Detecting recollection: Human evaluators can successfully assess the veracity of others' memories.

Humans have the highly adaptive ability to learn from others' memories. However, because memories are prone to errors, in order for others' memories to be a valuable source of information, we need to assess their veracity. Previous studies have shown that linguistic information conveyed in self-reported justifications can be used to train a machine-learner to distinguish true from false memories. But can humans also perform this task, and if so, do they do so in the same way the machine-learner does? Participants were presented with justifications corresponding to Hits and False Alarms and were asked to directly assess whether the witness's recognition was correct or incorrect. In addition, participants assessed justifications' recollective qualities: their vividness, specificity, and the degree of confidence they conveyed. Results show that human evaluators can discriminate Hits from False Alarms above chance levels, based on the justifications provided per item. Their performance was on par with the machine learner. Furthermore, through assessment of the perceived recollective qualities of justifications, participants were able to glean more information from the justifications than they used in their own direct decisions and than the machine learner did.

Intentional forgetting needs intentional remembering.

Episodic memories may become suppressed, both incidentally and intentionally. Incidental suppression is a result of a competition induced by interfering items or responses. In contrast, intentional suppression is said to result from conscious attempts to suppress certain memory items, and should thus not depend on competition induced by interfering items or responses. However, intentional suppression is typically engendered using the Think/No-Think paradigm, in which participants are required to retrieve some target items and to suppress others. Therefore, rather than intentional suppression, forgetting in this paradigm may reflect incidental suppression of No-Think items induced by interference via prior retrieval of the Think items. To distinguish between these possibilities, we tested participants (n = 40) using an adjusted suppression paradigm, which did not include the Think condition (ExcludeThink paradigm) and compared it with the standard suppression paradigm (IncludeThink paradigm; n = 39) which included a think condition. We found that suppression was not observed in the ExcludeThink paradigm, but only in the IncludeThink paradigm. These results indicate that interference via prior retrieval is necessary to induce forgetting. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Retrieval of temporal structure at recall can occur automatically.

Temporal-structure, namely, the order in which events unfold over time, is one of the fundamental principles of episodic memory organization. A seminal empirical demonstration of the prominence of temporal structure in memory organization is the Temporal Contiguity Effect (TCE), whereby the proximity between two items at encoding predicts the likelihood of those two items being retrieved consecutively during recall. Recent studies have found that TCE occurs under a wide variety of conditions in which strategic control processes at encoding are reduced or even eliminated. This suggests that the encoding of temporal structure occurs automatically. Extending these findings, in the current study we asked whether the retrieval of temporal structure, as reflected by indices of the TCE, is influenced by strategic control processes at retrieval. To manipulate participants' ability to rely on strategic control processes, we compared standard recall performance (Full Attention condition) to a condition in which attention was divided between recall and a concurrent task (Divided Attention condition), which has been shown to disrupt such control processes. Across two experiments-one with standard encoding conditions and one with continual distraction during encoding-we found no differences in any index of the TCE between the two conditions. These results are all the more striking considering that in both experiments, dividing attention negatively affected overall recall performance compared to the Full Attention condition. Thus, while recall performance is reduced when disrupting strategic processes, the ability to use temporal structure to drive recall is not affected.

Contextual reinstatement affects semantic organization.

The Context Dependency Effect is the well-established finding in which memory performance is enhanced under conditions in which the encoding and retrieval contexts overlap (i.e., Same-Context) and diminished when the overlap between encoding and retrieval contexts is low (i.e., Different-Context). Despite much research on context-dependent memory, most prior work examined only mean performance levels. The current experiment examined the influence of context change, manipulated by using three different pieces of background music, on semantic organization during free recall. Recall driven by semantic organization captures an important, ecologically valid aspect of memory retrieval: because narratives of real-life events are typically comprised of semantically related concepts (e.g., "sea," "bathing suit," and "sand" when recalling a trip to the beach), their recall is likely driven by semantic organization. Participants in the current study were tested in the same or different context as the material was learned. The results showed that although the mean number of correctly recalled items was numerically greater in the Same-Context condition compared to the Different-Context condition, the Context Dependency Effect was not significant. In contrast, however, semantic clustering-an established measure of semantic organization-was greater in the Different-Context condition compared to the Same-Context condition. Together, these results suggest that when contextual cues at recall are relatively meager, participants instead use semantic information as cues to guide memory retrieval. In line with previous findings, temporal organization, patterns of errors, and serial position analyses showed no differences between the two context conditions. The present experiment provides novel evidence on how external context change affects recall organization.

It's about time: Delay-dependent forgetting of item- and contextual-information.

