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Episodic Memory (episodic + memory)
Terms modified by Episodic Memory Selected AbstractsConfabulation, but not executive dysfunction discriminate AD from frontotemporal dementiaEUROPEAN JOURNAL OF NEUROLOGY, Issue 11 2004Z. Nedjam We examined confabulation and performance on frontal/executive tasks in Alzheimer's disease (AD) patients and patients with a diagnosis of probable frontotemporal dementia (FTD). Twenty-two patients with probable AD, 10 patients with probable FTD and 32 normal control subjects entered the study. Executive functions were assessed with the Modified Card Sorting test; a verbal fluency test; the Cognitive Estimation test; and the Stroop test. Confabulations were assessed with a modified version of the Confabulation Battery. The Confabulation Battery included 10 questions tapping each of the following domains: Episodic Memory (memories of personal past episodes), Semantic Memory (knowledge of famous facts and famous people), and Personal Future (personal plans). The results revealed that both AD patients and FTD patients were clearly and equally impaired on tests of executive functions. Both patients' groups confabulated across the three tasks of the Confabulation Battery, but FTD patients confabulated significantly more than AD patients on Episodic Memory and Personal Future. The results failed to provide any evidence of a correlation between the performance on frontal/executive tasks and the tendency to produce confabulatory reports. According to our results, confabulation, more than a deficit of frontal/executive functions, discriminate between AD and FTD. Therefore, screening for confabulation and, possibly, for other types of memory distortions may constitute a useful additional clinical tool in order to discriminate AD from FTD. [source] Working and Episodic Memory in HIV Infection, Alcoholism, and Their Comorbidity: Baseline and 1-Year Follow-Up ExaminationsALCOHOLISM, Issue 10 2009Rosemary Fama Background:, Selective memory deficits occur in individuals with human immunodeficiency virus (HIV) infection and those with chronic alcoholism, but the potential compounded effect of these conditions is seldom considered, despite the high prevalence of alcohol use disorders in HIV infection. Methods:, Here, we examined component processes of working and episodic memory in HIV infection and chronic alcoholism (ALC) in 4 subject groups (HIV, ALC, HIV + ALC, and normal controls) at baseline and 1-year follow-up. Accuracy scores, response times, and rate of information processing were assessed with subtests of the computerized neuropsychological test battery, the MicroCog. Results:, Although individuals with either HIV infection or alcoholism generally performed at normal levels, individuals comorbid with HIV infection and alcoholism were impaired relative to controls and to the single diagnosis groups on selective memory processes. Immediate episodic memory was impaired, whereas working memory remained intact. Ability to retain information over time was not impaired in the clinical groups. Little performance change between groups was detected over 1 year. Results could not be explained by amount of alcohol consumed over a lifetime, CD4 cell count, AIDS diagnosis, or HAART medication. Conclusions:, This study provides behavioral support for adverse synergism of HIV infection and chronic alcoholism on brain function and is consistent with neuroimaging reports of compromised hippocampal and associated memory structures related to episodic memory processes in these 2 conditions. [source] Changes in the Episodic Memory and Executive Functions of Abstinent and Relapsed Alcoholics Over a 6-Month PeriodALCOHOLISM, Issue 3 2009Anne Lise Pitel Background:, It is still unclear whether episodic memory and executive functions capacities can return to normal in abstinent patients over a 6-month period. Furthermore, the role of interim drinking in cognitive recovery is still not well known. Finally, further research is required to specify the predictive value of cognitive abilities at initial testing in the treatment outcome (abstinence or relapse). The aims of the present study were therefore to measure changes in episodic memory and executive functions over a 6-month period in abstinent and relapsed alcoholics and to ascertain whether neuropsychological results at treatment entry can predict treatment outcome at follow-up. Methods:, Fifty-four alcoholic patients and 54 matched control subjects performed baseline neuropsychological tasks assessing episodic memory, executive functions, the slave systems of working memory and attentional abilities. At the follow-up session (i.e., 6 months later), episodic memory and 3 executive functions (inhibition, flexibility, and updating) were re-examined in the alcoholic patients. Results:, Results showed that over the 6-month interval, the abstainers' episodic memory and executive performances had returned to normal, whereas the relapsers performed lower than before in the flexibility task. Episodic memory and executive functions recovery was correlated, in abstainers, with drinking history and age respectively. Finally, there was no significant difference regarding neuropsychological scores at baseline between abstainers and relapsers. Discussion:, Over the 6-month interval, abstainers normalized episodic memory and executive performances whereas relapsers obtained executive results which were more severely impaired, emphasizing the influence of interim drinking on cognitive changes. Episodic memory, executive functions, the slave systems of working memory and attentional abilities did not appear to be reliable predictors of treatment outcome over a 6-month interval. [source] Long-Term Episodic Memory in Children with Attention-Deficit/Hyperactivity DisorderLEARNING DISABILITIES RESEARCH & PRACTICE, Issue 1 2008Jeffrey S. Skowronek Twenty-nine grade-matched 4th,8th-grade males, 12 with attention-deficit/hyperactivity disorder (ADHD) (age M= 12.2 