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PubMed2004

A dissociation between implicit and explicit verbal memory in left temporal lobe epilepsy.

PURPOSE: Temporal lobe epilepsy patients are well known to present deficits on explicit verbal memory procedures (e.g., recall, recognition). The integrity of implicit memory procedures in these patients is not established. Previous studies in this area used implicit memory measures contaminated by the effects of explicit memory. METHODS: We examined the integrity of verbal implicit and explicit memory in left temporal lobe epilepsy (LTLE) patients and hypothesized that a clear dissociation in performance would be found with a relative preservation of implicit memory. TLE patients (n = 15) and age- and education-matched healthy normal patients (n = 15) were shown a 40-word study list, followed by a test phase requiring completion of word stems based on the study words or new/unseen words. Experimental conditions involved instructions to provide either the old (study) words or novel/nonlist words when completing the stem. Measures of automaticity and recollection provided uncontaminated indices of implicit and explicit memory, respectively. RESULTS: The data showed a significant difference (p < 0.001) between the patients (Recollection, 0.12; SD, 0.18) and controls (0.50, SD, 0.15) on the measure of explicit memory. In contrast, the patients (Automaticity, 0.51; SD, 0.11) and controls (0.45, SD, 0.18) performed similarly on the implicit memory measure, with patient scores clearly at normative levels based on other Process Dissociation Procedure data. CONCLUSIONS: The data demonstrate the integrity of implicit memory in LTLE patients. Finding a dissociation between the two forms of verbal memory in LTLE patients provides evidence that they rely on different neuroanatomic systems.

Adolescent↗

PubMed1993

Memory loss during pregnancy.

OBJECTIVE: To investigate possible impairment of memory during pregnancy. DESIGN: The performance of pregnant women in a variety of tests of memory was compared to that of controls. SETTING: The Bristol Maternity Hospital. SUBJECTS: Forty-eight volunteer pregnant women attending for routine antenatal checks were compared to 19 nonpregnant controls. MAIN OUTCOME MEASURES: Subjectively perceived rating of memory impairment, objective measures of recall, recognition and priming memory. RESULTS: Pregnant and control groups were given a series of tests of memory at the end of which they were asked to rate their own memory at present compared to some weeks ago (when they were not pregnant). Of the pregnant women 39 out of 48 (81%) rated their current memory as being impaired; only three out of 19 (16%) of the control subjects did so. Objective tests revealed that the pregnant group was significantly impaired in the recall of lists of words, particularly when learning was incidental rather than explicit. The pregnant group was also significantly impaired in two measures of priming memory. No significant deficit was found in recognition. The deficits were found for both primigravid and multigravid women, and were present in all trimesters of pregnancy. CONCLUSIONS: The majority of women believe their memory to be impaired during pregnancy. Objectively, during pregnancy there is significant impairment of memory as tested by recall or by priming, but not by recognition. The pattern of memory loss differs from that of other amnesic conditions. Information imparted to pregnant patients may not be retained as well as might be expected.

Adult↗

PubMed2006

Remote memory in temporal lobe epilepsy.

PURPOSE: The present study aims at characterizing remote memory in patients with temporal lobe epilepsy (TLE); it also considers the impact of its most important variables (lateralization of the lesion, duration of epilepsy, age at onset, and seizure frequency) on remote memory. METHODS: We examined the performance of 38 patients with unilateral TLE (19 right TLE and 19 left TLE) and 35 healthy subjects on six remote memory tasks. Memory for personal events was assessed by using the Autobiographical Memory Interview and the Modified Crovitz Test. Memory for public events was evaluated by means of photographs of famous faces and famous scenes, questions about famous events, and the Dead/Alive Test. RESULTS: Both right-TLE and left-TLE groups had impaired memory for autobiographic episodes and public events relative to normal subjects. In contrast, personal semantic memory was preserved. In addition, an effect of laterality was recorded, with right-TLE patients obtaining significantly better scores than left-TLE patients on every test. Duration of epilepsy, age at onset, and seizure frequency did not influence performance on remote memory measures. CONCLUSIONS: The comprehensive neuropsychological study of 38 TLE patients showed that this neurologic condition affects remote memory systems differently. We discuss the different factors that could account for this pattern of performance on the bases of both functional brain organization and memory theories.

