SEARCH · PubMed Health

Results for “memory”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,621 records · Page 90Linked to original sources

PubMed2006

Heightened false memory: a long-term sequela of severe closed head injury.

Declarative memory impairment is a common long-term sequela of severe closed head injury (CHI). Although veridical memory performance following severe CHI has received attention in the literature, little is known about false memory production in this population. Within the present study, both long-term survivors of severe CHI and matched control participants studied and were tested on six 12-items word lists from the Deese Roediger McDermott (DRM) paradigm. Word lists from the DRM are composed of words that are strongly semantically associated to a non-presented word (i.e., the critical lure). Prior studies have shown that healthy young adults show a high level of false recall and recognition memory for the critical lures, and it was hypothesized individuals with severe CHI would show heightened susceptibility to false memory compared to control participants due to difficulty with monitoring of memory. It was further hypothesized that severe CHI participants would show high confidence in their false memories. Consistent with hypotheses, results indicated that although severe CHI participants remembered fewer actual list items, they made more semantically related intrusion errors (recall) and false-positive responses (recognition) than the control participants. Severe CHI participants also showed greater confidence in their false memories than did control participants. The results are interpreted in the context of theoretical accounts of false memory, and possible structural and functional brain changes that might account for the Severe CHI group's memory performance are discussed.

Adolescent↗

PubMed2004

Mental relaxation improves long-term incidental visual memory.

Experimental evidence has linked increased arousal to enhanced memory retention. There is also evidence that procedures reducing arousal, i.e., mental relaxation, might improve memory, but conflicting results have been reported. To clarify this issue, we studied the effects of a single session of relaxation training on incidental visual long-term memory. Thirty-two relaxation-naive subjects viewed 280 slides without being told that there would be subsequent memory testing. Afterwards, subjects listened to a 12 min relaxation tape; 16 subjects relaxed by following the instructions (relaxation group), and the other 16 subjects pressed a button whenever a body part was mentioned (control group). While listening to the relaxation tape, high frequency heart rate variability (HRV) was greater and low frequency HRV was lower in the relaxation group, implying effective relaxation and increasing parasympathetic activation. The relaxation group had superior memory retention 4 weeks later (p = .004), indicating enhancement of long-term memory performance. This effect could not be explained by retroactive interference experienced in the control group because short-term memory performance immediately after the tape was slightly better in the control group. Retention of materials acquired after the relaxation session remained unaffected, suggesting relaxation has retrograde effects on memory consolidation. Our data demonstrate a favorable influence of relaxation on at least this aspect of learning. Our data also extend previous knowledge on the beneficial effects of ascending parasympathetic stimulation on memory retention in that enhanced long-term memory consolidation may also occur in the presence of central and descending parasympathetic activation triggered by willful psychomotor activity.

Adult↗

PubMed2005

Cytotoxic lesions of the hippocampus do not impair social recognition memory in socially housed rats.

Socially housed mice with cytotoxic lesions of the hippocampus do not exhibit social recognition memory 30 min following exposure to a juvenile mouse, however the social recognition memory of singly housed rats is unimpaired. The present study tests the hypothesis that social housing of rats could render social recognition memory hippocampally dependent as seen for mice. Rats were housed with juveniles or with adults. Two social recognition one-animal tests paralleling those used with mice were carried out. Seven social discrimination two-animal tests were also given. Sham operated and hippocampally lesioned rats had normal social memory at 30 min whether socially housed for 24, 48 h, 7 or 8 days prior to testing. These findings support other results indicating the hippocampus proper is not required for normal social memory in rats. In a final experiment, rats socially housed in groups of three since weaning, were tested for 30 min and 24 h social memory. Unlike mice, rats socially housed throughout life exhibited social memory only at 30 min, but not at 24 h. Manipulations that extend social memory in rats may be required to render social memory hippocampally dependent or rats and mice may differ in the neural mediation of social memory.

Animals↗

PubMed2006

Cholinergic activity in the insular cortex is necessary for acquisition and consolidation of contextual memory.

