performance.

Advantage conferred by overnight sleep on schema-related memory may last only a day

Study Objectives

Sleep contributes to declarative memory consolidation. Independently, schemas benefit memory. Here we investigated how sleep compared with active wake benefits schema consolidation 12 and 24 hours after initial learning.

Methods

Fifty-three adolescents (age: 15-19 years) randomly assigned into sleep and active wake groups participated in a schema-learning protocol based on transitive inference (i.e. If B > C and C > D then B > D). Participants were tested immediately after learning and following 12-, and 24-hour intervals of wake or sleep for both the adjacent (e.g. B-C, C-D; relational memory) and inference pairs: (e.g.: B-D, B-E, and C-E). Memory performance following the respective 12- and 24-hour intervals were analyzed using a mixed ANOVA with schema (schema, no-schema) as the within-participant factor, and condition (sleep, wake) as the between-participant factor.

Results

Twelve hours after learning, there were significant main effects of condition (sleep, wake) and schema, as well as a significant interaction, whereby schema-related memory was significantly better in the sleep condition compared to wake. Higher sleep spindle density was most consistently associated with greater overnight schema-related memory benefit. After 24 hours, the memory advantage of initial sleep was diminished.

Conclusions

Overnight sleep preferentially benefits schema-related memory consolidation following initial learning compared with active wake, but this advantage may be eroded after a subsequent night of sleep. This is possibly due to delayed consolidation that might occur during subsequent sleep opportunities in the wake group.

Clinical Trial Information

Name: Investigating Preferred Nap Schedules for Adolescents (NFS5) URL: https://clinicaltrials.gov/ct2/show/NCT04044885. Registration: NCT04044885.

The Catalyst Model of Change: Gratitude Interventions with Positive Long-Term Effects

How can gratitude interventions be designed to produce meaningful and enduring effects on people's well-being? To address this question, the author proposes the Catalyst Model of Change-this novel, practical, and empirically testable model posits five socially oriented behavioral pathways that channel the long-term effects of gratitude interventions as well as how to augment gratitude experiences in interventions to boost treatment effects and catalyze these behavioral pathways. Specifically, interventions that enhance the frequency, skills, intensity, temporal span, and variety of gratitude experiences are likely to catalyze the following post-intervention socially oriented behaviors: (a) social support-seeking behaviors, (b) prosocial behaviors, (c) relationship initiation and enhancement behaviors, (d) participation in mastery-oriented social activities, and (e) reduced maladaptive interpersonal behaviors, which, in turn, produce long-term psychological well-being. A unique feature of the Catalyst Model of Change is that gratitude experiences are broadly conceptualized to include not just gratitude emotions, cognitions, and disclosures, but also expressing, receiving, witnessing, and responding to interpersonal gratitude. To this end, gratitude interventions that provide multiple opportunities for social experiences of gratitude (e.g., members expressing gratitude to each other in a group) might offer the greatest promise for fostering durable, positive effects on people's psychological well-being.

Recollection and prior knowledge recruit the left angular gyrus during recognition

The human angular gyrus (AG) is implicated in recollection, or the ability to retrieve detailed memory content from a specific episode. A separate line of research examining the neural bases of more general mnemonic representations, extracted over multiple episodes, also highlights the AG as a core region of interest. To reconcile these separate views of AG function, the present fMRI experiment used a Remember-Know paradigm with famous (prior knowledge) and non-famous (no prior knowledge) faces to test whether AG activity could be modulated by both task-specific recollection and general prior knowledge within the same individuals. Increased BOLD activity in the left AG was observed during both recollection in the absence of prior knowledge (recollected > non-recollected or correctly rejected non-famous faces) and when prior knowledge was accessed in the absence of experiment-specific recollection (famous > non-famous correct rejections). This pattern was most prominent for the left AG as compared to the broader inferior parietal lobe. Recollection-related responses in the left AG increased with encoding duration and prior knowledge, despite prior knowledge being incidental to the recognition decision. Overall, the left AG appears sensitive to both task-specific recollection and the incidental access of general prior knowledge, thus broadening our notions of the kinds of mnemonic representations that drive activity in this region.

Continuously changing memories: a framework for proactive and non-linear consolidation

The traditional view of long-term memory is that memory traces mature in a predetermined 'linear' process: their neural substrate shifts from rapidly plastic medial temporal regions towards stable neocortical networks. We propose that memories remain malleable, not by repeated reinstantiations of this linear process but instead via dynamic routes of proactive and non-linear consolidation: memories change, their trajectory is flexible and reversible, and their physical basis develops continuously according to anticipated demands. Studies demonstrating memory updating, increasing hippocampal dependence to support adaptive use, and rapid neocortical plasticity provide evidence for continued non-linear consolidation. Although anticipated demand can affect all stages of memory formation, the extent to which it shapes the physical memory trace repeatedly and proactively will require further dedicated research.

