Concerns about confounds: False memory as an explanation for a hippocampus-supported implicit eye-movement-based relational memory effect

Steinkrauss and Slotnick (2024) propose that implicit eye-movement-based relational memory effects, predicted by hippocampal activity differences (Hannula & Ranganath, 2009), are due to an explicit false memory confound. However, the logic behind this claim is insufficiently fleshed out and alternative accounts of how false memory may have played out in this task were not considered. One such account would predict a pattern of results counter to the observed fMRI results, and another would be consistent with our original conclusions. These alternatives are described along with converging evidence from an additional fMRI study that was not considered by Steinkrauss and Slotnick.

Prefrontal neuronal ensembles link prior knowledge with novel actions during flexible action selection

We make decisions based on currently perceivable information or an internal model of the environment. The medial prefrontal cortex (mPFC) and its interaction with the hippocampus have been implicated in the latter, model-based decision-making; however, the underlying computational properties remain incompletely understood. We have examined mPFC spiking and hippocampal oscillatory activity while rats flexibly select new actions using a known associative structure of environmental cues and outcomes. During action selection, the mPFC reinstates representations of the associative structure. These awake reactivation events are accompanied by synchronous firings among neurons coding the associative structure and those coding actions. Moreover, their functional coupling is strengthened upon the reactivation events leading to adaptive actions. In contrast, only cue-coding neurons improve functional coupling during hippocampal sharp wave ripples. Thus, the lack of direct experience disconnects the mPFC from the hippocampus to independently form self-organized neuronal ensemble dynamics linking prior knowledge with novel actions.

Extended trajectory of spatial memory errors in typical and atypical development: The role of binding and precision

Spatial reconstruction, a method for evaluating how individuals remember the placement of objects, has traditionally been evaluated through the aggregate estimation of placement errors. However, this approach may obscure the nature of task errors. Specifically, recent data has suggested the importance of examining the precision of responses, as well as absolute performance on item-context bindings. In contrast to traditional analysis approaches based on the distance between the target and the reconstructed item, in this study we further explored three types of errors (swap error, global error, and local distance) that may all contribute to the distance, with particular emphasis on swap errors and local distance due to their associations with item-context bindings and memory precision, respectively. We examined these errors in children aged 3-18 years, making comparisons between children with typical development (TD) and children with Down syndrome (DS), a population with known memory challenges. As expected, older children outperformed younger children in terms of overall memory accuracy. Of importance is that we measured uneven maturational trajectories of memory abilities across the various error types. Specifically, both remembered locations (irrespective of object identity) and swap errors (object-location binding errors) align with the overall memory accuracy. Memory precision, as measured by local distance in simpler set size 2 trials, mirrored overall memory accuracy. However, for more complex set size 3 trials, local distance remained stable before age 8 and showed age-related change thereafter. The group with DS showed reduced precision compared to a TD matched group, and measures of precision, and to a lesser extent binding errors, correlated with standard neuropsychological outcomes. Overall, our study contributed to a fine-grained understanding of developing spatial memory ability in a large sample of typical developing children and a memory impaired population. These findings contribute to a growing body of research examining precision as a key factor in memory performance.

The "when" matters: Evidence from memory markers in the clinical continuum of Alzheimer's disease

OBJECTIVE

Cognitive assessment able to detect impairments in the early neuropathological stages of Alzheimer's disease (AD) is urgently needed. The visual short-term memory binding task (VSTMBT) and the Free and Cued Selective Reminding Test (FCSRT) have been recommended by the neurodegenerative disease working group as promising tests to aid in the early detection of AD. In this study, we investigated their complementary value across the clinical stages of the AD continuum.

METHOD

One hundred and seventeen older adults with subjective cognitive complaint (SCC), 79 with mild cognitive impairment (MCI), 31 patients with AD dementia (ADD), and 37 cognitively unimpaired (CU) subjects, underwent assessment with the VSTMBT and the picture version of the Spanish FCSRT.

RESULTS

After controlling for multiple comparisons, significant differences were found across groups. The VSTMBT was the only test that "marginally" differentiated between CU and SCC (d = 0.47, p = .052). Moreover, whereas the FCSRT showed a gradient (CU = SCC) > MCI > ADD, the VSTMBT gradient was CU > SCC > (MCI = ADD) suggesting that conjunctive binding deficits assessed by the latter may be sensitive to the very early stages of the disease.

CONCLUSIONS

Our results suggest that the VSTMBT and the FCSRT are sensitive to the clinical continuum of AD. Whereas the former detects changes in the early prodromal stages, the latter is more sensitive to the advanced prodromal stages of AD. These novel tests can aid in the early detection, monitor disease progression and response to treatment, and thus support drug development programs. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Integration of event experiences to build relational knowledge in the human brain

We investigated how the human brain integrates experiences of specific events to build general knowledge about typical event structure. We examined an episodic memory area important for temporal relations, anterior-lateral entorhinal cortex, and a semantic memory area important for action concepts, middle temporal gyrus, to understand how and when these areas contribute to these processes. Participants underwent functional magnetic resonance imaging while learning and recalling temporal relations among novel events over two sessions 1 week apart. Across distinct contexts, individual temporal relations among events could either be consistent or inconsistent with each other. Within each context, during the recall phase, we measured associative coding as the difference of multivoxel correlations among related vs unrelated pairs of events. Neural regions that form integrative representations should exhibit stronger associative coding in the consistent than the inconsistent contexts. We found evidence of integrative representations that emerged quickly in anterior-lateral entorhinal cortex (at session 1), and only subsequently in middle temporal gyrus, which showed a significant change across sessions. A complementary pattern of findings was seen with signatures during learning. This suggests that integrative representations are established early in anterior-lateral entorhinal cortex and may be a pathway to the later emergence of semantic knowledge in middle temporal gyrus.

Conscious awareness and memory systems in the brain

The term "memory" typically refers to conscious retrieval of events and experiences from our past, but experience can also change our behaviour without corresponding awareness of the learning process or the associated outcome. Based primarily on early neuropsychological work, theoretical perspectives have distinguished between conscious memory, said to depend critically on structures in the medial temporal lobe (MTL), and a collection of performance-based memories that do not. The most influential of these memory systems perspectives, the declarative memory theory, continues to be a mainstay of scientific work today despite mounting evidence suggesting that contributions of MTL structures go beyond the kinds or types of memory that can be explicitly reported. Consistent with these reports, more recent perspectives have focused increasingly on the processing operations supported by particular brain regions and the qualities or characteristics of resulting representations whether memory is expressed with or without awareness. These alternatives to the standard model generally converge on two key points. First, the hippocampus is critical for relational memory binding and representation even without awareness and, second, there may be little difference between some types of priming and explicit, familiarity-based recognition. Here, we examine the evolution of memory systems perspectives and critically evaluate scientific evidence that has challenged the status quo. Along the way, we highlight some of the challenges that researchers encounter in the context of this work, which can be contentious, and describe innovative methods that have been used to examine unconscious memory in the lab. This article is categorized under: Psychology > Memory Psychology > Theory and Methods Philosophy > Consciousness.

