Mj Summers

Longitudinal Deficits to Attention, Executive, and Working Memory in Subtypes of Mild Cognitive Impairment

OBJECTIVE Mild cognitive impairment (MCI) has emerged as a classification for a prodromal phase of cognitive decline that may precede the emergence of Alzheimers disease (AD). Recent research suggests that attention, executive, and working memory deficits may appear much earlier in the progression of AD than traditionally conceptualized, and may be more consistently associated with the later development of AD than memory processing deficits. The present study longitudinally tracked attention, executive and working memory functions in subtypes of MCI. METHOD In a longitudinal study, 52 amnestic MCI (a-MCI), 29 nonamnestic MCI (na-MCI), and 25 age- and education-matched controls undertook neuropsychological assessment of visual and verbal memory, attentional processing, executive functioning, working memory capacity, and semantic language at 10 month intervals. RESULTS Analysis by repeated measures ANOVA indicate that the a-MCI and na-MCI groups displayed a decline in simple sustained attention (ηp² = .054) with a significant decline on a task of divided attention (ηp² = .053) being evident in the a-MCI group. Stable deficits were found on other measures of attention, working memory and executive function in the a-MCI and na-MCI groups. The a-MCI group displayed stable impairments to visual and verbal memory. CONCLUSIONS The results indicate that a-MCI and na-MCI display a stable pattern of deficits to attention, working memory, and executive function. The decline in simple sustained attention in a-MCI and n-MCI groups and to divided attention in a-MCI may be early indicators of possible transition to dementia from MCI. However, further research is required to determine this.

Neuropsychological Measures Predict Decline to Alzheimer's Dementia From Mild Cognitive Impairment

OBJECTIVE Studies of Mild Cognitive Impairment (MCI) show elevated rates of conversion to dementia at the group level. However, previous studies of the trajectory of MCI identify great heterogeneity of outcomes, with a significant proportion of individuals with MCI remaining stable over time, changing MCI subtype classification, or reverting to a normal cognitive state at long-term follow-up. METHOD The present study examined individual outcomes at 20 months in a group of older adults classified according to MCI subtypes. A total of 106 participants, 81 with different subtypes of MCI and 25 healthy controls, undertook longitudinal neuropsychological assessment of visual and verbal memory, attentional processing, executive functions, working memory capacity, and semantic memory. RESULTS At 20 months 12.3% of the MCI group progressed to dementia, 62.9% continued to meet MCI criteria, and 24.7% reverted to unimpaired levels of function. A discriminant function analysis predicted outcome at 20 months on the basis of baseline neuropsychological test performance with 86.3% accuracy. The analysis indicated that a pattern of impairments on visual episodic memory, verbal episodic memory, short-term memory, working memory, and attentional processing differentiated between participants who developed dementia, recovered from MCI, or remained in stable MCI. CONCLUSIONS The results of the present study raise questions regarding the specificity of existing criteria for the subtypes of MCI, with these results indicating a high degree of instability in classification over time. In addition, the results suggest that multidomain MCI is the most reliable precursor stage to the development of AD.

Attention and working memory deficits in mild cognitive impairment

Mild cognitive impairment (MCI) has emerged as a classification for a prodromal phase of cognitive decline preceding the emergence of Alzheimers disease (AD). We examined neuropsychological functioning in a sample of 60 adults with amnestic-MCI (a-MCI), 32 with subjective complaints of memory impairment (subjective-MCI, s-MCI), 14 with mild AD, and 25 age-matched controls. Both the a-MCI and s-MCI groups displayed impaired attentional processing, working memory capacity, and semantic language, with a-MCI displaying additional impairments to verbal and/or visual memory. These results indicate that further research is needed to examine cognitive decline in nonamnestic variants of MCI.

Absence of a relationship between subjective memory complaint and objective memory impairment in mild cognitive impairment (MCI): is it time to abandon subjective memory complaint as an MCI diagnostic criterion?

BACKGROUND Subjective memory complaints are a requirement in the diagnosis of mild cognitive impairment (MCI) as they are thought to indicate a decline in objective memory performance. However, recent research suggests that the relationship between subjective memory complaint and objective memory impairment is less clear. Thus, it is possible that many people without subjective memory complaints who develop Alzheimers disease are precluded from a diagnosis of MCI. METHODS The present study examined the relationship between subjective memory complaint assessed using the Multifactorial Memory Questionnaire (MMQ) and objective memory impairment assessed using standard neuropsychological measures in cases of amnestic MCI (n = 48), non-amnestic MCI (n = 27), and unimpaired healthy participants (n = 64). RESULTS Correlational and regression analyses indicated that subjective memory complaints displayed a poor relationship with objective memory performance. A subsequent discriminant function analysis indicated that subjective memory complaints failed to improve the diagnostic accuracy of MCI and resulted in increased rates of false negative and false positive diagnoses. CONCLUSION The results of the present study suggest that a diagnostic criterion of subjective memory complaint reduces the accuracy of MCI diagnosis, resulting in an elevated rate of false positive and false negative diagnoses. The results of this study in conjunction with recent research indicate that a criterion of subjective memory complaint should be discarded from emerging diagnostic criteria for MCI.

Administration of DL-2-amino-5-phosphonovaleric acid (AP5) induces transient inhibition of reminder-activated memory retrieval in day-old chicks.

