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PubMed2005

Investigation of implicit memory during isoflurane anesthesia for elective surgery using the process dissociation procedure.

BACKGROUND: This prospective study evaluated memory function during general anesthesia for elective surgery and its relation to depth of hypnotic state. The authors also compared memory function in anesthetized and nonanesthetized subjects. METHODS: Words were played for 70 min via headphones to 48 patients (aged 18-70 yr) after induction of general anesthesia for elective surgery. Patients were unpremedicated, and the anesthetic regimen was free. The Bispectral Index (BIS) was recorded throughout the study. Within 36 h after the word presentation, memory was assessed using an auditory word stem completion test with inclusion and exclusion instructions. Memory performance and the contribution of explicit and implicit memory were calculated using the process dissociation procedure. The authors applied the same memory task to a control group of nonanesthetized subjects. RESULTS: Forty-seven patients received isoflurane, and one patient received propofol for anesthesia. The mean (+/- SD) BIS was 49 +/- 9. There was evidence of memory for words presented during light (BIS 61-80) and adequate anesthesia (BIS 41-60) but not during deep anesthesia (BIS 21-40). The process dissociation procedure showed a significant implicit memory contribution but not reliable explicit memory contribution (mean explicit memory scores 0.05 +/- 0.14, 0.04 +/- 0.09, and 0.05 +/- 0.14; mean automatic influence scores 0.14 +/- 0.12, 0.17 +/- 0.17, and 0.18 +/- 0.21 at BIS 21-40, 41-60, and 61-80, respectively). Compared with anesthetized patients, the memory performance of nonanesthetized subjects was better, with a higher contribution by explicit memory and a comparable contribution by implicit memory. CONCLUSION: During general anesthesia for elective surgery, implicit memory persists even in adequate hypnotic states, to a comparable degree as in nonanesthetized subjects.

Adolescent↗

PubMed1997

Differential susceptibility of naive and memory CD4+ T cells to the cytopathic effects of infection with human immunodeficiency virus type 1 strain LAI.

CD4+ T lymphocytes of individuals infected with human immunodeficiency virus type 1 (HIV-1) exhibit a qualitative defect in their ability to mount memory responses to previously encountered antigens although their responses to mitogens remain normal. T cells responsible for memory responses can be distinguished from naive T cells based on differential expression of isoforms of the tyrosine phosphatase CD45. It has been suggested that memory CD4+ T cells from infected individuals have a greater virus burden than naive CD4+ T cells and that this accounts for the loss of recall responses in infected individuals. However, it has been unclear whether naive and memory T cells are equally susceptible to infection and to the cytopathic effects of the virus. We therefore infected highly purified resting naive and memory CD4+ T cells from HIV-1-seronegative individuals with HIV-1(LAI). Infected cells were then stimulated with phytohemagglutinin to render them permissive for viral replication. Cell viability and growth rate were monitored for 8 to 10 days as indicators of cytopathic effects induced by HIV-1(LAI). Our results indicated that naive and memory CD4+ T cells display marked differences in susceptibility to the cytopathic effects induced by HIV-1(LAI), infection. The cytopathic effects induced by HIV-1(LAI) were much more severe in memory CD4+ T cells than in naive CD4+ T cells. Differential cytopathic effects in naive and memory T cells were not due to differences in virus entry into and replication in these cell populations. Rather, memory cells were more susceptible to cytopathic effects. Pronounced cytopathic effects in memory cells were clearly detectable at 7 day postinfection. Cell death occurred at the single-cell level and was not accompanied by syncytium formation. The growth rate of infected memory CD4+ T cells was also severely compromised compared to that of naive CD4+ T cells, whereas the growth rates of both uninfected naive and memory CD4+ T cells were approximately the same. At least a portion of the dying cells exhibited biochemical changes characteristic of apoptosis. These results suggest that the selective functional defects present in the memory CD4+ T-cell subset of HIV-1-infected individuals may in part be the result of the greater susceptibility of memory T cells to cytopathic effects induced by HIV-1.

