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 1,333 records · Page 74Linked to original sources

PubMedDate not supplied

An animal model of human-type memory loss based on aging, lesion, forebrain ischemia, and drug studies with the rat.

The goals of this research were to develop a within-subject test of spatial working memory and performance for the rat in a T-maze, based on a delayed alternation, or "win-shift" foraging strategy. Using this model, specific aims were to compare the effects of: (1) age, (2) basal forebrain, medial septal, and amygdala lesions, (3) four vessel occlusion (4-VO), forebrain ischemia, and (4) physostigmine, scopolamine, arecoline, piracetam, and clonidine on memory and performance of young middle-aged, and old rats. Aging significantly impaired working memory and performance of Long-Evans rats. Memory of septal and basal forebrain, but not of amygdala lesioned rats was significantly impaired without effects on performance. Transient, 4-VO forebrain ischemia produced significant memory impairment, without effects on performance, and highly selective CA1 cell loss in the hippocampus. Physostigmine enhanced working memory in middle-aged and old rats. Scopolamine impaired memory in young, middle-aged, and old rats. Physostigmine reversed the scopolamine impairments of working memory. Arecoline enhanced memory in old rats without effects on performance. Piracetam and clonidine had no direct effects on memory, but piracetam increased and clonidine decreased speed of performance. From the aging, lesion, ischemia, and drug studies it was concluded that there was a convergence of evidence from 4 different approaches for a critical role for the hippocampus, particularly the CA1 fields, in spatial working memory.

Aging↗

PubMed2002

Dissociating perceptual and conceptual implicit memory in multiple sclerosis patients.

Previous studies indicate that Multiple Sclerosis (MS) patients exhibit deficits in tests of explicit memory such as free recall, but show normal priming on implicit tests of memory such as word stem completion. However, the memory performance of patients with different MS disease subtypes has not been fully examined. In the current study, memory was assessed in Primary Progressive (PPMS), Relapsing Remitting (RRMS), and Secondary Progressive (SPMS) MS subgroups. Explicit memory as well as perceptual and conceptual implicit memory were examined using free recall, word fragment completion, and exemplar generation tests, respectively. All three groups of MS patients exhibited free recall deficits and normal priming on the exemplar generation test. However, the PPMS group exhibited a deficit in word fragment completion priming, whereas the RRMS and SPMS groups exhibited normal levels of priming on this task. Lesion load was assessed using magnetic resonance imaging and was negatively correlated with explicit memory performance, but it did not account for the observed deficits in perceptual implicit memory. The results indicate that PPMS patients exhibit a pattern of memory impairment that is distinct from that of the RRMS and SPMS groups. Moreover, the results indicate that perceptual implicit memory can be neurologically dissociated from conceptual implicit memory.

Adult↗

PubMed1998

Recognition memory in rats--I. Concepts and classification.

Recognition is the process by which a subject is aware that a stimulus has been previously experienced. It requires that the characteristics of events are perceived, discriminated, identified and then compared (matched) against a memory of the characteristics of previously experienced events. Understanding recognition memory, its underlying neuronal mechanisms, its dysfunction and alleviation of the latter by putative cognition enhancing drugs is a major research target and has triggered a wealth of animal studies. One of the most widely used animals for this purpose is the rat, and it is the rat's recognition memory which is the focus of this review. In this first part, concepts of recognition memory, stages of mnemonic processing and paradigms for the measurement of the rat's recognition memory will be discussed. In two subsequent articles (parts II and III) we will focus on the neuronal mechanisms underlying recognition memory in rats. Three major points arise from the comparison of paradigms that have in the past been used to assess recognition memory in rats. First, it should be realized that some tasks which, at face value, can all be considered to measure recognition memory in rats, may not assess recognition memory at all but may, for example, be based on recall rather than recognition. Second, it is evident that different types of recognition memory can be distinguished and that tasks differ in the type of recognition memory taxed. Some paradigms, for example, measure familiarity, whereas others assess recency. Furthermore, paradigms differ as to whether spatial stimuli or items are employed. Third, different processes, ranging from stimulus-response learning to the formation of concepts, may be involved to varying extent in different tasks. These are important considerations and question the predictive validity of the results obtained from studies examining, for example, the effects of putative cognition enhancing drugs.