years, SD= 1.48), and 17 without (age M= 11.5, SD= 1.59), completed two working memory tasks (digit span and the Simon game) and three long-term episodic memory tasks (a personal event memory task, story memory task, and picture recognition task). In line with clinical observations, children with ADHD performed worse than peers on all working memory tasks, but performed as well as or better than peers on long-term episodic tasks, demonstrating particularly detailed memory for personally experienced past events. Participants' parents also completed questionnaires about their children's memories in daily life. Parents rated children with ADHD lower than children without ADHD on working and semantic memory (e.g., remembering names, spelling, and math), but rated them as high or higher on memory for events. Implications for theory and educational practice are discussed. [source] Episodic memory,From brain to mindHIPPOCAMPUS, Issue 9 2006Janina Ferbinteanu Abstract Neuronal mechanisms of episodic memory, the conscious recollection of autobiographical events, are largely unknown because electrophysiological studies in humans are conducted only in exceptional circumstances. Unit recording studies in animals are thus crucial for understanding the neurophysiological substrate that enables people to remember their individual past. Two features of episodic memory,autonoetic consciousness, the self-aware ability to "travel through time", and one-trial learning, the acquisition of information in one occurrence of the event,raise important questions about the validity of animal models and the ability of unit recording studies to capture essential aspects of memory for episodes. We argue that autonoetic experience is a feature of human consciousness rather than an obligatory aspect of memory for episodes, and that episodic memory is reconstructive and thus its key features can be modeled in animal behavioral tasks that do not involve either autonoetic consciousness or one-trial learning. We propose that the most powerful strategy for investigating neurophysiological mechanisms of episodic memory entails recording unit activity in brain areas homologous to those required for episodic memory in humans (e.g., hippocampus and prefrontal cortex) as animals perform tasks with explicitly defined episodic-like aspects. Within this framework, empirical data suggest that the basic structure of episodic memory is a temporally extended representation that distinguishes the beginning from the end of an event. Future research is needed to fully understand how neural encodings of context, sequences of items/events, and goals are integrated within mnemonic representations of autobiographical events. © 2006 Wiley-Liss, Inc. [source] Dissociating the past from the present in the activity of place cellsHIPPOCAMPUS, Issue 9 2006Livia de Hoz Abstract It has been proposed that declarative memories can be dependent on both an episodic and a semantic memory system. While the semantic system deals with factual information devoid of reference to its acquisition, the episodic system, characterized by mental time travel, deals with the unique past experience in which an event took place. Episodic memory is characteristically hippocampus-dependent. Place cells are recorded from the hippocampus of rodents and their firing reflects many of the key characteristics of episodic memory. For example, they encode information about "what" happens "where," as well as temporal information. However, when these features are expressed during an animal's behavior, the neuronal activity could merely be categorizing the present situation and could therefore reflect semantic memory rather than episodic memory. We propose that mental time travel is the key feature of episodic memory and that it should take a form, in the awake animal, similar to the replay of behavioral patterns of activity that has been observed in hippocampus during sleep. Using tasks designed to evoke episodic memory, one should be able to see memory reactivation of behaviorally relevant sequences of activity in the awake animal while recording from hippocampus and other cortical structures. © 2006 Wiley-Liss, Inc. [source] Changes in the Episodic Memory and Executive Functions of Abstinent and Relapsed Alcoholics Over a 6-Month PeriodALCOHOLISM, Issue 3 2009Anne Lise Pitel Background:, It is still unclear whether episodic memory and executive functions capacities can return to normal in abstinent patients over a 6-month period. Furthermore, the role of interim drinking in cognitive recovery is still not well known. Finally, further research is required to specify the predictive value of cognitive abilities at initial testing in the treatment outcome (abstinence or relapse). The aims of the present study were therefore to measure changes in episodic memory and executive functions over a 6-month period in abstinent and relapsed alcoholics and to ascertain whether neuropsychological results at treatment entry can predict treatment outcome at follow-up. Methods:, Fifty-four alcoholic patients and 54 matched control subjects performed baseline neuropsychological tasks assessing episodic memory, executive functions, the slave systems of working memory and attentional abilities. At the follow-up session (i.e., 6 months later), episodic memory and 3 executive functions (inhibition, flexibility, and updating) were re-examined in the alcoholic patients. Results:, Results showed that over the 6-month interval, the abstainers' episodic memory and executive performances had returned to normal, whereas the relapsers performed lower than before in the flexibility task. Episodic memory and executive functions recovery was correlated, in abstainers, with drinking history and age respectively. Finally, there was no significant difference regarding neuropsychological scores at baseline between abstainers and relapsers. Discussion:, Over the 6-month interval, abstainers normalized episodic memory and executive performances whereas relapsers obtained executive