Influence of mild cognitive impairment and body mass index on white matter integrity assessed by diffusion tensor imaging

Mild cognitive impairment (MCI), a prodromal stage of Alzheimer's disease, is characterized by decreased memory and cognition, which are linked to degenerative changes in the brain. To assess whether white matter (WM) integrity is compromised in MCI, we collected diffusion-weighted images from 60 healthy older adults (OA) (69.16 ± 0.7) and 20 older adults with amnestic MCI (72.45 ± 1.9). WM integrity differences were examined using Tract-Based Spatial Statistics (TBSS). We hypothesized that those with MCI would have diminished WM integrity relative to OA. In a whole-brain comparison, those with MCI showed higher axial diffusivity in the splenium (SCC) and body of the corpus callosum (BCC), superior corona radiata (SCR), and the retrolenticular part of the internal capsule (RLIC) (p's < .05 TFCE-corrected). Additionally, significant between-group connectivity differences were observed using probabilistic tractography between the SCC, chosen from the TBSS results, and forceps major and minor (p-value's < .05). To further relate a physical health indicator to WM alterations, linear regression showed significant interactions between cognitive status and body mass index (BMI) on diffusivity outcome measures from probabilistic tractography (p-value-'s < .05). Additionally, we examined the association between relational memory, BMI, and WM integrity. WM integrity was positively associated with relational memory performance. These findings suggest that these regions may be more sensitive to early markers of neurodegenerative disease and health behaviors, suggesting that modifiable lifestyle factors may affect white matter integrity.

Relational memory weakness in autism despite the use of a controlled encoding task

Introduction

Recent work challenged past findings that documented relational memory impairments in autism. Previous studies often relied solely on explicit behavioral responses to assess relational memory integrity, but successful performance on behavioral tasks may rely on other cognitive abilities (e.g., executive functioning) that are impacted in some autistic individuals. Eye-tracking tasks do not require explicit behavioral responses, and, further, eye movements provide an indirect measure of memory. The current study examined whether memory-specific viewing patterns toward scenes differ between autistic and non-autistic individuals.

Methods

Using a long-term memory paradigm that equated for complexity between item and relational memory tasks, participants studied a series of scenes. Following the initial study phase, scenes were re-presented, accompanied by an orienting question that directed participants to attend to either features of an item (i.e., in the item condition) or spatial relationships between items (i.e., in the relational condition) that might be subsequently modified during test. At test, participants viewed scenes that were unchanged (i.e., repeated from study), scenes that underwent an "item" modification (an exemplar switch) or a "relational" modification (a location switch), and scenes that had not been presented before. Eye movements were recorded throughout.

Results

During study, there were no significant group differences in viewing directed to regions of scenes that might be manipulated at test, suggesting comparable processing of scene details during encoding. However, there was a group difference in explicit recognition accuracy for scenes that underwent a relational change. Marginal group differences in the expression of memory-based viewing effects during test for relational scenes were consistent with this behavioral outcome, particularly when analyses were limited to scenes recognized correctly with high confidence. Group differences were also evident in correlational analyses that examined the association between study phase viewing and recognition accuracy and between performance on the Picture Sequence Memory Test and recognition accuracy.

Discussion

Together, our findings suggest differences in the integrity of relational memory representations and/or in the relationships between subcomponents of memory in autism.

Dynamic interactions between memory and viewing behaviors: Insights from dyadic modeling of eye movements

Humans use eye movements to build visual memories. We investigated how the contributions of specific viewing behaviors to memory formation evolve over individual study epochs. We used dyadic modeling to explain performance on a spatial reconstruction task based on interactions among two gaze measures: (a) the entropy of the scanpath and (b) the frequency of item-to-item gaze transitions. To measure these interactions, our hypothesized model included causal pathways by which early-trial viewing behaviors impacted subsequent memory via downstream effects on later viewing. We found that lower scanpath entropy throughout the trial predicted better memory performance. By contrast, the effect of item-to-item transition frequency changed from negative to positive as the trial progressed. The model also revealed multiple pathways by which early-trial viewing dynamically altered late-trial viewing, thereby impacting memory indirectly. Finally, individual differences in scores on an independent measure of memory ability were found to predict viewing effectiveness, and viewing behaviors partially mediated the relation between memory ability and reconstruction accuracy. In a second experiment, the model showed a good fit for an independent dataset. These results highlight the dynamic nature of memory formation and suggest that the order in which eye movements occur can critically determine their effectiveness. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

What does the hippocampus do during working-memory tasks? A cognitive-neuropsychological perspective

In this commentary, we highlight the role of the hippocampus as a binding device that may explain its recruitment during associative working-memory paradigms. Furthermore, we argue that both functional neuroimaging research, as presented in Slotnick (this issue), and carefully designed lesion studies in patients with selective bilateral hippocampal damage are crucial for advancing our understanding of the neural structures and processing involved in human memory in general and disentangling the role of the hippocampus proper and other medial temporal lobe structures in working-memory function and long-term encoding specifically.

The Role of Relational Embeddedness in Enhancing Absorptive Capacity and Relational Performance of Internationalized SMEs: Evidence From Mainland China

The social network in the organizational learning process is a critical knowledge source to realize superior performance. The purpose of this study is to examine the relationship between relational memory, relational embeddedness, and absorptive capacity, and their impact on the relational performance of small and middle enterprises (SMEs). This study empirically verifies the research framework from 223 Chinese internationalized SMEs. The results confirm previous studies that indicate positive correlations among relational embeddedness, relational memory, and absorptive capacity. The results also indicate that relational embeddedness and relational memory have positive effects on relational performance. The findings show that relational memory plays a mediating role in the relationship between relational embeddedness, absorptive capacity, and relational performance.

Temporal order memory impairments in individuals with moderate-severe traumatic brain injury

INTRODUCTION

Temporal order memory is a core cognitive function that underlies much of our behavior. The ability to bind together information within and across events, and to reconstruct that sequence of information, critically relies upon the hippocampal relational memory system. Recent work has suggested traumatic brain injury (TBI) may particularly impact hippocampally mediated relational memory. However, it is currently unclear whether such deficits extend to temporal order memory, and whether deficits only arise at large memory loads. The present study assessed temporal order memory in individuals with chronic, moderate-severe TBI across multiple set sizes.

METHOD

Individuals with TBI and Neurotypical Comparison participants studied sequences of three to nine objects, one a time. At test, all items were re-presented in pseudorandom order, and participants indicated the temporal position (i.e., first, second, etc.) in which each object had appeared. Critically, we assessed both the frequency and the magnitude of errors (i.e., how far from its studied position was an item remembered).

RESULTS

Individuals with TBI were not impaired for the smallest set size, but showed significant impairments at 5+ items. Group differences in the error frequency did not increase further with larger set sizes, but group differences in error magnitude did increase with larger memory loads. Individuals with TBI showed spared performance for the first object of each list (primacy) but were impaired on the last object (recency), though error frequency was better for last compared to middle items.

CONCLUSIONS

Our findings demonstrate that TBI results in impaired temporal order memory for lists as small as five items, and that impairments are exacerbated with increasing memory loads. Assessments that test only small set sizes may be insufficient to detect these deficits. Further, these data highlight the importance of additional, sensitive measures in the assessment of cognitive impairments in TBI.