Apoptosis↗

PubMed2004

[Acceptance of memory impairment and satisfaction with life in patients with mild to moderate Alzheimer's disease].

In this study, we focused on acceptance of memory impairment and satisfaction with life in patients with mild to moderate Alzheimer's disease (AD). We interviewed 71 consecutive patients with AD and asked (1) whether they had memory loss, (2) whether they found trouble in life, and (3) how their daily life was. We categorized the patients into three groups based on awareness of memory loss and reference to the cause of memory loss. Cognitive functions were lower in patients who were not aware of memory loss. The rate of satisfaction with life was the highest in patients who were not aware of memory loss, and was the lowest in patients who complained of memory loss with reference to the cause of memory loss, indicating that patients could hardly accept their lives when memory impairment was a serious issue. However, in these patients, depression scores were not high, suggesting that they may somehow adapt themselves to their current status by defining the reason for memory loss. In patients who complained of memory impairment but did not refer to the cause of memory loss, there was a variation in awareness of memory loss and satisfaction with life. The present study indicated that we have to provide individual care and support for AD patients considering their level of acceptance of memory impairment.

Aged↗

PubMed2002

[Longitudinal study of procedural memory in patients with Alzheimer-type dementia].

We never forget how to ride a bicycle, and it is thought that procedural memories are retained for a long time. Recently, it was reported that patients with dementia of the Alzheimer type(DAT) could not only acquire, but also retain, long-lasting procedural memories. Previous group studies had shown procedural memory retention times of only 1 month in DAT patients, while amnesic patients and healthy people could retain such memories for 12 months. The relationship between the ability to retain procedural memory and the stage of the disease is not clear, as to date there has been no longitudinal study of procedural memory retention in DAT patients. Thus, we examined DAT patients' ability to retain long-term procedural memories (after 1, 5 and 20 months), and analyzed the relationship between procedural memory ability and the progress of disease. Motor-type procedural memory was examined using the mirror tracing task and the bi-manual coordinated tracing task. All three of the DAT patients showed improvement in their performance. The time required for the tracing was reduced between trials, and the improvement did not disappear between sessions, or rather, their times further decreased in subsequent sessions. Even the most severe DAT patient (Mini Mental State Examination(MMSE) score of 4) was able to acquire the procedural memory and retain it for at least 3 months. Furthermore, one of the subjects showed retention of the procedural memory at 20 months. Our results suggest that DAT patients can retain procedural memories for extended periods, with no relationship between retention ability and disease progression. It is possible for even severely demented patients to acquire and retain motor-type procedural memories. Cognitive rehabilitation in DAT appears to be effective, and it is possible for DAT patients to learn new things. It may be that DAT patients can ameliorate their quality of life by using retained procedural memory.

Aged↗

PubMedDate not supplied

Immunoglobulin M memory B cell decrease in inflammatory bowel disease.

BACKGROUND & OBJECTIVES: Memory B cells represent 30-60% of the B cell pool and can be subdivided in IgM memory and switched memory. IgM memory B cells differ from switched because they express IgM and their frequency may vary from 20-50% of the total memory pool. Switched memory express IgG, IgA or IgE and lack surface expression of IgM and IgD. Switched memory B cells derive from the germinal centres, whereas IgM memory B cells, which require the spleen for their survival and/or generation, are involved in the immune response to encapsulated bacteria. Since infections are one of the most frequent comorbid conditions in inflammatory bowel disease, we aimed to verify whether IgM memory B cell pool was decreased in Crohn's disease and ulcerative colitis patients. PATIENTS & METHODS: Peripheral blood samples were obtained from 22 Crohn's disease patients, 20 ulcerative colitis patients, 22 healthy controls and 18 splenectomized patients. To analyse peripheral blood lymphocytes, flow cytometry was performed using anti-CD19, anti-CD22, anti-CD27, anti-IgM, anti-IgD and anti-CD38 monoclonal antibodies. RESULTS: Circulating IgM memory B cells were significantly lower in Crohn's disease (median 7.1%, range 1.8-20.7) and ulcerative colitis patients (median 8.1%, range 2.1-18.8) in comparison to control subjects (median 14.0%, range 6.8-31.1). As expected, there was a highly significant difference in the proportion of IgM memory B cells between splenectomized patients (median 2.4%, range 0.9-6.9) and healthy controls. Crohn's disease patients with abscesses showed the lowest frequency of IgM memory B cells. DISCUSSION: Our findings show that peripheral IgM memory B cells are reduced in inflammatory bowel disease patients. Further studies are necessary to answer the question of whether high risk of infection (abscess development) is promoted by the reduction/depletion of IgM memory B-cell pool in inflammatory bowel disease.