Distinct multivariate structural brain profiles are related to variations in short- and long-delay memory consolidation across children and young adults

From early to middle childhood, brain regions that underlie memory consolidation undergo profound maturational changes. However, there is little empirical investigation that directly relates age-related differences in brain structural measures to memory consolidation processes. The present study examined memory consolidation of intentionally studied object-location associations after one night of sleep (short delay) and after two weeks (long delay) in normally developing 5-to-7-year-old children (n = 50) and young adults (n = 39). Behavioural differences in memory retention rate were related to structural brain measures. Our results showed that children, in comparison to young adults, retained correctly learnt object-location associations less robustly over short and long delay. Moreover, using partial least squares correlation method, a unique multivariate profile comprised of specific neocortical (prefrontal, parietal, and occipital), cerebellar, and hippocampal head and subfield structures in the body was found to be associated with variation in short-delay memory retention. A different multivariate profile comprised of a reduced set of brain structures, mainly consisting of neocortical (prefrontal, parietal, and occipital), hippocampal head, and selective hippocampal subfield structures (CA1-2 and subiculum) was associated with variation in long-delay memory retention. Taken together, the results suggest that multivariate structural pattern of unique sets of brain regions are related to variations in short- and long-delay memory consolidation across children and young adults.

Reactivation of schema representation in lateral occipital cortex supports successful memory encoding

Schemas provide a scaffold onto which we can integrate new memories. Previous research has investigated the brain activity and connectivity underlying schema-related memory formation. However, how schemas are represented and reactivated in the brain, in order to enhance memory, remains unclear. To address this issue, we used an object–location spatial schema that was learned over multiple sessions, combined with similarity analyses of neural representations, to investigate the reactivation of schema representations of object–location memories when a new object–scene association is learned. In addition, we investigated how this reactivation affects subsequent memory performance under different strengths of schemas. We found that reactivation of a schema representation in the lateral occipital cortex (LOC) during object–scene encoding affected subsequent associative memory performance only in the schema-consistent condition and increased the functional connectivity between the LOC and the parahippocampal place area. Taken together, our findings provide new insight into how schema acts as a scaffold to support the integration of novel information into existing cortical networks and suggest a neural basis for schema-induced rapid cortical learning.

Novel immersive virtual reality experiences do not produce retroactive memory benefits for unrelated material

The experience of novelty can enhance memory for information that occurs close in time, even if not directly related to the experience-a phenomenon called "behavioural tagging." For example, an animal exposed to a novel spatial environment shows improved memory for other information presented previously. This has been linked to neurochemical modulations induced by novelty, which affect consolidation of memories for experiences that were encoded around the same time. Neurophysiological research in animals has shown that novelty benefits weakly encoded but not strongly encoded information. However, a benefit that is selective to weak memories seems difficult to reconcile with studies in humans that have reported that novelty improves recollection, but not familiarity. One possibility is that the novelty increases activity in hippocampus, which is also associated with processes that enable recollection. This is consistent with another prediction of behavioural tagging theory, namely that novelty only enhances consolidation of information that converges on the same neuronal population. However, no study has directly explored the relationship between encoding strength and retrieval quality (recollection versus familiarity). We examined the effects of exposure to a novel immersive virtual reality environment on memory for words presented immediately beforehand, under either deep or shallow encoding tasks, and by testing both recall memory immediately, and recognition memory with remember/know instructions the next day. However, Bayes factors showed no evidence to support the behavioural tagging predictions: that novelty would improve memory, particularly for shallowly encoded words, and this improvement would differentially affect familiarity versus recollection.

Has the concept of systems consolidation outlived its usefulness? Identification and evaluation of premises underlying systems consolidation

Systems consolidation has mostly been treated as a neural construct defined by the time-dependent change in memory representation from the hippocampus (HPC) to other structures, primarily the neocortex. Here, we identify and evaluate the explicit and implicit premises that underlie traditional or standard models and theories of systems consolidation based on evidence from research on humans and other animals. We use the principle that changes in neural representation over time and experience are accompanied by corresponding changes in psychological representations, and vice versa, to argue that each of the premises underlying traditional or standard models and theories of systems consolidation is found wanting. One solution is to modify or abandon the premises or theories and models. This is reflected in moderated models of systems consolidation that emphasize the early role of the HPC in training neocortical memories until they stabilize. The fault, however, may lie in the very concept of systems consolidation and its defining feature. We propose that the concept be replaced by one of memory systems reorganization, which does not carry the theoretical baggage of systems consolidation and is flexible enough to capture the dynamic nature of memory from inception to very long-term retention and retrieval at a psychological and neural level. The term "memory system reorganization" implies that memory traces are not fixed, even after they are presumably consolidated. Memories can continue to change as a result of experience and interactions among memory systems across the lifetime. As will become clear, hippocampal training of neocortical memories is only one type of such interaction, and not always the most important one, even at inception. We end by suggesting some principles of memory reorganization that can help guide research on dynamic memory processes that capture corresponding changes in memory at the psychological and neural levels.