results which were more severely impaired, emphasizing the influence of interim drinking on cognitive changes. Episodic memory, executive functions, the slave systems of working memory and attentional abilities did not appear to be reliable predictors of treatment outcome over a 6-month interval. [source] Memory function in normal agingACTA NEUROLOGICA SCANDINAVICA, Issue 2003Lars-Göran Nilsson Basic findings obtained on memory functions in normal aging are presented and discussed with respect to five separate but interacting memory systems. These systems are: episodic memory, semantic memory, short-term memory, perceptual representation system and procedural memory. All available evidence from cross-sectional research shows that there is a linear, decreasing memory performance as a function of age for episodic memory. Longitudinal studies suggest, however, that this age deficit may be an overestimation, by showing a relatively stable performance level up to middle age, followed by a sharp decline. Studies on semantic memory, short-term memory, perceptual representation system, and procedural memory show a relatively constant performance level across the adult life span, although some tasks used to assess short-term memory and procedural memory have revealed an age deficit. Disregarding the mixed results for these latter two memory systems, it can be concluded that episodic memory is unique in showing an age deficit. Episodic memory is also unique in the sense that it is the only memory system showing gender differences in performance throughout the adult life span with a significantly higher performance for women. [source] Dorsal hippocampus involvement in delay fear conditioning depends upon the strength of the tone-footshock associationHIPPOCAMPUS, Issue 7 2008Jennifer J. Quinn Abstract The hippocampus is important for the formation of spatial, contextual, and episodic memories. For instance, lesions of the dorsal hippocampus (DH) produce demonstrable deficits in contextual fear conditioning. By contrast, it is generally agreed that the DH is not important for conditioning to a discrete cue (such as a tone or light) that is paired with footshock in a temporally contiguous fashion (delay conditioning). There are, however, some reports of hippocampus involvement in delay conditioning. The present series of experiments was designed to assess the conditions under which the hippocampus-dependent component of delay fear conditioning performance may be revealed. Here, we manipulated the number of conditioning trials and the intensity of the footshock in order to vary the strength of conditioning. The results indicate that the DH contributes to freezing performance to a delay conditioned tone when the conditioning parameters are relatively weak (few trials or low footshock intensity), but not when strong parameters are used. The results are discussed in terms of two parallel memory systems: a direct tone-footshock association that is independent of the hippocampus and a hippocampus-dependent memory for the conditioning session. © 2008 Wiley-Liss, Inc. [source] Reliving lifelong episodic autobiographical memories via the hippocampus: A correlative resting PET study in healthy middle-aged subjectsHIPPOCAMPUS, Issue 5 2008Pascale Piolino Abstract We aimed at identifying the cerebral structures whose synaptic function subserves the recollection of lifetime's episodic autobiographical memory (AM) via autonoetic consciousness. Twelve healthy middle-aged subjects (mean age: 59 years ± 2.5) underwent a specially designed cognitive test to assess the ability to relive richly detailed episodic autobiographical memories from five time periods using the Remember/Know procedure. We computed an index of episodicity (number of Remember responses justified by the recall of specific events and details) and an index of retrieval spontaneity, and additionally an index of semanticized memories (number of Know responses). The regional cerebral blood flow (rCBF) was measured in the resting state, with H2O15 as part of an activation PET study. The indexes were correlated with blood flow using volumes of interest in frontotemporal regions, including hippocampus and voxel-wise analyses in SPM. With both analyses, significant correlations were mainly found between the index of episodicity and rCBF in the medial temporal lobe, including hippocampus, across the five time periods (unlike the index of semanticized memories) and between the spontaneity index and rCBF in the prefrontal areas. These results highlight, in healthy subjects, the distinct role of these two structures in AM retrieval and support the view that the hippocampus is needed for reexperiencing detailed episodic memories no matter how old they are. © 2008 Wiley-Liss, Inc. [source] EMDR: A putative neurobiological mechanism of actionJOURNAL OF CLINICAL PSYCHOLOGY, Issue 1 2002Robert Stickgold Numerous studies have provided evidence for the efficacy of eye movement desensitization and reprocessing therapy (EMDR) in the treatment of posttraumatic stress disorder (PTSD), including recent studies showing it to be more efficient than therapist-directed flooding. But few theoretical explanations of how EMDR might work have been offered. Shapiro, in her original description of EMDR, proposed that its directed eye movements mimic the saccades of rapid eye movement sleep (REM), but provided no clear explanation of how such mimicry might lead to clinical improvement. We now revisit her original proposal and present a complete model for how EMDR could lead to specific improvement in PTSD and related conditions. We propose that the repetitive redirecting of attention in EMDR induces a neurobiological state, similar to that of REM sleep, which is optimally configured to support the cortical integration of traumatic memories into general semantic networks. We suggest that this integration can then lead to a reduction in the strength of hippocampally mediated episodic memories of the traumatic event as well as the