Information In Episodic Memory Research Articles

Chapter 25 - The temporal lobe in typical and atypical Alzheimer disease

Alzheimer disease (AD) is defined neuropathologically by abnormal extra-cellular β-amyloid plaques combined with intraneuronal tau aggregation. Patients sharing the same neuropathological features but presenting different clinical manifestations and evolutions have led to the notion of AD spectrum. This spectrum encompasses typical and atypical forms of AD. For all of them, specific parts of the temporal lobes, as well as their structural and functional connections with other brain regions, are affected. In typical amnestic late-onset Alzheimer's disease (>65 years old; LOAD), tau pathology gradually spreads to the brain from the medial temporal lobe (MTL). MTL is an inhomogeneous structure consisting of several subregions densely connected to each other and to other cortical and subcortical brain regions. These regions play a crucial role in the storage of information in episodic memory. In less common early-onset AD (<65 years old; EOAD), a large proportion of patients presents atypical clinical manifestations, in which memory impairment is not inaugural and predominant. Instead, these patients have predominant and/or isolated deficits in language, visuospatial, motor, or executive/behavioral functions. In atypical variants, brain damage is mainly centered on the posterior regions, with relative sparing of the MTL. However, the temporal lobe also appears to be variably and specifically damaged in some subtypes of EOAD. For example, the left superior temporal gyrus is the core of brain damage in the language variant, as well as the ventral regions of the temporal lobe play an important role in the clinic of the visual variant.

Time and Self in Episodic Memory and Confabulation

Confabulation is defined as the production of narrative descriptions of events that never happened, and is often observed in amnesia with basal forebrain lesions. However, little is known about the possible mechanisms related to confabulation. In this review article, we summarized previous neuropsychological and neuroimaging studies associated with confabulation, and proposed a hypothetical mechanism of confabulation. Previous studies have demonstrated that amnesic patients with confabulation after basal forebrain damage are impaired in the processing of time-related information in episodic memory and that activation of this region is significant during the processing of time-related information in episodic memory. In addition, confabulating patients with basal forebrain lesions extending to the medial prefrontal cortex (mPFC), medial temporal, and thalamic regions are likely to show significant disturbances in age-awareness and significant false memories in personally experienced events. Given the importance of the mPFC in the self-referential process and of the hippocampus in the integration of episodic components, the basal forebrain region could play an important role in orienting the self in time by acting as an interface between the mPFC and the hippocampus. Confabulation in basal forebrain amnesia could be caused by a decline of the time-self interaction.

Perception of time in microgravity and hypergravity during parabolic flight.

We explored the effect of gravity on the accuracy for estimating durations of 3.5, 7, and 14 s. Experiments were performed on board an Airbus A310 during parabolic flights eliciting repeated exposures to short periods of 0, 1, and 1.8 g. Two methods for obtaining duration estimates were used, reproduction and production of duration, in two conditions: a control counting condition and a concurrent reading condition. Simple reaction times were also measured to assess attention. The results showed that the temporal accuracies during the reproduction task in the concurrent reading condition were significantly underestimated in 0 g compared with 1 g. Reaction times were also longer in 0 g. However, there was no difference in duration estimates in the production tasks. These results suggest that the temporal underestimation in 0 g is caused by decreased selective attention and impaired retrieval of information in episodic memory.

Impaired verbal episodic memory in healthy older adults is marked by increased F2-Isoprostanes

Age-associated cognitive decline amongst otherwise healthy older individuals is a multifaceted characteristic of ageing. The role of oxidative stress biomarkers has been increasingly examined in the context of pathological aging conditions that affect cognition. Plasma F2-Isoprostane levels are a reliable index of systemic oxidative stress (specifically lipid peroxidation) and are elevated in dementia patients. Less is known about their role in healthy cognitive ageing. This study evaluated the relationship between F2-Isoprostanes and cognitive functioning in a cohort of 211 healthy elderly adults (60–75 years: Male; 88, Female; 123). Cognitive assessment included the Cognitive Drug Research (CDR) computerised assessment battery, which produces five validated factor scores (corresponding to ‘Quality of Episodic Memory’, ‘Speed of Memory’, Quality of Working Memory’, Power of Attention’ and ‘Continuity of Attention’). Participants with higher F2-Isoprostane levels had significantly lower Quality of Episodic Memory scores (suggesting inferior abilities in retaining and retrieving verbal information in episodic memory). This is, to our knowledge, the first report of compromised verbal episodic memory in healthy ageing humans being linked to increased levels of F2-Isoprostanes. These results have relevance for interventions aimed at improving cognitive performance in the healthy elderly.

