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PubMed1998

The development of memory.

This article reviews recent advances in understanding the changes in memory function that take place during the childhood years. Development of the following aspects of memory are considered: short-term memory, comprising phonological memory, visuospatial memory, and executive function; autobiographical memory; episodic memory, including eyewitness memory; and metamemory. Each of these aspects of memory function shows substantial qualitative change from infancy, through the preschool period, to the early school years. Beyond about 7 years of age, however, memory function appears adult-like in organisation and strategies, and shows only a gradual quantitative improvement through to early adolescence.

Child↗

PubMed1998

Dissociation of mnemonic and perceptual processes during spatial and nonspatial working memory using fMRI.

Neuroimaging studies in humans have consistently found robust activation of frontal, parietal, and temporal regions during working memory tasks. Whether these activations represent functional networks segregated by perceptual domain is still at issue. Two functional magnetic resonance imaging experiments were conducted, both of which used multiple-cycle, alternating task designs. Experiment 1 compared spatial and object working memory tasks to identify cortical regions differentially activated by these perceptual domains. Experiment 2 compared working memory and perceptual control tasks within each of the spatial and object domains to determine whether the regions identified in experiment 1 were driven primarily by the perceptual or mnemonic demands of the tasks, and to identify common brain regions activated by working memory in both perceptual domains. Domain-specific activation occurred in the inferior parietal cortex for spatial tasks, and in the inferior occipitotemporal cortex for object tasks, particularly in the left hemisphere. However, neither area was strongly influenced by task demands, being nearly equally activated by the working memory and perceptual control tasks. In contrast, activation of the dorsolateral prefrontal cortex and the intraparietal sulcus (IPS) was strongly task-related. Spatial working memory primarily activated the right middle frontal gyrus (MFG) and the IPS. Object working memory activated the MFG bilaterally, the left inferior frontal gyrus, and the IPS, particularly in the left hemisphere. Finally, activation of midline posterior regions, including the cingulate gyrus, occurred at the offset of the working memory tasks, particularly the shape task. These results support a prominent role of the prefrontal and parietal cortices in working memory, and indicate that spatial and object working memory tasks recruit differential hemispheric networks. The results also affirm the distinction between spatial and object perceptual processing in dorsal and ventral visual pathways.

Adult↗

PubMed1998

[Clinical evaluation of memory].

An assessment of memory is relevant in many clinical contexts, but its objectives differ from one situation to another. An initial investigation should make it possible to define these objectives and to formulate hypotheses following the interview with the patient and/or his family and with the help of the overall anamnestic data. The tests proposed would aim at answering the questions according to the particular case of the patient: the supposed disorders, a suggested diagnosis, but also demographic data such as age and educational level. Consequently there is no across-the-board examination of memory and this assessment must be situated in a specific theoretical context. Memory is no longer considered as a single but as a compound function made up of different, relatively independent systems. The examination not only seeks to show the deficits which have a certain significance according to the clinical context, but also aims at bringing out preserved abilities which may contribute to the establishing of the diagnosis and on which rehabilitation and cognitive management may be based. In this article we present several methods of memory assessment with reference to the ideas of Tulving and Schacter, who propose five different memory systems: episodic memory, working memory, semantic memory, perceptive representation system and procedural memory. These assessments are made using standardized tools (tests, questionnaires) and experimental paradigms which have recently emerged in clinical neuropsychology (study of priming effects, of acquisition of skills). One of the present issues is the problem of reconciling the use of standard tools with that of the more sophisticated paradigms drawn up in the light of the most recent theoretical models. Another objective is to relate the findings of these tests to the difficulties the patients have in their everyday lives and so to achieve an ecological understanding of memory disorders.

Humans↗

PubMed1999

Stability of naive and memory phenotypes on resting CD4 T cells in vivo.

The reliable identification of naive and memory CD4 T cells is critical to understanding the cellular basis of immunological memory. However, it has long been a controversial issue whether naive and memory phenotypes are stable among resting CD4 T cells in the absence of overt stimulation or whether the proposed memory phenotype is a transient, reversible one that represents recently activated cells. In this study, adoptively transferred, purified populations of naive or memory phenotype CD4 T cells are monitored over time to assess the stability of phenotypes and the functional capabilities of transferred cells. Studying both TCR transgenic and nontransgenic CD4 T cell populations allows one to control for the capacity to respond to environmental Ags in vivo. Several findings are reported. The first is that in the absence of Ag, both naive and memory phenotypes remain unchanged over time. Second, when changes are seen in populations of transferred naive phenotype CD4 T cells, they take place only when there is a potential for antigenic challenge, suggesting that it is an Ag-driven event. Furthermore, when a change from naive to memory phenotype is observed, these transferred donor cells also function as memory cells. Third, the ability of memory CD4 T cells to retain the memory phenotype is independent of specific Ag.