Animals↗

PubMed2001

Remembering familiar people: the posterior cingulate cortex and autobiographical memory retrieval.

Most functional imaging studies of memory retrieval investigate memory for standardized laboratory stimuli. However, naturally acquired autobiographical memories differ from memories of standardized stimuli in important ways. Neuroimaging studies of natural memories may reveal distinctive patterns of brain activation and may have particular value in assessing clinical disorders of memory. This study used functional magnetic resonance imaging to investigate brain activation during successful retrieval of autobiographical memories elicited by name-cued recall of family members and friends. The caudal part of the left posterior cingulate cortex was the most strongly activated region and was significantly activated in all eight subjects studied. Most subjects also showed significant activation of the left anterior orbitomedial, anterior middle frontal, precuneus, cuneus, and posterior inferior parietal cortices, and the right posterior cingulate and motor cortices.Our findings are consistent with prior studies showing posterior cingulate cortex activation during autobiographical memory retrieval. This region is also consistently activated during retrieval of standardized memory stimuli when experimental designs emphasizing successful retrieval are employed. Our results support the hypothesis that the posterior cingulate cortex plays an important role in successful memory retrieval. The posterior cingulate cortex has strong reciprocal connections with entorhinal and parahippocampal cortices. Studies of early Alzheimer's disease, temporal lobectomy, and hypoxic amnesia show that hypometabolism of the posterior cingulate cortex is an early and prominent indicator of pathology in these patients. Our findings suggest that autobiographical memory retrieval tasks could be used to probe the functional status of the posterior cingulate cortex in patients with early Alzheimer's disease or at risk for that condition.

Acoustic Stimulation↗

PubMed1999

Chronic administration of docosahexaenoic acid improves reference memory-related learning ability in young rats.

Wistar rats were fed a fish oil-deficient diet through three generations. The young (five-week-old) male rats of the third generation were randomly divided into two groups. Over 10 weeks, one group was perorally administered docosahexaenoic acid dissolved in 5% gum Arabic solution at 300 mg/kg/day; the other group received a similar volume of vehicle alone. Five weeks after starting the administration, the rats were tested for learning ability related to two types of memory, reference memory and working memory, with the partially (four of eight) baited eight-arm radial maze. Reference memory is information that should be retained until the next trial. Working memory is information that disappears in a short time. Entries into unbaited arms and repeated entries into visited arms were defined as reference memory errors and working memory errors, respectively. Docosahexaenoic acid administration over 10 weeks significantly reduced the number of reference memory errors, without affecting the number of working memory errors, and significantly increased the docosahexaenoic acid content and the docosahexaenoic acid/arachidonic acid ratio in both the hippocampus and the cerebral cortex. In addition, the ratio demonstrated a significantly negative correlation with the number of reference memory errors. These results suggest that chronic administration of docosahexaenoic acid is conducive to the improvement of reference memory-related learning ability, and that the docosahexaenoic acid/arachidonic acid ratio in the hippocampus or the cerebral cortex, or both, may be an indicator of learning ability.

Animals↗

PubMed1997

Spaced training induces normal long-term memory in CREB mutant mice.