Neural Mechanisms Underlying the Processing of Temporal Information in Episodic Memory and Its Disturbance

Episodic memory is defined as memory for personally experienced events, and includes memory content and contextual information of time and space. Previous neuroimaging and neuropsychological studies have demonstrated three possible roles of the temporal context in episodic memory. First, temporal information contributes to the arrangement of temporal order for sequential events in episodic memory, and this process is involved in the lateral prefrontal cortex. The second possible role of temporal information in episodic memory is the segregation between memories of multiple events, which are segregated by cues of different time information. The role of segregation is associated with the orbitofrontal regions including the orbitofrontal cortex and basal forebrain region. Third, temporal information in episodic memory plays an important role in the integration of multiple components into a coherent episodic memory, in which episodic components in the different modalities are combined by temporal information as an index. The role of integration is mediated by the medial temporal lobe including the hippocampus and parahippocampal gyrus. Thus, temporal information in episodic memory could be represented in multiple stages, which are involved in a network of the lateral prefrontal, orbitofrontal, and medial temporal lobe regions.

Disentangling the Role of the MEC and LEC in the Processing of Spatial and Non-Spatial Information: Contribution of Lesion Studies.

It is now widely accepted that the entorhinal cortex (EC) plays a pivotal role in the processing of spatial information and episodic memory. The EC is segregated into two sub-regions, the medial EC (MEC) and the lateral EC (LEC) but a comprehensive understanding of their roles across multiple behavioral contexts remains unclear. Considering that it is still useful to investigate the impact of lesions of EC on behavior, we review the contribution of lesion approach to our knowledge of EC functions. We show that the MEC and LEC play different roles in the processing of spatial and non-spatial information. The MEC is necessary to the use of distal but not proximal landmarks during navigation and is crucial for path integration, in particular integration of linear movements. Consistent with predominant hypothesis, the LEC is important for combining the spatial and non-spatial aspects of the environment. However, object exploration studies suggest that the functional segregation between the MEC and the LEC is not as clearly delineated and is dependent on environmental and behavioral factors. Manipulation of environmental complexity and therefore of cognitive demand shows that the MEC and the LEC are not strictly necessary to the processing of spatial and non-spatial information. In addition we suggest that the involvement of these sub-regions can depend on the kind of behavior, i.e., navigation or exploration, exhibited by the animals. Thus, the MEC and the LEC work in a flexible manner to integrate the “what” and “where” information in episodic memory upstream the hippocampus.

Memory processes and executive functioning: novel trends for research

The existence of processes common to memory systems and executive functioning was evidenced by studies in the domain of cerebral neuroimaging, individual differences (mainly in normal aging) and, to a lesser extent, neuropsychology. Executive functioning depends on a large antero-posterior brain network, some regions of which (the middle dorsolateral and ventrolateral cortex, the dorsal anterior cingulate cortex) are involved in a series of executive processes, but also in encoding and retrieval of information in episodic memory and short-term memory. A consequence of lesions in frontal areas is to impair strategical organization of the information to-be-processed (an executive process) and thus leads to a lower memory capacity in frontal patients. Moreover, executive abilities will influence both memory efficiency and the associated brain networks even in people without brain pathology. These data attest to the importance of the relationships between executive and memory processes for an optimal cognitive functioning. Recent advances in neuroimaging and electrophysiology data acquisition and analysis techniques should allow us to better determine and understand the fashion in which these relationships work.

