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PubMed2004

Effects of working memory load on long-term word priming.

Three experiments assessed the role of verbal and visuo-spatial working memory in supporting long-term repetition priming for written words. In Experiment 1, two priming tasks (word stem completion and category-exemplar production) were included with three levels of load on working memory: (1) without memory load, (2) memory load that involved storing a string of six digits, and (3) memory load that involved storing a graphic shape. Experiments 2 and 3 compared the effects of a verbal (Experiment 2) or a visual (Experiment 3) working memory load at encoding on both an implicit (word stem completion) and an explicit test (cued recall). The results show no effect of memory load in any of the implicit memory tests, suggesting that priming does not rely on working memory resources. By contrast, loading working memory at encoding causes a significant disruptive effect on the explicit memory test for words when the load is verbal but not visual.

Adult↗

PubMed2006

Islands of memory: Autobiographical remembering in amnestics.

In amnestics with anterograde amnesia, memories of post-onset autobiographical experiences, if present at all, are typically barren and impoverished. However, there have been sporadic reports of islands of memory--memories that are vivid, detailed, and specific to time and place. The aim of this study was to verify the presence of such memories and examine their incidence rate. Anterograde amnestics were interviewed in their home using a narrative interviewing strategy with a view to describing memory in everyday life. Each autobiographical memory of a post-onset event was coded for quantity-length, and quality-episodicity. In just over half of the amnestics (8 out of 14), a memory that was lengthy, rich in personal details, and localisable was recollected. The quantitative and qualitative aspects of these island memories were significantly different from the other autobiographical memories that the amnestics supplied. These memories were at odds with what would be expected on the basis of their performance on standardised memory instruments. Our findings suggest there is occasionally more variability in remembering of autobiographical experiences in some amnestics than has traditionally been believed.

Adult↗

PubMed2006

Episodic remembering creates access to involuntary conscious memory: demonstrating involuntary recall on a voluntary recall task.

The idea that involuntary memory retrieval might occur during voluntary memory retrieval can be traced back to Ebbinghaus (1885/1964). However, methodological challenges have stood in the way of testing this idea. Recent diary studies of naturally occurring involuntary memories have provided insights into how this idea could be tested (Berntsen, 1998; Mace, 2005b, 2006). These studies have shown that the contents of an involuntary memory sometimes trigger additional involuntary memories, a process called chaining. It was hypothesised that chaining should also occur on autobiographical memory tasks, and this was tested in the present study by asking participants in an autobiographical memory task to report the presence of involuntary memories while they were performing the task. The results showed that involuntary memories did occur when participants were recalling the past. The results also showed involuntary memories dissociating from voluntary memories on two independent measures, thereby enhancing the credibility of the results.

Adult↗

PubMed2002

Memory enhancement training for older adults with mild cognitive impairment: a preliminary study.

'Mild cognitive impairment' (MCI) in older adults refers to a significant decline in memory function but not other cognitive functions. Pharmacological and non-pharmacological treatments for MCI are needed. The present randomized clinical trial tests the efficacy of a cognitive and behavioral treatment to improve memory performance and participants' attitudes about their memory. A multi-faceted intervention that included education about memory loss, relaxation training, memory skills training, and cognitive restructuring for memory-related beliefs was compared to a no-treatment control condition. Outcomes included memory performance and appraisals of memory function and control. Results indicate that the treated group had significantly better memory appraisals than controls at the end of treatment and at a six-month follow-up. There were no differences between groups on memory performance at post-test but at follow-up the trained individuals showed a trend toward better word list recall than controls. Findings suggest that individuals with MCI can benefit from multi-component memory enhancement training. Further development of such training programs and tests of their efficacy alone and in combination with medications are needed.

Aged↗

PubMed2006

Comparison of adult age differences in verbal and visuo-spatial memory: the importance of 'pure', parallel and validated measures.

