Cognitively elite, cognitively normal, and cognitively impaired aging: neurocognitive status and stability moderate memory performance

Environmental enrichment and the aging brain: is it time for standardization?

Aging entails a progressive decline of cognitive abilities. However, since the brain is endowed with considerable plasticity, adequate stimulation can delay or partially compensate for age-related structural and functional impairment. Environmental enrichment (EE) has been reported to determine a wide range of cerebral changes. Although most findings have been obtained in young and adult animals, research has recently turned to aged individuals. Notably, EE can contribute identifying key lifestyle factors whose change can help extend the "mind-span", i.e., the time an individual lives in a healthy cognitive condition. Here we discuss specific methodological issues that can affect the outcomes of EE interventions applied to aged rodents, summarize the main variables that would need standardization (e.g., timing and duration, enrichment items, control animals and setting), and offer some suggestions on how this goal may be achieved. Reaching a consensus on EE experiment design would significantly reduce differences between and within laboratories, enable constructive discussions among researchers, and improve data interpretation.

Superior Memory Reduces 8-year Risk of Mild Cognitive Impairment and Dementia But Not Amyloid β-Associated Cognitive Decline in Older Adults

OBJECTIVE

To prospectively examine 8-year risk of clinical disease progression to mild cognitive impairment (MCI)/dementia in older adults ≥60 with superior episodic memory (SuperAgers) compared to those cognitively normal for their age (CNFA). Additionally, to determine the extent to which SuperAgers were resilient to the negative effects of elevated amyloid-beta (Aβ+) on cognition.

METHOD

Participants were classified as SuperAgers based on episodic memory performance consistent with younger adults aged 30-44 and no impairment on non-memory tests (n = 179), and were matched with CNFA on age, sex, education, and follow-up time (n = 179). Subdistribution hazard models examined risk of clinical progression to MCI/dementia. Linear mixed models assessed the effect of Aβ on cognition over time.

RESULTS

Prevalence of Aβ+ and APOE ε4 was equivalent between SuperAgers and CNFA. SuperAgers had 69%-73% reduced risk of clinical progression to MCI/dementia compared to CNFA (HR: 0.27-0.31, 95% CI: 0.11-0.73, p < .001). Aβ+ was associated with cognitive decline in verbal memory and executive function, regardless of SuperAger/CNFA classification. In the absence of Aβ+, equivalent age-related changes in cognition were observed between SuperAgers and CNFA.

CONCLUSIONS

SuperAgers displayed resilience against clinical progression to MCI/dementia compared to CNFA despite equivalent risk for Alzheimer's disease (AD); however, SuperAgers had no greater protection from Aβ+ than CNFA. The deleterious effects of Aβ on cognition persist regardless of baseline cognitive ability. Thus, superior cognitive performance does not reflect resistance against the neuropathological processes associated with AD, and the observed resilience for SuperAgers may instead reflect neuropsychological criteria for cognitive impairment.

Aged rats with different performances at environmental enrichment onset display different modulation of habituation and aversive memory

A wide agreement exists that environmental enrichment (EE) is most beneficial if introduced early in life, but numerous studies reported that also aged animals remain responsive. As age-related memory and cognition impairments are not uniform, an open question is whether EE might exert different effects in animals with different age-related deficits. A 12-week EE protocol was applied to late adult rats pretested for habituation and aversive memory. Animals were classified as low (LP) and high (HP) performers according to percent exploration change in Open Field test (OF) and as impaired (I) and not impaired (NI) according to latency in Step-through Passive Avoidance test (PA). Standard housing (SH) animals pretested by OF and PA, and naïve (non-pretested) EE and SH rats were used as controls. In comparison to pretest, after the housing protocol, EE LP ameliorated while EE HP and both SH HP and LP worsened their habituation pattern. The positive influence of EE on LP was probably due to the more active interaction with and the faster adaptation to surroundings promoted by continuous, multiple stimuli provided during the enriched housing. Regarding HP, EE did not boost the basal behavior, which likely represented the maximum achievable for that age, and the post housing exploration change dropped, as in SH animals, because of the retesting. After EE, a significant percentage of NI animals became I and a significant percentage of I animals became NI. The changes evidenced in the NI group likely depended on EE-related reduction of anxiety and the consequent more efficient coping with fearful situations. This hypothesis was strengthened by the observation that naïve EE animals were almost all I. Pretested EE I rats were not influenced by the rearing condition: their behavior was comparable to SH animals' behavior and determined by retesting. In conclusion, these results demonstrated that, when applied to aging rats, EE produces different effects based on pre-housing cognitive performances. The issue needs further analyses, but the observation that not all animals are able to take advantage of EE to the same extent suggests the opportunity to design individually tailored approaches to optimize their efficacy and minimize possible unwanted consequences.