Once fiercely rejected, the notion of delay-dependent forgetting from long-term memory has recently resurfaced. By this notion, the duration of the study-test delay predicts the magnitude of memory degradation. Our Representation Theory of Forgetting adopts the notion of delay-dependent forgetting, alongside interference due to similarity of representations as an additional cause of forgetting-rather than its sole cause, as has been largely argued in the past. This theory maintains that the causes of forgetting depend on the underlying memory representations. Because hippocampus-based memory representations are relatively distinct from one another, by the virtue of being associated with distinct contexts, they are not as likely as non-hippocampus representations to be forgotten due to interference from similar memories. Instead, as neurobiological evidence suggests, these representations may be forgotten over the passage of time. Thus, contextual-information should be particularly sensitive to delay-dependent forgetting in comparison to item-information. In the current study we tested this hypothesis by comparing the effects of short study-test delay (~2 min) to long delay (~15 min) on forgetting. In three experiments using three different memory paradigms, we obtained various measures of item- and contextual-information. Results converged to support our predictions: whereas most measures of contextual-information showed forgetting over time, item-information was less affected by delay and, at times, was not affected at all. Finally, different patterns of time-dependent forgetting of contextual-information were observed in recall and recognition, in line with the different roles of context in these tests. Our results provide novel evidence for the specific effects of delay on hippocampus-based, contextual memory representations.

Explicit Sequence Memory in Recall of Temporally-structured Episodes.

The order in which events unfold over time is an important scaffold aiding recollection. This study asks whether explicit order memory is enhanced for items sharing similar internally-driven temporal contexts. To tap internally-driven temporal context, we capitalized on the Temporal Contiguity Effect whereby recollection of one item promotes recall of adjacently-encoded items. We compared pairs encoded and retrieved contiguously (cont-enc-ret), whose items share internally-driven temporal contexts, to pairs retrieved, but not encoded, contiguously (cont-ret) and to pairs encoded, but not retrieved, contiguously (cont-enc). Cont-enc-ret pairs exhibited superior relative order over cont-ret pairs, supporting accounts emphasizing shared temporal context as opposed to temporal distinctiveness in driving sequence memory. No difference was found in absolute order between the pair types, in line with theories suggesting a dissociation between relative and absolute order. Additionally, cont-enc-ret and cont-enc pairs exhibited equivalent relative order, supporting the role of encoding as opposed to retrieval in the enhancement of relative order. Finally, cont-enc-ret pairs were perceived as closer than cont-enc pairs, supporting the claim that cont-enc-ret pairs constitute part of a temporally-coherent episode. Together, these results implicate internally-driven temporal context in the formation of temporally-structured episodes that enhances sequence memory of the items within the episode.

Fluency: A trigger of familiarity for relational representations?

According to Bastin et al.'s integrative memory model, familiarity may be attributed to both entity representations and relational representations. However, the model does not specify what triggers familiarity for relational representations. I argue that fluency is a key player in the attribution of familiarity regardless of the type of representation. Two lines of evidence are reviewed in support of my claim.

Recalling the firedog: Individual differences in associative memory for unitized and nonunitized associations among older adults.

Memory deficits in aging are characterized by impaired hippocampus-mediated relational binding-the formation of links between items in memory. By reducing reliance on relational binding, unitization of two items into one concept enhances associative recognition among older adults. Can a similar enhancement be obtained when probing memory with recall? This question has yet to be examined, because recall has been assumed to rely predominantly on relational binding. Inspired by recent evidence challenging this assumption, we investigated individual differences in older adults' recall of unitized and nonunitized associations. Compared with successfully aging individuals, older adults with mild memory deficits, typically mediated by the hippocampus, were impaired in recall of paired-associates in a task which relies on relational binding (study: "PLAY-TUNNEL"; test: PLAY-T?). In stark contrast, the two groups showed similar performance when items were unitized into a novel compound word (study: "LOVEGIGGLE"; test: LOVEG?). Thus, boosting nonrelational aspects of recall enhances associative memory among aging individuals with subtle memory impairments to comparable levels as successfully aging older adults.

Scale-invariant Characteristics of Forgetting: Toward a Unifying Account of Hippocampal Forgetting across Short and Long Timescales.

After over 100 years of relative silence in the cognitive literature, recent advances in the study of the neural underpinnings of memory-specifically, the hippocampus-have led to a resurgence of interest in the topic of forgetting. This review draws a theoretically driven picture of the effects of time on forgetting of hippocampus-dependent memories. We review evidence indicating that time-dependent forgetting across short and long timescales is reflected in progressive degradation of hippocampal-dependent relational information. This evidence provides an important extension to a growing body of research accumulated in recent years, showing that-in contrast to the once prevailing view that the hippocampus is exclusively involved in memory and forgetting over long timescales-the role of the hippocampus also extends to memory and forgetting over short timescales. Thus, we maintain that similar rules govern not only remembering but also forgetting of hippocampus-dependent information over short and long timescales.