Adult newborn granule cells confer emotional state-dependent adaptability in memory retrieval

Achieving optimal behavior requires animals to flexibly retrieve prior knowledge. Here, we show that adult newborn granule cells (anbGCs) mediate emotional state-dependent adaptability of memory retrieval. We find that acute social reward (aSR) enhances memory retrieval by increasing the reactivation of engram cells, while acute social stress (aSS) weakens retrieval and reduces the reactivation. Such bidirectional regulation relies on the activation of distinct populations of anbGCs by aSR and aSS, triggering opposing modifications of dDG activity, which is sufficient to regulate and predict the performance of memory retrieval. Concordantly, in emotional disorder models, aSR-dependent memory adaptability is impaired, while the effect of aSS remains intact. Together, our data revealed that anbGCs mediate adaptability of memory retrieval, allowing animals to flexibly retrieve memory according to the current emotional state, and suggested the essential roles of anbGCs in translating emotional information to the regulation of memory expression.

Astrocytes in CA1 modulate schema establishment in the hippocampal-cortical neuron network

Background

Schema, a concept from cognitive psychology used to explain how new information is integrated with previous experience, is a framework of acquired knowledge within associative network structures as biological correlate, which allows new relevant information to be quickly assimilated by parallel cortical encoding in the hippocampus (HPC) and cortex. Previous work demonstrated that myelin generation in the anterior cingulate cortex (ACC) plays a critical role for dynamic paired association (PA) learning and consolidation, while astrocytes in ACC play a vital role in cognitive decision-making. However, circuit components and mechanism involving HPC-anterior cingulate cortex (ACC) during schema formation remain uncertain. Moreover, the correlation between HPC-ACC circuit and HPC astrocytic activity is unclear.

Results

Utilizing a paired association (PA) behavioral paradigm, we dynamically recorded calcium signals of CA1-ACC projection neurons and ACC neurons during schema formation. Depending on the characteristics of the calcium signals, three distinct stages of schema establishment process were identified. The recruitment of CA1-ACC network was investigated in each stage under CA1 astrocytes Gi pathway chemogenetic activation. Results showed that CA1-ACC projecting neurons excitation gradually decreased along with schema development, while ACC neurons revealed an excitation peak in the middle stage. CA1 astrocytic Gi pathway activation will disrupt memory schema development by reducing CA1-ACC projection neuron recruitment in the initial stage and prevent both CA1-ACC projection neurons and ACC neuron excitation in the middle stage. CA1 astrocytes Gi markedly suppress new PA assimilation into the established memory schema.

Conclusions

These results not only reveal the dynamic feature of CA1-ACC network during schema establishment, but also suggest CA1 astrocyte contribution in different stages of schema establishment.

Activity theory as a framework for teaching mathematics: An experimental study

This article introduces activity theory and how it can be employed to instruct the topic of straight-line equations in a plane - Geometry 10. Using the activity theory approach, we studied and developed a teaching process. The procedure is divided into three stages: Phase 1: Motivation and goal orientation, in which teachers present situations to attract students to the lesson; Phase 2: Knowledge formation, in which students engage in a variety of learning activities to build the knowledge they need to learn; Phase 3: Practice and consolidation, in which many exercises are assigned to students to solve in order to consolidate their knowledge and assist teachers in detecting and correcting students' misconceptions. To examine the effectiveness of applying the proposed three-phase model, we used a two-group pretest-posttest experimental model to determine whether or not teaching with the activity theory approach is more effective than the traditional teaching method by testing four research hypotheses. The experimental teaching took place in the Mo Cay district of Ben Tre province, Vietnam. Both the experimental and control classes began with the same level of mathematics, which was then tested using inferential statistics. After completing the pedagogical experiment, we discovered that students in the experimental class who were taught using activity theory achieved better learning outcomes than students in the control class, who were taught using the traditional teaching method; in the experimental class, the number of weak students decreased in comparison to the original; however, the number of good students did not increase. This is an issue that requires further studies to find ways to influence a wide range of students with different levels of mathematics so that the effectiveness of teaching according to the activity theory approach is improved.

