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At least 289 records · Page 16Linked to original sources

PubMed1989

Hippocampal seizures disrupt working memory performance but not reference memory acquisition.

The effect of hippocampal seizures in rats was assessed in two spatial memory tasks: The reference memory task was a simultaneous two-choice discrimination in a T-maze. The working memory task was a delayed conditional discrimination in a radial arm maze. In each task the hippocampus of each rat was stimulated to seizure after the presentation of the information to be remembered. In the reference memory task, hippocampal seizures did not impair acquisition, whether the stimulation was given immediately after or 4 hr after the presentation of the stimuli to be remembered. In the working memory task, hippocampal seizures did impair performance in a group of the same rats. These results support the distinction between a trial-dependent working memory system that requires hippocampal function and a trial-independent memory system that does not depend on hippocampal function.

Animals↗

PubMed1996

Subjective memory complaints, psychological distress, and longitudinal change in objective memory performance.

Between 1992 and 1993, the Memory Function Questionnaire General Frequency of Forgetting Scale (MFQ-GEN), the Symptom Checklist-90-Revised General Severity Index (GSI), and Mayo Cognitive Factor Scales Learning and Retention (MCFS-LRN and MCFS-RET) current and change scores were obtained for 294 of 397 (74%) participants, ages 55-97 years, originally assessed in a 1988-1990 normative study. In multiple regression modeling, the GSI and MCFS-LRN current score contributed 20% and 3%, respectively, to MFQ-GEN variance. Thus, emotional status was a better predictor of subjective memory ratings than either absolute objective memory performance or objective longitudinal memory change. Persons who developed cognitive impairment over the longitudinal interval reported greater memory problems, but memory complaints had little sensitivity in identifying these persons. In an approximate census sample of these older people, minor memory problems were reported to be frequent but not serious.

Aged↗

PubMed2006

Feature-based memory-driven attentional capture: visual working memory content affects visual attention.

In 7 experiments, the authors explored whether visual attention (the ability to select relevant visual information) and visual working memory (the ability to retain relevant visual information) share the same content representations. The presence of singleton distractors interfered more strongly with a visual search task when it was accompanied by an additional memory task. Singleton distractors interfered even more when they were identical or related to the object held in memory, but only when it was difficult to verbalize the memory content. Furthermore, this content-specific interaction occurred for features that were relevant to the memory task but not for irrelevant features of the same object or for once-remembered objects that could be forgotten. Finally, memory-related distractors attracted more eye movements but did not result in longer fixations. The results demonstrate memory-driven attentional capture on the basis of content-specific representations.

Adolescent↗

PubMed2003

Effect of negative emotional content on working memory and long-term memory.

In long-term memory, negative information is better remembered than neutral information. Differences in processes important to working memory may contribute to this emotional memory enhancement. To examine the effect that the emotional content of stimuli has on working memory performance, the authors asked participants to perform working memory tasks with negative and neutral stimuli. Task accuracy was unaffected by the emotional content of the stimuli. Reaction times also did not differ for negative relative to neutral words, but on an n-back task using faces, participants were slower to respond to fearful faces than to neutral faces. These results suggest that although emotional content does not have a robust effect on working memory, in some instances emotional salience can impede working memory performance.

Adult↗

PubMed2006

Attachment and emotional memory: investigating the source and extent of avoidant memory impairments.

Attachment avoidance has been associated with impairments in memory for material with emotional, attachment-related themes (e.g., loss). In the present study the author investigated the source and extent of these memory deficits by examining working memory capacity for attachment-related and nonattachment-related material. Avoidance was associated with deficits in working memory for positive and negative attachment-related stimuli. However, avoidance was unrelated to working memory capacity for nonattachment-related stimuli, both emotional and nonemotional. These findings are consistent with the proposal that avoidant individuals defensively limit the processing of potentially distressing information. Attachment anxiety was unrelated to working memory capacity across word type. Implications of the findings for defensive strategies and emotional memory are discussed.

Adult↗

PubMed1999

Modelling T-cell memory by genetic marking of memory T cells in vivo.