The study compared age-related decrements in verbal and visuo-spatial memory across a broad elderly adult age range. Twenty-four young (18-25 years), 24 young-old (65-74 years), 24 middle-old (75-84 years) and 24 old-old (85-93 years) adults completed parallel recall and recognition measures of verbal and visuo-spatial memory from the Doors and People Test (Baddeley, Emslie & Nimmo-Smith, 1994). These constituted 'pure' and validated indices of either verbal or visuo-spatial memory. Verbal and visuo-spatial memory declined similarly with age, with a steeper decline in recall than recognition. Unlike recognition memory, recall performance also showed a heightened decline after the age of 85. Age-associated memory loss in both modalities was largely due to working memory and executive function. Processing speed and sensory functioning (vision, hearing) made minor contributions to memory performance and age differences in it. Together, these findings demonstrate common, rather than differential, age-related effects on verbal and visuo-spatial memory. They also emphasize the importance of using 'pure', parallel and validated measures of verbal and visuo-spatial memory in memory ageing research.

Adolescent↗

PubMed2003

Parasites and immune responses: memory illusion?

Immunological memory responses to intracellular protozoa and extracellular helminths govern host resistance and susceptibility to reinfection. Humans and livestock living in parasitic disease endemic regions face continuous exposure from a very early age that often leads to asymptomatic chronic infection over their entire lifespan. Fundamental immunological studies suggest that the generation of T-cell memory is driven by tightly coordinated innate and adaptive cellular immune responses rapidly triggered following initial host infection. A key distinguishing feature of immune memory maintenance between the majority of parasitic diseases and most bacterial or viral diseases is long-term antigen persistence. Consequently, functional parasite immune memory is in a continuous, dynamic flux between activation and deactivation producing functional parasite killing or functional memory cell death. In this sense, T-cell immune memory can be regarded as "memory illusion." Furthermore, due to the finite capacity of memory lymphocytes to proliferate, continuous parasite antigen stimulation may exceed a threshold level at some point in the chronically infected host. This may result in suboptimal effector immune memory leading to host susceptibility to reinfection, or immune dysregulation yielding disease reactivation or immune pathology. The goal of this review is to highlight, through numerous examples, what is currently known about T-cell immune memory to parasites and to provide compelling hypotheses on the survival and maintenance of parasite "memory illusion." These novel concepts are discussed in the context of rationale parasite vaccine design strategies.

Animals↗

PubMed1996

Identification of famous faces and famous names in early Alzheimer's disease. Relationship to anterograde episodic and general semantic memory.

We assessed remote memory in 33 patients with dementia of Alzheimer's type (DAT) with Mini-Mental State Examination (MMSE) scores between 17 and 30, and 30 matched controls using a Famous Faces Test and Famous Names Test designed to assess face recognition, identification and naming, and name recognition and identification, respectively, together with a range of anterograde episodic and semantic memory tests. Patients with DAT were impaired on all components of the remote memory tests, i.e. famous face recognition, identification and naming, and famous name recognition and identification. There was also evidence of a modest temporal gradient, with relatively greater impairment of more recent memory, which may be artefactual resulting from the very insidious onset of their anterograde amnesia. In contrast to the uniform impairment of anterograde memory, there was considerable heterogeneity in performance on remote memory. Although the DAT patient group's performance on remote memory measures was impaired with respect to controls, some patients had significant impairment on all measures, whereas others had intact remote memory. Overall, there was only a weak correlation between dementia severity and remote memory, and no correlation between performance on the Faces and Names tests and measures of anterograde memory. At a cognitive level, the deficit in face and name processing in DAT involved recognition, identification and naming. This would suggest that so called 'face and name recognition units', semantic knowledge of famous persons and post-semantic processing are all affected by the disease. There was also supporting evidence for the concept that recognition of famous faces and names both draw on common sources. Similar results were found for face and name identification. This suggests that face and name recognition units are closely linked, and that identification of a face or name accesses the same central pool of semantic knowledge regarding the famous person. Performance on famous names tests correlated, to a limited degree, with that on general semantic tests, suggesting that knowledge of famous people, at least as accessed by names, is associated with general semantic memory. By contrast, no correlation was found between performance on the famous faces and on other general semantic tasks.

Aged↗

PubMed1997

Working memory impairment in early multiple sclerosis. Evidence from an event-related potential study of patients with clinically isolated myelopathy.

