Search

Schemas are rich and complex knowledge structures about the typical unfolding of events in a context; for example, a schema of a dinner at a restaurant. In this Perspective, we suggest that reinforcement learning (RL), a computational theory of learning the structure of the world and relevant goal-oriented behaviour, underlies schema learning. We synthesize literature about schemas and RL to offer that three RL principles might govern the learning of schemas: learning via prediction errors, constructing hierarchical knowledge using hierarchical RL, and dimensionality reduction through learning a simplified and abstract representation of the world. We then suggest that the orbitomedial prefrontal cortex is involved in both schemas and RL due to its involvement in dimensionality reduction and in guiding memory reactivation through interactions with posterior brain regions. Last, we hypothesize that the amount of dimensionality reduction might underlie gradients of involvement along the ventral-dorsal and posterior-anterior axes of the orbitomedial prefrontal cortex. More specific and detailed representations might engage the ventral and posterior parts, whereas abstraction might shift representations towards the dorsal and anterior parts of the medial prefrontal cortex., Competing Interests: Competing interests: The authors declare no competing interests., (© 2025. Springer Nature Limited.)

According to the predictive processing framework, our brain constantly generates predictions based on past experiences and compares these predictions with incoming sensory information. When an event contradicts these predictions, it results in a prediction error (PE), which has been shown to enhance subsequent memory. However, the neural mechanisms underlying the influence of PEs on subsequent memory remain unclear. This study investigated the electrophysiological correlates during encoding and retrieval of events eliciting PEs. We employed a statistical learning task in which participants were presented with pairs of objects in sequence. Subsequently, while recording electroencephalography (EEG), we introduced PEs by replacing the second object of each pair with new objects and we then tested the participants' memory. Behaviorally, PEs did not enhance memory. During retrieval, we observed higher amplitudes in the recollection-related late positive component for violation items that were remembered compared to those that were forgotten. In contrast, no evidence for the presence of the FN400 component associated with familiarity was found. These results suggest that recollection, but not familiarity, plays a crucial role in the interplay between PE and memory. Contrary to our hypothesis, we did not observe a relationship between PEs and the P3 component during encoding. In conclusion, our study contributes to the growing body of knowledge concerning the intricate relationship between PEs and episodic memory. It sheds light on the underlying neural mechanisms involved and emphasizes the importance of recollection in this context., (© 2024 The Author(s). Psychophysiology published by Wiley Periodicals LLC on behalf of Society for Psychophysiological Research.)

Everyday life is composed of events organized by changes in contexts, with each event containing an unfolding sequence of occurrences. A major challenge facing our memory systems is how to integrate sequential occurrences within events while also maintaining their details and avoiding over-integration across different contexts. We asked if and how distinct hippocampal subfields come to hierarchically and, in parallel, represent both event context and subevent occurrences with learning. Female and male human participants viewed sequential events defined as sequences of objects superimposed on shared color frames while undergoing high-resolution fMRI. Importantly, these events were repeated to induce learning. Event segmentation, as indexed by increased reaction times at event boundaries, was observed in all repetitions. Temporal memory decisions were quicker for items from the same event compared to across different events, indicating that events shaped memory. With learning, hippocampal CA3 multivoxel activation patterns clustered to reflect the event context, with more clustering correlated with behavioral facilitation during event transitions. In contrast, in the dentate gyrus (DG), temporally proximal items that belonged to the same event became associated with more differentiated neural patterns. A computational model explained these results by dynamic inhibition in the DG. Additional similarity measures support the notion that CA3 clustered representations reflect shared voxel populations, while DG's distinct item representations reflect different voxel populations. These findings suggest an interplay between temporal differentiation in the DG and attractor dynamics in CA3. They advance our understanding of how knowledge is structured through integration and separation across time and context., (Copyright © 2024 the authors.)

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., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Introduction: Most hospitals and clinics utilize commercial grade displays for viewing wrist radiographs. There is no evidence regarding the role of the imaging display used to evaluate the radiographs. The aim of this study was to compare the rates of scaphoid fracture diagnosis by commercial grade and medical grade displays., Methods: Wrist radiographs of patients that had clinical signs of scaphoid fracture without findings on plain radiography (suspected scaphoid fractures) were retrospectively collected from ER department and interpreted for radiographic signs of fracture by four orthopedics seniors commercial grade and medical grade displays. The difference in fracture diagnosis rates were studied. Inter- and intra-observer variability were also studied., Results: Study population comprised of 175 high quality wrist radiographs were interpreted. Mean 48.25 (27%) scaphoid fractures were observed on commercial grade display compared to 66 (38.2%) on medical grade display ( p  = 0.076). The total inter-observer agreement could be defined as a moderate agreement (κ = 0.527, Accuracy = 0.77). Total agreement between all observers were observed in 86 (49.1%) cases compared to 89 (50.9%) cases when reviewing X-rays on commercial and medical displays, respectively., Discussion: The scaphoid fracture detection rate on medical grade display was not statistically higher compared to non-medical grade displays, but we did find a tendency toward medical grade display. We found that in a substantial number of cases, our observers recognize signs of fracture that were initially evaluated as "suspected fracture" by the ER physicians. As a pilot study, we found evidence that support the need for a prospective study designed to compare the observations to a gold standard modality, such as MRI. We believe utilizing medical grade displays can increase the rate of diagnosis in cases of clinically suspected scaphoid fractures and better manage the clinical scenario of a suspected scaphoid fracture., Competing Interests: There is no conflict of interest in this study., (© 2022 Published by Elsevier B.V. on behalf of Professor P K Surendran Memorial Education Foundation.)