Adoptive Transfer↗

PubMed2006

[Alzheimer's disease and human memory].

Memory disorders observed in Alzheimer's disease gave rise, from the eighties, to a detailed analysis into the framework of cognitive neuropsychology which aimed at describing the deficits of very specific processes. Beyond their clinical interest, these studies contributed to the modelisation of human memory thanks to the characterization of different memory systems and their relationships. The first part of this paper gives an overview of the memory deficits in Alzheimer's disease and insists on particular cognitive phenomena. Hence, several examples are developed in the domains of semantic memory (such as hyperpriming and hypopriming effects) and autobiographical memory. Recent results highlight the existence of severe autobiographical amnesia observed in all neurodegenerative diseases, though with contrasting profiles: Ribot's gradient in Alzheimer's disease (showing that remote memories are better preserved than recent ones), reverse gradient in semantic dementia and no clear gradient in the frontal variant of frontotemporal dementia. The second part of this article presents advances in cognitive neuroscience searching to disclose the cerebral substrates of these cognitive deficits in Alzheimer's disease. The studies using functional imaging techniques are the most informative regarding this problematic. While showing the dysfunctions of an extended network, they emphasize the selectivity of cerebral damages that are at the root of very specific cognitive dysfunctions, coming close in that way to the conceptions of cognitive neuropsychology. These neuroimaging studies unravel the existence of compensatory mechanisms, which until recently were clearly missing in the literature on neurodegenerative diseases. These different researches lead to a wide conception of human memory, not just limited to simple instrumental processes (encoding, storage, retrieval), but necessarily covering models of identity and continuity of the subject, which interact in a dynamic way with eminently changing memory representations.

Alzheimer Disease↗

PubMed2001

Hippocampal complex and retrieval of recent and very remote autobiographical memories: evidence from functional magnetic resonance imaging in neurologically intact people.

It has been argued that the role of the hippocampus in memory is time-limited: during a period of memory consolidation, other brain regions such as the neocortex are said to acquire the ability to support memory retention and retrieval on their own. An alternative view is that retention and retrieval of memory for autobiographical episodes depend on the hippocampal complex, regardless of the age of the memory. We examined the participation of the hippocampal complex in a functional magnetic resonance imaging (fMRI) study in which participants were asked to recollect autobiographical events that occurred either within the last 4 years or more than 20 years ago. We found equivalent levels of hippocampal activation in both conditions in all participants (N = 10). In addition, activation in neocortical regions did not differ as a function of the age of the memory, even though most of the recent memories recalled were less than 2 years old and the remote memories more than 35 years old. The results support the notion that the hippocampal complex participates in retention and recovery of even very old autobiographical memories, and place boundary conditions on theories of memory consolidation.

Autobiographies as Topic↗

PubMed2001

Subjective ratings of prospective memory deficits in MDMA ('ecstasy') users.

Chronic use of MDMA (3,4-methylenedioxymethamphetamine), or 'ecstasy', is associated with significant cognitive impairments, particularly in laboratory and field tests of memory for previously encoded material. Less is known about the effects of a history of MDMA use on aspects of everyday cognitive functioning-of which prospective memory (typically characterised as 'remembering to do something at some future point') is an important aspect. Self-ratings of prospective memory among 30 regular ecstasy users (taking the drug 10 or more times per month) and 31 ecstasy-free controls were compared. Each participant completed the Prospective Memory Questionnaire, which measures self-rated error frequencies relating to three aspects of prospective memory (short-term habitual, long-term episodic and internally cued); the scale also records the use of strategies to aid remembering. Compared with non-users, ecstasy users reported significantly more self-rated errors in prospective memory, an effect which was evident after co-varying levels of other drug use. There were no significant differences in the use of strategies to aid memory. These findings provide new insights into prospective memory dysfunction in recreational drug users. Prospective memory deficits may be related to the reported serotonergic and frontal lobe deficits in chronic MDMA users. It is necessary to use more objective tasks to assess putative prospective memory deficits in ecstasy users. Copyright 2001 John Wiley & Sons, Ltd.