The Relational Trip Task, a novel ecological measure of relational memory: data from a schizophrenia sample

INTRODUCTION

Relational memory (RM) is severely impaired in schizophrenia. Unitisation can circumvent RM impairments in clinical populations as measured by the transverse-patterning (TP) task, a well-established measure of RM capacity. We compared memory performance on a new ecological RM measure, the Relational Trip Task (RTT), to that of TP at baseline and examined the effects of a unitisation intervention in RTT performance. RTT involves learning relational information of real-life stimuli, such as the relationship between people and places or objects.

METHODS

TP and RTT performances were examined in 45 individuals with schizophrenia. TP-impaired participants (n = 22) were randomised to either the intervention or an active control group. TP and RTT were administered again after unitisation training. Task validity and reliability were assessed. Intervention group's pre- and post-RTT accuracies were compared and contrasted to that in the control group.

RESULTS

RTT and TP were moderately correlated. TP non-learners had inferior performance in RTT at baseline. Improvement in RTT performance after unitisation training was observed in the intervention group; no pre-post improvement was observed in the control group.

CONCLUSION

RTT has an acceptable criterion validity and excellent alternate-form reliability. Unitisation seemed to be successfully generalized to support associations of real-life stimuli.

Attentional Measures of Memory in Typically Developing and Hypoxic-Ischemic Injured Infants

Hypoxic–ischemic injury (HII) at birth has been found to relate to differences in development, including decreased memory performance. The current study assessed recognition memory in 6- and 12-month-old HII infants and typically developing (TD) infants using two eye-tracking paradigms well suited to explore explicit memory processes early in life: visual paired comparison (VPC) and relational memory (RM). During the VPC, infants were familiarized to a face and then tested for their novelty preference immediately and after a two-minute delay. At 6 months, neither HII nor TD showed a VPC novelty preference at immediate delay, but at 12 months, both groups did; after the two-minute delay, no group showed a novelty preference. During RM, infants were presented with blocks containing a learning phase with three different scene–face pairs, and a test phase with one of the three scenes and all three faces appearing simultaneously. When there was no interference from other scene–face pairs between learning and test, 6-month-old TD showed evidence of an early novelty preference, but when there was interference, they revealed an early familiarity preference. For 12-month-old TD, some evidence for a novelty preference during RM was seen regardless of interference. Although HII and TD showed similar recognition memory on the VPC, when looking at RM, HII infants showed subtle differences in their attention to the familiar and novel faces as compared to their TD peers, suggesting that there might be subtle differences in the underlying memory processing mechanisms between HII and TD. More work is needed to understand how these attentional patterns might be predictive of later memory outcomes.

[The role of sleep in the relational memory processes]

Background and purpose

A growing body of evidence suggests that sleep plays an essential role in the consolidation of different memory systems, but less is known about the beneficial effect of sleep on relational memory processes and the recognition of emotional facial expressions, however, it is a fundamental cognitive skill in human everyday life. Thus, the study aims to investigate the effect of timing of learning and the role of sleep in relational memory processes.

Methods

84 young adults (average age: 22.36 (SD: 3.22), 21 male/63 female) participated in our study, divided into two groups: evening group and morning group indicating the time of learning. We used the face-name task to measure relational memory and facial expression recognition. There were two sessions for both groups: the immediate testing phase and the delayed retesting phase, separated by 24 hours.

Results

84 young adults (average age: 22.36 (SD: 3.22), 21 male/63 female) participated in our study, divided into two groups: evening group and morning group indicating the time of learning. We used the face-name task to measure relational memory and facial expression recognition. There were two sessions for both groups: the immediate testing phase and the delayed retesting phase, separated by 24 hours.

Conclusion

Our results suggest that the timing of learning and sleep plays an important role in the stabilizing process of memory representation to resist against forgetting.

Linking the Puzzle Pieces of the Past: A Study of Relational Memory in Children with Autism Spectrum Disorder

Our memories are made of detailed sensory information representing the puzzle pieces of our personal past. The type of memory integrating sensory features is referred to as relational memory. The main objective of this study was to investigate whether relational memory is affected in children with autism spectrum disorder (ASD) since altered relational memory may contribute to atypical episodic memory observed in ASD. We also examined the association between perceptual style and relational memory abilities. Children with ASD (n = 14) and typically developed (TD) children (n = 16, 9-15 years old) completed a memory task with three conditions: two single-feature conditions measuring memory for objects and locations, and one relational memory condition measuring memory for objects and their locations combined. The Children's embedded figures test was administered to measure perceptual style. The ASD group selected more incorrect stimuli (false alarms) than the TD group, resulting in a lower proportion of correctly recognized targets across all memory conditions. The ASD group did not display a more local perceptual style than the TD group. However, perceptual style was associated with improved memory abilities across conditions. Our findings indicate that the overall memory performance of children with ASD is less stable, leading them to more incorrect responses than TD children. This may be due to the executive demands of the memory tasks, rather than specific impairments in memory binding. Autism Res 2020, 13: 1959-1969. © 2020 International Society for Autism Research and Wiley Periodicals LLC LAY SUMMARY: The present study shows that children with autism have a less stable memory than typically developed children, which is reflected in a higher amount of incorrect memory responses. Overall, our results indicate that children with autism display difficulties in differentiating previously studied from novel information when solving both single-feature memory tasks and a relational memory task (requiring memory of combination of features). These difficulties may have implications for how children with autism remember episodes from their personal past.

Relational Memory at Short and Long Delays in Individuals With Moderate-Severe Traumatic Brain Injury

Memory deficits are a common and frequently-cited consequence of moderate-severe traumatic brain injury (TBI). However, we know less about how TBI influences relational memory, which allows the binding of the arbitrary elements of experience and the flexible use and recombination of relational representations in novel situations. Relational memory is of special interest for individuals with TBI, given the vulnerability of the hippocampus to injury mechanisms, as well as a growing body of literature establishing the role of relational memory in flexible and goal-directed behavior. In this study, participants with and without a history of moderate-severe TBI completed a continuous relational memory task for face-scene pairings. Participants with TBI exhibited a disruption in relational memory not only when tested after a delay, but also when tested with no experimenter-imposed delay after stimulus presentation. Further, canonical assessments of working and episodic memory did not correspond with performance on the face-scene task, suggesting that this task may tap into relational memory differently and with greater sensitivity than standardized memory assessments. These results highlight the need for rigorous assessment of relational memory in TBI, which is likely to detect deficits that have specific consequences for community reintegration and long-term functional outcomes.