memories' associated, amygdala-dependent, negative affect. Experimental data in support of this model are reviewed and possible tests of the model are suggested. © 2002 John Wiley & Sons, Inc. J Clin Psychol 58: 61,75, 2002. [source] Memory fragments as components of autobiographical knowledgeAPPLIED COGNITIVE PSYCHOLOGY, Issue 3 2007Darryl Bruce Adults described and dated two kinds of personal remembrances: a fragment,a memory moment that is largely bereft of context,and an episodic, personal event memory,a narrative that consists of a number of related events. In Experiment 1 subjects reported memories from when they were 0,8 years of age and in Experiment 2, from when they were 0,16 years of age. Fragments were judged to be older than event memories, especially in Experiment 2 where the estimated ages of most fragments were from 0 to 8 years and of most episodic memories, from 8 to 16 years. Ratings of various features of the two kinds of memories also differed. We conclude that isolated memory moments possess validity and that although they are most likely to arise when the autobiographical memory system is not fully developed, they can also originate during a time when it is. Copyright © 2006 John Wiley & Sons, Ltd. [source] Critical evaluation of cognitive dysfunctions as endophenotypes of schizophreniaACTA PSYCHIATRICA SCANDINAVICA, Issue 2 2004S. Kéri Objective:, Cognitive dysfunctions are potential endophenotypes of schizophrenia. The aim of this study was to investigate whether recent evidence indeed suggests that cognitive dysfunctions are potent indicators of specific genetic traits that represent susceptibility for schizophrenia. Method:, Studies including large, well-defined samples and controlled cognitive assessment have been reviewed. Results:, Evidence suggests that schizophrenia patients and their unaffected biological relatives are impaired in several cognitive domains, including working memory, executive functions, sustained attention, verbal episodic memory, processing of visual and auditory stimuli, and smooth pursuit eye movements. However, these impairments are present only in a limited proportion of subjects, showing low specificity and sensitivity and high variability. Linkage with specific genes is weak. Conclusion:, Although some results are promising, at present cognitive dysfunctions cannot be considered as highly sensitive and specific endophenotypes of schizophrenia. [source] Ketamine use, cognition and psychological wellbeing: a comparison of frequent, infrequent and ex-users with polydrug and non-using controlsADDICTION, Issue 1 2009Celia J. A. Morgan ABSTRACT Introduction Preliminary research has indicated that recreational ketamine use may be associated with marked cognitive impairments and elevated psychopathological symptoms, although no study to date has determined how these are affected by differing frequencies of use or whether they are reversible on cessation of use. In this study we aimed to determine how variations in ketamine use and abstention from prior use affect neurocognitive function and psychological wellbeing. Method We assessed a total of 150 individuals: 30 frequent ketamine users, 30 infrequent ketamine users, 30 ex-ketamine users, 30 polydrug users and 30 controls who did not use illicit drugs. Cognitive tasks included spatial working memory, pattern recognition memory, the Stockings of Cambridge (a variant of the Tower of London task), simple vigilance and verbal and category fluency. Standardized questionnaires were used to assess psychological wellbeing. Hair analysis was used to verify group membership. Results Frequent ketamine users were impaired on spatial working memory, pattern recognition memory, Stockings of Cambridge and category fluency but exhibited preserved verbal fluency and prose recall. There were no differences in the performance of the infrequent ketamine users or ex-users compared to the other groups. Frequent users showed increased delusional, dissociative and schizotypal symptoms which were also evident to a lesser extent in infrequent and ex-users. Delusional symptoms correlated positively with the amount of ketamine used currently by the frequent users. Conclusions Frequent ketamine use is associated with impairments in working memory, episodic memory and aspects of executive function as well as reduced psychological wellbeing. ,Recreational' ketamine use does not appear to be associated with distinct cognitive impairments although increased levels of delusional and dissociative symptoms were observed. As no performance decrements were observed in the ex-ketamine users, it is possible that the cognitive impairments observed in the frequent ketamine group are reversible upon cessation of ketamine use, although delusional symptoms persist. [source] Major and minor depression in Parkinson's disease: a neuropsychological investigationEUROPEAN JOURNAL OF NEUROLOGY, Issue 9 2006A. Costa Previous studies have failed to distinguish the differential contribution of major and minor depression to cognitive impairment in patients with idiopathic Parkinson's disease (PD). This study was aimed at investigating the relationships among major depression (MD), minor depression (MiD) and neuropsychological deficits in PD. Eighty-three patients suffering from PD participated in the study. MD and MiD were diagnosed by means of a structured interview (SCID-I) based on the DSM-IV criteria, and severity of depression was evaluated by the Beck Depression Inventory. For the neuropsychological assessment, we used standardized scales that measure verbal and visual episodic memory, working memory, executive functions, abstract reasoning and visual-spatial and language abilities. MD patients performed worse than PD patients without depression on two long-term verbal episodic memory tasks, on an abstract reasoning task and on three measures of executive functioning. The MiD patients' performances on the same tests fell between those of the other two groups of PD patients but did not show significant differences. Our