Immunological memory is the ability of the immune system to respond with enhanced vigour to pathogens that have been encountered in the past. Following infection or immunization, most effector T cells undergo apoptotic cell death, but a small fraction of these cells, proportional to the early antigen load and initial clonal burst size, persist in the host as a stable pool of memory T cells. The existence of immunological memory has been recognized for over 2,000 years, but our understanding of this phenomenon is limited, primarily because memory lymphocytes cannot be unequivocally identified as they lack specific, permanent markers. Here we have developed a transgenic mouse model system whereby memory T cells and their precursors can be irreversibly marked with a reporter gene and thus can be unambiguously identified. Adoptive transfer of marked CD8+ T cells specific for lymphocytic choriomeningitis virus protected naive recipients following viral challenge, demonstrating that we have marked memory T cells. We also show that cytotoxic effector lymphocytes that develop into memory T cells can be identified in the primary response.

Adoptive Transfer↗

PubMed2004

MHC class Ia-restricted memory T cells inhibit expansion of a nonprotective MHC class Ib (H2-M3)-restricted memory response.

Listeria monocytogenes infection generates major histocompatibility complex (MHC) class Ia-restricted and MHC class Ib-(H2-M3)-restricted effector and memory CD8+ T cells. However, only MHC class Ia-restricted memory cells expand after rechallenge, and it is unknown if MHC class Ib-restricted memory CD8+ T cells generated by vaccination are protective. We show here that H2-M3-restricted memory CD8+ T cells were capable of secondary expansion but, in contrast to primary H2-M3-restricted effector cells, failed to provide protective immunity. In lm-immune mice, MHC class Ia-restricted memory CD8+ T cells prevented the expansion of H2-M3-restricted memory T cell populations by limiting dendritic cell antigen presentation. Thus, protective immunity by H2-M3-restricted T cells is limited to primary infection, indicating that memory MHC class Ia-restricted T cells prevent nonessential immune responses during secondary infection.

Animals↗

PubMed2003

CD4 T cell memory derived from young naive cells functions well into old age, but memory generated from aged naive cells functions poorly.

Age-related declines in immune function have an impact on both primary and memory responses. In this study, we have examined the ability of naive CD4 T cells from young and aged T cell receptor transgenic mice to establish functional memory. We found that memory cells generated from young CD4 T cells responded well to antigen, even a year after generation, whereas memory cells derived from CD4 T cells from aged mice responded poorly both ex vivo and in vivo. Memory cells generated from aged naive cells proliferate less, produce reduced levels of cytokines, and exhibit reduced cognate helper function, compared with memory cells generated by using young naive cells. These results indicate that it is the age of the naive T cell when it first encounters antigen, rather than the age when it reencounters antigen, that is critical for good memory CD4 T cell function.

Aging↗

PubMed1994

Delayed emergence of effects of memory-enhancing drugs: implications for the dynamics of long-term memory.

Many theories of memory postulate that processing of information outlasts the learning situation and involves several different physiological substrates. If such physiologically distinct mechanisms or stages of memory do in fact exist, they should be differentially affected by particular experimental manipulations. Accordingly, a selective improvement of the processes underlying short-term memory should be detectable only while the information is encoded in the short-term mode, and a selective influence on long-term memory should be detectable only from the moment when memory is based on the long-term trace. Our comparative study of the time course of the effects of the cholinergic agonist arecoline, the gamma-aminobutyric acid type B receptor antagonist CGP 36742, the angiotensin-converting enzyme inhibitor captopril, and the nootropic oxiracetam, four substances with completely different primary sites of action, show that the memory-enhancing effects consistently come into evidence no sooner than 16-24 h after the learning trial. On the one hand, this finding suggests that all these substances act by way of the same type of mechanism; on the other hand, it demonstrates that the substrate modulated by the compounds forms the basis of memory only after 16-24 h. From the observation that animals also show clear signs of retention during the first 16 h--i.e., before the effects of the substances are measurable--it can be inferred that retention during this time is mediated by other mechanisms that are not influenced by any of the substances.

Animals↗

PubMed2002

Expertise, attention, and memory in sensorimotor skill execution: impact of novel task constraints on dual-task performance and episodic memory.