Modifiable Risk Factors Discriminate Memory Trajectories in Non-Demented Aging: Precision Factors and Targets for Promoting Healthier Brain Aging and Preventing Dementia

BACKGROUND

Non-demented cognitive aging trajectories are characterized by vast level and slope differences and a spectrum of outcomes, including dementia.

OBJECTIVE

The goal of AD risk management (and its corollary, promoting healthy brain aging) is aided by two converging objectives: 1) classifying dynamic distributions of non-demented cognitive trajectories, and 2) identifying modifiable risk-elevating and risk-reducing factors that discriminate stable or normal trajectory patterns from declining or pre-impairment patterns.

METHOD

Using latent class growth analysis we classified three episodic memory aging trajectories for n = 882 older adults (baseline Mage=71.6, SD=8.9, range = 53-95, female=66%): Stable (SMA; above average level, sustained slope), Normal (NMA; average level, moderately declining slope), and Declining (DMA; below average level, substantially declining slope). Using random forest analyses, we simultaneously assessed 17 risk/protective factors from non-modifiable demographic, functional, psychological, and lifestyle domains. Within two age strata (Young-Old, Old-Old), three pairwise prediction analyses identified important discriminating factors.

RESULTS

Prediction analyses revealed that different modifiable risk predictors, both shared and unique across age strata, discriminated SMA (i.e., education, depressive symptoms, living status, body mass index, heart rate, social activity) and DMA (i.e., lifestyle activities [cognitive, self-maintenance, social], grip strength, heart rate, gait) groups.

CONCLUSION

Memory trajectory analyses produced empirical classes varying in level and slope. Prediction analyses revealed different predictors of SMA and DMA that also varied by age strata. Precision approaches for promoting healthier memory aging-and delaying memory impairment-may identify modifiable factors that constitute specific targets for intervention in the differential context of age and non-demented trajectory patterns.

Two Behavioral Tests Allow a Better Correlation Between Cognitive Function and Expression of Synaptic Proteins

The molecular substrate of age-associated cognitive decline (AACD) is still elusive. Evidence indicates that AACD is related to synaptic impairment in hippocampus, but different hippocampal regions play different roles, with the dorsal hippocampus (DH) associated to spatial learning, and the ventral hippocampus (VH) crucial for emotionality. If changes in hippocampal function contributes to AACD, this contribution may be reflected in alterations of synaptic protein levels. A commonly used approach to investigate this issue is western blotting. When this technique is applied to the entire hippocampus and the cognitive impairment is evaluated by a single task, changes in expression of a protein might undergo a "dilution effect", as they may occur only in a given hippocampal region. We show that two behavioral tests yield more accurate results than one test in evaluating the function of the whole rat hippocampus by studying the expression of synaptotagmin 1 (SYT1), a vesicular protein whose expression in aged hippocampus is reportedly inconsistent. Analysis of SYT1 levels in the whole hippocampus of rats selected by the Morris water maze (MWM) test only failed to highlight a difference, whereas analysis of SYT1 levels in the whole hippocampus of rats categorized by both the MWM and the step-through passive avoidance (STPA) tests demonstrated a significant increase of SYT1 level in impaired rats. These findings, besides showing that SYT1 increases in impaired aged rats, suggest that using the whole hippocampus in blotting studies may prevent false negative results only if animals are categorized with tests exploring both DH and VH.