Experiences with a high emotional content (aversive) tend to be stored as long-term memories; however, there are also contextual recollections, which form a significant part of our memories. Different research has shown that the insular cortex (IC) plays an important role during aversive memory formation, yet its role during incidental/non-aversive learning like pre-exposure contextual memory formation has received little attention. The objective of this research was to establish the role of cholinergic activity in the IC through its muscarinic receptors during the formation of inhibitory avoidance (IA) memory, as well as during pre-exposure contextual memory, using a paradigm such as latent inhibition (LI). Rats with bilateral cannulae directed into the IC were trained in the LI paradigm of IA or IA task alone. The muscarinic antagonist receptor scopolamine was infused bilaterally into the IC 5 min before the pre-exposure into the dark chamber of the IA cage, one day before the conventional IA training or during the IA training day. During the IA test, the entrance latency into the dark chamber of the IA cage was measured as an index of contextual memory. The results showed that scopolamine infused before and after IA training disrupts inhibitory avoidance memory. Also, it showed that the pre-exposed saline-infused animals (LI) had a lower entrance latency compared to the group not pre-exposed (IA). However, the group that received scopolamine into the IC before, but not after, the pre-exposure to the dark chamber, presented a similar latency to the IA group, showing a blockade of the latent inhibition of the IA. These results suggest that cholinergic activity in the insular cortex is necessary during the acquisition and consolidation of avoidance memory, but appears necessary only during the acquisition of pre-exposure non-aversive contextual memory.

Analysis of Variance↗

PubMed1987

Immunological discrimination between self and non-self by precursor depletion and memory accumulation.

We study processes by which T-lymphocytes "learn" to discriminate "self" from "non-self". We show that intrinsic features of the T cell activation and proliferation process are sufficient to tolerize (self) reactive T-lymphocyte clones. Self vs non-self discrimination therefore develops without any down-regulatory (e.g. suppressive) interactions. T-lymphocyte clones will expand by proliferation only if the IL2 concentration is high enough to induce a proliferation rate larger than the rate of cell decay. This concentration is the proliferation threshold. Because effector T cells are short-lived the proliferation threshold must be quite high. Such high numbers of cells producing IL2 are achieved only when sufficient (memory) precursors are activated. Self and non-self antigens differ with respect the number of (memory) precursor cells they accumulate, as a result of two processes, i.e. precursor depletion and memory accumulation, and can thus be discriminated. Precursor depletion: the dynamics of long-lived precursors can cause tolerization. In neonatal circumstances precursor influx is still low, newborn cells reacting with self antigens are immediately activated, generating (few), i.e. fewer than the proliferation threshold, effectors that decay rapidly. Thus total lymphocyte numbers remain low, yielding self tolerance. Conversely, large doses of similar antigens introduced in mature systems push "their" lymphocyte clone over the proliferation threshold because a large (accumulated) precursor population is rapidly activated. Small doses are however low zone tolerized. Memory accumulation: peripheral T-lymphocyte populations in fact consist of a mixture of virgin precursors and memory cells. If the formation process of (long-lived) memory cells is taken into account and virgin precursors are made short-lived, the proliferation threshold again accounts for self non-self discrimination. Memory cells accumulate when antigenic restimulation is low; it is low when the antigen concentration and/or the antigen affinity is low. Therefore self antigens, which are present in relatively high concentrations, fail to accumulate high affinity memory cells, and are hence tolerated. Memory cells crossreacting to self antigens with low affinity, however accumulate neonatally, pushing those clones over the proliferation threshold whenever "their" high affinity antigen enters the immune system. Thus the model generates differences in the antigenicity (i.e. memory precursor frequency) of self and non-self.(ABSTRACT TRUNCATED AT 400 WORDS)

Antigens↗

PubMed2002

Influence of age and executive functioning on verbal memory of inpatients with depression.

BACKGROUND: Despite many studies demonstrating memory and executive impairments in young and old depressed patients, the relationships between age, executive functioning and memory have not been evaluated in depression. The aim of this study was to investigate if older patients were more vulnerable than younger patients to the impact of depression on memory and if the differences between young and old depressed could be related to executive functioning. METHODS: Forty-nine inpatients, with unipolar and bipolar depression, ranging in age from 19 to 72 years were compared with 70 controls on a verbal memory task. Age cut-off of 45 years was used as a categorical variable to divide subjects into subgroups. A subset of patients (n=41) was also evaluated with the modified version of the Wisconsin Card Sorting Test and separated into a non-dysexecutive group and a group of patients with mild-executive impairment. RESULTS: Depressed patients exhibited memory deficits with a pattern of memory failure -- impaired free recall and normal cued recall and recognition -- interpreted as a retrieval problem. Both age and executive function influenced memory performance in depression, however neither group x age interaction nor age x executive status interaction were significant. Multiple regression analysis showed that free recall scores were related to age and psychomotor retardation in depressed patients. CONCLUSION: Age and executive functioning have different influences on the memory performance of depressed patients. Our findings support an 'executive memory decline hypothesis' in young as well as old depressed patients. The memory deficits in depression may be associated with both trait and state factors and raise questions about the long-term cognitive functioning of patients with recurrent affective disorders.