Brain Activity and Functional Coupling Changes Associated with Self-Reference Effect during Both Encoding and Retrieval

Information that is processed with reference to oneself, i.e. Self-Referential Processing (SRP), is generally associated with better remembering compared to information processed in a condition not related to oneself. This positive effect of the self on subsequent memory performance is called as Self-Reference Effect (SRE). The neural basis of SRE is still poorly understood. The main goal of the present work was thus to highlight brain changes associated with SRE in terms of activity and functional coupling and during both encoding and retrieval so as to assess the relative contribution of both processes to SRE. For this purpose, we used an fMRI event-related self-referential paradigm in 30 healthy young subjects and measured brain activity during both encoding and retrieval of self-relevant information compared to a semantic control condition. We found that SRE was associated with brain changes during the encoding phase only, including both greater activity in the medial prefrontal cortex and hippocampus, and greater functional coupling between these brain regions and the posterior cingulate cortex. These findings highlight the contribution of brain regions involved in both SRP and episodic memory and the relevance of the communication between these regions during the encoding process as the neural substrates of SRE. This is consistent with the idea that SRE reflects a positive effect of the reactivation of self-related memories on the encoding of new information in episodic memory.

Memory Self-Efficacy Beliefs Modulate Brain Activity when Encoding Real-World Future Intentions

BackgroundWhile the use of different cognitive strategies when encoding episodic memory information has been extensively investigated, modulation of brain activity by memory self-efficacy beliefs has not been studied yet.Methodology/Principal FindingsSixteen young adults completed the prospective and retrospective metamemory questionnaire, providing individual subjective judgments of everyday memory function. The day after, using functional magnetic resonance imaging, the participants had to memorize real-world intentions (e.g., return a book to the library), which were performed later on in a virtual environment. Participants also performed offline cognitive tasks evaluating executive functions, working memory, and attention. During encoding, activity was found in medial temporal lobe, left prefrontal cortex, medial parietal regions, occipital areas, and regions involved in (pre)motor processes. Based on results from the questionnaire, the group was split into low and high memory self-efficacy believers. Comparison of encoding-related brain activity between the 2 groups revealed that the low memory self-efficacy believers activated more the hippocampus bilaterally, right posterior parahippocampal cortex, precuneus, and left lateral temporal cortex. By contrast, more activity was found in dorsal anterior cingulate gyrus for the high-memory believers. In addition, the low-memory believers performed more poorly at feature binding and (at trend) manipulating visuospatial information in working memory.Conclusion/SignificanceOverall, these findings indicate that memory self-efficacy beliefs modulate brain activity during intentional encoding. Low memory self-efficacy believers activated more brain areas involved in visuospatial operations such as the hippocampus. Possibly, this increase reflects attempts to compensate for poor performance of certain neurocognitive processes, such as feature binding. By contrast, high-memory believers seemed to rely more on executive-like processes involved in cognitive control.

Interference with episodic memory retrieval following transcranial stimulation of the inferior but not the superior parietal lobule

Although posterior parietal cortex (PPC) has been traditionally associated with spatial attention and sensorimotor functions, recent neuroimaging evidence has suggested the involvement of regions of left PCC (LPPC) in memory retrieval. Yet, the role of the parietal lobe in memory-related functions is still controversial. Here we investigated the causal involvement of different LPPC regions in episodic memory retrieval using repetitive transcranial magnetic stimulation (rTMS) during a task that provided both objective and subjective measures of item recognition and source memory. Stimulation sites were identified on the basis of a recent fMRI study showing the involvement of regions of the default mode network (DMN), such as the angular gyrus (AG) in the inferior parietal lobule (IPL), during search for relevant information in episodic memory, and regions of the dorsal attention network (DAN), such as the superior parietal lobule (SPL), during perceptual search. We predicted a selective disruption of memory performance following rTMS stimulation of the left AG relative to a sham condition or stimulation of the left SPL. We found a modest but significant decrease of sensitivity for item recognition when AG was directly compared to SPL, but not to sham stimulation. A stronger effect was however observed for the criterion of source memory judgments when comparing AG with both SPL and sham stimulation, suggesting that the rTMS over AG affects subjective aspects of source monitoring associated with the weighing of relevant retrieved information for source attribution.