Two experiments explored the attention and memory processes governing sensorimotor skill. Experiment 1 compared novice and experienced golf putting performance in single-task (putting in isolation) and dual-task conditions (putting while performing an auditory word search task). At specific intervals, participants also produced episodic descriptions of specific putts. Experiment 2 assessed novice performance following training on the same putting task. In Experiment 1, experienced golfers did not differ in putting accuracy from single-to dual-task conditions and, compared to novices, had higher recognition memory for words heard while putting but diminished episodic memories of specific putts. However, when using an s-shaped arbitrarily weighted "funny putter" designed to disrupt the mechanics of skill execution, experienced golfers produced extensive episodic memories of specific putts but showed decreased dual-task putting accuracy and recognition memory for secondary task words. Trained novices produced results intermediate between the untrained novices and experienced golfers. As predicted by current theories of practice-based automaticity, expertise leads to proceduralized control that does not require constant attention. Resources are free to devote to secondary task demands, yet episodic memory for primary task performance is impoverished. Novel task constraints (e.g., a funny putter) increase attention to execution, compromising secondary task performance but enhancing memory for skill execution.

Attention↗

PubMed1990

Problems of learning and memory: one or multiple memory systems?

Learning, and hence memory, is ubiquitous not only throughout the animal kingdom, but apparently throughout many regions of the brain. Is all learning reducible to a single common form? Neuropsychological dissociations suggest that the mammalian brain possesses a number of different and potentially independent memory systems, with different mechanisms and anatomical dispositions, some of which are neurally widely dispersed and others of which are narrowly organized. Among the types considered are: (i) short-term memory; (ii) knowledge and skills; (iii) stable associative memory; (iv) event memory; and (v) priming. As double or multiple dissociations do not lead to logically inevitable conclusions, it has been argued that an alternative to multiple memory systems is variable modes of processing. But these, too, would be dissociable on the same lines of evidence. Dissociations, if strong and absolute, have strong pragmatic power when they are combined with evolutionary and neuroscientific evidence. Multiple memory systems may possibly share some common cellular mechanisms, but such mechanisms do not define the separate properties at the systems level.

Amnesia↗

PubMed2006

Depletion of serotonin selectively impairs short-term memory without affecting long-term memory in odor learning in the terrestrial slug Limax valentianus.

The terrestrial slug Limax is able to acquire short-term and long-term memories during aversive odor-taste associative learning. We investigated the effect of the selective serotonergic neurotoxin 5,7-dihydroxytryptamine (5,7-DHT) on memory. Behavioral studies indicated that 5,7-DHT impaired short-term memory but not long-term memory. HPLC (high-performance liquid chromatography) analysis revealed that 5,7-DHT significantly reduced serotonin content in the central nervous system. The present study suggests that acquisition, retention, and/or retrieval of short-term memory involves serotonin, and neither acquisition nor retrieval of long-term memory requires serotonin at a level as high as that required for short-term memory.

5,7-Dihydroxytryptamine↗

PubMed2004

CD27- CD4+ memory T cells define a differentiated memory population at both the functional and transcriptional levels.

The memory T-cell population is a heterogeneous population, including both effector cells, which exert a direct secondary immune response, and resting or intermediate cells, which serve as a reservoir and exert a possible regulatory role. To further dissect the T-cell memory population residing in the CD4+ CD45RO+ T-cell pool, we studied the functional properties of memory populations identified by the CD27 marker. This marker clearly divides the memory population into two groups. One group consists of effector cells lacking CD27 and displaying a high antigen recall response. The other group consists of an intermediate memory population, displaying CD27. This latter group lacks an antigen recall response and requires costimulation for T-cell receptor triggering. To evaluate the function of the CD27+ memory pool, we analysed the transcriptional profile, using high-density microarray technology. These gene data strongly support the different functional profiles of CD27+ and CD27- memory populations, in terms of protein expression and the capacity to respond to antigen.

CD4-Positive T-Lymphocytes↗

PubMed1997

The neurobiology of emotionally influenced memory. Implications for understanding traumatic memory.