BACKGROUND: The cAMP responsive element binding protein (CREB) is a transcription factor the activity of which is modulated by increases in the intracellular levels of cAMP and calcium. Results from studies with Aplysia, Drosophila and mice indicate that CREB-activated transcription is required for long-term memory. Furthermore, a recent study found that long-term memory for olfactory conditioning can be induced with a single trial in transgenic Drosophila expressing a CREB activator, whereas in normal flies, with presumably lower CREB-mediated transcription levels, conditioning requires multiple spaced trials. This suggests that CREB-mediated transcription is important in determining the type of training required for long-term memory of olfactory conditioning in Drosophila. Interestingly, studies with cultured Aplysia neurons indicated that removing a CREB repressor promoted the formation of long-term facilitation, a cellular model of non-associative memory. RESULTS: Here, we have confirmed that mice lacking the alpha and Delta CREB proteins (CREBalphaDelta-) have abnormal long-term, but not short-term, memory, as tested in an ethologically meaningful task. Importantly, additional spaced training can overcome the profound memory deficits of CREBalphaDelta- mutants. Increasing the intertrial interval from 1 to 60 minutes overcame the memory deficits of the CREBalphaDelta- mice in three distinct behavioral tasks: contextual fear conditioning, spatial learning and socially transmitted food preferences. CONCLUSIONS: Previous findings and results presented here demonstrate that CREB mutant mice have profound long-term memory deficits. Importantly, our findings indicate that manipulations of CREB function can affect the number of trials and the intertrial interval required for committing information to long-term memory. Remarkably, this effect of CREB function is not restricted to simple conditioning tasks, but also affects complex behaviours such as spatial memory and memory for socially transmitted food preferences.

Animals↗

PubMed1987

Remote memory in a patient with amnesia due to hypoxia.

It has been suggested that amnesic patients suffer a selective loss of episodic memory while semantic memory remains well preserved. To assess the validity of this idea we studied remote memory in an amnesic patient, (M.R.L.), using several different measures that differ in the extent to which they engage episodic or semantic memory. On two different versions of the Albert et al. (1979) remote memory battery M.R.L. displayed severe retrograde amnesia (RA) extending backwards in time for about 15 years with excellent preservation of older memories. With standard recall instructions his overall performance on the Crovitz test of autobiographical memory was impaired and all of M.R.L.'s specific, temporally dated memories were given from the first half of his life. When asked to reconstruct his past residential history in detail, M.R.L. provide specific and generally accurate information for residences occupied from his boyhood until 1970, but thereafter his memory became quite unreliable. On a test of knowledge of terms commonly employed in the surveying profession, in which he worked for the past 20 years, M.R.L.'s performance was also impaired. The consistent pattern of RA displayed by this patient on all of the tests of remote memory indicates that both episodic and semantic memory are impaired in amnesia.

Amnesia↗

PubMed2005

The contribution of implicit and explicit memory to the effects of errorless learning: a comparison between young and older adults.

There is evidence that the prevention of errors during learning might be helpful in improving an impaired memory performance, both in amnesia as well as in normal age-related memory decline. Although errorless learning is a promising technique for use in rehabilitation practice, the underlying mechanisms are unclear. That is, it has been suggested that the beneficial effects of errorless learning operate through implicit memory, whereas others implicate that it is explicit memory that is responsible for the enhanced memory performance after errorless learning. The current study examined the contribution of implicit and explicit memory function to the memory performance after errorless and errorful learning using the process-dissociation procedure. A group of young adults (N=40) was compared to a matched group of older individuals (N=40) on a spatial memory task (i.e., learning the locations of everyday objects in a room). The results clearly show age-related decline in explicit spatial memory, while implicit spatial memory was unaffected. Furthermore, the young group benefited from errorless learning compared to errorful learning, while the older group did not show a difference between the two learning conditions. Also, it was found that the effects of errorful learning were related to explicit memory function, and not implicit processing, corroborating and extending recent findings.

Adult↗

PubMed1999

Implicit and explicit memory functioning in children with heavy prenatal alcohol exposure.

Prenatal alcohol exposure is associated with widespread and devastating neurodevelopmental deficits. Numerous reports have suggested memory deficits in both humans and animals exposed prenatally to alcohol. However, the nature of these memory deficits remains to be characterized. Recently children with fetal alcohol syndrome were shown to have learning and memory deficits on a verbal learning and memory measure that involved free recall and recognition memory. The current study seeks to further characterize memory functioning in children with heavy prenatal alcohol exposure by evaluating priming performance. The choice of task is also relevant given previous studies of memory performance in patient groups with and without involvement of the basal ganglia, a group of structures known to be affected in fetal alcohol syndrome. Three groups were evaluated for lexical priming, free recall, recognition memory, and verbal fluency: (1) children with heavy prenatal alcohol exposure; (2) children with Down syndrome; and (3) nonexposed controls. The children with Down syndrome showed significantly less priming than alcohol-exposed children, who did not differ from controls. In addition, the alcohol-exposed children were impaired on the free recall task but not on the recognition memory task, whereas the children with Down syndrome performed significantly worse than the alcohol-exposed group on both tasks. Finally, on the verbal fluency task, children with heavy prenatal alcohol exposure were impaired on both category and letter fluency, but the degree of impairment was greater for letter fluency. These results further characterize the memory deficits in children with heavy prenatal alcohol exposure suggesting that in spite of learning and memory deficits, they are able to benefit from priming of verbal information.