results indicate that MD in PD is associated with a qualitatively specific neuropsychological profile that may be related to an alteration of prefrontal and limbic cortical areas. Moreover, the same data suggest that in these patients MiD and MD may represent a gradual continuum associated with increasing cognitive deficits. [source] The role of the medial temporal lobe in autistic spectrum disordersEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 3 2005C. H. Salmond Abstract The neural basis of autistic spectrum disorders (ASDs) is poorly understood. Studies of mnemonic function in ASD suggest a profile of impaired episodic memory with relative preservation of semantic memory (at least in high-functioning individuals). Such a pattern is consistent with developmental hippocampal abnormality. However, imaging evidence for abnormality of the hippocampal formation in ASD is inconsistent. These inconsistencies led us to examine the memory profile of children with ASD and the relationship to structural abnormalities. A cohort of high-functioning individuals with ASD and matched controls completed a comprehensive neuropsychological memory battery and underwent magnetic resonance imaging for the purpose of voxel-based morphometric analyses. Correlations between cognitive/behavioural test scores and quantified results of brain scans were also carried out to further examine the role of the medial temporal lobe in ASD. A selective deficit in episodic memory with relative preservation of semantic memory was found. Voxel-based morphometry revealed bilateral abnormalities in several areas implicated in ASD including the hippocampal formation. A significant correlation was found between parental ratings reflecting autistic symptomatology and the measure of grey matter density in the junction area involving the amygdala, hippocampus and entorhinal cortex. The data reveal a pattern of impaired and relatively preserved mnemonic function that is consistent with a hippocampal abnormality of developmental origin. The structural imaging data highlight abnormalities in several brain regions previously implicated in ASD, including the medial temporal lobes. [source] Performance deficit of ,7 nicotinic receptor knockout mice in a delayed matching-to-place task suggests a mild impairment of working/episodic-like memoryGENES, BRAIN AND BEHAVIOR, Issue 6 2006C. Fernandes Patients with schizophrenia exhibit deficits in a range of cognitive functions, particularly working and episodic memory, which are thought to be core features of the disorder. Memory dysfunction in schizophrenia is familial and thus a promising endophenotype for genetic studies. Both human and animal studies suggest a role for the neural nicotinic acid receptor family in cognition and specifically the ,7-receptor subunit in schizophrenia and its endophenotypes. Consequently, we tested mice lacking the ,7 subunit of the neural nicotinic receptor (B6.129S7-Chrna7tm1Bay/J) in the delayed matching-to-place (DMP) task of the Morris water maze, a measure of working/episodic memory akin to human episodic memory. We report that a minor impairment in ,7 knockout mice was observed in the DMP task, with knockout mice taking longer to find the hidden platform than their wildtype controls. This suggests a role for the ,7 subunit in working/episodic memory and a potential role for the ,7 neural nicotinic receptor gene (CHRNA7) in schizophrenia and its endophenotypes. [source] A single-trace dual-process model of episodic memory: A novel computational account of familiarity and recollectionHIPPOCAMPUS, Issue 2 2010Andrea Greve Abstract Dual-process theories of episodic memory state that retrieval is contingent on two independent processes: familiarity (providing a sense of oldness) and recollection (recovering events and their context). A variety of studies have reported distinct neural signatures for familiarity and recollection, supporting dual-process theory. One outstanding question is whether these signatures reflect the activation of distinct memory traces or the operation of different retrieval mechanisms on a single memory trace. We present a computational model that uses a single neuronal network to store memory traces, but two distinct and independent retrieval processes access the memory. The model is capable of performing familiarity and recollection-based discrimination between old and new patterns, demonstrating that dual-process models need not to rely on multiple independent memory traces, but can use a single trace. Importantly, our putative familiarity and recollection processes exhibit distinct characteristics analogous to those found in empirical data; they diverge in capacity and sensitivity to sparse and correlated patterns, exhibit distinct ROC curves, and account for performance on both item and associative recognition tests. The demonstration that a single-trace, dual-process model can account for a range of empirical findings highlights the importance of distinguishing between neuronal processes and the neuronal representations on which they operate. © 2009 Wiley-Liss, Inc. [source] The role of medial temporal lobe in retrieving spatial and nonspatial relations from episodic and semantic memoryHIPPOCAMPUS, Issue 1 2010Lee Ryan Abstract This study examined the involvement of medial temporal lobe, especially the hippocampus, in processing spatial and nonspatial relations using episodic and semantic versions of a relational judgment task. Participants studied object arrays and were tested on different types of relations between pairs of objects. Three prevalent views of hippocampal function were considered. Cognitive map theory (O'Keefe and Nadel (1978) The Hippocampus as a Cognitive Map. USA: Oxford University Press) emphasizes hippocampal involvement in spatial relational tasks. Multiple trace theory (Nadel and Moscovitch (1997) Memory consolidation, retrograde amnesia and the hippocampal complex Curr Opin Neurobiol 7:217,227) emphasizes hippocampal involvement in episodic tasks. Eichenbaum