Factor structure of the National Alzheimer's Coordinating Centers uniform dataset neuropsychological battery: an evaluation of invariance between and within groups over time.

The neuropsychological battery from the National Alzheimer's Disease Coordinating Center is designed to provide a sensitive assessment of mild cognitive disorders for multicenter investigations. Comprising 8 common neuropsychological tests (12 measures), the battery assesses cognitive domains affected early in the course of Alzheimer disease. We examined the factor structure of the battery across levels of cognition [normal, mild cognitive impairment, dementia] based on Clinical Dementia Rating scores to determine cognitive domains tapped by the battery. Using data pooled from 29 Alzheimer's Disease Centers funded by National Institute on Aging, exploratory factor analysis was used to derive a general model using half of the sample; 4 factors representing memory, attention, executive function, and language were identified. Confirmatory factor analysis was used on the second half of the sample to evaluate invariance between groups and within groups over 1 year. Factorial invariance testing included systematic addition of constraints and comparisons of nested models. The general confirmatory factor analysis model had a good fit. As constraints were added, model fit deteriorated slightly. Comparisons within groups showed stability over 1 year. In a range of cognition from normal to dementia, factor structures and factor loadings will vary little. Further work is needed to determine whether domains become more or less distinct in severely cognitively compromised individuals.

Operationalizing diagnostic criteria for Alzheimer's disease and other age-related cognitive impairment-Part 1.

In this article, the challenges faced by several noted population studies for Alzheimer dementia in operationalizing current clinical diagnostic criteria for Alzheimer's disease (AD) have been reviewed. Differences in case ascertainment, methodological biases, cultural and educational influences on test performance, inclusion of special populations such as underrepresented minorities and the oldest old, and detection of the earliest symptomatic stages of underlying AD have been considered. Classification of Alzheimer dementia may be improved by the incorporation of biomarkers for AD if the sensitivity, specificity, and predictive value of the biomarkers are established and if they are appropriate for epidemiological studies, as may occur should a plasma biomarker be developed. Biomarkers for AD could also facilitate studies of the interactions of various forms of neurodegenerative disorders with cerebrovascular disease, resulting in "mixed dementia".

Emotional enhancement of perceptual priming is preserved in aging and early-stage Alzheimer's disease.

Perceptual priming for emotionally-negative and neutral scenes was tested in early-stage Alzheimer's disease (AD) patients and healthy younger, middle-aged and older adults. In the study phase, participants rated the scenes for their arousal properties. In the test phase, studied and novel scenes were initially presented subliminally, and the exposure duration was gradually increased until a valence categorization was made. The difference in exposure duration required to categorize novel versus studied items was the dependent measure of priming. Aversive content increased the magnitude of priming, an effect that was preserved in healthy aging and AD. Results from an immediate recognition memory test showed that the priming effects could not be attributable to enhanced explicit memory for the aversive scenes. These findings implicate a dissociation between the modulatory effect of emotion across implicit and explicit forms of memory in aging and early-stage AD.

Explaining age differences in temporal working memory.

To determine the cognitive mechanisms underlying age differences in temporal working memory (WM), the authors examined the contributions of item memory, associative memory, simple order memory, and multiple item memory, using parallel versions of the delayed-matching-to-sample task. Older adults performed more poorly than younger adults on tests of temporal memory, but there were no age differences in nonassociative item memory, regardless of the amount of information to be learned. In contrast, a combination of associative and simple order memory, both of which were reduced in older adults, completely accounted for age-related declines in temporal memory. The authors conclude that 2 mechanisms may underlie age differences in temporal WM, namely, a generalized decline in associative ability and a specific difficulty with order information.