Adolescent↗

PubMed1999

Memory performance of geriatric and nongeriatric chronic schizophrenic patients: a cross-sectional study.

Memory functioning has been studied extensively in nongeriatric schizophrenic patients, leading to the suggestion that schizophrenic patients manifest a "subcortical" pattern of memory deficits. Few previous studies examined very poor outcome patients with a chronic course of hospitalization. This study examined the association of age and global cognitive dysfunction with verbal and spatial learning and delayed recall, as well as examining differential impairments in delayed recall as compared to delayed recognition memory. Sixty-six chronic schizophrenic patients were studied, with 30 of these patients over the age of 65. Verbal (California Verbal Learning Test) and spatial (Biber Figure Learning Test) serial learning and delayed memory tests were administered. All aspects of memory functioning were correlated with estimates of global cognitive status. When global cognitive status was controlled, age effects were still found for the majority of the memory measures. Delayed recognition memory was not spared, being performed as poorly as delayed recall. In contrast to previous studies of better-outcome patients with schizophrenia, geriatric patients with chronic schizophrenia performed more poorly than nongeriatric patients. The lack of sparing of delayed recognition memory suggests that previous findings of specific recall memory deficit and a subcortical profile of memory impairments may apply to schizophrenic patients with less severe global cognitive impairments. These data suggest that poor-outcome patients may have a pattern of memory impairments that has some features in common with cortical dementia.

Adult↗

PubMed2001

Instructional manipulations and age differences in memory: now you see them, now you don't.

The instructions for most explicit memory tests use language that emphasizes the memorial component of the task. This language may put older adults at a disadvantage relative to younger adults because older adults believe that their memories have deteriorated. Consequently, typical explicit memory tests may overestimate age-related decline in cognitive performance. In 2 experiments, older and younger adults performed a memory test on newly learned trivia. In both experiments, age differences were obtained when the instructions emphasized the memory component of the task (memory emphasis) but not when the instructions did not emphasize memory (memory neutral). These findings suggest that aspects of the testing situation. such as experimental instructions, may exaggerate age differences in memory performance and need to be considered when designing studies investigating age differences in memory.

Adolescent↗

PubMed1988

A three-year follow-up of older adult participants in a memory-skills training program.

This study examined the long-term effects of participation in a self-taught memory training program. In all, 27 memory training and 13 nontraining participants were assessed at approximately 3-year follow-ups. Assessment of these groups prior to the introduction of training had revealed nonsignificant differences in memory performance but marked differences in level of memory complaints, with training participants evidencing higher levels of complaints. The current assessment again demonstrated overall nonsignificant differences in memory performance but significant differences in memory complaints between the two groups. More specifically, the training group evidenced significant decreases in memory performance over the 3-year interval, but no significant changes in memory complaints were observed for either group. Thus, memory training appeared to have little long-term effect on memory functioning. Future research should explore long-term maintenance strategies in memory training with older adults.

Aged↗

PubMed2000

Fear memories require protein synthesis in the amygdala for reconsolidation after retrieval.