Adult↗

PubMed1993

Stimulation of antigen-specific T- and B-cell memory in local as well as systemic lymphoid tissues following oral immunization with cholera toxin adjuvant.

In the present study we investigated immunological memory at the cellular level following oral immunization using cholera toxin (CT) as the mucosal adjuvant. We found that memory cells, isolated from mice orally primed with keyhole limpet haemocyanin (KLH) admixed with CT adjuvant 8 months earlier, responded by increased proliferation to antigen-challenge in vitro. In contrast, unstimulated memory cells or KLH-stimulated cells from naive mice did not respond. Memory cells were isolated from different lymphoid tissues; spleen (SP), mesenteric lymph nodes (MLN), Peyer's patches (PP) as well as the intestinal lamina propria (LP). Thus, oral immunization using CT adjuvant promoted the generation of memory cells that were present in both systemic and local intestinal lymphoid tissues. The demonstration of lymphokine production in the KLH-responsive cultures indicated the presence of antigen-specific memory T cells. Lymphokine production early in culture was dominated by interleukin-2 (IL-2), which peaked on day 2-3, followed by IL-5 and, in particular, interferon-gamma (IFN-gamma) which increased over time. Lamina propria memory cells were found to proliferate poorly to recall antigen in vitro compared to lymphocytes from SP or MLN. In contrast, very significant production of IL-5 and, in particular, IFN-gamma was demonstrable in LP cell cultures. The use of CT adjuvant also stimulated the generation of antigen-specific memory B cells following oral immunization. This was evidenced by KLH-specific antibody production in antigen-challenged memory lymphocyte cultures. The memory B cells produced IgM anti-KLH, while no detectable antigen-specific IgG or IgA was found. Unstimulated memory cells or naive cells failed to produce anti-KLH antibodies. These in vitro findings provide evidence that oral immunization using CT adjuvant stimulates both antigen-specific memory T and B cells. Furthermore, our data suggest the existence of memory B cells following oral CT adjuvant immunization which have retained the ability to produce IgM and which therefore probably have not undergone terminal isotype switch differentiation to other isotypes and thus have not deleted the mu constant heavy-chain gene. Finally, our data also suggest that memory T and B cells, either sessile in the various lymphoid tissues or recirculating, can be activated by antigen in situ in, for example, lymph nodes and spleen and, more importantly, in the intestinal LP itself.

Adjuvants, Immunologic↗

PubMed1997

[Human memory and its animal models].

The term memory expresses the ability of the human or animal CNS to store information. Memory can be classified according to different principles. Short-term memory and long-term memory represent the basic classification. Within the long-term memory, a declarative and a nondeclarative form can be distinguished. The declarative memory provides a consciously accessible record of individual previous experiences. Nondeclarative memory includes motor skills, perceptual procedures and simple conditioned reactions. It is characteristic for nondeclarative knowledge, that the individual is not well aware what exactly he learned. Formation of the declarative memory traces requires processing in the hippocampus, while nondeclarative learning does not. Studies on animals suggest that declarative memory is stored by changes in synaptic strength at contacts involving NMDA receptors in the hippocampus. The ion channel associated with the NMDA receptor is usually blocked by Mg2-. It becomes unblocked only when the postsynaptic cell is depolarized, for instance during simultaneous activation of NMDA and nonNMDA receptors. Resulting Ca2+ influx into the postsynaptic cell initiates activation of second-messenger kinases followed by strengthening the synapses that were activated during depolarization. The molecular substrate of nondeclarative memory in unknown. Both forms of memory can be modelled in laboratory animals and analyzed experimentally. An analogy of declarative memory requires memory-stored cognitive maps of the outside world and lists of expected consequences of various actions. Motor learning can serve as a suitable model of complex nondeclarative (procedural) memory.