Auditory and visual event-related potentials were recorded during a short-term memory task in 24 patients who had recently presented with symptomatically and clinically isolated spinal cord syndromes suspected to be due to multiple sclerosis, and in 24 matched control subjects. Event-related potentials (ERPs) were recorded during two sequential components of the working memory task, first the temporary active memorizing of sets of digits and secondly, their subsequent manipulation, namely digit-probe recognition and matching. The patients' reaction times were slower and showed larger increments than those of the control subjects as the number of items to be memorized was increased. The patients' ERPs during both memorizing and probe matching/recognition phases differed significantly from control subjects for both auditory and visual presentations. The more marked changes were seen in a subgroup of eight patients who had the lowest levels of performance on a battery of general tests of memory and who also made significantly more errors in the working memory task as the memory load increased. In this subgroup, the abnormalities of the ERPs during recognition and matching tests occurred in the component of the response that has been shown to be sensitive to memory loading in healthy control subjects. This study provides objective evidence of subclinical working memory dysfunction in patients at an early stage of demyelinating disease, i.e. when they first present with clinically isolated spinal cord lesions and before they have developed symptoms of cognitive or memory dysfunction. The defect at this early stage is either restricted to processes involved in the formation of a memory trace or, more probably, involves both trace formation and the mechanisms that underly recognition ('retrieval') and matching of memory traces in working memory.

Adult↗

PubMed2001

Unilateral temporal lobectomy patients show lateralized topographical and episodic memory deficits in a virtual town.

A large-scale virtual reality town was used to test the topographical and episodic memory of patients with unilateral temporal lobe damage. Seventeen right and 13 left temporal lobectomy patients were compared with 16 healthy matched control subjects. After they had explored the town, subjects' topographical memory was tested by requiring them to navigate to specific locations in the town. The ability to recognize scenes from and draw maps of the virtual town was also assessed. Following the topographical memory tests, subjects followed a route around the same town but now collected objects from two different characters in two different locations. Episodic memory for various aspects of these events was then assessed by paired forced-choice recognition tests. The results showed an interaction between laterality and test type such that the right temporal lobectomy (RTL) patients were worse on tests of topographical memory, and the left temporal lobectomy (LTL) patients worse on tests of context-dependent episodic memory. Specifically, the RTL group was impaired on navigation, scene recognition and map drawing relative to control subjects. They were also impaired on recognition of objects in the episodic memory task. The LTL group was impaired relative to control subjects on their memory for contextual aspects of the events, such as who gave them the objects, the order in which objects were received and the locations in which they received them. They were also mildly impaired on topographical memory, but less so than the RTL group. These results suggest that topographical memory is predominately mediated by structures in the right medial temporal lobe, whereas the context-dependent aspects of episodic memory in this non-verbal test are more dependent on the left medial temporal lobe.

Adult↗

PubMed2003

Working memory and executive functions in transient global amnesia.

Transient global amnesia (TGA) is usually considered to produce a profound impairment of long-term episodic memory, while at the same time sparing working memory. However, this neuropsychological dissociation has rarely been examined in detail. While a few studies have assessed some components of working memory in TGA, the results that have been obtained are far from conclusive. To clarify this issue, we carried out a comprehensive investigation of working memory in 10 patients during a TGA attack. In the first study, we report the results from three patients examined with a battery of neuropsychological tests designed to assess each of the three subcomponents of Baddeley's model of working memory. In a second study, seven different patients underwent neuropsychological investigations that focused specifically on the central executive system, using a protocol derived from a study by Miyake and colleagues. Our findings showed that subcomponents of working memory, such as the phonological loop and visuo-spatial sketch pad, were spared in TGA patients. Specific executive functions that entailed inhibitory control, dual task performance, updating and shifting mechanisms were also found to be normal. However, we found significantly impaired performance for the Brown-Peterson test, and that TGA patients were significantly impaired in the recollection of their episodic memories. They also made reduced numbers of 'remember' compared with 'know' judgments in the episodic memory test several days after TGA. On the basis of our findings, it would appear that the episodic memory deficit during TGA is not related to elementary aspects of executive functioning. Our data also highlight the nature of the cognitive mechanisms involved in the Brown-Peterson task, which may well depend on long-term memory (such as the process of semantic encoding). Lastly, the selective deficit in recollective episodic memories observed in TGA may be principally related to medial temporal lobe abnormalities that have been reported in this syndrome.