'New' memories are initially labile and sensitive to disruption before being consolidated into stable long-term memories. Much evidence indicates that this consolidation involves the synthesis of new proteins in neurons. The lateral and basal nuclei of the amygdala (LBA) are believed to be a site of memory storage in fear learning. Infusion of the protein synthesis inhibitor anisomycin into the LBA shortly after training prevents consolidation of fear memories. Here we show that consolidated fear memories, when reactivated during retrieval, return to a labile state in which infusion of anisomycin shortly after memory reactivation produces amnesia on later tests, regardless of whether reactivation was performed 1 or 14 days after conditioning. The same treatment with anisomycin, in the absence of memory reactivation, left memory intact. Consistent with a time-limited role for protein synthesis production in consolidation, delay of the infusion until six hours after memory reactivation produced no amnesia. Our data show that consolidated fear memories, when reactivated, return to a labile state that requires de novo protein synthesis for reconsolidation. These findings are not predicted by traditional theories of memory consolidation.

Amnesia↗

PubMed2003

Low frequency of plasma nerve-growth factor detection is associated with death of memory B lymphocytes in HIV-1 infection.

Nerve growth factor (NGF) regulates B cell activation and differentiation and is an autocrine survival factor for memory B lymphocytes. We have reported recently that the number of memory B cells is reduced during HIV-1 infection. In this study we evaluated whether alteration in the NGF supply was involved in memory B cell loss in HIV-1-infected subjects. High rate of cell death in vitro was observed in memory B cells from HIV-1-infected individuals compared to uninfected donors (26.2 +/- 2.5%versus 7.9 +/- 1.4%, P < 0.001). The increased expression of Fas on memory B cells from infected subjects did not enhance the susceptibility of the cells to Fas-mediated apoptosis in vitro. The frequency of NGF detection in plasma from HIV-1-infected subjects was significantly lower than in healthy donors (33.6%versus 63.6%, P < 0.001). Also, the median plasma NGF in HIV-1-infected individuals was significantly lower than in uninfected controls (5 versus 14 pg/ml, respectively, P < 0.01). Interestingly, the plasma NGF level was correlated directly 1 to the percentage of memory B cells (P < 0.05). HIV-1-infected subjects with a low number of peripheral memory B cells had a reduced incidence of plasmatic NGF (7.4%) compared to patients with a normal level of memory B cells (37%, P < 0.01). Moreover, the addition of recombinant NGF (1 micro g/ml) to cultures of purified B cells reduced cell death of memory B cells from HIV-1-infected subjects from 24.04 +/- 3.0% to 17.4 +/- 1.3% (P < 0.01). HIV-1-infected individuals also carried higher levels of natural anti-NGF autoantibodies compared to uninfected subjects. In conclusion, we found that memory B cells from HIV-1-infected individuals are primed for cell death. Our study suggests an association between low frequency of plasma NGF detection and the increased cell death of memory B lymphocytes observed during HIV-1 infection. Low levels of NGF in plasma may be due to reduced supply or to NGF binding to natural anti-NGF autoantibodies.

Autoantibodies↗

PubMed2002

Memory deficits after resection from left or right anterior temporal lobe in humans: a meta-analytic review.

PURPOSE: Memory deficits in epileptic patients have been found in some, but not all studies assessing the effects of side of seizures and resection from a temporal lobe on cognitive performance. The purpose of this study was to provide a quantitative review of previous studies on this issue. METHODS: Based on conventional meta-analytic procedures, we identified 33 studies that assessed verbal and nonverbal memory performance before and after anterior temporal lobectomy. The Logical Memory and Visual Reproduction subtests from the Wechsler Memory Scale were used. These studies were then subjected to two levels of analyses: (a) vote-counting procedure, and (b) effect-size calculations and comparisons. RESULTS: Overall, the data confirmed previous findings that verbal memory tasks are sensitive to left hemisphere dysfunction. The efficacy of a "nonverbal" task for tapping function in the nondominant (right) hemisphere was not confirmed, although a trend supporting this speculation was observed. With regard to the comparison of changes in verbal and nonverbal memory before and after resection from a temporal lobe, a clear trend was observed for decline in verbal memory function after resection from the left, especially significant for immediate verbal recall. A trend for contralateral improvement on nonverbal memory also was observed. The pattern of memory change after resection from the right temporal lobe was less clear. CONCLUSIONS: The findings of this study suggest that side of epileptic seizure and surgical resection from a temporal lobe affect verbal memory functions. The relations between the laterality of epileptic seizure, surgical resection from the temporal lobe, and nonverbal memory are to be verified by further research.