Adult↗

PubMed2003

Exercise training increases the näive to memory T cell ratio in old mice.

Aging is associated with changes in T cells including involution of the thymus gland and an imbalance in the proportion of näive (CD44lo) and memory (CD44hi) T cells in the periphery. Reversal of these changes may improve immunity in the aged. We sought to determine whether 4 months of moderately intense treadmill running (EXC; 5 days/week, 45 min/day, 13-22 m/min) in 2 month (Y) and 18 month (O) old male Balb/c mice would alter T lymphocyte profiles in the thymus and spleen when compared to sedentary controls (CON). Splenocytes and thymocytes were harvested 24-48 h after the last exercise session and analyzed using immunofluorescence and flow cytometry. While there were significant age-related changes (lower cell number, altered subsets) in the thymuses of O when compared to Y mice, exercise training failed to affect any of these measures in mice of either age. Aged mice exhibited a significantly (p < .05) higher percentage of splenic memory cells and a lower percentage of näive cells in both the CD4 and CD8 T cell subsets. Interestingly, exercise training significantly (p < .05) increased the percentage of näive and decreased the percentage of memory cells in both the CD4+ (69.6+/-1.7% näive and 30.4+/-1.7% memory for OCON vs. 75.0+/-1.5% näive and 25.0+/-1.5% memory in OEXC) and CD8+ (60.0+/-2.6% näive and 40.0+/-2.6% memory in OCON vs. 76.7+/-2.7% näive and 23.3+/-2.7% memory in OEXC) T cells subsets in O, but not Y, mice. This effect was due to a decrease in the absolute number of memory cells and not an increase in the absolute number of näive cells. We conclude that 4 months of EXC has little restorative effect on the thymus in aged mice, but can restore the percentages of näive and memory cells in the spleen towards that of young mice, perhaps due to removal of memory cells.

Aging↗

PubMed2003

Semantic memory and the human hippocampus.

It has been unclear whether the hippocampus is uniquely important for episodic memory (memory for events that are specific to time and place) or whether the hippocampus is also important for learning and remembering facts (semantic memory). In two studies, we assessed the capacity for semantic memory in patients with bilateral damage thought to be restricted primarily to the hippocampal region who developed memory impairment at a known time. Since the onset of their memory impairment, the patients have acquired less factual knowledge than controls. The patients also exhibit temporally limited retrograde amnesia for factual information from the several years preceding the onset of memory impairment. Remote memory for factual knowledge (from 11-30 years before amnesia) is intact. The results show that the hippocampal region supports semantic memory as well as episodic memory and that its role in the acquisition and storage of semantic knowledge is time limited.

Adult↗

PubMed1994

An experimental phenomenological approach to delusional memory in schizophrenia and late paraphrenia.

A preliminary model is described to account for the 'reality testing' of memories (after Johnson & Raye, 1981) in an attempt to explain delusional memory. Two routes are proposed: route one involves evaluation of the factual content of the memories against stored general knowledge. Route two relies on the evaluation of the perceptual and narrative characteristics of memories with the assumption that the stronger these characteristics, the more likely the memory is to be real. The integrity of these routes is examined in four patients with delusional memories, using standardized tests. The results suggest that in these cases, general knowledge is essentially intact while the perceptual characteristics of delusional memories are stronger than real memories which in turn, are stronger than fantasies. This could lead the evaluation system to accept delusional memories as true memories despite their implausibility. The roles of rehearsal and affect are probably important in this and require further study.

Adult↗

PubMed2002

Categoric overgeneral autobiographical memory in adolescents with major depressive disorder.