and Cohen's ((2001) From Conditioning to Conscious Recollection: Memory Systems of the Brain. USA: Oxford University Press) relational theory predicts equivalent hippocampal involvement in all relational tasks within both semantic and episodic memory. The fMRI results provided partial support for all three theories, though none of them fit the data perfectly. We observed hippocampal activation during all relational tasks, with increased activation for spatial compared to nonspatial relations, and for episodic compared to semantic relations. The placement of activation along the anterior-posterior axis of the hippocampus also differentiated the conditions. We suggest a view of hippocampal function in memory that incorporates aspects of all three theories. © 2009 Wiley-Liss, Inc. [source] Evidence for episodic memory in a pavlovian conditioning procedure in ratsHIPPOCAMPUS, Issue 12 2007Jamus O'Brien Abstract In an effort to evaluate episodic memory processes in the rat, we developed a novel Pavlovian conditioning procedure. Rats explored two distinctive contexts, one in the morning and the other in the evening. Subsequently, either in the morning or the evening, they received a foot shock immediately upon entry into a third context that equally resembled the two explored contexts. When conditioned freezing was measured at an intermediate time of day, rats showed significantly more fear of the context congruent with the time of day of the foot shock. Thus, rats automatically form an integrated time,place memory that can be flexibly updated by future events, essential characteristics of episodic memory. © 2007 Wiley-Liss, Inc. [source] Memory in the aging brain: Doubly dissociating the contribution of the hippocampus and entorhinal cortexHIPPOCAMPUS, Issue 11 2007Andrew P. Yonelinas Abstract Since the time of Aristotle it has been thought that memories can be divided into two basic types; conscious recollections and familiarity-based judgments. Neuropsychological studies have provided indirect support for this distinction by suggesting that different regions within the human medial temporal lobe (MTL) are involved in these two forms of memory, but none of these studies have demonstrated that these brain regions can be fully dissociated. In a group of nondemented elderly subjects, we found that performance on recall and recognition tests was predicted preferentially by hippocampal and entorhinal volumes, respectively. Structural equation modeling revealed a double dissociation, whereby age-related reductions in hippocampal volume resulted in decreases in recollection, but not familiarity, whereas entorhinal volume was preferentially related to familiarity. The results demonstrate that the forms of episodic memory supported by the human hippocampus and entorhinal cortex can be fully dissociated, and indicate that recollection and familiarity reflect neuroanatomically distinct memory processes. © 2007 Wiley-Liss, Inc. [source] Episodic memory,From brain to mindHIPPOCAMPUS, Issue 9 2006Janina Ferbinteanu Abstract Neuronal mechanisms of episodic memory, the conscious recollection of autobiographical events, are largely unknown because electrophysiological studies in humans are conducted only in exceptional circumstances. Unit recording studies in animals are thus crucial for understanding the neurophysiological substrate that enables people to remember their individual past. Two features of episodic memory,autonoetic consciousness, the self-aware ability to "travel through time", and one-trial learning, the acquisition of information in one occurrence of the event,raise important questions about the validity of animal models and the ability of unit recording studies to capture essential aspects of memory for episodes. We argue that autonoetic experience is a feature of human consciousness rather than an obligatory aspect of memory for episodes, and that episodic memory is reconstructive and thus its key features can be modeled in animal behavioral tasks that do not involve either autonoetic consciousness or one-trial learning. We propose that the most powerful strategy for investigating neurophysiological mechanisms of episodic memory entails recording unit activity in brain areas homologous to those required for episodic memory in humans (e.g., hippocampus and prefrontal cortex) as animals perform tasks with explicitly defined episodic-like aspects. Within this framework, empirical data suggest that the basic structure of episodic memory is a temporally extended representation that distinguishes the beginning from the end of an event. Future research is needed to fully understand how neural encodings of context, sequences of items/events, and goals are integrated within mnemonic representations of autobiographical events. © 2006 Wiley-Liss, Inc. [source] Dissociating the past from the present in the activity of place cellsHIPPOCAMPUS, Issue 9 2006Livia de Hoz Abstract It has been proposed that declarative memories can be dependent on both an episodic and a semantic memory system. While the semantic system deals with factual information devoid of reference to its acquisition, the episodic system, characterized by mental time travel, deals with the unique past experience in which an event took place. Episodic memory is characteristically hippocampus-dependent. Place cells are recorded from the hippocampus of rodents and their firing reflects many of the key characteristics of episodic memory. For example, they encode information about "what" happens "where," as well as temporal information. However, when these features are expressed during an animal's behavior, the neuronal activity could merely be categorizing the present situation and could therefore reflect semantic memory rather than episodic memory. We propose that mental time travel is the key feature of episodic memory and that it should take a form, in the awake animal, similar to the replay of behavioral patterns of activity that has been observed in hippocampus during sleep. Using tasks