Associative information in memory: Evidence from cued recall

The representation of item and associative information in episodic memory was investigated using cued recall and single item recognition. In the first four experiments, participants studied two lists constructed such that some items presented in a pair during List 1 were rearranged to create new pairs in List 2 and were accompanied by pairs exclusive to List 2. List 1 was composed of either word–face pairs (Experiment 1 and 3) or word–word and face–face pairs (Experiment 2 and 4). Participants were tested for their memory of the second list containing only word-face pairs. When the test required associative information (i.e., cued recall), interference was specific to pair-type. Specifically, repeating items in the same pair-type across lists led to a greater number of correct and incorrect responses but repeating items in different pair-types did not change performance. When the test did not require associative information (i.e., single item recognition), interference was not specific to pair-type; hits and false alarms were higher for items presented on List 1. In the final experiment, the number of studied pairs and single items was independently manipulated and a pair-specific list length effect was observed. That is, performance in cued recall was modulated by the number of studied pairs, but not the number of studied individual items. Together, these data suggest that information specific to the pair-type (i.e., associative information) is stored and strategically utilized during memory search.

A stable hippocampal representation of a space requires its direct experience

In humans and other mammals, the hippocampus is critical for episodic memory, the autobiographical record of events, including where and when they happen. When one records from hippocampal pyramidal neurons in awake, behaving rodents, their most obvious firing correlate is the animal's position within a particular environment, earning them the name "place cells." When an animal explores a novel environment, its pyramidal neurons form their spatial receptive fields over a matter of minutes and are generally stable thereafter. This experience-dependent stabilization of place fields is therefore an attractive candidate neural correlate of the formation of hippocampal memory. However, precisely how the animal's experience of a context translates into stable place fields remains largely unclear. For instance, we still do not know whether observation of a space is sufficient to generate a stable hippocampal representation of that space because the animal must physically visit a spot to demonstrate which cells fire there. We circumvented this problem by comparing the relative stability of place fields of directly experienced space from merely observed space following blockade of NMDA receptors, which preferentially destabilizes newly generated place fields. This allowed us to determine whether place cells stably represent parts of the environment the animal sees, but does not actually occupy. We found that the formation of stable place fields clearly requires direct experience with a space. This suggests that place cells are part of an autobiographical record of events and their spatial context, consistent with providing the "where" information in episodic memory.

The construction of semantic memory: grammar-based representations learned from relational episodic information.

After acquisition, memories underlie a process of consolidation, making them more resistant to interference and brain injury. Memory consolidation involves systems-level interactions, most importantly between the hippocampus and associated structures, which takes part in the initial encoding of memory, and the neocortex, which supports long-term storage. This dichotomy parallels the contrast between episodic memory (tied to the hippocampal formation), collecting an autobiographical stream of experiences, and semantic memory, a repertoire of facts and statistical regularities about the world, involving the neocortex at large. Experimental evidence points to a gradual transformation of memories, following encoding, from an episodic to a semantic character. This may require an exchange of information between different memory modules during inactive periods. We propose a theory for such interactions and for the formation of semantic memory, in which episodic memory is encoded as relational data. Semantic memory is modeled as a modified stochastic grammar, which learns to parse episodic configurations expressed as an association matrix. The grammar produces tree-like representations of episodes, describing the relationships between its main constituents at multiple levels of categorization, based on its current knowledge of world regularities. These regularities are learned by the grammar from episodic memory information, through an expectation-maximization procedure, analogous to the inside–outside algorithm for stochastic context-free grammars. We propose that a Monte-Carlo sampling version of this algorithm can be mapped on the dynamics of “sleep replay” of previously acquired information in the hippocampus and neocortex. We propose that the model can reproduce several properties of semantic memory such as decontextualization, top-down processing, and creation of schemata.