Adult↗

PubMed1987

Phonological similarity effects, memory span and developmental reading disorders: the nature of the relationship.

Eight-and 11-year-old poor readers of average and below average intelligence carried out a visually presented immediate memory task, recalling strings of similar- and dissimilar-sounding letters. Task difficulty was adjusted for each child by determining memory span for the dissimilar items prior to the memory task. All poor reader groups recalled significantly more dissimilar- than similar-sounding items, and the magnitude of these effects was comparable to those shown by their chronological and reading age controls. A close association was found between memory span and reading age, such that average intelligence poor readers had memory spans indistinguishable from those of their reading age controls. Furthermore, a highly significant correlation was found between memory span and reading age. However, it was concluded that this relationship could not be primarily due to a substantial immediate memory component in word recognition as the below average intelligence poor readers had poorer memory spans than the brighter poor readers, yet they had very similar reading ages. Additionally, a weaker association was found between memory span and non-word reading than between memory span and word reading. It was hypothesized that recognition difficulties may be the primary problem underlying both poor word recognition and immediate memory impairments in children with reading disorders.

Child↗

PubMed2006

Involvement of the anterior cingulate cortex in the expression of remote spatial memory.

Although the hippocampus plays a crucial role in the formation of spatial memories, as these memories mature they may become additionally (or even exclusively) dependent on extrahippocampal structures. However, the identity of these extrahippocampal structures that support remote spatial memory is currently not known. Using a Morris water-maze task, we show that the anterior cingulate cortex (ACC) plays a key role in the expression of remote spatial memories in mice. To first evaluate whether the ACC is activated after the recall of spatial memory, we examined the expression of the immediate early gene, c-fos, in the ACC. Fos expression was elevated after expression of a remote (1 month old), but not recent (1 d old), water-maze memory, suggesting that ACC plays an increasingly important role as a function of time. Consistent with the gene expression data, targeted pharmacological inactivation of the ACC with the sodium channel blocker lidocaine blocked expression of remote, but spared recent, spatial memory. In contrast, inactivation of the dorsal hippocampus disrupted expression of spatial memory, regardless of its age. We further showed that inactivation of the ACC blocked expression of remote spatial memory in two different mouse strains, after training with either a hidden or visible platform in a constant location, and using the AMPA receptor antagonist CNQX. Together, our data provide evidence that circuits supporting spatial memory are reorganized in a time-dependent manner, and establish that activity in neurons intrinsic to the ACC is critical for processing remote spatial memories.

6-Cyano-7-nitroquinoxaline-2,3-dione↗

PubMed2003

Short-term, delayed, and working memory are impaired during hypoglycemia in individuals with type 1 diabetes.

OBJECTIVE: To examine the effects of acute insulin-induced hypoglycemia on short-term, delayed, and working memory in individuals with type 1 diabetes. RESEARCH DESIGN AND METHODS: A hyperinsulinemic glucose clamp was used to maintain arterialized blood glucose level at either 4.5 mmol/l (euglycemia) or 2.5 mmol/l (hypoglycemia) on two separate occasions in 16 adults with type 1 diabetes. The participants completed tests of immediate and delayed verbal memory, immediate and delayed visual memory, and working memory during each experimental condition. Two other mental tests, the Trail Making B Test and the Digit Symbol Test, were also administered. RESULTS: Performance in tests of immediate verbal and immediate visual memory was significantly impaired during hypoglycemia. The effect of hypoglycemia on working memory and delayed memory was more profound. Performance in the nonmemory tests, the Trail Making B Test, and the Digit Symbol Test also deteriorated during hypoglycemia. CONCLUSIONS: All of the memory systems examined in the present study were affected significantly by acute hypoglycemia, particularly working memory and delayed memory. Mild (self-treated) hypoglycemia is common in individuals with insulin-treated diabetes; therefore, these observed effects of hypoglycemia on memory are of potential clinical importance because they could interfere with many everyday activities.

Acute Disease↗

PubMed2000

[Suboptimal health and memory performance of elderly].