designed to evoke episodic memory, one should be able to see memory reactivation of behaviorally relevant sequences of activity in the awake animal while recording from hippocampus and other cortical structures. © 2006 Wiley-Liss, Inc. [source] Functional connectivity with the hippocampus during successful memory formationHIPPOCAMPUS, Issue 8 2005Charan Ranganath Abstract Although it is well established that the hippocampus is critical for episodic memory, little is known about how the hippocampus interacts with cortical regions during successful memory formation. Here, we used event-related functional magnetic resonance imaging (fMRI) to identify areas that exhibited differential functional connectivity with the hippocampus during processing of novel objects that were subsequently remembered or forgotten on a postscan test. Functional connectivity with the hippocampus was enhanced during successful, as compared with unsuccessful, memory formation, in a distributed network of limbic cortical areas,including perirhinal, orbitofrontal, and retrosplenial/posterior cingulate cortex,that are anatomically connected with the hippocampal formation. Increased connectivity was also observed in lateral temporal, medial parietal, and medial occipital cortex. These findings demonstrate that successful memory formation is associated with transient increases in cortico-hippocampal interaction. © 2005 Wiley-Liss, Inc. [source] Consolidation of CS and US representations in associative fear conditioningHIPPOCAMPUS, Issue 5 2004Paul W. Frankland Abstract Much attention has been paid to the associative processes that are necessary to fuse together representations of the various components of an episodic memory. In the present study, we focus on the processes involved in the formation of lasting representations of the individual components that make up a fear-conditioning episode. In one-trial contextual fear conditioning experiments, weak conditioning to context occurs if the shock is delivered immediately following placement of the animal in a novel conditioning apparatus, a phenomenon known as the immediate shock deficit. We show that the immediate shock deficit in mice may be alleviated by pre-exposure to either the context or shock. In using this approach to temporally dissect a contextual fear-conditioning task into its constituent representational and associative processes, we are able to examine directly the processes that are important for formation of lasting representations of the context conditioned stimulus (CS) or unconditioned stimulus (US). Our data indicate that the formation of a lasting representation of the context or shock engages protein synthesis-dependent processes. Furthermore, genetic disruption of cAMP-responsive element binding protein (CREB), a transcription factor that regulates the synthesis of new proteins required for long-term memory, disrupts the formation of lasting context memories. We go on to show that the stress hormone epinephrine modulates the consolidation of a context memory, and reverses consolidation deficits in the CREB-deficient mice. Finally we show that disrupting either NMDA or calcium/calmodulin-dependent kinase II (CaMKII) function impairs consolidation of context memories. Together, these data suggest that this approach is particularly suited for the characterization of molecular and cellular processes underlying the formation of stimulus representations. © 2004 Wiley-Liss, Inc. [source] Neuropsychological correlates of hippocampal and rhinal cortex volumes in patients with mesial temporal sclerosisHIPPOCAMPUS, Issue 8 2003Catherine E. O'Brien Abstract Considerable progress has been made toward understanding the function of the primate rhinal cortex, comprising the entorhinal (ErC) and perirhinal (PrC) cortices. However, translating animal models to human memory has been limited by the technological problems associated with characterizing neural structures in vivo. Functional correlates of hippocampal and rhinal cortex volume changes were examined in a sample of 61 temporal lobe epilepsy patients with mesial temporal sclerosis (MTS; 33 left, 28 right). Patients were administered the Wechsler Adult Intelligence Scale (revised or third edition), the Wechsler Memory Scale (revised or third edition), and a spatial maze task. Neuropsychological data, together with rhinal cortex and hippocampal volumes, collected in our earlier study (O'Brien CE, Bowden SC, Whelan G, Cook MJ, unpublished observations), were analyzed using multiple regression. The only significant predictor of verbal memory function was the difference score between the volume of left hippocampus and the left PrC. Spatial maze scores were predicted by the bilateral sum of ErC volume. The difference score between the left hippocampus and left PrC volumes was the most powerful predictor of verbal episodic memory. Right hippocampal volume was not a significant predictor of nonverbal episodic memory. Verbal and nonverbal semantic memory were not significantly predicted by any combination of rhinal cortex structures. This quantitative study suggests a lateralized or material-specific memory function for the left hippocampus and left PrC, in contrast to the bilateral role of the ErC. The left hippocampus and left PrC appear to act on verbal memory function through an opposing relationship. Finally, differentiation between hippocampal and subhippocampal components in terms of episodic and semantic memory, respectively, could not be supported by the current data. © 2003 Wiley-Liss, Inc. [source] Dissociable neural responses in the hippocampus to the retrieval of facial identity and emotion: An event-related fMRI studyHIPPOCAMPUS, Issue 4 2003Tetsuya Iidaka Abstract In studies with brain-damaged patients and experimental animals, the medial temporal lobe, including the hippocampus and parahippocampal gyrus, has been found to play a critical role in establishing declarative or episodic memory. We measured the neural response in these structures, using event-related