DL-2-Amino-5-phosphonovaleric acid (50 microM) administered immediately after a visual reminder presented to day-old chickens between 7.5 min and 24 h following a single trial passive avoidance learning task produced transient losses of memory on retention test, an effect not observed in the absence of a reminder or when the reminder was given 48 h post learning. The duration of the transient deficits decreased with increasing interval between training and the reminder trial. The time of onset of memory loss after the reminder trial appeared to increase with increasing interval between the training and the reminder trials. The results suggest that, for a period of at least up to 24 h after passive avoidance training, retrieval of memory may lead to processes which are sensitive to inhibition by the NMDA receptor antagonist AP5, with the duration of sensitivity post retrieval decreasing as the period of memory consolidation increases. The results extend previously reported findings and suggest the possibility that consolidation of a stable memorial representation of a learning experience may take over several days and may entail the concurrent laying down of a stable retrieval mechanism.

Relationship between education and age-related cognitive decline: a review of recent research.

The association between level of educational attainment and cognitive performance is well studied. People with higher education perform better across a broad range of cognitive tasks. However, there is uncertainty as to whether education moderates the trajectory of age‐related cognitive decline. This review paper addresses the potential link between education and age‐related cognitive decline by evaluating relevant research published since 2000. Studies reporting data on education and its association with the rate of cognitive decline across various cognitive domains were reviewed. A total of 10 studies were identified with a mean follow‐up period of 7.6 years; each contained a population‐based, non‐demented sample. In the majority of studies, results showed that education did not moderate age‐associated cognitive decline. The few studies that did find an association between education and decline in specific cognitive functions should be interpreted with caution because of methodological issues. The literature reveals little consistent evidence that normal age‐related cognitive decline is moderated by education attainment. This supports a passive theory of cognitive reserve: people with a higher level of education will continue to perform at a higher level of cognitive functioning than their lower educated peers, which may delay the onset of impairment in the future.

Effect of atorvastatin on cognitive function in patients from the lipid lowering and onset of renal disease (LORD) trial

Study Objective. To examine the effect of atorvastatin on cognitive function by testing two hypotheses: that atorvastatin 10 mg/day would impair cognitive function, and that other biochemical and demographic measures would better predict cognitive performance than atorvastatin alone.

Memory retrieval in the day-old chick: a psychobiological approach.

This review integrates a series of studies conducted examining memory retrieval processes in the day-old chick. On the basis of these studies it is proposed that two processes are activated following retrieval of a memory. The first is an immediate memory recall or retrieval mechanism responsible for the chicks ability to remember the information and respond appropriately to the stimulus. The second process is activated following the completion of the first immediate retrieval phase. Further, it is proposed that the function of this secondary phase may be to allow for the modification of a memory undergoing storage processes. It is proposed that the processes of memory formation and memory retrieval are parallel at a cellular level, but at the functional level of information transfer they are interdependent.

Administration of glutamate following a reminder induces transient memory loss in day-old chicks

Monosodium glutamate (4.0 mM) administered immediately after a visual reminder presented to day-old chickens between 7.5 min and 24 h following a single trial passive avoidance learning task produced transient losses of memory on retention test, an effect not observed in the absence of a reminder or when the reminder was given 48 h post-learning. The duration of the transient deficit decreased with increasing interval between the training and the reminder trial. The time of onset of memory loss after the reminder trial appeared to increase with increasing interval between the training and the reminder trials. The results suggest that, for a period of at least up to 24 h after passive avoidance training, retrieval of memory may lead to processes which are sensitive to inhibition by glutamate, with the duration of sensitivity post-retrieval decreasing as the period of memory consolidation increases. The results extend previously reported findings with rodents and suggest the possibility that consolidation of a stable memorial representation of a learning experience may take place over several days and may entail the concurrent laying down of a stable retrieval mechanism.

APOE and BDNF Val66Met polymorphisms combine to influence episodic memory function in older adults

Genetic polymorphisms of apolipoprotein E (APOE) and brain-derived neurotrophic factor (BDNF) have shown inconsistent associations with healthy adult cognitive functions. Recent investigations have suggested that APOE polymorphisms do not contribute to non-pathological cognitive function and that any effect is likely due to prodromal Alzheimers disease (AD). Similarly, although BDNF Val66Met polymorphisms affect hippocampal morphology and function, associations with learning and/or memory have not always been found. This study sought to determine whether APOE and BDNF polymorphisms were associated, either independently or in combination, with adult cognition. Comprehensive neuropsychological assessments were conducted on 433 older adults, aged 50-79 years (M=62.16, SD=6.81), which yielded measures of episodic memory, working memory, executive function, and language processing. Participants underwent comprehensive neuropsychological assessment to ensure that only cognitively intact individuals comprised the sample. APOE and BDNF polymorphic data were used as predictors in general linear models that assessed composite cognitive domain variables, while covarying for education and age. Although no main effects for APOE or BDNF were found, the analysis identified a significant APOE×BDNF interaction that predicted episodic memory performance (p=.02, η(2)=.02). Post-hoc analyses demonstrated that in BDNF Val homozygotes, the cognitive consequences of APOE polymorphisms were minimal. However, in BDNF Met carriers, the hypothesized beneficial/detrimental effects of APOE polymorphisms were found. Our data show that concurrent consideration of both APOE and BDNF polymorphisms are required in order to witness a cognitive effect in healthy older adults.