Journal Article↗

PubMed2000

Gender, Memory, and Hippocampal Volumes: Relationships in Temporal Lobe Epilepsy.

Previous research has suggested bilateral hippocampal support for verbal memory in women with early left-hemisphere injury and that women experience better verbal memory outcome following anterior temporal lobectomy (ATL). The present study investigated two issues: (1) Do women have better verbal memory outcome following ATL compared with men? (2) Are verbal memory abilities differentially supported by the right and left hippocampus in males and females? Verbal memory performance [Wechsler Memory Scale: Logical Memory (LM) savings score] was assessed in 70 patients who underwent ATL. MRI volumetric measurements of the left and right hippocampus were performed. No LM savings score difference was found between groups preoperatively although a statistically significant gender effect (P < 0.04) was found for postoperative LM savings scores. Females displayed better postoperative memory performance, regardless of side of surgery. Preoperative verbal memory performance was not associated with right or left hippocampal volumes in either left or right ATL females, although the right hippocampus was positively associated with memory performance for left ATL males. Hippocampal volumes were not associated with postoperative LM savings scores for any group. Results suggest that prose recall was only modestly influenced by gender and that bilateral hippocampal support for prose recall was not present in our female patients.

Journal Article↗

PubMed2002

Memory Complaints in Medically Refractory Epilepsy: Relationship to Epilepsy-Related Factors.

This study reports the results of a multicenter study on memory complaints in 252 patients with epilepsy who presented with subjective complaints about memory problems in daily life. Memory complaints were measured with a standardized memory questionnaire (GKLE). The main purpose was to analyze the type of memory complaints and to examine the relationship between subjective complaints and several epilepsy-related factors. These include seizure type, lateralization and location of the focus, etiology, duration, age at onset, and antiepileptic medication. As expected patients experienced significantly more memory complaints. In particular, patients of older age and higher intelligence level complained more about their memory functioning. Although the clinical significance is marginal, neuroticism showed a significant relationship to the total complaint score. The total amount of subjective complaints is not related to the localization or lateralization of the epileptic disturbances. Patients with a longer duration of epilepsy complained significantly more about memory problems, especially about retrieving information from memory. All other epilepsy-related factors showed no relationship to memory complaints.

Journal Article↗

PubMed1997

The Effects of a Limited Memory Capacity on Foraging Behavior

We introduce a simple mathematical model to describe the behavior of a forager with a limited memory capacity in the presence of two prey types that differ in their energetic values. The model is used to analyze the effect of memory capacity on foraging behavior and on foraging energetics and it contrasts with classic optimal foraging theory, which implicitly assumes that the forager has an infinite memory capacity. Classic optimal foraging theory dictates that the low value prey type should be invariably excluded from the diet when the high value type exceeds some critical relative frequency and invariably consumed otherwise. Our model forager behaves similarly except that, as its memory capacity declines, it is increasingly predisposed to consume the low value prey when it is suboptimal to do so. Nevertheless, our analysis indicates that the energetic efficiency of a forager with an infinite memory capacity can be approximated by a forager with a memory of modest capacity, perhaps one that contains information about 5-20 previously consumed prey items. In our model, memory constraints necessarily result in so-called "partial preferences" being exercised towards the low value prey type. Thus, limited memory capacity offers a possible explanation for observed violations of the "zero-one" rule of optimal diet composition. We also find a resemblance to a sigmoidal shape in the relationship between the representation of each prey type in the diet and its relative frequency. Thus, the memory-constrained forager exhibits behavior that resembles the type III functional response. Therefore, it is possible that memory constraints such as we envisage can contribute to the explanation of both partial preferences and functional responses. Copyright 1997 Academic Press

Journal Article↗

PubMed1995

Input- and output-monitoring in implicit and explicit memory.

