The relation of neuropsychological measures to levels of cognitive functioning in elderly individuals: a discriminant analysis approach

Enhanced cognitive activity--over and above social or physical activity--is required to protect Alzheimer's mice against cognitive impairment, reduce Abeta deposition, and increase synaptic immunoreactivity

Although social, physical, and cognitive activities have each been suggested to reduce the risk of Alzheimer's disease (AD), epidemiologic studies cannot determine which activity or combination of activities is most important. To address this question, mutant APP transgenic AD mice were reared long-term in one of four housing conditions (impoverished, social, social+physical, or complete enrichment) from 1(1/2) through 9 months of age. Thus, a stepwise layering of social, physical, and enhanced cognitive activity was created. Behavioral evaluation in a full battery of sensorimotor, anxiety, and cognitive tasks was carried out during the final 5 weeks of housing. Only AD mice raised in complete enrichment (i.e., enhanced cognitive activity) showed: (1) protection against cognitive impairment, (2) decreased brain beta-amyloid deposition, and (3) increased hippocampal synaptic immunoreactivity. The protection provided by enhanced cognitive activity spanned multiple cognitive domains (working memory, reference learning, and recognition/identification). Cognitive and neurohistologic benefits of complete enrichment occurred without any changes in blood cytokine or corticosterone levels, suggesting that enrichment-dependent mechanisms do not involve changes in the inflammatory response or stress levels, respectively. These results indicate that the enhanced cognitive activity of complete enrichment is required for cognitive and neurologic benefit to AD mice-physical and/or social activity are insufficient. Thus, our data suggest that humans who emphasize a high lifelong level of cognitive activity (over and above social and physical activities) will attain the maximal environmental protection against AD.

Optimized neuropsychological procedures at different stages of dementia diagnostics

OBJECTIVE

To establish a staged procedure in dementia diagnostics and to propose specific, abbreviated test batteries suitable for the three diagnostic stages: Primary medical care, neuro-psychiatry, and memory clinic.

METHODS

A total of 159 participants underwent comprehensive clinical, neurological, neuropsychological, and MRI examinations. The neuropsychological examination took approximately 90 min per individual and was based on tests of verbal and visual memory, language, abstract thinking, attention, visuo-constructive and spatial functions. Stepwise discriminant analyses were performed to identify which subset of the 18 variables of the comprehensive test battery was the most appropriate to differentiate between specific diagnostic groups, and which variables could be discarded to abbreviate the test battery without substantial loss in diagnostic accuracy.

RESULTS

The abbreviated versions of the test battery retained adequate diagnostic accuracy. The accuracy decreased by maximally 4%, whereas the test administration time dropped substantially from previously 90 min to a maximum of 50 min.

CONCLUSION

Depending on the diagnostic question, a specifically abbreviated version of the comprehensive test battery can be used without unacceptably reducing diagnostic accuracy.

Lifelong immunization with human beta-amyloid (1-42) protects Alzheimer's transgenic mice against cognitive impairment throughout aging

Although both active and passive beta-amyloid (Abeta) immunotherapy have been shown to protect against or lessen cognitive impairment in various Alzheimer's transgenic mouse lines, these studies have focused on a single task and involved standard statistical analysis. Because Alzheimer's disease impacts multiple cognitive domains, the current study employed an extensive behavioral battery and multimetric analysis therein to determine the impact of Abeta immunization given throughout most of adult life (from 2-16 1/2 months of age) to APP+PS1 transgenic mice. At both adult (4 1/2-6 month) and aged (15-16 1/2 month) test points, the same 6-week behavioral battery was administered. Results indicate that Abeta immunotherapy partially or completely protected APP+PS1 mice at both test points from otherwise impaired performance in a variety of tasks spanning multiple cognitive domains (reference learning/memory, working memory, search/recognition). At both adult and aged test points, the cognitive benefits of Abeta immunotherapy were evident even when behavioral measures were analyzed collectively (as "overall" performance) through discriminant function analysis. Since behavioral protection at the 15-16 1/2 month test point occurred without a decrease in (or correlation to) Abeta deposition, the mechanism of Abeta immunotherapy's action most likely involves neutralization/removal of small Abeta oligomers from the brain. However, in factor analysis performed at this aged test point, brain Abeta deposition measures loaded heavily with key cognitive measures. Collectively, our results suggest that the entire process of Abeta deposition deleteriously impacts cognitive performance and that Abeta-based preventative strategies can provide long-term cognitive benefits extending well into older age.