The influence of health-related incidents on memory test performance and subjective memory ratings was assessed in a) a group of healthy older adults recruited via the register of population (group 1: N = 117, mean age 62 years, range 46-89) and b) a group of healthy older subjects having memory complaints and applying for memory training (group 2: N = 111, mean age 63 years, range 45-85). The study tries to cross-validate a previous study, where the presence and frequency of health-related incidents were related to cognitive performance. The presence of 9 categories of health-related incidents (consultation of a neurologist, systemic diseases, repeated mild concussions, repeated anaesthesia, use of psychotropic medication, alcohol use, other neurotoxic factors, such as exposure to organic solvents, psychiatric disorders, birth complications or developmental problems) was assessed in a semi-structured interview. Memory performance was assessed with a battery covering different aspects of memory. Memory self-ratings were assessed with questionnaires asking for frequencies of memory failures and a general judgement of memory capacity. Health-related incidents occurred in about half of both subject groups and were not related to age or other demographic characteristics. In both subject groups, the presence, nor the number of health-related incidents was related to memory performance or memory complaints and there was no interaction with age. The results are not in agreement with the notion that health-related indices explain age differences in cognitive performance.

Age Factors↗

PubMed2003

[The validation of a Japanese version of the Everyday Memory Checklist].

UNLABELLED: We developed a Japanese version of the Everyday Memory Checklist(EMC), which was originally made by Wilson et al. to assess everyday memory problems, and examined its reliability and validity in assessing brain-damaged patients with memory deficits. SUBJECTS AND METHODS: The subjects consisted of 393 brain-damaged patients with memory deficits aged between 17 and 90 years with the mean MMSE of 24.6, and 132 control subjects aged between 19 and 86 years with the mean MMSE of 28.5. Patients' everyday memory problems were both self-evaluated and evaluated by their caregivers, while those of control subjects were only self-evaluated with the EMC. RESULTS: The test-retest reliability of the EMC evaluated in 149 randomly selected patients was acceptably high with intraclass correlation coefficient (0.950 for caregiver-evaluated scores and 0.759 for self-evaluated scores). The standard memory test scores were significantly correlated with the EMC scores of the patients evaluated by the caregivers; among them the scores of the Rivermead Behavioural Memory Test were most highly correlated with the EMC scores. On the other hand, the scores of the non-memory cognitive test scores were not significantly correlated with the EMC scores. The self-evaluated EMC scores of the patients were significantly lower than those of the patients evaluated by the caregivers, and were not correlated with memory test scores or with non-memory cognitive test scores. As the EMC scores of control subjects over 60 years were significantly higher than the scores of the subjects under 59 years, we compared the EMC scores between the patients and the control subjects after we divided each subject into two groups depending on age. The EMC scores of the patients evaluated by the caregivers were significantly higher than the score of the control subjects in groups of both over 60 years and under 59 years. However, the self-evaluated EMC scores of the patient were not significantly higher than the EMC scores of the control subjects. In the analysis of the diagnostic accuracy, the EMC scores of the patients evaluated by the caregivers correctly classified 40.9% of patients and 92.9% of normal subjects by setting the cut-off scores of 14/15 in subjects under 59 years, and classified 50.2% of patients and 85.5% of normal subjects by setting the cut-off scores of 16/17 in subjects over 60 years. CONCLUSION: When caregivers evaluated the amnesic patients, the Japanese version of the EMC is reliable and valid in assessing everyday memory problems.

Aged↗

PubMed2006

Distraction as a key determinant of impaired memory in patients with fibromyalgia.

OBJECTIVE: Patients with fibromyalgia (FM) frequently complain of poor memory, severe enough to affect job performance and to lead to disability. Yet common practices in neurocognitive examinations often fail to document cognitive abnormalities that match the severity of their memory complaints. Often, neuropsychologists gauge memory competence with measures free of distraction and produce high rates of normality on neurocognitive examination. We hypothesized that neurocognitive tests encoded with a source of stimulus competition that interferes with the processing and/or absorption of information would be better than others in gauging FM memory competence. METHODS: Thirty-five patients with FM and 35 controls, matched for age and sex, and presenting with complaints of memory loss, completed cognitive measures with and without stimulus competition. RESULTS: Eleven (31.4%) patients with FM showed impairment on at least one measure of memory encoded free of stimulus competition. By comparison, 30 (85.7%) showed impairment on at least one measure encoded with a source of stimulus competition. The Auditory Consonant Trigram detected impairment in 29 (82.6%) cases, and was by far the most sensitive measure. FM patients lost information at a 58% rate following a 9 second distraction. This loss was disproportionate to the loss shown by both age matched controls with memory problems (40%) and to normative values (20%) based on individuals free of memory problems. CONCLUSION: The findings validate the perception of failing memory in patients with FM and are the first psychometric based evidence to our knowledge of short-term memory problems in FM linked to interference from a source of distraction. Adding a source of distraction caused the majority of FM patients to retain new information poorly, and may be integral to an understanding of FM memory problems. Much needs to be learned about why new information is disproportionately lost by FM populations when a source of distraction enters the experiential field.