Cross-Situational Statistical Learning of New Words Despite Bilateral Hippocampal Damage and Severe Amnesia

Word learning requires learners to bind together arbitrarily-related phonological, visual, and conceptual information. Prior work suggests that this binding can be robustly achieved via incidental cross-situational statistical exposure to words and referents. When cross-situational statistical learning (CSSL) is tested in the laboratory, there is no information on any given trial to identify the referent of a novel word. However, by tracking which objects co-occur with each word across trials, learners may acquire mappings through statistical association. While CSSL behavior is well-characterized, its brain correlates are not. The arbitrary nature of CSSL mappings suggests hippocampal involvement, but the incremental, statistical nature of the learning raises the possibility of neocortical or procedural learning systems. Prior studies have shown that neurological patients with hippocampal pathology have word-learning impairments, but this has not been tested in a statistical learning paradigm. Here, we used a neuropsychological approach to test whether patients with bilateral hippocampal pathology (N = 3) could learn new words in a CSSL paradigm. In the task, patients and healthy comparison participants completed a CSSL word-learning task in which they acquired eight word/object mappings. During each trial of the CSSL task, participants saw two objects on a computer display, heard one novel word, and selected the most likely referent. Across trials, words were 100% likely to co-occur with their referent, but only 14.3% likely with non-referents. Two of three amnesic patients learned the associations between objects and word forms, although performance was impaired relative to healthy comparison participants. Our findings show that the hippocampus is not strictly necessary for CSSL for words, although it may facilitate such learning. This is consistent with a hybrid account of CSSL supported by implicit and explicit memory systems, and may have translational applications for remediation of (word-) learning deficits in neurological populations with hippocampal pathology.

Semantic Search as Pattern Completion across a Concept

What role does the hippocampus play in semantic memory? In a recent paper, Cutler et al. use a vector space model of semantics to characterize semantic search deficits in hippocampal amnesia. We relate their findings to properties of the hippocampal neural code and to controversies regarding hippocampal contributions to cognition.

Activation of stimulus-specific processing regions at retrieval tracks the strength of relational memory

Many theories of episodic memory posit that the subjective experience of recollection may be driven by the activation of stimulus-specific cortical regions during memory retrieval. This study examined cortical activation during associative memory retrieval to identify brain regions that support confidence judgments of source memory in stimulus-specific ways. Adjectives were encoded with either a picture of a face or a scene. During a source memory test, the word was presented alone and the participant was asked if the word had been previously paired with a face or a scene. We identified brain regions that were selectively active when viewing pictures of scenes or faces with a separate localizer scan. We then identified brain regions that were differentially activated to words during the source memory test that had been previously paired with faces or scenes, masked by the localizer activations, and examined how those regions were modulated by the strength of the source memory. Bilateral amygdala activation tracked source memory confidence for faces, while parahippocampal cortex tracked source memory confidence for scenes. The magnitude of the activation of these domain-specific perceptual-processing brain regions during memory retrieval may contribute to the subjective strength of episodic recollection.

Searching for Semantic Knowledge: A Vector Space Semantic Analysis of the Feature Generation Task

A recent neuropsychological study found that amnesic patients with hippocampal damage (HP) and severe declarative memory impairment produce markedly fewer responses than healthy comparison (CO) participants in a semantic feature generation task (Klooster and Duff, 2015), consistent with the idea that hippocampal damage is associated with semantic cognitive deficits. Participants were presented with a target word and asked to produce as many features of that word as possible (e.g., for target word "book," "read words on a page"). Here, we use the response sequences collected by Klooster and Duff (2015) to develop a vector space model of semantic search. We use this model to characterize the dynamics of semantic feature generation and consider the role of the hippocampus in this search process. Both HP and CO groups tended to initiate the search process with features close in semantic space to the target word, with a gradual decline in similarity to the target word over the first several responses. Adjacent features in the response sequence showed stronger similarity to each other than to non-adjacent features, suggesting that the search process follows a local trajectory in semantic space. Overall, HP patients generated features that were closer in semantic space to the representation of the target word, as compared to the features generated by the CO group, which ranged more widely in semantic space. These results are consistent with a model in which a compound retrieval cue (containing a representation of the target word and a representation of the previous response) is used to probe semantic memory. The model suggests that the HP group's search process is restricted from ranging as far in semantic space from the target word, relative to the CO group. These results place strong constraints on the structure of models of semantic memory search, and on the role of hippocampus in probing semantic memory.

Self-Reference enhances memory for multi-element events judged likely to happen in young and older adults

We investigated whether the strategy of self-reference can benefit memory for multi-element events, a kind of relational memory that is relatively less studied but highly relevant to daily life. Young and older adults imagined different person-object-location events with reference to themselves and two famous others (i.e., George Clooney and Oprah Winfrey), rated the likelihood that each event would happen, and then completed incidental memory tests on different pairs of elements within the event. We found that self-reference enhanced memory for object-location and person-object pairs in both age groups. Such self-reference effects were observed consistently only for events rated as likely to happen. There was also an overall memory advantage for the higher-likelihood events, which did not differ between young and older adults. Further, the self-reference effects were not correlated with memory functioning in either age group. Retrieval of within-event associations showed a significant level of dependency, which did not differ as a function of reference condition or likelihood category. These findings highlight the ways in which self-reference and prior knowledge improve relational memory, and suggest that the advantage of self-reference is not attributable to increased dependence of elements within complex events.

Spatial relational memory in individuals with traumatic brain injury

Introduction: Relational memory is the ability to bind arbitrary relations between elements of experience into durable representations and the flexible expression of these representations. It is well known that individuals with traumatic brain injury (TBI) have declarative memory impairments, but less is known about how TBI affects relational memory binding, the deficit at the heart of declarative, or relational, memory impairment. The aim of the current study is to examine such deficits.Method: We used a spatial reconstruction task (SRT) with 29 individuals with TBI and 23 normal comparison (NC) participants to investigate four different types of spatial relations: (A) identity-location relations, i.e., the relationship between a specific item and its known location; (B) item-item relations, or the relationship between one item and another; (C) item-display relations, or the relationship between an item and its position in the display; and (D) compound-item relations, i.e., relations that involve combinations of A, B, and C.Results: Our data revealed that individuals with TBI showed impairments in learning identity-location relations and increased compound errors compared to NCs. We also found evidence that when item identity is disregarded, individuals with TBI do not perform differently from NCs. An exploratory analysis revealed that while relational memory performance was significantly correlated with scores on the California Verbal Learning Test (CVLT), more participants with TBI exhibited impairment on the SRT than of the CVLT.Conclusions: Our findings show that relational memory is impaired following TBI, and provide preliminary evidence for an easy-to-administer task with increased sensitivity to memory impairment.

Differential development of relational memory and pattern separation

Researchers have taken a number of different approaches in their exploration of hippocampal function. One approach seeks to describe hippocampal function by probing the memory representations that the hippocampus supports. Another approach focuses on the role of the hippocampus in pattern separation and completion. Each of these approaches to understanding hippocampal function utilizes a distinct set of specialized tasks, and both of these task sets are known to be sensitive to changes in hippocampal function with age and disease status. But the question remains whether the tasks utilized in these two approaches tap into the same aspects of hippocampal function. We explored this question in the context of hippocampal development. Preadolescent children (N = 73) and young adults (N = 41) completed an identical battery of cognitive tasks consisting of a spatial reconstruction relational memory task, the mnemonic similarity task (MST)-an object-based pattern separation task, and a novel hybrid task-the Object Discrimination and Distribution (ODD) Task-designed to integrate and simultaneously tax pattern separation and spatial relational memory. Children did not demonstrate impairments in lure discrimination relative to young adults on either the object-based pattern separation task or for aspects of the ODD task that required pattern separation in the absence of relational memory demands but performed more poorly across aspects of tasks that required relational binding.