Previous experiments have shown that the procedure of questioning subjects retrospectively about the input and output status of information (input and output monitoring) is a useful method for assessing the awareness states of subjects during implicit and explicit memory tasks. The main purpose of the present study was to investigate whether the previous findings could be extended to other implicit and explicit memory tasks. We were especially interested in whether differences in input- and output-monitoring performance can be observed when both the implicit and explicit memory tasks are conceptual ones. In a final tet phase, the target items from the study phase and new distractor items were presented. In a recognition-like situation, subjects had to decide whether an item had been presented in the study phase (input status), as well as whether they had produced the item in the memory-test phase (output status). In all three experiments judgments about the input status-but only for those items that had been produced in the implicit or in the explicit memory test--were more precise after explicit than after implicit memory testings. This finding was not influenced by the distinction between perceptual and conceptual-memory tasks (Exp. 1), and was obtained under conditions in which the implicit and the explicit memory tasks were both conceptual and differed only in test instructions (Exps. 2 and 3). These results suggest that not only subjects performing a perceptual test of implicit memory, but also subjects in a conceptual implicit test were less aware of using information from a previous study episode than subjects who received memory instructions. It is concluded that requiring judgments about the input status of information is a good method for assessing subjects' test awareness and is preferable to the use of a questionnaire (Exp. 3). In contrast, in all three experiments no differences were found with the output-monitoring measure between implicit and explicit test conditions.

Adult↗

PubMed1996

Chronic nicotine working and reference memory effects in the 16-arm radial maze: interactions with D1 agonist and antagonist drugs.

Chronic nicotine infusion has been found in a series of studies in our laboratory to significantly improve choice accuracy of rats in the eight-arm radial maze. The current study was designed to compare the effects of chronic nicotine infusion on working and reference memory in a 16-arm radial maze. Nicotine was administered to female Sprague-Dawley rats at approximately 5 mg/kg per day SC via osmotic minipumps. Controls received saline infusions. Chronic nicotine infusion significantly lowered the number of working memory errors compared to controls, whereas the number of reference memory errors was not significantly affected. The modest nicotine-induced reduction in working memory errors was seen as a main effect over the 4 weeks of infusion, but the clearest effect was seen in weeks 3-4 of nicotine administration. For the 2 weeks after withdrawal, the nicotine effect was no longer evident. Acute D1 challenges were given with the D1 agonist dihydrexidine (0, 0.25, 0.5 and 1 mg/kg) and the D1 antagonist SCH 23390 (0, 0.005, 0.015 and 0.05 micrograms/kg) during weeks 3-4 of chronic nicotine administration and weeks 1-2 after withdrawal from nicotine. Dihydrexidine caused a modest dose-related increase in reference memory errors but not working memory errors in the nicotine-treated, but not the control rats. The D1 antagonist SCH 23390 caused a modest though significant decrease in reference memory errors but not working memory errors in the control, but not the nicotine-treated rats. The behavioral specificity of chronic nicotine infusion was demonstrated with selective improvement in working memory function. Pharmacological interactions were seen with chronic nicotine treatment increasing responsivity to D1 agonist and decreasing responsivity to a D1 antagonist with regard to reference memory. The mechanisms of this interaction are still undiscovered.

Animals↗

PubMed1998

The effect of pain on memory for affective words.

Memory is a key cognitive variable in pain management, but lacks extensive research. This study is a replication and extension of Seltzer and Yarczower's investigation of pain's influence on memory for affective words, which found fewer positive words and more negative words recalled if subjects were in acute pain (versus no pain). In the present study, two experiments were conducted: one with a recall memory test and one with a recognition memory test. One hundred sixty undergraduate subjects were randomly placed in one of four groups: two groups had the same condition (pain or no pain) for both the encoding task and memory test, and two groups had mixed conditions (pain at encoding-no pain at memory test or no pain at encoding-pain at memory test). Pain was induced by 0 degrees-2 degrees C water immersion. At encoding, subjects categorized words by judging them as either positive or negative. Results of both experiments show that pain impairs memory. In neither experiment were differences found on memory for positive and negative words. These results do not support Seltzer and Yarczower's discriminative effects of pain on word category, but they are consistent with other research using acute pain manipulations and chronic pain populations, suggesting that pain interferes with memory. It is hypothesized that pain depletes scarce attentional resources, thereby interfering with concurrent cognitive tasks such as thinking, reasoning, and remembering.

Adult↗

PubMed2006

Acute treatment with the antidepressants bupropion and sertraline do not influence memory retrieval in man.