Amygdala sensitivity for negative information as a neural marker for negative memory bias across psychiatric diagnoses

Self-referent negative memory bias is a known risk factor for depression, but recent evidence suggests its function as a transdiagnostic cognitive depressotypic marker. The amygdala's sensitivity for negative information is considered a neurobiological depressotypic marker. However, their relationship remains unknown. We transdiagnostically investigated the association between the amygdala's sensitivity, self-referent negative memory bias and its two components: negative endorsement bias and negative recall bias. Patients (n= 125) with (multimorbid) stress-related and neurodevelopmental psychiatric disorders and healthy controls (n= 78) performed an fMRI task to assess the amygdala's sensitivity for negative information and a task outside the scanner for the biases. Linear regression models assessed their associations. The left amygdala's sensitivity for negative information was significantly positively associated with negative recall bias in patients, but not controls. There were no significant associations with self-referent negative memory bias or negative endorsement bias or between the two depressotypic markers. Thus, the left amygdala's sensitivity for negative information may be considered a neural marker of negative memory bias across psychiatric diagnoses. Further research on the interactons with known determinants such as genetic predisposition is required to fully understand the relationship between the amygdala's sensitivity for negative information and these biases.

Schematic information influences memory and generalisation behaviour for schema-relevant and -irrelevant information

Schemas modulate memory performance for schema-congruent and -incongruent information. However, it is assumed they do not influence behaviour for information irrelevant to themselves. We assessed memory and generalisation behaviour for information related to an underlying pattern, where a schema could be extracted (schema-relevant), and information that was unrelated and therefore irrelevant to the extracted schema (schema-irrelevant). Using precision measures of long-term memory, where participants learnt associations between words and locations around a circle, we assessed memory and generalisation for schema-relevant and -irrelevant information. Words belonged to two semantic categories: human-made and natural. For one category, word-locations were clustered around one point on the circle (clustered condition), while the other category had word-locations randomly distributed (non-clustered condition). The presence of an underlying pattern in the clustered condition allows for the extraction of a schema that can support both memory and generalisation. At test, participants were presented with old (memory) and new (generalisation) words, requiring them to identify a remembered location or make a best guess. The presence of the clustered pattern modulated memory and generalisation. In the clustered condition, participants placed old and new words in locations consistent with the underlying pattern. In contrast, for the non-clustered condition, participants were less likely to place old and new non-clustered words in locations consistent with the clustered condition. Therefore, we provide evidence that the presence of schematic information modulates memory and generalisation for schema-relevant and -irrelevant information. Our results highlight the need to carefully construct appropriate schema-irrelevant control conditions such that behaviour in these conditions is not modulated by the presence of a schema. Theoretically, models of schema processing need to account for how the presence of schematic information can have consequences for information that is irrelevant to itself.

Beyond the hippocampus: boundary conditions for cortical connectivity and activity over time

By including four different time intervals and controlling for behavioral confounds, Tallman et al. (this issue) found that brain connectivity of cortical regions with the vmPFC or with the hippocampus changed over time, although hippocampal activity did not change significantly. This study shed light on how memory is consolidated as it ages. Further studies could clarify the extent to which other factors, such as memory content, influence brain connectivity with more than two time intervals. The roles of different cortical regions in memory consolidation should also be addressed.

Social experiences switch states of memory engrams through regulating hippocampal Rac1 activity

It is well known that silent memory engrams in pathological or artificial conditions can be artificially switched into the latent state for retrieval by natural recall cues. Thus, physiological strategies that depend on the underlying molecular mechanisms for switching between silent state and latent state are a subject for investigation. Here, we show that social experiences stimulated switching between latent and silent engrams to achieve flexible memory accessibility and also reveal the basic molecular mechanism of: 1) social reward turning silent engram to latent via suppression of Rac1 activity in CA1 neurons of the hippocampus; and 2) social stress switching latent memory engram into silent through activating Rac1. Together, this work demonstrates emotion-driven bidirectional switching between latent and silent engrams.

In pathological or artificial conditions, memory can be formed as silenced engrams that are unavailable for retrieval by presenting conditioned stimuli but can be artificially switched into the latent state so that natural recall is allowed. However, it remains unclear whether such different states of engrams bear any physiological significance and can be switched through physiological mechanisms. Here, we show that an acute social reward experience switches the silent memory engram into the latent state. Conversely, an acute social stress causes transient forgetting via turning a latent memory engram into a silent state. Such emotion-driven bidirectional switching between latent and silent states of engrams is mediated through regulation of Rac1 activity–dependent reversible forgetting in the hippocampus, as stress-activated Rac1 suppresses retrieval, while reward recovers silenced memory under amnesia by inhibiting Rac1. Thus, data presented reveal hippocampal Rac1 activity as the basis for emotion-mediated switching between latent and silent engrams to achieve emotion-driven behavioral flexibility.