Exercise and Hippocampal Memory Systems

No medications prevent or reverse age-related cognitive decline. Physical activity (PA) enhances memory in rodents, but findings are mixed in human studies. As a result, exercise guidelines specific for brain health are absent. Here, we re-examine results from human studies, and suggest the use of more sensitive tasks to evaluate PA effects on age-related changes in the hippocampus, such as relational memory and mnemonic discrimination. We discuss recent advances from rodent and human studies into the underlying mechanisms at both the central and peripheral levels, including neurotrophins and myokines that could contribute to improved memory. Finally, we suggest guidelines for future research to help expedite well-founded PA recommendations for the public.

Fast mappers, slow learners: Word learning without hippocampus is slow and sparse irrespective of methodology

Rapid word learning without the hippocampus is an alluring prospect - it holds the promise of remediating a common learning deficit associated with aging (healthy or pathological) and certain neurological conditions. Despite recent reports indicating rapid, non-hippocampal word learning by amnesic adults after contrastive 'fast-mapping' exposure, several replications have failed. These failures stand in contrast to successful but slow learning by amnesic patients under other conditions, and this pattern suggests that rapid word learning in adulthood is hippocampus-dependent and relational irrespective of learning format. However, much remains to be studied, and important methodological and theoretical considerations are highlighted here.

Reconstructing relational information

Hippocampal involvement in learning and remembering relational information has an extensive history, often focusing specifically on spatial information. In humans, spatial reconstruction (SR) paradigms are a powerful tool for evaluating an individuals' spatial-relational memory. In SR tasks, participants study locations of items in space and subsequently reconstruct the studied display after a short delay. Previous work has revealed that patients with hippocampal damage are impaired both in overall placement accuracy as well as on a specific measure of relational memory efficacy, "swaps" (i.e., when the relative location of two items is reversed). However, the necessity of the hippocampus for other types of spatial-relational information involved in reconstruction behaviors (e.g., where in the environment and relative to which other items an item was located) have not yet been investigated systematically. In this work, three patients with hippocampal damage and nine healthy matched comparison participants performed an SR task. An analysis framework was developed to independently assess three first-order types of relations: (1) memory for the binding of specific item identities to locations, (2) memory for arrangement of items in relation to each other or the environment bounds, regardless of memory for the item identity, and (3) higher-order, compound relational errors (i.e., errors involving multiple pieces of relational information). Reconstruction errors were evaluated to determine the degree to which patients and comparisons differed (or not) on each type of spatial-relational information. Data revealed that the primary group difference in performance was for identity-location information. However, when the locations of items were evaluated without regarding the identities, no group difference was found in the number of item placements to studied locations. The present work provides a principled approach to analysis of SR data and clarifies our understanding of the types of spatial relations impaired in hippocampal damaged.

Self-reference enhances relational memory in young and older adults

The present study investigated the influence of self-reference on two kinds of relational memory, internal source memory and associative memory, in young and older adults. Participants encoded object-location word pairs using the strategies of imagination and sentence generation, either with reference to themselves or to a famous other (i.e., George Clooney or Oprah Winfrey). Both young and older adults showed memory benefits in the self-reference conditions compared to other-reference conditions on both tests, and the self-referential effects in older adults were not limited by low memory or executive functioning. These results suggest that self-reference can benefit relational memory in older adults relatively independently of basic memory and executive functions.

Temporal binding function of dorsal CA1 is critical for declarative memory formation

Temporal binding, the process that enables association between discontiguous stimuli in memory, and relational organization, a process that enables the flexibility of declarative memories, are both hippocampus-dependent and decline in aging. However, how these two processes are related in supporting declarative memory formation and how they are compromised in age-related memory loss remain hypothetical. We here identify a causal link between these two features of declarative memory: Temporal binding is a necessary condition for the relational organization of discontiguous events. We demonstrate that the formation of a relational memory is limited by the capability of temporal binding, which depends on dorsal (d)CA1 activity over time intervals and diminishes in aging. Conversely, relational representation is successful even in aged individuals when the demand on temporal binding is minimized, showing that relational/declarative memory per se is not impaired in aging. Thus, bridging temporal intervals by dCA1 activity is a critical foundation of relational representation, and a deterioration of this mechanism is responsible for the age-associated memory impairment.

Memory for relations in the short term and the long term after medial temporal lobe damage

A central idea about the organization of declarative memory and the function of the hippocampus is that the hippocampus provides for the coding of relationships between items. A question arises whether this idea refers to the process of forming long-term memory or whether, as some studies have suggested, memory for relations might depend on the hippocampus even at short retention intervals and even when the task falls within the province of short-term (working) memory. The latter formulation appears to place the operation of relational memory into conflict with the idea that working memory is independent of medial temporal lobe (MTL) structures. In this report, the concepts of relational memory and working memory are discussed in the light of a simple demonstration experiment. Patients with MTL lesions successfully learned and recalled two word pairs when tested directly after learning but failed altogether when tested after a delay. The results do not contradict the idea that the hippocampus has a fundamental role in relational memory. However, there is a need for further elaboration and specification of the idea in order to explain why patients with MTL lesions can establish relational memory in the short term but not in long-term memory. © 2017 Wiley Periodicals, Inc.

Hippocampal gamma-band Synchrony and pupillary responses index memory during visual search

Memory for scenes is supported by the hippocampus, among other interconnected structures, but the neural mechanisms related to this process are not well understood. To assess the role of the hippocampus in memory-guided scene search, we recorded local field potentials and multiunit activity from the hippocampus of macaques as they performed goal-directed search tasks using natural scenes. We additionally measured pupil size during scene presentation, which in humans is modulated by recognition memory. We found that both pupil dilation and search efficiency accompanied scene repetition, thereby indicating memory for scenes. Neural correlates included a brief increase in hippocampal multiunit activity and a sustained synchronization of unit activity to gamma band oscillations (50-70 Hz). The repetition effects on hippocampal gamma synchronization occurred when pupils were most dilated, suggesting an interaction between aroused, attentive processing and hippocampal correlates of recognition memory. These results suggest that the hippocampus may support memory-guided visual search through enhanced local gamma synchrony. © 2016 Wiley Periodicals, Inc.

Visual short-term memory for high resolution associations is impaired in patients with medial temporal lobe damage

The medial temporal lobe (MTL) plays a critical role in episodic long-term memory, but whether the MTL is necessary for visual short-term memory is controversial. Some studies have indicated that MTL damage disrupts visual short-term memory performance whereas other studies have failed to find such evidence. To account for these mixed results, it has been proposed that the hippocampus is critical in supporting short-term memory for high resolution complex bindings, while the cortex is sufficient to support simple, low resolution bindings. This hypothesis was tested in the current study by assessing visual short-term memory in patients with damage to the MTL and controls for high resolution and low resolution object-location and object-color associations. In the location tests, participants encoded sets of two or four objects in different locations on the screen. After each set, participants performed a two-alternative forced-choice task in which they were required to discriminate the object in the target location from the object in a high or low resolution lure location (i.e., the object locations were very close or far away from the target location, respectively). Similarly, in the color tests, participants were presented with sets of two or four objects in a different color and, after each set, were required to discriminate the object in the target color from the object in a high or low resolution lure color (i.e., the lure color was very similar or very different, respectively, to the studied color). The patients were significantly impaired in visual short-term memory, but importantly, they were more impaired for high resolution object-location and object-color bindings. The results are consistent with the proposal that the hippocampus plays a critical role in forming and maintaining complex, high resolution bindings. © 2016 Wiley Periodicals, Inc.