Adult↗

PubMed1987

The chronic effects of alcohol on memory. A contrast between a unitary and dual system approach.

Recent studies have indicated that impairment of memory is a common cognitive deficit related to long-term alcohol consumption. Such deficits range from subtle disturbance through a "subclinical" amnesic disorder to full-blown Korsakoff syndrome. This finding is congenial with the hypothesized continuum of alcohol-related impairment of memory. Among alcoholics, this memory impairment appears to be etiologically distinct from the commonly observed deficits in abstracting and problem-solving abilities. In the present chapter, a dual and a unitary formulation of memory are contrasted in their ability to present a coherent account of what memory tasks Korsakoff amnesics can and cannot do. The explanations offered by unitary theory are weak compared to those derived from the theory that memory consists of two distinct systems--experiential and abstractive memory. We indicate how the pattern of responding on standard clinical tests of memory can be coherently analyzed post hoc within the dual formulation. A number of experimental predictions are also presented based on the theory that Korsakoff amnesics have a profound impairment of experiential memory, whereas the abstractive system is essentially normal. Such experiments should clarify the nature both of Korsakoff amnesia and of memory itself. In conclusion, we indicated that memory disorders related to alcoholism can be understood in terms of a gradient, or continuum, of impairment of the experiential system.

Alcohol Amnestic Disorder↗

PubMed1990

Screening for early dementia using memory complaints from patients and relatives.

This study examined whether the subjective impression of memory function might differentiate healthy elderly subjects from patients with memory complaints, and whether memory complaints differed between patients with and without a dementing illness. Both self-assessment and relatives' responses on a new memory questionnaire differentiated patient groups from control subjects. The relatives' form measuring deterioration in memory function over time identified dementing individuals from those with non-dementing causes for their memory complaints. Factor analysis indicated that patients' memory complaints correlated with depression rather than objective memory performance, while relatives' ratings correlated with objective memory scores, not depression. Stepwise discriminant function analyses showed that objective memory testing greatly improved specificity but not sensitivity of the subjective memory questionnaire alone.

Aged↗

PubMed2001

Mild cognitive impairments predict dementia in nondemented elderly patients with memory loss.

BACKGROUND: Some elderly individuals exhibit significant memory deficits but do not have dementia because their general intellect is preserved and they have no impairments in everyday activities. These symptoms are often a precursor to Alzheimer disease (AD), but sometimes dementia does not occur, even after many years of observation. There is currently no reliable way to distinguish between these 2 possible outcomes in an individual patient. We hypothesized that clear impairments in at least 1 cognitive domain in addition to memory would help identify those who will progress to AD. OBJECTIVE: To determine whether nondemented patients with impairments in memory and other domains are more likely than those with memory impairment alone to develop AD. DESIGN AND METHODS: In a retrospective study, we evaluated 48 nondemented, nondepressed patients with clinical and psychometric evidence of memory impairment who were followed up for 2 or more years. Age-adjusted normative criteria were used to identify whether additional impairments were present in language, attention, motor visuospatial function, and verbal fluency at this initial evaluation. The presence or absence of dementia after 2 years and at the most recent neurological evaluation was compared in subjects with normal scores in all 4 of these cognitive areas apart from memory (M-) and those with impairment in 1 or more of these areas (M+). Outcomes were adjusted for age, intelligence at initial evaluation, and years of education. RESULTS: Of the 48 nondemented patients with memory loss, 17 met M- criteria, leaving 31 in the M+ group. Deficits in block design were the most frequent abnormality other than memory loss. At the 2-year follow-up, 1 M- subject (6%) had progressed to AD, whereas 15 (48%) of the M+ group had progressed to AD (P =.003). At the most recent follow-up (mean +/- SD, 4.0 +/- 2.0 years), 4 (24%) of the M- patients progressed to AD compared with 24 (77%) of the M+ patients (P<.001). CONCLUSIONS: Among nondemented elderly patients, memory loss alone rarely progresses to dementia in the subsequent 2 years. However, the risk of dementia is significantly increased among patients with clear cognitive impairments beyond memory loss. Further study is needed to determine whether patients with impairments limited to memory loss have a distinctive clinical course or pathophysiology.