BACKGROUND: Categoric, overgeneral autobiographical memory is more common in depressed adults than controls and predicts persistence of depression. This cross-sectional study investigated whether, compared with non-depressed psychiatric cases and community controls, first episode major depressive disorder (MDD) in adolescents is associated with categoric overgeneral memory retrieval. METHODS: Ninety-six clinically referred adolescents (aged 12-17 years) with MDD, 26 non-depressed psychiatric cases and a sample of 33 community controls were recruited. All subjects were assessed using the Kiddie-Schedule for Schizophrenia and Affective Disorders, and completed Williams' cued Autobiographical Memory Test and the Mood and Feelings Questionnaire. Hamilton Depression Rating Scales were completed with MDD subjects, as an index of depression severity. RESULTS: Adolescents with current first episode MDD retrieved more categoric overgeneral memories than controls, but not than non-depressed psychiatric cases. Adolescents in full remission from a recent episode of MDD retrieved more categoric memories to positive cues than controls. Categoric memory in MDD was related to observer-rated and self-reported severity, but not to the pattern of co-morbid diagnoses. There were negative correlations between IQ and categoric memories in both clinical cases and controls. A positive correlation between categoric memory to negative cues and self-reported depressive symptoms was found in clinical cases (but not controls). CONCLUSIONS: In adolescents, increased categoric overgeneral memory is associated with, but not specific to first episode MDD. Positive categoric memories are also increased in fully remitted MDD as compared to controls.

Adolescent↗

PubMed1995

Differential effects of aging on memory for content and context: a meta-analysis.

The authors reviewed the evidence of age differences in episodic memory for content of a message and the context associated with it. Specifically, the authors tested a hypothesis that memory for context is more vulnerable to aging than memory for content. In addition, the authors inquired whether effort at encoding and retrieval and type of stimulus material moderate the magnitude of age differences in both memory domains. The results of the meta-analysis of 46 studies confirmed the main hypothesis: Age differences in context memory are reliably greater than those in memory for content. Tasks that required greater effort during retrieval yielded larger age differences in content but not in context memory. The greatest magnitude of age differences in context memory was observed for those contextual features that were more likely to have been encoded independently from content. Possible mechanisms that may underlie age differences in context memory-attentional deficit, reduced working memory capacity, and failure of inhibitory processing are discussed.

Adult↗

PubMed1992

Can reading ability be measured with tests of memory and processing speed?

The author investigated the possibility of estimating reading ability using tests of memory and processing speed that have significantly reduced reading requirements. Four hundred three air force trainees were given tests of their working memory and long-term memory processes, as well as a standardized reading test. A multiple correlation of .79 indicated that global reading ability is substantially correlated with memory processes. Additional analyses indicated that word knowledge and comprehension, the two major components of reading ability, were both explained by the same set of memory process factors, namely, long-term memory processes, semantic memory retrieval speed, and working memory capacity. These results, which are consistent with the view that memory ability underlies reading ability, support the endeavor of measuring reading ability with memory and processing speed tasks.

Adult↗

PubMed1997

Implicit memory effects when using pictures with children and adults: hypermnesia too?

Pictorial stimuli were used to investigate implicit- and explicit-memory phenomena in 3 experiments. The general procedure involved the presentation of a series of pictures during a study phase, followed by an implicit-memory test and an explicit-memory test. In the implicit-memory test, participants were presented with picture fragments and were instructed to write down what the fragment looked like. In the explicit-memory test, participants were asked to make a yes/no recognition decision regarding each picture. For children, implicit memory for pictures was robust when they were tested after a 48-hr interval, but that effect declined after 1 week; a similar implicit-memory effect for pictures was seen with college students; and the time course of the implicit-memory effect for pictures among college students (all short intervals of less than 1 week-1, 2, 3, 4, and 5 days) produced a more elevated implicit-memory performance than during the immediate testing condition. Hypermnesia may have been the cause of the increase in memory performance over the short intervals.

Adult↗

PubMed1992

Implicit and explicit memory in young, old, and demented adults.

Previous study of scopolamine and memory (Grober et al., 1989) showed that young adults given moderate or high doses of scopolamine maintained maximum cued recall in spite of a dose-dependent decrement in free recall when memory was assessed by cued selective reminding (CSR), a procedure which circumvents inattention and induces semantic processing. Intact recall by CSR indicates either that scopolamine impairs memory indirectly through effects on attention and information processing or that it impairs explicit memory but not implicit memory. In the present study which was done to determine if CSR reflects explicit or implicit memory, a free association test was used to estimate implicit memory after CSR was administered; explicit memory was estimated with a final trial of cued recall. Data from young, nondemented, and demented adults indicate that CSR reflects explicit memory supporting the interpretation of the previous study that scopolamine does not produce direct impairment of explicit memory.

Adolescent↗

PubMed2001

Memory for events and their spatial context: models and experiments.