Animals↗

PubMed2000

Are memory complaints predictive for dementia? A review of clinical and population-based studies.

OBJECTIVES: To review studies that have reported on the prevalence of memory complaints and the relationship between memory complaints and impairment or decline (dementia) in elderly individuals. DATA SOURCES AND STUDY SELECTION: All publications in the English language relating to memory complaints, memory impairment, cognitive disorder and dementia in MEDLINE, PSYCHLIT and EMBASE computerized databases, together with a search of relevant citations. DATA SYNTHESIS: The prevalence of memory complaints, defined as everyday memory problems, shows a large variation of approximately 25 - 50%. A high age, female gender and a low level of education are generally associated with a high prevalence of memory complaints. In community-based samples of elderly subjects an association has been found between memory complaints and memory impairment, after adjustment for depressive symptomatology. Memory complaints predict dementia after a follow-up of at least 2 years, in particular in those with mild cognitive impairment, defined as Mini Mental State Examination (MMSE) > 23. Memory complaints in highly educated elderly subjects may be predictive of dementia even when there is no indication of cognitive impairment on short cognitive screen tests. The shift in methodology which is noticeable in the recently published major studies is discussed as a possible explanation for the established association between memory complaints and decline in memory (or dementia) in elderly subjects. Three methodological factors, in particular, are responsible for the results: community-based sampling, longitudinal design and the treatment of variables such as depression, cognitive impairment and level of education. CONCLUSION: Memory complaints in elderly people should no longer be considered merely as an innocent age-related phenomenon or a symptom of depression. Instead, these complaints deserve to be taken seriously, at least as a possible early sign of dementia.

Aged↗

PubMed1993

Spatial memory in amnesia: evidence from Korsakoff patients.

Two experiments are reported which investigated a hypothesised disproportionate deficit in amnesic spatial memory. Korsakoff amnesic memory for the locations of objects or words placed on a grid was compared to control memory which had been attenuated by longer delays before testing. The effects of incidental versus intentional encoding of the locations were compared. No significant evidence of a disproportionate spatial memory deficit in Korsakoff amnesia was found, intentional instructions did not improve Korsakoff amnesic spatial memory scores, and there was no significant evidence of a trade-off of item memory and location memory specific to the Korsakoff amnesic group. Rather, intentional instructions significantly reduced item memory in both Korsakoff amnesics and normal controls, while having no effect on spatial memory. When location was scored by lenient criteria, there was no significant difference between groups for this measure, nor for recall and recognition memory for these items. Thus Korsakoff amnesic memory was very similar to that of control memory attenuated by longer delays before testing. The Korsakoff amnesic subjects' memory therefore differed quantitatively rather than qualitatively from that of control subjects' memory.

Adult↗

PubMedDate not supplied

Memory reactivation and consolidation during sleep.

Do our memories remain static during sleep, or do they change? We argue here that memory change is not only a natural result of sleep cognition, but further, that such change constitutes a fundamental characteristic of declarative memories. In general, declarative memories change due to retrieval events at various times after initial learning and due to the formation and elaboration of associations with other memories, including memories formed after the initial learning episode. We propose that declarative memories change both during waking and during sleep, and that such change contributes to enhancing binding of the distinct representational components of some memories, and thus to a gradual process of cross-cortical consolidation. As a result of this special form of consolidation, declarative memories can become more cohesive and also more thoroughly integrated with other stored information. Further benefits of this memory reprocessing can include developing complex networks of interrelated memories, aligning memories with long-term strategies and goals, and generating insights based on novel combinations of memory fragments. A variety of research findings are consistent with the hypothesis that cross-cortical consolidation can progress during sleep, although further support is needed, and we suggest some potentially fruitful research directions. Determining how processing during sleep can facilitate memory storage will be an exciting focus of research in the coming years.