Overlap between hippocampal pre-encoding and encoding patterns supports episodic memory.

It is well-established that whether the information will be remembered or not depends on the extent to which the learning context is reinstated during post-encoding rest and/or at retrieval. It has yet to be determined, however, if the fundamental importance of contextual reinstatement to memory extends to periods of spontaneous neurocognitive activity prior to learning. We thus asked whether memory performance can be predicted by the extent to which spontaneous pre-encoding neural patterns resemble patterns elicited during encoding. Individuals studied and retrieved lists of words while undergoing fMRI-scanning. Multivoxel hippocampal patterns during resting periods prior to encoding resembled hippocampal patterns at encoding most strongly for items that were subsequently remembered. Furthermore, across subjects, the magnitude of similarity correlated with a behavioral measure of episodic recall. The results indicate that the neural context before learning is an important determinant of memory.

A Remember/Know Examination of Free-recall Reveals Dissociative Roles of Item- and Context-Information over Time.

It is well-established that the ability to freely recall information is driven by the extent to which the context at encoding is reinstated at retrieval. Still, when asked to judge the subjective quality of one's memories giving Remember/Know (R/K) judgments, people tend to classify a substantial proportion of recalls as being devoid of context. We suggest that R- and K-recalls differ with regard to their reliance on context- and item-information, with R-recalls driven primarily by contextual-information (e.g., associations evoked by the study-items) and K-recalls driven primarily by information pertaining to the items (e.g., semantic information). Memory was tested both immediately after study and in a final free-recall test conducted ~20 minutes after encoding-a timescale which is akin to real-life events. In line with our predictions, as compared to K-recalls, R-recalls show stronger contextual effects, but similarly strong item-related effects over these timescales. Furthermore, drawing on theories regarding the forgetting of item- and contextual information, we hypothesized and found that R- and K-recalls are differentially affected by the passage of time. Our findings provide several converging pieces of evidence for differential roles of item and contextual information in driving recall and thus highlight the need to extend longstanding theories of free-recall to account for cases in which recall relies less on context.

Forgetting Patterns Differentiate Between Two Forms of Memory Representation.

For decades, there has been controversy about whether forgetting is caused by decay over time or by interference from irrelevant information. We suggest that forgetting occurs because of decay or interference, depending on the memory representation. Recollection-based memories, supported by the hippocampus, are represented in orthogonal patterns and are therefore relatively resistant to interference from one another. Decay should be a major source of their forgetting. By contrast, familiarity-based memories, supported by extrahippocampal structures, are not represented in orthogonal patterns and are therefore sensitive to interference. In a study in which we manipulated the postencoding task-interference level and the length of the delay between study and testing, we provide direct evidence in support of our representation theory of forgetting. Recollection and familiarity were measured using the remember/know procedure. We show that the causes of forgetting depend on the nature of the underlying memory representation, which places the century-old puzzle of forgetting in a coherent framework.

When items 'pop into mind': variability in temporal-context reinstatement in free-recall.

It is well established that performance in free-recall is mediated by an individual's ability to reinstate the study-context during retrieval. This notion is supported by an abundance of evidence and is reflected in prominent models of memory. Introspectively, however, we often feel that a memory just 'pops into mind' and its recall is not accompanied by contextual detail. Here we ask whether this introspection is honored by the cognitive system. Namely, do items one recalls vary in the extent to which their contexts are reinstated? Previous research has provided evidence that indeed recall of some items relies on only little, if any, contextual reinstatement. This evidence pertains to one aspect of context: the concurrent, static encoding context of items, as tapped by the source-memory paradigm. However, because real-life events are strongly embedded in time, it is crucial to also investigate the dynamic, temporal aspects of context. To do so, we capitalized on one of the seminal findings linking recall with temporal-context: the temporal-contiguity effect, whereby the closer two items at study, the higher the probability that they will be retrieved one after the other during test. Using the Remember/Know paradigm, we show that in free-recall, 'Remember' retrievals, which are supposedly accompanied by contextual reinstatement, produce a larger temporal-contiguity effect as compared to 'Know' retrievals. Furthermore, 'Know' retrievals are more likely to be followed by retrieval errors (e.g., intrusions) than 'Remember' retrievals. These findings provide evidence that recalled items vary in the degree to which their temporal-context is reinstated.

How we forget may depend on how we remember.