Aged↗

PubMed2004

Functional MRI predicts post-surgical memory following temporal lobectomy.

Temporal lobectomy is an effective therapy for medically refractory temporal lobe epilepsy (TLE), but may be complicated by amnestic syndromes. Therefore, pre-surgical evaluation to assess the risk/benefit ratio for surgery is required. Intracarotid amobarbital testing (IAT) is currently the most widely used method for assessing pre-surgical memory lateralization, but is relatively invasive. Over the past decade functional MRI (fMRI) has been shown to correlate with IAT for language lateralization, and also for memory lateralization in a small number of patients. This study was carried out to compare fMRI during memory encoding with IAT testing for memory lateralization, and to assess the predictive value of fMRI during memory encoding for post-surgical memory outcome. Thirty-five patients with refractory TLE undergoing pre-surgical evaluation for temporal lobectomy and 30 normal subjects performed a complex visual scene-encoding task during fMRI scanning at 1.5 T using a 10-min protocol. Encoding performance was evaluated with subsequent recognition testing. Twenty-three patients also completed the same task again outside the scanner, an average of 6.9 months following surgery. A region of interest (ROI) analysis was used to quantify activation within hippocampal and a larger mesial temporal lobe ROI consisting of hippocampus, parahippocampus and fusiform gyrus (HPF) as defined by a published template. Normal subjects showed almost symmetrical activation within these ROI. TLE patients showed greater asymmetry. Asymmetry ratios (ARs) from the HPF ROI correlated significantly with memory lateralization by intracarotid amobarbital testing. HPF ARs also correlated significantly with memory outcome, as determined by a change in scene recognition between pre-surgical and post-surgical trials. When absolute activation within the HPF ROI was considered, a significant inverse correlation between activation ipsilateral to temporal lobectomy and memory outcome was observed, with no significant correlation in the contralateral HPF ROI. Although further technical improvements and prospective clinical validation are required, these results suggest that mesial temporal memory activation detected by fMRI during complex visual scene encoding correlates with post-surgical memory outcome and supports the notion that this approach will ultimately contribute to patient management.

Adult↗

PubMed2004

A naturalistic analysis of autobiographical memories triggered by olfactory visual and auditory stimuli.

The emotional and content qualities of autobiographical memories evoked by three memory cue items (campfire, fresh-cut grass, popcorn) presented in olfactory, visual and auditory form were examined using a new repeated measures paradigm. Results revealed that memories recalled by odors were significantly more emotional and evocative than those recalled by the same cue presented visually or auditorily. However, there were no differences in the content features (vividness, specificity) of memories as a function of cue-form. These findings support previous research in both laboratory and naturalistic settings and is the first comparative sensory memory study to include auditory variants of memory cues. The present data contribute to a growing body of evidence indicating that there is a privileged relationship between olfaction and emotion during recollection. Various subject factors such as age, sex and region of residence were also examined and some were found to affect the quality of memories in interaction with the specific memory cue items, indicating that prior experience is a primary influence in autobiographical memory. Questions for future investigation regarding how odor-evoked memories may be different from other memory experiences are suggested.

Acoustic Stimulation↗

PubMed2006

No sex differences in memory formation during general anesthesia.

BACKGROUND: Women respond differently to anesthesia than men, initially recovering more rapidly, but having more postoperative morbidity. Studies on surgical patients report evidence of memory formation during anesthesia. However, sex differences in memory formation have not been explored. Therefore, the authors investigated sex differences in the implicit and explicit memory formation during general anesthesia. METHODS: With ethics committee approval, 120 consenting adult patients scheduled to undergo surgery during general anesthesia were recruited. Intraoperatively, 16 target words were presented to patients via headphones, and the Bispectral Index was recorded. Postoperatively, memory for presented words was tested using a word stem completion test. The test was divided into inclusion and exclusion parts, to delineate implicit and explicit memory contributions. RESULTS: Target and distracter hit rates were similar in men and women. For the whole study group, there was a significant difference between inclusion target hit rate (0.42) and base hit rate (0.39) (P = 0.01). Buchner's model suggested that this memory formation was attributable to both implicit and explicit memory. A Bispectral Index value greater than 50 was the only significant predictor of inclusion target hit rate. None of the patients were able to consciously recall the words presented during surgery. CONCLUSIONS: Patients showed greater memory performance for words presented during general anesthesia than for words not presented. However, sex differences in memory formation were not observed. A relation between hypnotic state and memory during sevoflurane anesthesia was also established, suggesting that memory formation is possible even at hypnotic depths considered to be adequate anesthesia.