Abstraction and generalization in statistical learning: implications for the relationship between semantic types and episodic tokens

Statistical approaches to emergent knowledge have tended to focus on the process by which experience of individual episodes accumulates into generalizable experience across episodes. However, there is a seemingly opposite, but equally critical, process that such experience affords: the process by which, from a space of types (e.g. onions-a semantic class that develops through exposure to individual episodes involving individual onions), we can perceive or create, on-the-fly, a specific token (a specific onion, perhaps one that is chopped) in the absence of any prior perceptual experience with that specific token. This article reviews a selection of statistical learning studies that lead to the speculation that this process-the generation, on the basis of semantic memory, of a novel episodic representation-is itself an instance of a statistical, in fact associative, process. The article concludes that the same processes that enable statistical abstraction across individual episodes to form semantic memories also enable the generation, from those semantic memories, of representations that correspond to individual tokens, and of novel episodic facts about those tokens. Statistical learning is a window onto these deeper processes that underpin cognition.This article is part of the themed issue 'New frontiers for statistical learning in the cognitive sciences'.

The Effect of Emotion and Reward Contingencies on Relational Memory in Major Depression: An Eye-Movement Study with Follow-Up

Background: Episodic memory disturbances were found to constitute a potential trait marker for major depression (MD). The recall of positive or rewarding information in a relational context is specifically impaired. Eye-movement recording constitutes a novel, direct approach to examine implicit memory performance. Here we aimed to assess the effect of emotional context and implicit virtual monetary reward or loss on viewing patterns in association with relational memory in a 6-months follow-up study in MD.

Materials and Methods: Twenty-eight patients with MD and 30 healthy participants were trained to associate a face (happy/sad/neutral) with a background scene. After each pair a virtual monetary reward or loss appeared briefly. During testing, scenes were presented as a cue and then overlaid with three previously studied faces. Participants were asked to recall the matching face if present (Match trials), with eye-movements and subsequent forced-choice recognition being recorded.

Results: Explicit recognition of the matching face was impaired in the MD group as compared to controls. In correlation with this, viewing of the matching face was significantly reduced in the MD group. We found a significant interaction of group (MD vs HC) with the relational memory condition (Match and Non-match), facial emotion and monetary reward and loss. MD patients attended longer to previously rewarded stimuli, but significantly less to sad faces in the Match condition. The relational memory impairment persisted at follow-up and correlated with symptom severity both at baseline and follow-up. Viewing patterns associated with previous virtual reward were associated with clinical symptoms at follow-up.

Conclusion: Our current results provide novel evidence for a specific relational memory impairment in MD as supported by abnormal eye-movement behavior and a deficit in explicit recognition. MD patients showed an attentional bias to rewarded stimuli and decreased viewing of sad faces when relational memory information was present.

Direct brain recordings reveal hippocampal rhythm underpinnings of language processing

Language is classically thought to be supported by perisylvian cortical regions. Here we provide intracranial evidence linking the hippocampal complex to linguistic processing. We used direct recordings from the hippocampal structures to investigate whether theta oscillations, pivotal in memory function, track the amount of contextual linguistic information provided in sentences. Twelve participants heard sentences that were either constrained ("She locked the door with the") or unconstrained ("She walked in here with the") before presentation of the final word ("key"), shown as a picture that participants had to name. Hippocampal theta power increased for constrained relative to unconstrained contexts during sentence processing, preceding picture presentation. Our study implicates hippocampal theta oscillations in a language task using natural language associations that do not require memorization. These findings reveal that the hippocampal complex contributes to language in an active fashion, relating incoming words to stored semantic knowledge, a necessary process in the generation of sentence meaning.

Effect of emotion on memory for words and their context

Emotion influences various cognitive processes, such as memory. This beneficial or detrimental effect can be studied with verbal material, yet in this case a broad term of context has to be taken into account. The present work reviews recent literature and proposes that traditional differentiation between semantic and environmental context should be replaced with a novel conceptualization of hippocampus-dependent relational memory and item memory (related to the activations of cuneus and left amygdala). Additionally, instead of list-learning paradigms, words should be memorized in the context of sentences or stories for better control over their meaning. The recent evidence suggests that of particular importance for ecological validity in research paradigms is the presence of communicative and social context of verbal material related to such processes as theory of mind and brain activations in temporoparietal junction, posterior cingulate cortex, and dorsal medial prefrontal cortex. We propose that studying memory of verbal material within context gives a better understanding of enhancing and impairing effects of emotion as well as of the underlying brain mechanisms.

The effectiveness of unitization in mitigating age-related relational learning impairments depends on existing cognitive status

Binding relations among items in the transverse patterning (TP) task is dependent on the integrity of the hippocampus and its extended network. Older adults have impaired TP learning, corresponding to age-related reductions in hippocampal volumes. Unitization is a training strategy that can mitigate TP impairments in amnesia by reducing reliance on hippocampal-dependent relational binding and increasing reliance on fused representations. Here we examined whether healthy older adults and those showing early signs of cognitive decline would also benefit from unitization. Although both groups of older adults had neuropsychological performance within the healthy range, their TP learning differed both under standard and unitized training conditions. Healthy older adults with impaired TP learning under standard training benefited from unitized training. Older adults who failed the Montreal Cognitive Assessment (MoCA) showed greater impairments under standard conditions, and showed no evidence of improvement with unitization. These individuals' failures to benefit from unitization may be a consequence of early deficits not seen in older adults who pass the MoCA.

The Role of Medial Temporal Lobe Regions in Incidental and Intentional Retrieval of Item and Relational Information in Aging

Considerable neuropsychological and neuroimaging work indicates that the medial temporal lobes are critical for both item and relational memory retrieval. However, there remain outstanding issues in the literature, namely the extent to which medial temporal lobe regions are differentially recruited during incidental and intentional retrieval of item and relational information, and the extent to which aging may affect these neural substrates. The current fMRI study sought to address these questions; participants incidentally encoded word pairs embedded in sentences and incidental item and relational retrieval were assessed through speeded reading of intact, rearranged, and new word-pair sentences, while intentional item and relational retrieval were assessed through old/new associative recognition of a separate set of intact, rearranged, and new word pairs. Results indicated that, in both younger and older adults, anterior hippocampus and perirhinal cortex indexed incidental and intentional item retrieval in the same manner. In contrast, posterior hippocampus supported incidental and intentional relational retrieval in both age groups and an adjacent cluster in posterior hippocampus was recruited during both forms of relational retrieval for older, but not younger, adults. Our findings suggest that while medial temporal lobe regions do not differentiate between incidental and intentional forms of retrieval, there are distinct roles for anterior and posterior medial temporal lobe regions during retrieval of item and relational information, respectively, and further indicate that posterior regions may, under certain conditions, be over-recruited in healthy aging. © 2016 Wiley Periodicals, Inc.