Substantial evidence from animal and human subject studies converges on the view that memory for emotionally arousing events is modulated by an endogenous memory-modulating system consisting, at minimum, of stress hormones and the amygdaloid complex. Within the normal range of emotions experienced, this system is viewed as an evolutionarily adaptive method of creating memory strength that is, in general, proportional to memory importance. In conditions of extreme emotional stress, the operation of this normally adaptive system may underly the formation of strong, "intrusive" memories characteristic of PTSD. An improved understanding of the neurobiology of memory modulation should lead to an improved ability to treat or prevent traumatic memories.

Brain↗

PubMed2005

Traumatic memories are not necessarily accurate memories.

Some therapists, as well as other commentators, have suggested that memories of horrific trauma are buried in the subconscious by some special process, such as repression, and are later reliably recovered. We find that the evidence provided to support this claim is flawed. Where, then, might these memory reports come from? We discuss several research paradigms that have shown that various manipulations can be used to implant false memories--including false memories for traumatic events. These false memories can be quite compelling for those who develop them and can include details that make them seem credible to others. The fact that a memory report describes a traumatic event does not ensure that the memory is authentic.

Child↗

PubMed2006

Characterizing the circulating, gliadin-specific CD4+ memory T cells in patients with celiac disease: linkage between memory function, gut homing and Th1 polarization.

Celiac disease (CD) is a chronic, immune-mediated disorder of the gut, driven by T cells reacting locally to a distinct antigen, gliadin. Thus, CD offers the opportunity to study the T cell memory response to gliadin and whether gut tropism and T helper cell type 1 (Th1) polarization, which characterize the effector phase, are preserved in the memory progeny. It is notable that previous studies yielded conflicting results as to the presence of gliadin-specific memory CD4+ T cells in the peripheral blood of CD patients. However, we used a different and highly sensitive approach based on fluorescein-derived label dilution, whereby the memory cells are identified operationally by their greater capacity to proliferate upon re-encounter with antigen. Thus, using flow cytometry, we could resolve multiple successive generations as well as immunophenotype the dividing cells. Here, we show that the peripheral blood lymphocyte of some CD patients on a gliadin-free diet, but not healthy donors, contains a detectable population of CD4+ memory T cells specific for deamidated gliadin. Moreover, these gliadin-specific memory T cells are marked by a distinctive phenotype: They express high levels of the gut-homing beta7 integrins and primarily produce interferon-gamma and tumor necrosis factor alpha. We conclude that memory for gliadin-derived antigens within the circulating CD4+ T cells is linked with gut tropism as well as Th1 polarization.

Adolescent↗

PubMed2006

Memory impairment and awareness of memory deficits in early-stage Alzheimer's disease.

Recognition memory of auditory verbal learning tests and awareness of memory deficits were examined in 24 individuals with early-stage Alzheimer's disease (AD) using a performance prediction-postdiction paradigm. Individuals with AD displayed impaired recognition memory, and recognition performance correlated positively with regional cerebral blood flow at rest in bilateral prefrontal areas and the left medial temporal area. In addition, underawareness of memory deficits was also marked even at this early stage. Individuals with AD retrospectively overestimated memory performance after actual performance, but appeared to benefit from feedback, and displayed intact online awareness of memory dysfunction, leading to normal prediction of the second session. However, individuals with AD failed to retrospectively incorporate incidents of memory failure into generalized self-belief systems. Brain/ behavior correlational analyses suggest that the prefrontal cortex and posterior dorsomedial regions including the precuneus may be involved in self-awareness.

Aged↗

PubMed2006

Thinking about memories for everyday and shocking events: do people use ease-of-retrieval cues in memory judgments?

Extant research shows that people use retrieval ease, a feeling-based cue, to judge how well they remember life periods. Extending this approach, we investigated the role of retrieval ease in memory judgments for single events. In Experiment 1, participants who were asked to recall many memories of an everyday event (New Year's Eve) rated retrieval as more difficult and judged their memory as worse than did participants asked to recall only a few memories. In Experiment 2, this ease-of-retrieval effect was found to interact with the shocking character of the remembered event: There was no effect when the event was highly shocking (i.e., learning about the attacks of September 11, 2001), whereas an effect was found when the event was experienced as less shocking (due either to increased distance to "9/11" or to the nonshocking nature of the event itself). Memory vividness accounted for additional variance in memory judgments, indicating an independent contribution of content-based cues in judgments of event memories.

Adult↗