A sleep schedule incorporating naps benefits the transformation of hierarchical knowledge

Study Objectives

The learning brain establishes schemas (knowledge structures) that benefit subsequent learning. We investigated how sleep and having a schema might benefit initial learning followed by rearranged and expanded memoranda. We concurrently examined the contributions of sleep spindles and slow-wave sleep to learning outcomes.

Methods

Fifty-three adolescents were randomly assigned to an 8 h Nap schedule (6.5 h nocturnal sleep with a 90-minute daytime nap) or an 8 h No-Nap, nocturnal-only sleep schedule. The study spanned 14 nights, simulating successive school weeks. We utilized a transitive inference task involving hierarchically ordered faces. Initial learning to set up the schema was followed by rearrangement of the hierarchy (accommodation) and hierarchy expansion (assimilation). The expanded sequence was restudied. Recall of hierarchical knowledge was tested after initial learning and at multiple points for all subsequent phases. As a control, both groups underwent a No-schema condition where the hierarchy was introduced and modified without opportunity to set up a schema. Electroencephalography accompanied the multiple sleep opportunities.

Results

There were main effects of Nap schedule and Schema condition evidenced by superior recall of initial learning, reordered and expanded memoranda. Improved recall was consistently associated with higher fast spindle density but not slow-wave measures. This was true for both nocturnal sleep and daytime naps.

Conclusion

A sleep schedule incorporating regular nap opportunities compared to one that only had nocturnal sleep benefited building of robust and flexible schemas, facilitating recall of the subsequently rearranged and expanded structured knowledge. These benefits appear to be strongly associated with fast spindles.

Clinical Trial registration

NCT04044885 (https://clinicaltrials.gov/ct2/show/NCT04044885).

A direct lateral entorhinal cortex to hippocampal CA2 circuit conveys social information required for social memory

The hippocampus is essential for different forms of declarative memory, including social memory, the ability to recognize and remember a conspecific. Although recent studies identify the importance of the dorsal CA2 region of the hippocampus in social memory storage, little is known about its sources of social information. Because CA2, like other hippocampal regions, receives its major source of spatial and non-spatial information from the medial and lateral subdivisions of entorhinal cortex (MEC and LEC), respectively, we investigated the importance of these inputs for social memory. Whereas MEC inputs to CA2 are dispensable, the direct inputs to CA2 from LEC are both selectively activated during social exploration and required for social memory. This selective behavioral role of LEC is reflected in the stronger excitatory drive it provides to CA2 compared with MEC. Thus, a direct LEC → CA2 circuit is tuned to convey social information that is critical for social memory.

Educational Neuroscience Training for Teachers' Technological Pedagogical Content Knowledge Construction

The attention to the laws of the brain and the mechanism of learning in the smart education era becomes the starting point for the convergence and development of education and neuroscience, which also inspired educational neuroscience (EN) affecting the teacher’s development. Although teachers always have a general curiosity about EN and its applications, the limited knowledge hinders their general practice, neuromyths begin to emerge, and there is no evidence to directly show the connection between EN and teachers’ technological pedagogical content knowledge (TPACK) knowledge. Based on an EN teacher training program for 216 teachers, this study verifies that EN training programs can promote teachers’ understanding of EN-related knowledge, and EN is also correlated to teachers’ TPACK. However, the EN training program does not promote high well-being and satisfaction. The research also analyzes the process of teachers’ EN knowledge dissemination based on interviews, and the research conclusion can further reveal the necessity of EN training for teachers in the future.

Retrosplenial cortex in spatial memory: focus on immediate early genes mapping

The ability to form, retrieve and update autobiographical memories is one of the most fascinating features of human behavior. Spatial memory, the ability to remember the layout of the external environment and to navigate within its boundaries, is closely related to the autobiographical memory domain. It is served by an overlapping brain circuit, centered around the hippocampus (HPC) where the cognitive map index is stored. Apart from the hippocampus, several cortical structures participate in this process. Their relative contribution is a subject of intense research in both humans and animal models. One of the most widely studied regions is the retrosplenial cortex (RSC), an area in the parietal lobe densely interconnected with the hippocampal formation. Several methodological approaches have been established over decades in order to investigate the cortical aspects of memory. One of the most successful techniques is based on the analysis of brain expression patterns of the immediate early genes (IEGs). The common feature of this diverse group of genes is fast upregulation of their mRNA translation upon physiologically relevant stimulus. In the central nervous system they are rapidly triggered by neuronal activity and plasticity during learning. There is a widely accepted consensus that their expression level corresponds to the engagement of individual neurons in the formation of memory trace. Imaging of the IEGs might therefore provide a picture of an emerging memory engram. In this review we present the overview of IEG mapping studies of retrosplenial cortex in rodent models. We begin with classical techniques, immunohistochemical detection of protein and fluorescent in situ hybridization of mRNA. We then proceed to advanced methods where fluorescent genetically encoded IEG reporters are chronically followed in vivo during memory formation. We end with a combination of genetic IEG labelling and optogenetic approach, where the activity of the entire engram is manipulated. We finally present a hypothesis that attempts to unify our current state of knowledge about the function of RSC.