The computational role of the hippocampus in memory has been characterized as: (i) an index to disparate neocortical storage sites; (ii) a time-limited store supporting neocortical long-term memory; and (iii) a content-addressable associative memory. These ideas are reviewed and related to several general aspects of episodic memory, including the differences between episodic, recognition and semantic memory, and whether hippocampal lesions differentially affect recent or remote memories. Some outstanding questions remain, such as: what characterizes episodic retrieval as opposed to other forms of read-out from memory; what triggers the storage of an event memory; and what are the neural mechanisms involved? To address these questions a neural-level model of the medial temporal and parietal roles in retrieval of the spatial context of an event is presented. This model combines the idea that retrieval of the rich context of real-life events is a central characteristic of episodic memory, and the idea that medial temporal allocentric representations are used in long-term storage while parietal egocentric representations are used to imagine, manipulate and re-experience the products of retrieval. The model is consistent with the known neural representation of spatial information in the brain, and provides an explanation for the involvement of Papez's circuit in both the representation of heading direction and in the recollection of episodic information. Two experiments relating to the model are briefly described. A functional neuroimaging study of memory for the spatial context of life-like events in virtual reality provides support for the model's functional localization. A neuropsychological experiment suggests that the hippocampus does store an allocentric representation of spatial locations.

Animals↗

PubMed2007

Reconsolidation of episodic memories: a subtle reminder triggers integration of new information.

Recent demonstrations of "reconsolidation" suggest that memories can be modified when they are reactivated. Reconsolidation has been observed in human procedural memory and in implicit memory in infants. This study asks whether episodic memory undergoes reconsolidation. College students learned a list of objects on Day 1. On Day 2, they received a reminder or not, and then learned a second list. Memory for List 1 was tested immediately on Day 2 (Experiment 2) or on Day 3 (Experiment 1). Although the reminder did not moderate the number of items recalled from List 1 on either day, subjects who received a reminder incorrectly intermixed items from the second list when recalling List 1 on Day 3. Experiment 2 showed that this effect does not occur immediately and thus is time-dependent. The reminder did not affect memory for List 2 on Day 3 (Experiment 3), demonstrating that modification occurred only for the original memory (List 1). The study demonstrates the crucial role of reminders for the modification of episodic memory, that reconsolidation of episodic memory is time-dependent, and, in contrast to previous reconsolidation findings, that reconsolidation is also a constructive process, one that supports the incorporation of new information in memory.

Adult↗

PubMed2004

When remembering is not enough: reflecting on self-defining memories in late adolescence.

This study examined which kinds of self-defining memories show spontaneous references to larger meanings, and listener responses to two kinds of meaning-lessons and insights. Narratives of three self-defining memories and episodes of telling the memories to others were collected from each of 168 late adolescents (M age=19). Narratives were coded for event type (relationship, mortality, achievement, and leisure) and for references to tension and to meaning (lesson or insight). Narratives of memorable episodes of having told the memories to others were coded for listener response (positive or negative). References to meaning emerged in one-fourth of the memory narratives, and meaning was more common for self-defining memory narratives that contained references to tension. Memories that reportedly had not been told to others in the past showed the same proportion of meaning as did memories that had been told to others (23%), with insights more prevalent than lessons. For memories that had been told to others, insights were more likely to be accepted by listeners than lessons. Implications were discussed for understanding the development of meaning in self-defining memories and the collaborative construction of identity.

Adolescent↗

PubMed2001

Control of chart memory for retesting acuity.

BACKGROUND: Enhancement of visual acuity has been demonstrated when retesting takes place within 24 hours and appears to be due to chart memory. Significant chart letter subset memory has been found after a single acuity measurement and can still be present 10 days after an examination involving several acuity measurements. Control of chart memory may increase the precision of acuity measurement. METHOD: A single acuity measurement was used to establish chart letter subset memory. Retroactive interference methods for the inhibition of chart letter memory have been compared using a letter recognition memory test. The experimental methods used to promote forgetting included a spelling backward exercise and near acuity assessment using a contra-chart. The contra-chart is constructed from the 16 letters not involved in the distance chart that was used to establish chart memory. RESULTS: Assessment of near vision using a contra-chart was found to inhibit chart letter memory. CONCLUSIONS: The contra-chart appears to have research and clinical applications that require control of measurement imprecision due to chart memory. Contra-charts obviate the need to use equivalent charts, which have the disadvantages of being difficult to use and control only for memory of letter sequences. The contra-chart can be included easily in an examination protocol for research or in a clinical examination sequence for which it will have the additional purpose of providing a guide to near vision performance.

Journal Article↗