Adolescent↗

PubMed1977

Levodopa, parkinsonism, and recent memory.

Much controversy has existed concerning behavioral changes attributed to L-dopa treatment in parkinsonian patients. Disagreement existed pertaining to the question of whether improved functioning was temporally limited. The present study proposed to research the shorter and longer range effects of L-dopa onmemory. It was hypothesized that equated nonparkinsonian individuals would perform better than parkinsonian patients on all memory measures, and that shorter range L-dopa would perform better than longer range L-dopa patients. It was also hypothesized that the greater the functional deficiency, and the greater the symptom severity, the poorer memory functioning would be. Level of dosage was hypothesized to have no differential effect on memory functioning. Three groups of 20 subjects were tested. The short term (20 parkinsonian patients on L-dopa for 22 months or less) and the long term (20 parkinsonian patients on L-dopa for 40 months or more) patients were chosen from the neurological clinic at St. Barnabas Hospital, Bronx, N.Y. Testability was assessed by the neurologis and by WAIS Vocabulary performance. The third group consisted of spouses of the patients. All groups were equated with regard to sex, age, education, and where applicable, length of illness, functional status, and symptom severity. The instruments used to measure memory consisted of the Guild Memory Test, the Memory Span for Objects, the Knox Cube, and the Tactile Memory Test. WAIS Vocabulary scaled score was used as a covariate in an analysis of covariance on each of the nine memory subtests. Statistically significant differences were obtained at the .01 level among groups on all measures. Orthogonal comparisons resulted in significant differences at the .01 level between parkinsonian patients and nonparkinsonian subjects on all measures. Short term and long term L-dopa patients differed significantly on six of the nine measures, notably those testing verbal types of memory. Significant correlations were obtained between functional deficiency and eight measures; however, symptom severity correlated with only one measure. None of the memory measures correlated significantly with level of dosage. The major conclusion was reached that all of the initial improvement shown following L-dopa initiation is not sustained permanently; the elevated level of memory functioning appears to be temporally limited.

Humans↗

PubMed1990

Inhibition of alloresponsive naive and memory T cells by CD7 and CD25 antibodies and by cyclosporine.

Human naive and memory T cells can be isolated from each other by their CD45RA and CD45RO expression, respectively. This enables the assessment of their differential sensitivities to immunosuppressive agents for the first time. We have investigated the ability of cyclosporine or CD7 and CD25 antibodies to selectively block alloantigen stimulated naive and memory T cells in vitro. CD7 antibodies blocked the proliferation of naive (P less than 0.025) but not memory T cells in a primary MLR. CD25 antibody inhibited both naive and memory subsets but a significantly greater effect was found on the memory T cells (P less than 0.005). The constitutive CD7 and CD25 antigen expression on resting naive or memory T cells was related to the inhibitory activities of these antibodies on both subsets. Accordingly, naive T cells expressed more CD7 antigen than memory cells while memory T cells displayed low levels of CD25 antigen that was absent from naive populations before activation. Cyclosporine, like CD25 antibody, inhibited both subsets in a primary MLR but had a greater effect on memory cells (P less than 0.02). Memory T cells, therefore, are more dependent than naive cells on IL-2 for proliferation. There was great individual variation in the ability of CsA to block the MLR. The simultaneous addition of CD25 or CD7 antibody together with CsA, however, enhanced the MLR inhibition as the effects of all three were additive. This suggested interference by these agents at different points during T cell activation. Thus, in CsA sensitive individuals, one-tenth of the optimal CsA concentration together with CD25 antibody maintained maximum immunosuppression in vitro. These results demonstrate the possibility of using CD7 and CD25 antibodies for selective inhibition of naive or memory T cells and also the possibility of augmenting the inhibition of and reducing the CsA concentration required for clinically effective immunosuppression.