When our experience violates our predictions, it is adaptive to update our knowledge to promote a more accurate representation of the world and facilitate future predictions. Theoretical models propose that these mnemonic prediction errors should be encoded into a distinct memory trace to prevent interference with previous, conflicting memories. We investigated this proposal by repeatedly exposing participants to pairs of sequentially presented objects (A → B), thus evoking expectations. Then, we violated participants' expectations by replacing the second object in the pairs with a novel object (A → C). The following item memory test required participants to discriminate between identical old items and similar lures, thus testing detailed and distinctive item memory representations. In two experiments, mnemonic prediction errors enhanced item memory: Participants correctly identified more old items as old when those items violated expectations during learning, compared with items that did not violate expectations. This memory enhancement for C items was only observed when participants later showed intact memory for the related A → B pairs, suggesting that strong predictions are required to facilitate memory for violations. Following up on this, a third experiment reduced prediction strength prior to violation and subsequently eliminated the memory advantage of violations. Interestingly, mnemonic prediction errors did not increase gist-based mistakes of identifying old items as similar lures or identifying similar lures as old. Enhanced item memory in the absence of gist-based mistakes suggests that violations enhanced memory for items' details, which could be mediated via distinct memory traces. Together, these results advance our knowledge of how mnemonic prediction errors promote memory formation., (© 2021 Bein et al.; Published by Cold Spring Harbor Laboratory Press.)

An adaptive memory system rarely learns information tabula rasa, but rather builds on prior knowledge to facilitate learning. How prior knowledge influences the neural representation of novel associations remains unknown. Here, participants associated pairs of faces in two conditions: a famous, highly familiar face with a novel face or two novel faces while undergoing fMRI. We examine multivoxel activity patterns corresponding to individual faces before and after learning. The activity patterns representing members of famous-novel pairs becomes separated in the hippocampus, that is, more distinct from one another through learning, in striking contrast to paired novel faces that become similar. In the left inferior frontal gyrus, however, prior knowledge leads to integration, and in a specific direction: the representation of the novel face becomes similar to that of the famous face after learning, suggesting assimilation of new into old memories. We propose that hippocampal separation might resolve interference between existing and newly learned information, allowing cortical assimilation. Thus, associative learning with versus without prior knowledge relies on radically different computations.

When our experience violates our predictions, it is adaptive to upregulate encoding of novel information, while down-weighting retrieval of erroneous memory predictions to promote an updated representation of the world. We asked whether mnemonic prediction errors promote hippocampal encoding versus retrieval states, as marked by distinct network connectivity between hippocampal subfields. During fMRI scanning, participants were cued to internally retrieve well-learned complex room-images and were then presented with either an identical or a modified image (0-4 changes). In the left hemisphere, we find that CA1-entorhinal connectivity increases, and CA1-CA3 connectivity decreases, with the number of changes. Further, in the left CA1, the similarity between activity patterns during cued-retrieval of the learned room and during the image is lower when the image includes changes, consistent with a prediction error signal in CA1. Our findings provide a mechanism by which mnemonic prediction errors may drive memory updating-by biasing hippocampal states.

Event Related Potentials (ERPs) are widely used to study category-selective EEG responses to visual stimuli, such as the face-selective N170 component. Typically, this is done by flashing stimuli at the point of static gaze fixation. While allowing for good experimental control, these paradigms ignore the dynamic role of eye-movements in natural vision. Fixation-related potentials (FRPs), obtained using simultaneous EEG and eye-tracking, overcome this limitation. Various studies have used FRPs to study processes such as lexical processing, target detection and attention allocation. The goal of this study was to carefully compare face-sensitive activity time-locked to an abrupt stimulus onset at fixation, with that time-locked to a self-generated fixation on a stimulus. Twelve participants participated in three experimental conditions: Free-viewing (FRPs), Cued-viewing (FRPs) and Control (ERPs). We used a multiple regression approach to disentangle overlapping activity components. Our results show that the N170 face-effect is evident for the first fixation on a stimulus, whether it follows a self-generated saccade or stimulus appearance at fixation point. The N170 face-effect has similar topography across viewing conditions, but there were major differences within each stimulus category. We ascribe these differences to an overlap of the fixation-related lambda response and the N170. We tested the plausibility of this account using dipole simulations. Finally, the N170 exhibits category-specific adaptation in free viewing. This study establishes the comparability of the free-viewing N170 face-effect with the classic event-related effect, while highlighting the importance of accounting for eye-movement related effects.