functional magnetic resonance imaging, while six healthy subjects performed the retrieval task for facial identity and emotion, respectively. Under the identity condition, the subjects participated in a yes/no recognition test for neutral faces learned before the scanning. Under the emotion condition, the subjects learned the faces with positive or negative expression and retrieved their expressions from neutral cue faces. The results showed that the left hippocampus is primarily involved in the identification of learned faces, and that the adjacent parahippocampal gyrus responds more to target than to distracter events. These results indicate a specific engagement of the left hippocampal regions in conscious recollection and identification of physiognomic facial features. The activity in the right hippocampus increased under both the identity and emotion conditions. The present results may relate with the functional model of face recognition in which the left hemisphere contributes to the processing of detailed features and the right hemisphere is efficient in the processing of global features. Hippocampus 2003;13:429,436. © 2003 Wiley-Liss, Inc. [source] Differential contributions of the parahippocampal place area and the anterior hippocampus to human memory for scenesHIPPOCAMPUS, Issue 6 2002Stefan Köhler Abstract Past neuroimaging research has identified a parahippocampal place area (PPA) in the posterior medial temporal lobe (MTL), which responds preferentially to visual scenes and plays a role in episodic memory for this class of stimuli. In the present positron emission tomography study, we examined to what extent the functional characteristics of the PPA resemble those of other, more anterior MTL regions across various learning and recognition-memory tasks. We also determined whether the involvement of the PPA in recognition of previously studied scenes is specific to a particular type of scene information. We found that, like the PPA, anterior hippocampal regions showed a novelty response (higher activation for novel than repeated scenes) and a stimulus-related response (higher activation for scenes than objects) during learning, indicating that MTL structures other than the PPA contribute to the encoding of novel stimulus relationships in scenes. However, these anterior hippocampal regions showed no involvement during recognition of either spatial or nonspatial information contained in scenes. The PPA, by contrast, was consistently involved in recognition of all types of scene details, presumably through interactions with co-activated parietal and occipitotemporal cortices. We suggest that MTL contributions from the PPA are sufficient to support recognition of scenes when the task can be based on a perceptually based familiarity process. Hippocampus 2002;12:718,723. © 2002 Wiley-Liss, Inc. [source] Coherence in consciousness: Paralimbic gamma synchrony of self-reference links conscious experiencesHUMAN BRAIN MAPPING, Issue 2 2010Hans C. Lou Abstract A coherent and meaningful percept of the world is essential for human nature. Consequently, much speculation has focused on how this is achieved in the brain. It is thought that all conscious experiences have reference to the self. Self-reference may either be minimal or extended, i.e., autonoetic. In minimal self-reference subjective experiences are self-aware in the weak sense that there is something it feels like for the subject to experience something. In autonoetic consciousness, consciousness emerges, by definition, by retrieval of memories of personally experienced events (episodic memory). It has been shown with transcranial magnetic stimulation (TMS) that a medial paralimbic circuitry is critical for self-reference. This circuitry includes anterior cingulate/medial prefrontal and posterior cingulate/medial parietal cortices, connected directly and via thalamus. We here hypothesized that interaction in the circuitry may bind conscious experiences with widely different degrees of self-reference through synchrony of high frequency oscillations as a common neural event. This hypothesis was confirmed with magneto-encephalography (MEG). The observed coupling between the neural events in conscious experience may explain the sense of unity of consciousness and the severe symptoms associated with paralimbic dysfunction. Hum Brain Mapp, 2010. © 2009 Wiley-Liss, Inc. [source] Effects of lorazepam on visual perceptual abilitiesHUMAN PSYCHOPHARMACOLOGY: CLINICAL AND EXPERIMENTAL, Issue 3 2008S. Pompéia Abstract Objective To evaluate the effects of an acute dose of the benzodiazepine (BZ) lorazepam in young healthy volunteers on five distinguishable visual perception abilities determined by previous factor-analytic studies. Methods This was a double-blind, cross-over design study of acute oral doses of lorazepam (2,mg) and placebo in young healthy volunteers. We focused on a set of paper-and-pencil tests of visual perceptual abilities that load on five correlated but distinguishable factors (Spatial Visualization, Spatial Relations, Perceptual Speed, Closure Speed, and Closure Flexibility). Some other tests (DSST, immediate and delayed recall of prose; measures of subjective mood alterations) were used to control for the classic BZ-induced effects. Results Lorazepam impaired performance in the DSST and delayed recall of prose, increased subjective sedation and impaired tasks of all abilities except Spatial Visualization and Closure Speed. Only impairment in Perceptual Speed (Identical Pictures task) and delayed recall of prose were not explained by sedation. Conclusion Acute administration of lorazepam, in a dose that impaired episodic memory, selectively affected different visual perceptual abilities before and after controlling for sedation. Central executive demands and sedation did not account for results, so impairment in the Identical Pictures task may be attributed to lorazepam's visual processing alterations. Copyright © 2008 John Wiley & Sons, Ltd. [source] | ||||||||||||||||||||||||||||