Antibodies, Monoclonal↗

PubMed2000

Behavioural pharmacology and its contribution to the molecular basis of memory consolidation.

Recent findings have significantly advanced our understanding the mechanisms of memory formation. Most of these advances stemmed from behavioural pharmacology research involving, particularly, the localized infusion of drugs with specific molecular actions into specific brain regions. This approach has revealed brain structures involved in different memory types and the main neurotransmitter systems and sequence of metabolic cascades that participate in memory consolidation. Biochemical studies and, in several cases, studies of genetically manipulated animals, in which receptors or enzymes affected by the various drugs were absent or overexpressed, have complemented the pharmacological research. Although most studies have concentrated on the involvement of the hippocampus, many have also investigated the entorhinal cortex, other regions of the cortex, and the amygdala. Behavioural pharmacology has been of crucial importance in establishing the major neurohumoral and hormonal systems involved in the modulation of memory formation. These systems act on specific steps of memory formation in the hippocampus and in the entorhinal, parietal, and cingulate cortex. A specialized system mediated by the basolateral amygdaloid nucleus, and involving several neuromodulatory systems, is activated by emotional arousal and serves to regulate memory formation in other brain regions. The core mechanisms involved in the formation of explicit (declarative) memory are in many respects similar to those of long-term potentiation (LTP), particularly in the hippocampus. However, there are also important differences between memory formation and LTP. Memory formation involves numerous modulatory influences, the co-participation of various brain regions other than the hippocampus, and some properties that are specific to memory and absent in LTP (i.e. flexibility of response). We discuss the implications of these similarities and differences for understanding the neural bases of memory.

Animals↗

PubMed2004

Verbal and visuospatial learning and memory function in children with moderate prenatal alcohol exposure.

BACKGROUND: This study investigated the effects of moderate prenatal alcohol exposure on learning and memory in 14-year-old adolescents. The Children's Memory Scale was used to assess learning and memory function in the verbal/auditory and visual/spatial domains. In addition, both short- and long-term memory function were assessed. METHODS: Data were collected as part of the Maternal Health Practices and Child Development Project, a longitudinal study including 580 children and their mothers. Women were assessed during each trimester of pregnancy and with their children from birth to 16 years of age. At age 14, memory function was evaluated using the Children's Memory Scale, an assessment tool that measures learning and immediate and delayed memory function in the verbal and visual-spatial domains. RESULTS: Prenatal alcohol exposure during the first trimester predicted deficits in learning, short-term memory, and long-term memory, specifically in the verbal domain. Deficits in performance were specific to learning and memory of word-pairs. In addition, deficits in memory were mediated by learning performance. CONCLUSIONS: Results demonstrated that prenatal alcohol exposure lead to deficits in encoding processes as indicated by deficits in verbal learning. Initial deficits in acquisition were responsible for deficits in immediate and delayed recall of verbal information in children who were exposed to alcohol during pregnancy but did not have fetal alcohol syndrome.

Adolescent↗

PubMed2003

Episodic and semantic memory in bilingual and monolingual children.

Although bilinguality has been reported to confer advantages upon children with respect to various cognitive abilities, much less is known about the relation between memory and bilinguality. In this study, 60 (30 girls and 30 boys) bilingual and 60 (30 girls and 30 boys) monolingual children in three age groups (mean ages 8.5, 10.5 and 12.5 years) were compared on episodic memory and semantic memory tasks. Episodic memory was assessed using subject-performed tasks (with real or imaginary objects) and verbal tasks, with retrieval by both free recall and cued recall. Semantic memory was assessed by word fluency tests. Positive effects of bilingualism were found on both episodic memory and semantic memory at all age levels. These findings suggest that bilingual children integrate and/or organize the information of two languages, and so bilingualism creates advantages in terms of cognitive abilities (including memory). Some sex differences were also found in episodic memory but not in semantic memory. This episodic memory difference was found with younger children.

Adolescent↗