Like yin and yang, novelty and familiarity are typically described as separate-yet-complementary aspects of an experience, two ends of a single continuum. However, novelty and familiarity are also multifaceted. For instance, novelty can sometimes result in enhanced mnemonic performance, whereas at other times familiarity is better remembered. As previous investigations focused primarily on the experimental aspect of novelty, the mechanisms supporting conceptual novelty (the novel combination of two previously unrelated existing concepts) remain unclear. Importantly, conceptual novelty can be recognized as such only when compared with preexperimental familiar knowledge, regardless of experimental status. Here we applied a combined repetition suppression/subsequent memory fMRI paradigm, focusing on the conceptual aspect of novelty and familiarity as the subject matter. Conceptual novelty was characterized by sustained neural activity; familiarity, on the other hand, exhibited repetition effects in multiple cortical regions, a subset of which was modulated by successful encoding. Subsequent memory of novelty was associated only with activation differences in a distinct set of regions, including the hippocampus and medial cortical regions. These results suggest that conceptual novelty (a) does not (easily) trigger the repetition suppression phenomenon but requires sustained neural recruitment and (b) activates dedicated encoding mechanisms. Conceptual familiarity, in contrast, allows rapid neural processing that depends upon existing neural representations. Overall, these findings challenge the definition of novelty as a unitary concept. Furthermore, they bear important implications for research into the neural bases of knowledge representation and recognition memory.

A fundamental challenge in the study of learning and memory is to understand the role of existing knowledge in the encoding and retrieval of new episodic information. The importance of prior knowledge in memory is demonstrated in the congruency effect-the robust finding wherein participants display better memory for items that are compatible, rather than incompatible, with their pre-existing semantic knowledge. Despite its robustness, the mechanism underlying this effect is not well understood. In four studies, we provide evidence that demonstrates the privileged explanatory power of the elaboration-integration account over alternative hypotheses. Furthermore, we question the implicit assumption that the congruency effect pertains to the truthfulness/sensibility of a subject-predicate proposition, and show that congruency is a function of semantic relatedness between item and context words.

Prior knowledge is known to influence the encoding of new events. Specifically, recent theoretical frameworks suggest that positively correlated hippocampus (HC)-medial prefrontal cortex (mPFC) activity is involved in creating enduring traces of events inconsistent with our prior knowledge. Events that are consistent with our schemas are suggested to be encoded via mPFC-cortical interactions. Previous studies examined differences in functional connectivity between subsequently remembered and forgotten items, but the source of these differences was not addressed. Therefore, the involvement of the inter-regions functional connectivity in subsequent remembering or subsequent forgetting of events is unknown. In this study, in addition to probing for a remembered-forgotten difference in functional connectivity, we also examined how connectivity differed from baseline in each of the memory conditions. At encoding, the participants were presented with pairs of semantically related (schema-consistent) and semantically unrelated (schema-inconsistent) words. A surprise recognition test was administered, and a subsequent memory analysis evaluating potential interactions with the HC and mPFC was conducted. Consistent with the suggested frameworks, subsequent memory modulated HC-mPFC connectivity only in schema-inconsistent events. Importantly, the HC and mPFC were positively correlated with respect to subsequently remembered schema-inconsistent items, whereas the subsequently forgotten schema-inconsistent events did not differ from baseline. We also found that positively correlated activity of the mPFC with visual and parietal regions mediated subsequent memory of schema-inconsistent items. Therefore, inconsistent events may be encoded by a network of cortical and medial temporal lobe regions., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Recognition tests in which participants indicate whether they recognize items using binary yes/no response options have typically yielded "yes" responses at equal rates for unattended old items and new items. Because most responses to unattended stimuli in such tests are "no" responses, we reasoned that a closer examination of "no" responses might reveal memory for unattended items. We modified a classic paradigm to allow participants to indicate high and low levels of confidence in their responses. As in earlier studies, the overall proportion of "yes" responses did not differ between unattended old items and new items. However, there was a crossover effect in the "no" responses: More high-confidence "no" responses were given for new items than for unattended old items, whereas more low-confidence "no" responses were given for unattended old items than for new items. These results indicate explicit memory for unattended material presented under high perceptual load. Our findings suggest that the null effects obtained in previous studies may not have stemmed from failures of perception or memory, but rather may have been due to insufficiently sensitive memory assessment.