Selective scanpath repetition during memory-guided visual search

Visual search efficiency improves with repetition of a search display, yet the mechanisms behind these processing gains remain unclear. According to Scanpath Theory, memory retrieval is mediated by repetition of the pattern of eye movements or "scanpath" elicited during stimulus encoding. Using this framework, we tested the prediction that scanpath recapitulation reflects relational memory guidance during repeated search events. Younger and older subjects were instructed to find changing targets within flickering naturalistic scenes. Search efficiency (search time, number of fixations, fixation duration) and scanpath similarity (repetition) were compared across age groups for novel (V1) and repeated (V2) search events. Younger adults outperformed older adults on all efficiency measures at both V1 and V2, while the search time benefit for repeated viewing (V1-V2) did not differ by age. Fixation-binned scanpath similarity analyses revealed repetition of initial and final (but not middle) V1 fixations at V2, with older adults repeating more initial V1 fixations than young adults. In young adults only, early scanpath similarity correlated negatively with search time at test, indicating increased efficiency, whereas the similarity of V2 fixations to middle V1 fixations predicted poor search performance. We conclude that scanpath compression mediates increased search efficiency by selectively recapitulating encoding fixations that provide goal-relevant input. Extending Scanpath Theory, results suggest that scanpath repetition varies as a function of time and memory integrity.

Memory deficit in patients with schizophrenia and posttraumatic stress disorder: relational vs item-specific memory

It has been well established that patients with schizophrenia have impairments in cognitive functioning and also that patients who experienced traumatic events suffer from cognitive deficits. Of the cognitive deficits revealed in schizophrenia or posttraumatic stress disorder (PTSD) patients, the current article provides a brief review of deficit in episodic memory, which is highly predictive of patients' quality of life and global functioning. In particular, we have focused on studies that compared relational and item-specific memory performance in schizophrenia and PTSD, because measures of relational and item-specific memory are considered the most promising constructs for immediate tangible development of clinical trial paradigm. The behavioral findings of schizophrenia are based on the tasks developed by the Cognitive Neuroscience Treatment Research to Improve Cognition in Schizophrenia (CNTRICS) initiative and the Cognitive Neuroscience Test Reliability and Clinical Applications for Schizophrenia (CNTRACS) Consortium. The findings we reviewed consistently showed that schizophrenia and PTSD are closely associated with more severe impairments in relational memory compared to item-specific memory. Candidate brain regions involved in relational memory impairment in schizophrenia and PTSD are also discussed.

Brain activation during associative short-term memory maintenance is not predictive for subsequent retrieval

Performance on working memory (WM) tasks may partially be supported by long-term memory (LTM) processing. Hence, brain activation recently being implicated in WM may actually have been driven by (incidental) LTM formation. We examined which brain regions actually support successful WM processing, rather than being confounded by LTM processes, during the maintenance and probe phase of a WM task. We administered a four-pair (faces and houses) associative delayed-match-to-sample (WM) task using event-related functional MRI (fMRI) and a subsequent associative recognition LTM task, using the same stimuli. This enabled us to analyze subsequent memory effects for both the WM and the LTM test by contrasting correctly recognized pairs with incorrect pairs for either task. Critically, with respect to the subsequent WM effect, we computed this analysis exclusively for trials that were forgotten in the subsequent LTM recognition task. Hence, brain activity associated with successful WM processing was less likely to be confounded by incidental LTM formation. The subsequent LTM effect, in contrast, was analyzed exclusively for pairs that previously had been correctly recognized in the WM task, disclosing brain regions involved in successful LTM formation after successful WM processing. Results for the subsequent WM effect showed no significantly activated brain areas for WM maintenance, possibly due to an insensitivity of fMRI to mechanisms underlying active WM maintenance. In contrast, a correct decision at WM probe was linked to activation in the “retrieval success network” (anterior and posterior midline brain structures). The subsequent LTM analyses revealed greater activation in left dorsolateral prefrontal cortex and posterior parietal cortex in the early phase of the maintenance stage. No supra-threshold activation was found during the WM probe. Together, we obtained clearer insights in which brain regions support successful WM and LTM without the potential confound of the respective memory system.

Measuring Memory Reactivation With Functional MRI: Implications for Psychological Theory

Environmental cues often remind us of earlier experiences by triggering the reactivation of memories of events past. Recent evidence suggests that memory reactivation can be observed using functional MRI and that distributed pattern analyses can even provide evidence of reactivation on individual trials. The ability to measure memory reactivation offers unique and powerful leverage on theoretical issues of long-standing interest in cognitive psychology, providing a means to address questions that have proven difficult to answer with behavioral data alone. In this article, we consider three instances. First, reactivation measures can indicate whether memory-based inferences (i.e., generalization) arise through the encoding of integrated cross-event representations or through the flexible expression of separable event memories. Second, online measures of memory reactivation may inform theories of forgetting by providing information about when competing memories are reactivated during competitive retrieval situations. Finally, neural reactivation may provide a window onto the role of replay in memory consolidation. The ability to track memory reactivation, including at the individual trial level, provides unique leverage that is not afforded by behavioral measures and thus promises to shed light on such varied topics as generalization, integration, forgetting, and consolidation.

The development of hippocampal-dependent memory functions: Theoretical comments on Jabès and Nelson review (2015)

Studies investigating the development of memory processes and their neural substrates have flourished over the last two decades. The review by Jabès and Nelson (2015) adds an important piece to our understanding of the maturation of different elements and circuits within the hippocampal system and their association with the progressive development of hippocampal-dependent memory processes in humans. In this accompanying commentary, we explore some additional connections between the nonhuman primate work and the human data, and take the opportunity to highlight some common and additional interpretations of the results. This commentary makes three points: (1) the recognition processes present in the first few days of life may be linked to the early maturation of the medial temporal cortical areas instead of, or in addition to, the early maturation of the subiculum; (2) recent findings on the differential protracted maturation of spatial relational memory processes in monkeys further support the notion proposed by Jabès and Nelson that this protracted development may reflect progressive maturation of the CA1 field of the hippocampus followed by further maturation of CA3/dentate gyrus; (3) finally, further considerations of the differential maturation of the longitudinal hippocampal axis and of the diencephalon are proposed as additional contributors to the refinement of episodic memory functions during development.

Navigating life

The discoveries of "place cells" in the hippocampus and "grid cells" in the entorhinal cortex are landmark achievements in relating behavior to neural activity, permitting analysis of a powerful system for spatial representation in the brain. The contributions of this work include not only the empirical findings but also the approach this work pioneered of examining neural activity in complex behaviors with real ecological validity in freely moving animals, and of attempting to place the findings in the larger context of how the neural representations of space are used in service of real-world behavior, namely what the Nobel committee described as permitting us to "navigate our way through a complex environment." These discoveries and approaches have had far-ranging impact on and implications for work in human cognitive neuroscience, where we see (1) confirmation in humans that the hippocampus and overlying MTL cortex are critically engaged in supporting a relational representation of space, and that it can be used for flexible spatial navigation and (2) evidence that these regions are also critically involved in aspects of relational memory not limited to space, and in the flexible use of hippocampal memory extending beyond spatial navigation. Recent work, using tasks that emphasize the requirement for the active use of memory in online processing, just as spatial navigation has long placed such a requirement on rodents, suggests that the hippocampus and related MTL cortex can support the navigating of environments even more complex than what is needed in spatial navigation. It allows us to use memory in guiding upcoming actions and choices to act optimally in and on the world, permitting us to navigate life in all its beautiful complexity.