Accuracy of hippocampal network activity is disrupted by neuroinflammation: rescue by memantine

Understanding how the hippocampus processes episodic memory information during neuropathological conditions is important for treatment and prevention applications. Previous data have shown that during chronic neuroinflammation the expression of the plasticity related behaviourally-induced immediate early gene Arc is altered within the CA3 and the dentate gyrus; both of these hippocampal regions show a pronounced increase in activated microglia. Low doses of memantine, a low to moderate affinity open channel uncompetitive N-Methyl-d-aspartate receptor antagonist, reduce neuroinflammation, return Arc expression to control levels and attenuate cognitive deficits induced by lipopolysaccharide. Here we investigate whether neuroinflammation affects the accuracy of information processing in the CA3 and CA1 hippocampal regions and if this is modified by memantine treatment. Using the immediate early gene-based brain-imaging method called cellular analysis of temporal activity by fluorescence in situ hybridization, it is possible to detect primary transcripts at the genomic alleles; this provides exceptional temporal and cellular resolution and facilitates the mapping of neuronal activity. Here, we use this method to compare the neuronal populations activated by two separate experiences in CA1 and CA3 and evaluate the accuracy of information processing during chronic neuroinflammation. Our results show that the CA3 pyramidal neuron activity is not stable between two exposures to the same environment context or two different contexts. CA1 networks, however, do not differ from control conditions. These data suggest that during chronic neuroinflammation, the CA3 networks show a disrupted ability to encode spatial information, and that CA1 neurons can work independently of CA3. Importantly, memantine treatment is able to partially normalize information processing in the hippocampus, suggesting that when given early during the development of the pathology memantine confers neuronal and cognitive protection while indirectly prevents pathological microglial activation.

Field Dependency and Brand Cognitive Structures

This research examines the impact of field dependency on the way people structure brand information in memory. The authors propose that a person's level of field dependency is an important determinant of the way information is stored in memory. Specifically, the authors argue that field independents are more likely to extract and integrate episodic information to form overall brand beliefs, while field dependents tend to store more detailed, episodic information in memory and are less likely to generalize information across product categories. The authors further propose that this effect is moderated by level of expertise and that such differences have important implications for how people evaluate marketing communications. The results from five studies support their propositions.

Executive functioning and memory as potential mediators of the episodic feeling-of-knowing accuracy

The study focused on the cognitive determinants of the accuracy of feeling-of-knowing (FOK) judgments made on episodic memory information. An individual differences approach was used on a sample of healthy older adults assessed on an episodic FOK task and on several neuropsychological measures. At a global level of analysis of FOK accuracy, the contributions of four general cognitive processes—episodic memory, executive functioning, fluid intelligence and processing speed—were examined concurrently. Stepwise regression analyses showed that executive functioning accounted for the major part of variance on FOK accuracy, followed by a significant contribution of episodic memory. After controlling for executive and memory involvement, fluid intelligence and processing speed no longer accounted for significant variance. At a more detailed level of analysis of FOK accuracy, the contributions of three specific executive processes—shifting, updating and inhibition—were assessed. The results revealed shifting function as the primary executive process engaged in the production of accurate FOK judgments in episodic memory. Some hypotheses are put forward to better understand the central role of executive functioning in the production of accurate FOK judgments.

Independent Codes for Spatial and Episodic Memory in Hippocampal Neuronal Ensembles

Hippocampal neurons were recorded under conditions in which the recording chamber was varied but its location remained unchanged versus conditions in which an identical chamber was encountered in different places. Two forms of neuronal pattern separation occurred. In the variable cue-constant place condition, the firing rates of active cells varied, often over more than an order of magnitude, whereas the location of firing remained constant. In the variable place-constant cue condition, both location and rates changed, so that population vectors for a given location in the chamber were statistically independent. These independent encoding schemes may enable simultaneous representation of spatial and episodic memory information.

Neurofisiología de la interacción entre la atención y la memoria episódica: revisión de estudios en modalidad visual

Attention is the process that provides us with the capacity to select perceptions or internal representations for conscious processing and action. Given that episodic memory is where our personal experiences are stored together with the context they take place in, it has been observed that disturbances affecting attention, whether they are due to neurological disorders or experimental manipulation, deteriorate the storage of episodic information. The aim of this study is to explain, from a neurophysiological perspective, how the processes of attention and memory interact with each other and which areas of the brain are involved in those processes. This objective is motivated by the fact that, despite empirical evidence supporting the interaction between the two processes, to our knowledge no reviews dealing with such an interaction have been published to date in the literature. In this work attention and memory are defined in terms of the neurophysiological changes that take place when the two processes occur. In what follows we offer a description of the systems that constitute attention, as well as those involved in the acquisition and recognition of information in episodic memory. Finally, we propose a possible explanation of how the mechanisms of interaction between these two processes work. The system of attention and the system of episodic memory are brought into play at the same time; the prefrontal cortex, in particular, plays a role in both processes. Attention seems to precede the mechanisms behind the acquisition of information while it is held during recognition.