Aged↗

PubMed2001

Episodic memory in primates.

Episodic memory refers to a system of memory with the capacity to recollect specific events from an individual's life. Some psychologists have suggested that episodic memory is a uniquely human phenomenon. We challenge that idea and present evidence that great apes and other primates may possess episodic-like memory. We review criteria developed to assess episodic-like memory in nonhumans, and how they apply to primates. In particular, we discuss the criteria of Clayton et al. [2001], who stated that episodic-like memory is based on the retrieval of multiple and integrated components of an event. We then review eight studies examining memory in great apes and apply the Clayton et al. criteria to each of them. We summarize the evidence that is compatible with the existence of episodic-like memory, although none of the data completely satisfy the Clayton et al. criteria. Morover, feelings of pastness and feelings of confidence, which mark episodic memory in humans, have not been empirically addressed in nonhuman primates. Future studies should be directed at these aspects of memory in primates. We speculate on the functional significance of episodic memory in nonhuman primates.

Animals↗

PubMed2006

Subjective complaints and self-evaluation of memory test performance in Questionable dementia.

BACKGROUND: The clinical significance of subjective memory complaints in elderly subjects has been an area of active research. In this study, we evaluated subjective complaints and self-evaluation of memory test performance in subjects with Questionable dementia (QD) and mild Alzheimer's disease (AD). METHODS: Ninety-two subjects (35 cognitively intact normal controls NC, 33 QD, and 24 mild AD) were assessed. Subjective memory complaints were evaluated using a memory inventory for the Chinese (MIC); objective assessment of awareness was assessed by the self-evaluation of own memory test performance. Cognitive function was assessed with the Alzheimer's Disease Assessment Scale-Cognitive subscale (ADAS-Cog), Category Verbal Fluency Test (CVFT) and Executive Interview (EXIT-25). Depressive symptoms were evaluated with the Cornell Scale for Depression in Dementia (CSDD). RESULTS: The total number of subjective memory complaints (MI-tol) were significantly different between different subject groups (Kruskal Wallis test, chi2 = 13.19, p = 0.001). Significant correlations between scores of the MI-tol and CSDD (r = 0.33, p < 0.001), CMMSE (r = -0.33, p < 0.001), CDR (r = 0.36, p < 0.001) were found. In self-evaluation of memory test performance, the NC group tended to under-estimate while the AD subjects tended to over-estimate their performance. Group differences in the discrepancies of self-evaluation of memory performance were significant for both the immediate (Kruskal Wallis test, chi2 = 9.86, p = 0.007) and delayed recall (Kruskal Wallis test, chi2 = 10.55, p < 0.001) trials. CONCLUSIONS: Subjects with QD and mild AD showed higher frequency of subjective memory complaints, reflecting that the subjects still retain some ability to appreciate own memory function. However, the trend for over-estimation of performance in AD subjects suggests that the precision of estimation may be suboptimal. Moreover, depressive symptoms may affect the presentation of memory complaints and this factor should be carefully considered in future prospective studies.

Aged↗

PubMed1999

The effect of midazolam on implicit memory tests.

Substantial empirical evidence exists suggesting that there are distinct forms of explicit and implicit memory. However, methodological problems have hampered attempts to identify the nature of the information processing underlying these forms of memory. These problems include the contamination of performance on implicit memory tests by explicit memory processes, as well as a host of difficulties inherent in correlational approaches that involve amnesiac subjects. In this paper we attempt to explore whether midazolam, a benzodiazepine used in surgical anesthesia, might be useful for studying implicit memory. Specifically, we attempt to determine whether midazolam produces selective effects on explicit, as opposed to implicit, memory. We focus on midazolam because of prior studies demonstrating that benzodiazepines do not affect implicit memory and because its rapid pharmacokinetics ensure that sedative effects are minimized when testing occurs at relatively short retention intervals. The results of an experiment using free recall, fragment completion and perceptual identification tests suggest that midazolam diminishes memory in implicit and explicit memory tests, although the diminution is proportionally larger in explicit memory. These results constrain the inferences that may be drawn when midazolam is used to explore implicit memory.