Humans↗

PubMed1996

Role of cortical N-methyl-D-aspartate receptors in auditory sensory memory and mismatch negativity generation: implications for schizophrenia.

Working memory refers to the ability of the brain to store and manipulate information over brief time periods, ranging from seconds to minutes. As opposed to long-term memory, which is critically dependent upon hippocampal processing, critical substrates for working memory are distributed in a modality-specific fashion throughout cortex. N-methyl-D-aspartate (NMDA) receptors play a crucial role in the initiation of long-term memory. Neurochemical mechanisms underlying the transient memory storage required for working memory, however, remain obscure. Auditory sensory memory, which refers to the ability of the brain to retain transient representations of the physical features (e.g., pitch) of simple auditory stimuli for periods of up to approximately 30 sec, represents one of the simplest components of the brain working memory system. Functioning of the auditory sensory memory system is indexed by the generation of a well-defined event-related potential, termed mismatch negativity (MMN). MMN can thus be used as an objective index of auditory sensory memory functioning and a probe for investigating underlying neurochemical mechanisms. Monkeys generate cortical activity in response to deviant stimuli that closely resembles human MMN. This study uses a combination of intracortical recording and pharmacological micromanipulations in awake monkeys to demonstrate that both competitive and noncompetitive NMDA antagonists block the generation of MMN without affecting prior obligatory activity in primary auditory cortex. These findings suggest that, on a neurophysiological level, MMN represents selective current flow through open, unblocked NMDA channels. Furthermore, they suggest a crucial role of cortical NMDA receptors in the assessment of stimulus familiarity/unfamiliarity, which is a key process underlying working memory performance.

Animals↗

PubMed1998

Ecological validity of list-learning tests and self-reported memory in healthy individuals and those with temporal lobe epilepsy.

We evaluated in patients with temporal lobe epilepsy (TLE) and healthy volunteers whether list-learning tests of episodic verbal/figural memory and subjective self-reports reliably indicate "Memory in Reality" (MIR). MIR was assessed by the incidental memory of the neuropsychological test event one week after testing. Subjective Memory was assessed by a questionnaire (SMQ). Patients achieved poorer results than controls in all measures of memory. Correlation and multiple regression analysis indicates that list-learning is highly predictive regarding performance in MIR. MIR predominantly relied on verbal memory in patients and on visual/figural memory in controls. Subjective memory differentiated patients and controls but it correlated to MIR only in subjects with unimpaired memory. In conclusion, the data indicate a high ecological validity of list-learning paradigms and they seriously question the diagnostic value of self-reported memory. They also indicate that incidentally acquired knowledge might be differentially represented in patients with a memory disorder and healthy persons.

Adult↗

PubMed2002

Insensitivity of visual short-term memory to irrelevant visual information.

Several authors have hypothesized that visuo-spatial working memory is functionally analogous to verbal working memory. Irrelevant background speech impairs verbal short-term memory. We investigated whether irrelevant visual information has an analogous effect on visual short-term memory, using a dynamic visual noise (DVN) technique known to disrupt visual imagery (Quinn & McConnell, 1996b). Experiment I replicated the effect of DVN on pegword imagery. Experiments 2 and 3 showed no effect of DVN on recall of static matrix patterns, despite a significant effect of a concurrent spatial tapping task. Experiment 4 showed no effect of DVN on encoding or maintenance of arrays of matrix patterns, despite testing memory by a recognition procedure to encourage visual rather than spatial processing. Serial position curves showed a one-item recency effect typical of visual short-term memory. Experiment 5 showed no effect of DVN on short-term recognition of Chinese characters, despite effects of visual similarity and a concurrent colour memory task that confirmed visual processing of the characters. We conclude that irrelevant visual noise does not impair visual short-term memory. Visual working memory may not be functionally analogous to verbal working memory, and different cognitive processes may underlie visual short-term memory and visual imagery.

Adolescent↗