Building memories on prior knowledge: behavioral and fMRI evidence of impairment in early Alzheimer's disease

Impaired memory is a hallmark of prodromal Alzheimer's disease (AD). Prior knowledge associated with the memoranda improves memory in healthy individuals, but we ignore whether the same occurs in early AD. We used functional MRI to investigate whether prior knowledge enhances memory encoding in early AD, and whether the nature of this prior knowledge matters. Patients with early AD and Controls underwent a task-based fMRI experiment where they learned face-scene associations. Famous faces carried pre-experimental knowledge (PEK), while unknown faces with which participants were familiarized prior to learning carried experimental knowledge (EK). Surprisingly, PEK strongly enhanced subsequent memory in healthy controls, but importantly not in patients. Partly nonoverlapping brain networks supported PEK vs. EK associative encoding in healthy controls. No such networks were identified in patients. In addition, patients displayed impaired activation in a right sub hippocampal region where activity predicted successful associative memory formation for PEK stimuli. Despite the limited sample sizes of this study, these findings suggest that the role prior knowledge in new learning might have been so far overlooked and underestimated in AD patients. Prior knowledge may drive critical differences in the way healthy elderly and early AD patients learn novel associations.

The HexMaze: A Previous Knowledge Task on Map Learning for Mice

New information is rarely learned in isolation; instead, most of what we experience can be incorporated into or uses previous knowledge networks in some form. Previous knowledge in form of a cognitive map can facilitate knowledge acquisition and will influence how we learn new spatial information. Here, we developed a new spatial navigation task where food locations are learned in a large, gangway maze to test how mice learn a large spatial map over a longer time period—the HexMaze. Analyzing performance across sessions as well as on specific trials, we can show simple memory effects as well as multiple effects of previous knowledge of the map accelerating both online learning and performance increases over offline periods when incorporating new information. We could identify the following three main phases: (1) learning the initial goal location; (2) faster learning after 2 weeks when learning a new goal location; and then (3) the ability to express one-session learning, leading to long-term memory effect after 12 weeks. Importantly, we are the first to show that buildup of a spatial map is dependent on how much time passes, not how often the animal is trained.

Durable memories and efficient neural coding through mnemonic training using the method of loci

Mnemonic techniques, such as the method of loci, can powerfully boost memory. We compared memory athletes ranked among the world's top 50 in memory sports to mnemonics-naïve controls. In a second study, participants completed a 6-week memory training, working memory training, or no intervention. Behaviorally, memory training enhanced durable, longer-lasting memories. Functional magnetic resonance imaging during encoding and recognition revealed task-based activation decreases in lateral prefrontal, as well as in parahippocampal and retrosplenial cortices in both memory athletes and participants after memory training, partly associated with better performance after 4 months. This was complemented by hippocampal-neocortical coupling during consolidation, which was stronger the more durable memories participants formed. Our findings advance knowledge on how mnemonic training boosts durable memory formation through decreased task-based activation and increased consolidation thereafter. This is in line with conceptual accounts of neural efficiency and highlights a complex interplay of neural processes critical for extraordinary memory.

Midbrain circuits of novelty processing

Novelty triggers an increase in orienting behavior that is critical to evaluate the potential salience of unknown events. As novelty becomes familiar upon repeated encounters, this increase in response rapidly habituates as a form of behavioral adaptation underlying goal-directed behaviors. Many neurodevelopmental, psychiatric and neurodegenerative disorders are associated with abnormal responses to novelty and/or familiarity, although the neuronal circuits and cellular/molecular mechanisms underlying these natural behaviors in the healthy brain are largely unknown, as is the maladaptive processes that occur to induce impairment of novelty signaling in diseased brains. In rodents, the development of cutting-edge tools that allow for measurements of real time activity dynamics in selectively identified neuronal ensembles by gene expression signatures is beginning to provide advances in understanding the neural bases of the novelty response. Accumulating evidence indicate that midbrain circuits, the majority of which linked to dopamine transmission, promote exploratory assessments and guide approach/avoidance behaviors to different types of novelty via specific projection sites. The present review article focuses on midbrain circuit analysis relevant to novelty processing and habituation with familiarity.