OBJECTIVE: Several evidences implicate that monoamines play a modulatory role in the brain mechanisms underlying encoding and retrieval of emotional memories. Recent experiments demonstrate that acute monoaminergic potentiation with the antidepressants bupropion or sertraline enhance the retrieval of longterm emotional memory in rodents. In the present study, we tested the hypothesis that acute monoaminergic re-uptake inhibition with these antidepressants might enhance retrieval of emotional memory in man. METHODS: The central monoaminergic system was stimulated with either bupropion or sertraline in a double-blind, randomized, placebo-controlled design with 105 healthy adult subjects divided in three groups (placebo, 150 mg-bupropion and 50 mg-sertraline). Memory was evaluated with a 'surprise' memory test 7 days after the presentation of an emotional story and with a word-cued autobiographical memory test. RESULTS: A total of 99 volunteers completed the experimental procedures. Contrasting to our prediction, we found no memory enhancing effect for either drug in both memory tests. All groups showed the expected heightened memory performance to the middle 'emotive' phase of the story. CONCLUSION: Stimulation of the central monoaminergic system with the antidepressants bupropion and sertraline did not enhance the retrieval of long-term emotional memories in man.

Adolescent↗

PubMed2004

The effect of burn injury on adolescents autobiographical memory.

Autobiographical memory recall was investigated in two female adolescent groups; one group who had experienced a burn injury and a matched control group. The Burn group was not currently depressed or anxious, but scored significantly higher on the intrusion subscale of the impact of event scale compared to controls. Two autobiographical memory tasks, the autobiographical memory cueing task and the Children's Autobiographical Memory Inventory (CAMI), were used. For the cueing task, the Burn group was significantly slower to recall specific memories. This group also recalled significantly fewer specific memories and significantly more extended overgeneral memories. For the CAMI, the burns group produced significantly lower semantic and episodic recall. The Burn group also produced significant correlations between sub-scales of the impact of event scale and selected measures on the autobiographical memory tasks. Higher intrusion scores were associated with less detailed episodic recall. Higher avoidance scores were associated with longer latencies to recall memories to negative cue words and fewer specific memories to all cue words. These results are discussed from the perspective that the Burn group experienced intrusive thoughts which interfered with normal autobiographical functioning.

Adolescent↗

PubMed2006

False claims about false memory research.

Pezdek and Lam [Pezdek, K. & Lam, S. (2007). What research paradigms have cognitive psychologists used to study "False memory," and what are the implications of these choices? Consciousness and Cognition] claim that the majority of research into false memories has been misguided. Specifically, they charge that false memory scientists have been (1) misusing the term "false memory," (2) relying on the wrong methodologies to study false memories, and (3) misapplying false memory research to real world situations. We review each of these claims and highlight the problems with them. We conclude that several types of false memory research have advanced our knowledge of autobiographical and recovered memories, and that future research will continue to make significant contributions to how we understand memory and memory errors.

Child↗

PubMed2004

The effects of memory trace strength on eyewitness recall in children with and without intellectual disabilities.

Children with mild moderate intellectual disabilities (ID) were compared with typically developing peers of the same chronological age (CA) on an eyewitness memory task in which memory trace strength was manipulated to examine whether increased memory trace strength would benefit those with ID more than those without ID. No evidence was found for this claim or for the notion that different mechanisms are implicated in memory processes for children with ID versus CA controls. Fuzzy-trace theory was also used to contrast question types that probed verbatim memory versus gist memory. Manipulations of trace strength, when used with immediate recall (to reduce the impact of decay), were predicted to improve verbatim memory more than gist memory. The results broadly supported the predictions. Performance was not improved in the stronger trace strength condition on measures of recall that tapped gist memory (e.g., open-ended recall), whereas performance was significantly better in the stronger trace strength condition on two of the three measures of recall that tapped verbatim memory (i.e., closed misleading questions, open-ended specific questions). Differences in performance between the groups were quite marked on several question types, supporting previous findings that those with ID have certain vulnerabilities as potential witnesses compared with peers of the same CA.

Adolescent↗

PubMed2006

Linking implicit and explicit memory: common encoding factors and shared representations.

Dissociations between implicit and explicit memory have featured prominently in theories of human memory. However, similarities between the two forms of memory have been less studied. One open question concerns whether implicit and explicit memory share encoding resources. To explore this question, we employed a subsequent memory design in which several novel scenes were repeated once during an fMRI session and explicit memory for the scenes was unexpectedly tested afterward. Subsequently remembered scenes produced more behavioral priming and neural attenuation-two conventional measures of implicit memory-than did subsequently forgotten scenes. Moreover, brain-behavior correlations between these two implicit measures were mediated by subsequent memory. Finally, tonic activity, possibly reflecting the natural time course of attention, was predictive of subsequent memory. These results suggest that implicit and explicit memory are subject to the same encoding factors and can rely on similar perceptual processes and representations.

Adolescent↗