Relational Memory Processes in Adults with Autism Spectrum Disorder

Research into memory in Autism Spectrum Disorder (ASD) suggests intact item memory but difficulties in forming relations between items (Bowler, Gaigg, & Lind, 2011). In this study, we tested memory for items as well as for sequential, spatial, and associative relations between items with the same paradigm using abstract shapes in ASD and typically developing (TD) individuals. Participants studied shape triplets on a computer screen and memory was subsequently tested either for the individual items making up the triplets, the screen-locations, the order or the combinations of items presented at study. Contrary to our predictions, performance was significantly lower in the ASD group on all four tasks. The result raises questions about how intact item memory is in ASD, which role task complexity plays, and how item-specific versus relational processing affect task performance. One possibility is that TD individuals relied more on relational processing in the current study and might have therefore had an advantage over ASD individuals. This idea is supported by the result of a preliminary analysis of age-related differences in memory across the midadult lifespan in both groups. Age seems to affect order memory less in ASD compared with TD individuals where it leads to a significant decrease in performance. This might indicate a decrease in relational processing in TD but not ASD individuals with increasing age. More research is needed to answer questions about the change in cognition in ASD individuals across the lifespan.

Long-lasting enhancements of memory and hippocampal-cortical functional connectivity following multiple-day targeted noninvasive stimulation

Noninvasive stimulation can alter the function of brain networks, although the duration of neuroplastic changes are uncertain and likely vary for different networks and stimulation parameters. We have previously shown that multiple-day repetitive transcranial magnetic stimulation can influence targeted hippocampal-cortical networks, producing increased functional MRI connectivity of these networks and concomitant improvements in memory that outlast stimulation by ∼24 h. Here, we present new analyses showing that multiple-day targeted stimulation of hippocampal-cortical networks produces even longer-lasting enhancement. The ability to learn novel, arbitrary face-word pairings improved over five consecutive daily stimulation sessions, and this improvement remained robust at follow-up testing performed an average of 15 days later. Furthermore, stimulation increased functional MRI connectivity of the targeted portion of the hippocampus with distributed regions of the posterior hippocampal-cortical network, and these changes in connectivity remained robust at follow-up testing. Neuroplastic changes of hippocampal-cortical networks caused by multiple-day noninvasive stimulation therefore persist for extended periods. These findings have implications for the design of multiple-day stimulation experiments and for the development of stimulation-based interventions for memory disorders.

Episodic Recollection Difficulties in ASD Result from Atypical Relational Encoding: Behavioral and Neural Evidence

Memory functioning in Autism Spectrum Disorder (ASD) is characterized by impairments in the encoding of relational but not item information and difficulties in the recollection of contextually rich episodic memories but not in the retrieval of relatively context‐free memories through processes of familiarity. The neural underpinnings of this profile and the extent to which encoding difficulties contribute to retrieval difficulties in ASD remain unclear. Using a paradigm developed by Addis and McAndrews [2006; Neuroimage, 33, 1194–1206] we asked adults with and without a diagnosis of ASD to study word‐triplets during functional Magnetic Resonance Imaging (fMRI) scanning that varied in the number of category relations amongst component words. Performance at test confirmed attenuated recollection in the context of preserved familiarity based retrieval in ASD. The results also showed that recollection but not familiarity based retrieval increases as a function of category relations in word triads for both groups, indicating a close link between the encoding of relational information and recollection. This link was further supported by the imaging results, where blood oxygen level dependent (BOLD) signal responses in overlapping regions of the inferior prefrontal cortex were sensitive to the relational encoding manipulation as well as the contrast between recollection versus familiarity based retrieval. Interestingly, however, there was no evidence of prefrontal signal differentiation for this latter contrast in the ASD group for whom signal changes in a left hippocampal region were also marginally attenuated. Together, these observations suggest that attenuated levels of episodic recollection in ASD are, at least in part, attributable to anomalies in relational encoding processes. Autism Res2015, 8: 317–327. © 2015 International Society for Autism Research, Wiley Periodicals, Inc.

The impact of intermediate-term alcohol abstinence on memory retrieval and suppression

Background: The nature of episodic memory deficit in intermediate-term abstinence from alcohol in alcohol dependence (AD) is not yet clarified. Deficits in inhibitory control are commonly reported in substance use disorders. However, much less is known about cognitive control suppressing interference from memory. The Think/No-think (TNT) paradigm is a well established method to investigate inhibition of associative memory retrieval.

Methods: Thirty-six unmedicated patients with AD and 36 healthy controls (HCs) performed the TNT task. Thirty image–word pairs were trained up to a predefined accuracy level. Cued recall was examined in three conditions: Think (T) for items instructed to-be-remembered, No-think (NT) assessing the ability to suppress retrieval and Baseline (B) for general relational memory. Premorbid IQ, clinical variables and impulsivity measures were quantified.

Results: AD patients had a significantly increased demand for training. Baseline memory abilities and effect of practice on retrieval were not markedly different between the groups. We found a significant main effect of group (HC vs. AD) × condition (B, T, and NT) and a significant difference in mean NT–B scores for the two groups.

Discussion: AD and HC groups did not differ essentially in their baseline memory abilities. Also, the instruction to focus on retrieval improved episodic memory performance in both groups. Crucially, control participants were able to suppress relational words in the NT condition supporting the critical effect of cognitive control processes over inhibition of retrieval. In contrast to this, the ability of AD patients to suppress retrieval was found to be impaired.

The role of the hippocampus in flexible cognition and social behavior

Successful behavior requires actively acquiring and representing information about the environment and people, and manipulating and using those acquired representations flexibly to optimally act in and on the world. The frontal lobes have figured prominently in most accounts of flexible or goal-directed behavior, as evidenced by often-reported behavioral inflexibility in individuals with frontal lobe dysfunction. Here, we propose that the hippocampus also plays a critical role by forming and reconstructing relational memory representations that underlie flexible cognition and social behavior. There is mounting evidence that damage to the hippocampus can produce inflexible and maladaptive behavior when such behavior places high demands on the generation, recombination, and flexible use of information. This is seen in abilities as diverse as memory, navigation, exploration, imagination, creativity, decision-making, character judgments, establishing and maintaining social bonds, empathy, social discourse, and language use. Thus, the hippocampus, together with its extensive interconnections with other neural systems, supports the flexible use of information in general. Further, we suggest that this understanding has important clinical implications. Hippocampal abnormalities can produce profound deficits in real-world situations, which typically place high demands on the flexible use of information, but are not always obvious on diagnostic tools tuned to frontal lobe function. This review documents the role of the hippocampus in supporting flexible representations and aims to expand our understanding of the dynamic networks that operate as we move through and create meaning of our world.