The power of children's sleep - Improved declarative memory consolidation in children compared with adults

Post-learning slow wave sleep (SWS) is known to support declarative memory consolidation. As SWS is more abundant in young population, we suggested that sleep-dependent memory consolidation processes could occur at a faster pace in school-aged children. After learning new associations between non-objects and their functions, retrieval performance was tested in 30 children (7–12 years) and 34 adults (20–30 years) during an immediate (IR) and a delayed retrieval (DR) session separated by either a Sleep or a Wake condition. Sleep led to stabilized memory retrieval performance only in children, not in adults, whereas no age-related difference was observed after a similar period of wakefulness. Hence, our results suggest more efficient sleep-dependent declarative memory consolidation processes in children compared with adults, an effect potentially ascribed to more abundant and deeper SWS during childhood.

Muscarinic-Dependent miR-182 and QR2 Expression Regulation in the Anterior Insula Enables Novel Taste Learning

In a similar manner to other learning paradigms, intact muscarinic acetylcholine receptor (mAChR) neurotransmission or protein synthesis regulation in the anterior insular cortex (aIC) is necessary for appetitive taste learning. Here we describe a parallel local molecular pathway, where GABA_A receptor control of mAChR activation causes upregulation of miRNA-182 and quinone reductase 2 (QR2) mRNA destabilization in the rodent aIC. Damage to long-term memory by prevention of this process, with the use of mAChR antagonist scopolamine before novel taste learning, can be rescued by local QR2 inhibition, demonstrating that QR2 acts downstream of local muscarinic activation. Furthermore, we prove for the first time the presence of endogenous QR2 cofactors in the brain, establishing QR2 as a functional reductase there. In turn, we show that QR2 activity causes the generation of reactive oxygen species, leading to modulation in Kv2.1 redox state. QR2 expression reduction therefore is a previously unaccounted mode of mAChR-mediated inflammation reduction, and thus adds QR2 to the cadre of redox modulators in the brain. The concomitant reduction in QR2 activity during memory consolidation suggests a complementary mechanism to the well established molecular processes of this phase, by which the cortex gleans important information from general sensory stimuli. This places QR2 as a promising new target to tackle neurodegenerative inflammation and the associated impediment of novel memory formation in diseases such as Alzheimer’s disease.

How to optimize knowledge construction in the brain

Well-structured knowledge allows us to quickly understand the world around us and make informed decisions to adequately control behavior. Knowledge structures, or schemas, are presumed to aid memory encoding and consolidation of new experiences so we cannot only remember the past, but also guide behavior in the present and predict the future. However, very strong schemas can also lead to unwanted side effects such as false memories and misconceptions. To overcome this overreliance on a schema, we should aim to create robust schemas that are on the one hand strong enough to help to remember and predict, but also malleable enough to avoid such undesirable side effects. This raises the question as to whether there are ways to deliberately influence knowledge construction processes, with the goal to reach such optimally balanced schemas. Here, we will discuss how the mnemonic processes in our brains build long-term knowledge and, more specifically, how different phases of memory formation (encoding, consolidation, retrieval, and reconsolidation) contribute to this schema build-up. We finally provide ways how to best keep a balance between generalized semantic and detailed episodic memories, which can prove very useful in, e.g., educational settings.

Transcranial Magnetic Stimulation of the Medial Prefrontal Cortex Decreases Emotional Memory Schemas

Mood-congruent memory bias is a critical characteristic of depression, but the underlying neural mechanism is largely unknown. Negative memory schemas might enhance encoding and consolidation of negative experiences, thereby contributing to the genesis and perpetuation of depressive pathology. To investigate this relationship, we aimed to perturb medial prefrontal cortex (mPFC) processing, using neuronavigated transcranial magnetic stimulation (TMS) targeting the mPFC. Forty healthy volunteers first underwent a negative mood induction to activate negative schema processing after which they received either active inhibitory (N = 20) or control (N = 20) stimulation to the mPFC. Then, all participants performed the encoding of an emotional false memory task. Recall and recognition performance was tested the following morning. Polysomnographic data were recorded continuously during the night before and after encoding. We observed a significantly lower false recognition of negative critical lures following mPFC inhibition, but no differences in veridical memory. These findings were supported by reaction time data, showing a relative slower response to negative compared with positive critical lures. The current findings support previous causal evidence for a role of the mPFC in schema memory processing and further suggest a role of the mPFC in memory bias.

Naïve to expert: Considering the role of previous knowledge in memory

In humans, most of our new memories are in some way or another related to what we have already experienced. However, in memory research, especially in non-human animal research, subjects are often mostly naïve to the world. But we know that previous knowledge will change how memories are processed and which brain areas are critical at which time point. Each process from encoding, consolidation, to memory retrieval will be affected. Here, we summarise previous knowledge effects on the neurobiology of memory in both humans and non-human animals, with a special focus on schemas - associative network structures. Furthermore, we propose a new theory on how there may be a continuous gradient from naïve to expert, which would modulate the importance and role of brain areas, such as the hippocampus and prefrontal cortex.