Animals↗

PubMed2005

Socioaffective factors modulate working memory in schizophrenia patients.

Working memory deficit in schizophrenia is a core cognitive feature of the disorder and is reliably associated with abnormalities of the prefrontal circuitry. Working memory deficits are also associated with impaired social functioning and present a major obstacle toward successful rehabilitation in schizophrenia. Although the role of prefrontal cortex in working memory has been extensively investigated, the intricate relations among the prefrontal circuitry, working memory and social behaviors are not clearly understood. In this study, we manipulated social context and observed its effects on spatial working memory. In experiment 1, the effects of social and asocial reinforcements on spatial working memory were examined in schizophrenic patients and healthy controls. The results show that social but not asocial reinforcements facilitated spatial working memory in schizophrenic patients. In experiment 2, the effects of human voice reinforcements (with or without affect) on working memory was investigated. Voice reinforcements did not facilitate working memory relative to the no-reinforcement condition. There was no difference between high-affect vs flat-affect voice conditions. In experiment 3, the effects of direct and indirect social interactions on spatial working memory were studied. Direct but not indirect social interaction facilitated working memory in schizophrenic patients. These results suggest that social context might facilitate working memory in schizophrenic patients perhaps by activating frontal lobe systems. In addition, the possibility of improving cognitive functions such as working memory using seemingly non-cognitive methods might lead to potential remediation strategies.

Adult↗

PubMed2006

Human memory development and its dysfunction after early hippocampal injury.

Cognitive memory involves long-term memories for facts (semantic memory) and personal experiences (episodic memory) that can be brought to mind. There is consensus that the hippocampus and related medial temporal lobe (MTL) structures are crucial for adult cognitive memory, but much less is known about their contribution to memory during infancy and childhood. We argue that the MTL is involved in memory from early in life, supporting recognition memory within the first postnatal months and recall memory within the first year. We propose that normal development involves a sequence in which a form of semantic-like memory emerges first, whereas the characteristics of episodic memory develop only later with progressive development of the hippocampus. Early bilateral injury to the hippocampus disrupts this normal pattern such that memory skills cannot develop beyond the stage of semantic memories. This review is part of the INMED/TINS special issue "Nature and nurture in brain development and neurological disorders", based on presentations at the annual INMED/TINS symposium (http://inmednet.com/).

Brain Injuries↗

PubMed2004

What happens to information to be suppressed in working-memory tasks? Short and long term effects.

The study explored, from an individual differences point of view, what happens to information to be suppressed in a working-memory task at short and long term. In particular, it was examined whether control mechanisms of irrelevant information in working memory imply their complete elimination from working memory or just the modulation of their activation. To this end, we compared the fate of irrelevant information in groups of subjects with high and low reading comprehension (Experiments 1 and 2) and subjects with high and low working memory (Experiments 1, 2, 3, and 4). All the experiments presented a working-memory task devised by De Beni, Palladino, Pazzaglia, and Cornoldi (1998), which required participants to process lists of words, to tap when a word from a particular category was presented, and then to recall only the last items in each list. Results confirmed that participants with high reading comprehension also have higher working memory and make less intrusion errors due to irrelevant items that have to be processed but then discarded. Furthermore, it was found that participants with low working memory have slightly better implicit (Experiment 1) and explicit memory (Experiments 3 and 4) of highly activated irrelevant information. Nevertheless, in a long-term recognition test, participants with high and low reading comprehension/working memory presented a similar pattern of memory for different types of irrelevant information (Experiment 2), whereas in a short-term memory recognition test, low-span participants presented a facilitation effect in the time required for the recognition of highly activated irrelevant information (Experiment 4). It was concluded that efficient working-memory performance is related to the temporary reduction of activation of irrelevant information but does not imply its elimination from memory.