Usage-Based Models of Language (review)

Reviewed by: Usage-based models of language ed. by Michael Barlow, Suzanne Kemmer Jean-Christophe Verstraete Usage-based models of language. Ed. by Michael Barlow and Suzanne Kemmer. Stanford: CSLI Publications, 2000. Pp. xxviii, 356. ISBN 1575862204. $22.95. Usage-based models of language provides an overview of recent work in linguistics that takes usage data seriously in modeling and theory formation, regarding language use not just as an instantiation of more abstract structures, but as a driving force that shapes and changes these structures. The editors’ introduction to the volume is a useful discussion of [End Page 875] some basic theoretical and methodological issues in usage-based approaches to language, such as the importance of patterns of frequency and variation in language change, the role of cognitive mechanisms as functional constraints on language structure, and the importance of contextual and cultural factors. The other papers in the volume elaborate specific aspects of usage-based approaches, ranging from highly programmatic papers that discuss what a linguistic model should look like if it takes usage data seriously, over psycholinguistic and computational experiments relating to the cognitive aspects of a usage-based approach, to data-intensive papers that show what it actually means to implement such an approach in linguistic description. The papers by Ronald Langacker and Sydney Lamb are the most programmatic ones in the volume: Langacker discusses why and how his model of ‘cognitive grammar’ is usage-based, and Lamb examines the theoretical and methodological prerequisites for network models of language. The articles by Brian MacWhinney and by Connie Dickinson and Talmy Givón both report on experiments that investigate the neural and cognitive aspects of usage-based models. MacWhinney provides an interesting overview of his work on connectionist modeling of language learning and acquisition, and Dickinson and Givón investigate the relationship between conversational interaction and the storage of information in episodic memory. The five other papers illustrate the implementation of a usage-based approach with data from different linguistic domains. Joan Bybee looks at phonetic variation relating to t/d deletion in Chicano English, showing that it is not distributed evenly over the lexicon and that it varies with the frequency of lexical items, and investigating the implications of these observations for phonological theory. Mira Ariel contrasts NP detachment and accessibility theory as two alternative explanations for the development of agreement markers from pronouns, and shows how synchronic patterns of usage in a corpus of Modern Hebrew can be used as evidence for the explanatory adequacy of accessibility theory. Arie Verhagen investigates the diachrony of causative constructions in Dutch, and argues that changes in the relative frequency of the two basic causative verbs laten and doen can be related to changes in cultural conceptions of authority. Douglas Biber illustrates how corpora can be used to study patterns of association between various linguistic features on different levels, and between linguistic and nonlinguistic features. Michael Barlow, finally, studies grammatical variation in collocations on the basis of corpora and provides an explanation in terms of blending theory. Taken together, the articles in this volume form a welcome introduction to usage-based models of language, with convincing arguments for the importance of taking usage data seriously, and interesting implementations of usage-based approaches on different linguistic levels. Jean-Christophe Verstraete University of Leuven Copyright © 2004 Linguistic Society of America

Attentional blink differences between adolescent dyslexic and normal readers

The goal of this study was to evaluate the possibility that dyslexic individuals require more working memory resources than normal readers to shift attention from stimulus to stimulus. To test this hypothesis, normal and dyslexic adolescents participated in a Rapid Serial Visual Presentation experiment (Raymond, Shapiro, & Arnell, 1992). Surprisingly, the result showed that the participants with dyslexia produced a shallower attentional blink than normal controls. This result may be interpreted as showing differences in the way the two groups encode information in episodic memory. They also fit in a cascade-effect perspective of developmental dyslexia.