Prior Knowledge Predicts Early Consolidation in Second Language Learning

Language learning occurs in distinct phases. Whereas some improvement is evident during training, offline memory consolidation processes that take place after the end of training play an important role in learning of linguistic information. The timing of offline consolidation is thought to depend on the type of task, with generalization of implicit knowledge suggested to take more time and sleep to consolidate. The current study aims to investigate individual differences in the timing of consolidation following learning of morphological inflections in a novel language in typical adults. Participants learned to make plural inflections in an artificial language, where inflection was based on morpho-phonological regularities. Participants were trained in the evening, and consolidation was measured after two intervals: 12 h (one night) and 36 h (two nights) post training. We measured both inflection of trained items, which may rely on item-specific learning, and generalization to new untrained items, which requires extraction of morpho-phonological regularities. The results for both trained and un-trained items showed two patterns of consolidation: early versus late, that is while some participants improved during the first night, others, who deteriorated in performance during the first night, improved in the later consolidation interval. Importantly, phonological awareness in L1 predicted early consolidation for trained items. Furthermore, there was no association between participants' consolidation trajectory in trained and untrained items. Our results suggest that consolidation timing depends on the interaction between task characteristics and individual abilities. Moreover, the results show that prior meta-linguistic knowledge predicts the quality of early consolidation processes. These results are consistent with studies in rodents and humans, showing that prior knowledge accelerates consolidation of newly learnt episodic memory. Finally, the rate of consolidation across exposures to the language might explain some of the variability found in the attained level of second language proficiency.

From Conditioning to Emotion: Translating Animal Models of Learning to Human Psychopathology

Emotional responses are not static but change as a consequence of learning. Organisms adapt to emotional events and these adaptations influence the way we think, behave, and feel when we encounter similar situations in the future. Integrating recent work from rodent models and research on human psychopathology, this article lays out a model describing how affective events cause learning and can lead to anxiety and depression: affective events are linked to conditioned stimuli and contexts. Affective experiences entrain oscillatory synchrony across distributed neural circuits, including the prefrontal cortex, hippocampus, amygdala, and nucleus accumbens, which form associations that constitute the basis of emotional memories. Consolidation of these experiences appears to be supported by replay in the hippocampus—a process by which hippocampal firing patterns recreate the firing pattern that occurred previously. Generalization of learning occurs to never before experienced contexts when associations form across distinct but related conditioned stimuli. The process of generalization, which requires cortical structures, can cause memories to become abstracted. During abstraction, the latent, overlapping features of the learned associations remain and result in the formation of schemas. Schemas are adaptive because they facilitate the rapid processing of conditioned stimuli and prime behavioral, cognitive, and affective responses that are the manifestations of the accumulation of an individual’s conditioned experiences. However, schemas can be maladaptive when the generalization of aversive emotional responses are applied to stimuli and contexts in which affective reactions are unnecessary. I describe how this process can lead to not only mood and anxiety disorders but also psychotherapeutic treatment.

The impact of sleep deprivation on declarative memory

Sleep plays a crucial role in memory stabilization and integration, yet many people obtain insufficient sleep. This review assesses what is known about the level of sleep deprivation that leads to impairments during encoding, consolidation and retrieval of declarative memories, and what can be determined about the underlying neurophysiological processes. Neuroimaging studies that deprived sleep after learning have provided some of the most compelling evidence for sleep's role in the long-term reorganization of memories in the brain (systems consolidation). However, the behavioral consequences of losing sleep after learning-shown by increased forgetting-appear to recover over time and are unaffected by more common forms of partial sleep restriction across several nights. The capacity to encode new memories is the most vulnerable to sleep loss, since long-term deficits have been observed after total and partial sleep deprivation, while retrieval mechanisms are relatively unaffected. The negative impact of sleep loss on memory has been explored extensively after a night of total sleep deprivation, but further research is needed on the consequences of partial sleep loss over many days so that impairments may be generalized to more common forms of sleep loss.

In memoriam: John Lisman - commentaries on CaMKII as a memory molecule

Shortly before he died in October 2017, John Lisman submitted an invited review to Molecular Brain on 'Criteria for identifying the molecular basis of the engram (CaMKII, PKMζ)'. John had no opportunity to read the referees' comments, and as a mark of the regard in which he was held by the neuroscience community the Editors decided to publish his review as submitted. This obituary takes the form of a series of commentaries on Lisman's review. At the same time we are publishing as a separate article a longer response by Todd Sacktor and André Fenton entitled 'What does LTP tell us about the roles of CaMKII and PKMζ in memory?' which presents the case for a rival memory molecule, PKMζ.