Adult↗

PubMed2000

Disturbed memory and amnesia related to intensive care.

Patients, when admitted to an intensive care unit (ICU), have one thing in common: their illness is life-threatening. Patients may remain on ICU in a critical condition, needing support with their breathing, circulation, and/or kidneys for varying lengths of time, from days to weeks. During that time the patients will receive sedative and analgesic drugs to ensure compliance with artificial ventilation. Patients recovering from critical illness frequently have little or no recall of their period in ICU, or remember nightmare, hallucinations, or paranoid delusions. The nature, extent and reason for these difficulties, have been under-reported and consequently our purpose was to conduct a review of memory problems experienced by ICU patients. A systematic literature review of computer databases (Medline, PsycLit, and CINAHL) identified 25 relevant papers. In addition, other relevant articles were obtained, citation lists and associated articles retrieved. Due to lack of research on processes underlying memory problems in ICU patients all articles that introduced an insight into possible mechanisms were included in the review. There seem to be two possible processes contributing to memory problems in ICU patients. First the illness and treatment may have a general dampening effect on memory. Delirium and sleep disturbance are both common in ICU patients. Delirium can result in a profound amnesia for the period of confusion. Sleep deprivation exacerbates the confusional state. Slow wave sleep is important for the consolidation of episodic memories. Treatment administered to patients in ICU can have effects on memory. Opiates, benzodiazepines, sedative drugs such as propofol, adrenaline, and corticosteroids can all influence memory. In addition, the withdrawal of drugs, such as benzodiazepines, can cause profound withdrawal reactions, which may contribute to delirium. Second, we hypothesise that there is a process that affects memory negatively for external events but enhances memory for internal events. The physical constraints and social isolation experienced by ICU patients and the life-threatening nature of the illness may increase the experience of hypnagogic hallucinations. Attentional shift during hypnagogic images from external stimuli to internally generated images would explain why ICU patients have such poor recall of external ICU events, but can clearly remember hallucinations and nightmares. Patients describe these memories as being very vivid and this is explored in terms of flashbulb memory formation. The absence of memories for real events on ICU can result in ICU patients remembering paranoid delusions of staff trying to kill them, with little information to reject these vivid memories as unreal. This has implications for patients' future psychological health.

Critical Care↗

PubMed2000

Prospective and retrospective memory in normal ageing and dementia: a questionnaire study.

Frequency of prospective memory and retrospective memory failures was rated on a 16-item questionnaire by 862 volunteers, from five groups: patients with Alzheimer Disease (rated by carers), carers of Alzheimer Disease patients, elderly, young, and a group of married couples. Reported memory failures were highest for Alzheimer Disease patients, and lowest for carers, with elderly and young controls in between. More prospective memory than retrospective memory failures were reported in all groups, although the difference was small for Alzheimer Disease patients who were rated near ceiling for both. Prospective memory failures of Alzheimer Disease patients were reported as more frustrating for carers than retrospective memory failures; prospective memory and retrospective memory failures frustrated Alzheimer Disease patients equally. Data from the couples indicated that there were no biases resulting from rating on behalf of someone else. These results suggest that: (1) normal ageing has no greater effect on self-reported retrospective memory than prospective memory failures, (2) the relatively small number of memory failures reported by carers may result from comparing themselves with the Alzheimer Disease patients in their care, and (3) prospective memory failures have a greater impact on the lives of the carers and are therefore more likely to be reported as early indicants of the disease.

Adolescent↗

PubMed1992

Improving memory and control beliefs through cognitive restructuring and self-generated strategies.