Anti-Anxiety Agents↗

PubMed2002

Homeostatic proliferation but not the generation of virus specific memory CD8 T cells is impaired in the absence of IL-15 or IL-15Ralpha.

The generation and efficient maintenance of antigen specific memory T cells is essential for long-lasting immunological protection. Antigen specific memory CD8 T cells are known to be maintained via antigen-independent homeostatic proliferation. However, signals that drive memory T cell generation and/or influence the slow turnover of memory T cells are unknown. Recently, IL-15 has received attention for its potential effect on memory CD8 T cells. In this report we examine the role of IL-15 in the generation and maintenance of virus specific memory CD8 T cells using mice deficient in either IL-15 or the IL-15 receptor a chain. Both cytokine and receptor deficient mice mount a robust CD8 T cell response to infection with lymphocytic choriomeningitis virus (LCMV) that is initially only slightly lower than in control mice. Further, virus specific memory CD8 T cells are generated in both IL-15 -/- and IL-15Ralpha -/- mice. However, longitudinal analysis reveals a slow attrition of LCMV specific memory CD8 T cells in the absence of IL-15 signals. Indeed, direct examination of homeostatic proliferation reveals a severe defect in the turnover of antigen specific memory CD8 T cells in the absence of IL-15. Together these results suggest that IL-15 is not essential for the generation of memory CD8 T cells, but is required for homeostatic proliferation to maintain populations of memory cells over long periods of time.

Animals↗

PubMed1995

Transient global amnesia: memory and metamemory.

Twenty patients (mean age 64 years) with a previous episode of transient global amnesia (TGA) were examined to assess the functioning of objective memory (by using the Randt Memory Test), the metamemory capacities (Sehulster Memory Scale), the residual level of retrograde amnesia (Questionnaire of Remote Events), and the level of depression (Geriatric Depression Scale). Patients with residual retrograde amnesia scored significantly lower than non-amnesic ones on indices of both short-term and long-term memory, and for one of three main metamemory components, namely self-rating of memory functioning through comparison with memory functioning of peers (Set3). Age, time interval from TGA attack and TGA duration did not prove to influence memory and metamemory scores. Retrograde amnesia and depression were rather substantially associated (1/5), and this association was found to negatively influence nearly all memory and metamemory scores. Depression level showed a positive correlation with short-term memory functioning in non-amnesics. The different pattern and strength of the relationships between metamemory components and objective memory dimensions observed in amnesics and non-amnesics indicate that metamemory evaluations are more closely related to memory functioning in amnesics than in non-amnesics.

Aged↗

PubMed2006

Acute dose of MDMA (75 mg) impairs spatial memory for location but leaves contextual processing of visuospatial information unaffected.

RATIONALE: Research concerning spatial memory in 3,4-methylenedioxymethamphetamine (MDMA) users has presented conflicting results showing either the presence or absence of spatial memory deficits. Two factors may have confounded results in abstinent users: memory task characteristics and polydrug use. OBJECTIVES: The present study aims to assess whether a single dose of MDMA affects spatial memory performance during intoxication and withdrawal phase and whether spatial memory performance after MDMA is task dependent. MATERIALS AND METHODS: Eighteen recreational MDMA users participated in a double-blind, placebo-controlled, three-way crossover design. They were treated with placebo, MDMA 75 mg, and methylphenidate 20 mg. Memory tests were conducted between 1.5 and 2 h (intoxication phase) and between 25.5 and 26 h (withdrawal phase) post-dosing. Two spatial memory tasks of varying complexity were used that required either storage of stimulus location alone (spatial memory task) or memory for location as well as processing of content or contextual information (change blindness task). RESULTS: After a single dose of MDMA, the subjects made larger localization errors and responded faster compared to placebo in the simple spatial memory task during intoxication phase. Inaccuracy was not due to increased response speed, as determined by regression analysis. Performance in the change blindness task was not affected by MDMA. Methylphenidate did not affect performance on any of the tasks. CONCLUSION: It is concluded that a single dose of MDMA impairs spatial memory for location but leaves processing of contextual information intact.

Adult↗