Recent developments reveal that memories relying on the hippocampus are relatively resistant to interference, but sensitive to decay. The hippocampus is vital to recollection, a form of memory involving reinstatement of a studied item within its spatial-temporal context. An additional form of memory known as familiarity does not involve contextual reinstatement, but a feeling of acquaintance with the studied items. Familiarity depends more on extrahippocampal structures that do not have the properties promoting resistance to interference. These notions led to the novel hypothesis that the causes of forgetting depend on the memories' nature: memories depending on recollection are more vulnerable to decay than interference, whereas for memories depending on familiarity, the reverse is true. This review provides comprehensive evidence for this hypothesis.

Encoding-related brain activity dissociates between the recollective processes underlying successful recall and recognition: a subsequent-memory study.

The subsequent-memory (SM) paradigm uncovers brain mechanisms that are associated with mnemonic activity during encoding by measuring participants' neural activity during encoding and classifying the encoding trials according to performance in the subsequent retrieval phase. The majority of these studies have converged on the notion that the mechanism supporting recognition is mediated by familiarity and recollection. The process of recollection is often assumed to be a recall-like process, implying that the active search for the memory trace is similar, if not identical, for recall and recognition. Here we challenge this assumption and hypothesize - based on previous findings obtained in our lab - that the recollective processes underlying recall and recognition might show dissociative patterns of encoding-related brain activity. To this end, our design controlled for familiarity, thereby focusing on contextual, recollective processes. We found evidence for dissociative neurocognitive encoding mechanisms supporting subsequent-recall and subsequent-recognition. Specifically, the contrast of subsequent-recognition versus subsequent-recall revealed activation in the Parahippocampal cortex (PHc) and the posterior hippocampus--regions associated with contextual processing. Implications of our findings and their relation to current cognitive models of recollection are discussed.

Putting Humpty together and pulling him apart: accessing and unbinding the hippocampal item-context engram.

A remarkable act of memory entails binding different forms of information. We focus on the timeless question of how the bound engram is accessed such that its component features-item and context-are extracted. To shed light on this question, we investigate the dynamics between brain structures that together mediate the binding and extraction of item and context. Converging evidence has implicated the Parahippocampal cortex (PHc) in contextual processing, the Perirhinal cortex (PRc) in item processing, and the hippocampus in item-context binding. Effective connectivity analysis was conducted on fMRI data gathered during retrieval on tests that differ with regard to the to-be-extracted information. Results revealed that recall is initiated by context-related PHc activity, followed by hippocampal item-context engram activation, and completed with retrieval of the study-item by the PRc. The reverse path was found for recognition. We thus provide novel evidence for dissociative patterns of item-context unbinding during retrieval.

Event congruency and episodic encoding: a developmental fMRI study.

A known contributor to adults' superior memory performance compared to children is their differential reliance on an existing knowledge base. Compared to those of adults, children's semantic networks are less accessible and less established, a difference that is also thought to contribute to children's relative resistance to semantically related false alarms. Using the "congruency effect" - the memory advantage of congruity, we manipulated the encoded stimuli in the present experiment such that the use of the knowledge base at encoding was more - or less - accessible in both children and adults. While being scanned, 15 children (ages 8-11) and 18 young adults saw printed noun/color combinations and were asked to indicate whether each combination existed in nature. A subsequent recognition test was administered outside of the scanner. Behaviorally, although overall memory was higher in the adult group compared to the children, both age groups showed the congruency effect to the same extent. A comparison of the neural substrates supporting the congruency effect between adults and children revealed that whereas adults recruited regions primarily associated with semantic-conceptual processing (e.g., the left PFC and parietal and occipito-temporal cortices), children recruited regions earlier in the processing stream (e.g., the right occipital cortex). This evidence supports the hypothesis that early in development, episodic encoding depends more on perceptual systems, whereas top-down frontal control and parietal structures become more prominent in the encoding process with age. This developmental switch contributes to adults' superior memory performance but may render adults more vulnerable to committing semantically based errors.

Cooperation between the hippocampus and the striatum during episodic encoding.

The hippocampus and the striatum are thought to play distinct roles in learning and memory, each supporting an independent memory system. A fundamental question is whether, and how, these systems interact to jointly contribute to learning and memory. In particular, it remains unknown whether the striatum contributes selectively to implicit, habitual learning, or whether the striatum may also contribute to long-term episodic memory. Here, we show with functional magnetic resonance imaging (fMRI) that the hippocampus and the striatum interact cooperatively to support episodic memory formation. Participants were scanned during a memory encoding paradigm and, subsequently, were tested for memory of encoded items. fMRI data revealed that successful memory was associated with greater activity in both the hippocampus and the striatum (putamen) during encoding. Furthermore, activity in the hippocampus and the striatum was correlated within subjects for items that were later remembered, but not for items that were forgotten. Finally, across subjects, the strength of the correlation between the hippocampus and the striatum predicted memory success. These findings provide novel evidence for contributions of both the striatum and the hippocampus to successful episodic encoding and for a cooperative interaction between them.