Memory problems are a major source of concern among older adults. The goal of this research was to evaluate methods for improving memory performance and beliefs about memory ability and control. Men and women between the ages of 60 and 85 were randomly assigned to one of five treatment groups: (1) cognitive restructuring to promote adaptive beliefs about memory, (2) memory skills training, (3) combined cognitive restructuring and memory skills training, (4) practice on memory tasks, and (5) a no-contact control group. Beliefs about memory (ability and control) and memory performance (working memory, recall of text materials, categorizable word list, and names and faces) were assessed at a pretest and two posttests. As predicted, those receiving the combined treatment showed the greatest increases in their sense of control and perceived ability to improve memory. Results indicated that all groups improved equally on the memory tasks, although those who had received memory training were more likely to report at the second posttest that they had begun using new strategies for remembering things.

Adaptation, Psychological↗

PubMed2001

Memory, delusions, and the development of acute posttraumatic stress disorder-related symptoms after intensive care.

OBJECTIVE: To examine prospectively the relationship between memories of intensive care (ICU) and levels of anxiety after ICU discharge, the stability of these memories with time, and their relationship to the development of acute posttraumatic stress disorder (PTSD)-related symptoms. DESIGN: Case series cohort assessed by interview at 2 and 8 wks after ICU discharge. SETTING: District general hospital (serving a population of 350,000) general intensive care unit. PATIENTS: Memories of ICU and anxiety levels were studied in 45 patients after ICU discharge. Thirty patients were examined again at 8 wks to assess memory stability and development of acute PTSD-related symptoms. MEASUREMENTS AND MAIN RESULTS: Standardized interviews and questionnaires were used to assess memory for ICU, anxiety, and depression 2 wks after ICU discharge. In addition, PTSD-related symptoms and panic were assessed 8 wks after ICU discharge. A total of 33 of 45 patients had delusional memories from ICU at 2 wks; nine of the patients with delusional memories had no factual memories, and these patients had higher anxiety levels 2 wks after ICU discharge (p < .0001). Thirty patients had paired assessments at 2 and 8 wks. Those patients who had no factual recall of ICU but had delusional memories at 2 wks scored highly for PTSD-related symptoms and panic attacks at 8 wks (p = .023 and .014, respectively). The only predictors of possible acute PTSD-related symptoms at the 8-wk assessment were trait anxiety (p = .006) and having delusional memories without recall of factual events in the ICU at 2 wks (p < .0001). Only delusional memories were retained over time, whereas the recall of factual events in the ICU declined. CONCLUSIONS: We propose that the development of acute PTSD-related symptoms may be related more to recall of delusions alone. This study suggests that even relatively unpleasant memories for real events during critical illness may give some protection from anxiety and the later development of PTSD-related symptoms when memories of delusions are prominent.

Acute Disease↗

PubMedDate not supplied

Stability of recent and remote contextual fear memory.

Following initial encoding, memories undergo a prolonged period of reorganization. While such reorganization may occur in many different memory systems, its purpose is not clear. Previously, we have shown that recall of recent contextual fear memories engages the dorsal hippocampus (dHPC). In contrast, recall of remote contextual fear memories engages a number of different cortical regions, including the anterior cingulate cortex (ACC). To examine whether this reorganization leads to greater memory stability, we examined reconsolidation of 1 d-old (recent) and 36 d-old (remote) contextual fear memory in mice. We infused the protein synthesis inhibitor, anisomycin (ANI), into either the dHPC or ACC immediately following retrieval of either a recent or remote contextual fear memory. In the dHPC, ANI infusions disrupted subsequent expression of recent, but not remote, contextual fear memory. Similar infusions into the ACC had no effect on either recent or remote contextual fear memories, whereas systemically applied ANI blocked subsequent remote memory expression when long re-exposure durations were used. Together, these data suggest that as memories mature they become increasingly stable. Furthermore, the dissociation between the effects of systemically and centrally administered ANI on remote memory suggests that stability is due, in part, to the distributed nature of remote contextual fear memories.

Animals↗