Erfolgreiches kognitives Altern: Zusammenhang der kognitiven Leistungen mit Aktivität und Zufriedenheit

Zusammenfassung. Für erfolgreiches Altern sind Kognition, Zufriedenheit und tägliche Aktivitäten relevante Faktoren. In dieser Studie werden Zusammenhänge zwischen diesen Faktoren aufgedeckt. Bei 167 Senioren (60 bis 98 Jahre) wurden Aktivität und Zufriedenheit in einem Interview, Kognition durch die Neuropsychological Assessment Battery (dt. Version) erfasst. Alle Faktoren zeigen eine negative Altersentwicklung. Aktivitäten korrelieren mit allen Faktoren; insbesondere stehen Alltagsaktivitäten und kognitive Aktivitäten positiv mit Kognition im Zusammenhang, soziale Aktivität ist davon unabhängig. Die kognitiven Funktionsbereiche Aufmerksamkeit, Sprache und exekutive Funktionen variieren mit Aktivität und Zufriedenheit, Gedächtnis nur mit kognitiven Aktivitäten, Wahrnehmung ist davon unabhängig. Dies könnte bedeuten, dass kognitive Aktivitäten spezifisch mit der kognitiven Leistung und soziale Aktivitäten spezifisch mit der emotionalen Bewertung zusammenhängen und als Schutzfaktoren während der Entwicklung wirken könnten.

Episodic memory in normal aging and Alzheimer disease: Insights from imaging and behavioral studies

Age-related cognitive changes often include difficulties in retrieving memories, particularly those that rely on personal experiences within their temporal and spatial contexts (i.e., episodic memories). This decline may vary depending on the studied phase (i.e., encoding, storage or retrieval), according to inter-individual differences, and whether we are talking about normal or pathological (e.g., Alzheimer disease; AD) aging. Such cognitive changes are associated with different structural and functional alterations in the human neural network that underpins episodic memory. The prefrontal cortex is the first structure to be affected by age, followed by the medial temporal lobe (MTL), the parietal cortex and the cerebellum. In AD, however, the modifications occur mainly in the MTL (hippocampus and adjacent structures) before spreading to the neocortex. In this review, we will present results that attempt to characterize normal and pathological cognitive aging at multiple levels by integrating structural, behavioral, inter-individual and neuroimaging measures of episodic memory.

Word Recall: Cognitive Performance Within Internet Surveys

BACKGROUND

The use of online surveys for data collection has increased exponentially, yet it is often unclear whether interview-based cognitive assessments (such as face-to-face or telephonic word recall tasks) can be adapted for use in application-based research settings.

OBJECTIVE

The objective of the current study was to compare and characterize the results of online word recall tasks to those of the Health and Retirement Study (HRS) and determine the feasibility and reliability of incorporating word recall tasks into application-based cognitive assessments.

METHODS

The results of the online immediate and delayed word recall assessment, included within the Women's Health and Valuation (WHV) study, were compared to the results of the immediate and delayed recall tasks of Waves 5-11 (2000-2012) of the HRS.

RESULTS

Performance on the WHV immediate and delayed tasks demonstrated strong concordance with performance on the HRS tasks (ρc=.79, 95% CI 0.67-0.91), despite significant differences between study populations (P<.001) and study design. Sociodemographic characteristics and self-reported memory demonstrated similar relationships with performance on both the HRS and WHV tasks.

CONCLUSIONS

The key finding of this study is that the HRS word recall tasks performed similarly when used as an online cognitive assessment in the WHV. Online administration of cognitive tests, which has the potential to significantly reduce participant and administrative burden, should be considered in future research studies and health assessments.

APOE and COMT polymorphisms are complementary biomarkers of status, stability, and transitions in normal aging and early mild cognitive impairment

Objective: Research has reported associations among selected genetic susceptibility biomarkers and risk of (a) normal cognitive aging decrements, (b) established mild cognitive impairment (MCI), and (c) sporadic Alzheimer's disease (AD). In focusing on the transitional normal-to-early MCI phase, we examine associations among three theoretically relevant polymorphisms (APOE [rs429358, rs7412], BDNF [rs6265], COMT [rs4680]) and both baseline cognitive status (MCI vs. normal aging) and two-wave (four-year) longitudinal stability or change profiles. The latter included three profiles: (a) stable as normal aging, (b) stable or chronic impairment (MCI-to-MCI), and (c) emergence of impairment (normal-to-MCI).

Method: Genotyped older adults (n = 237 at baseline; age range = 64–91; 62% women) from the Victoria Longitudinal Study were examined for (a) independent and interactive associations of three genetic polymorphisms with (b) two objectively classified cognitive status groups (not-impaired controls (NIC) and MCI) at (c) both baseline and across a two-wave (four-year) longitudinal interval.

Results: First, logistic regression revealed that the presence of at least one APOE ε4 allele (the risk factor for AD) was linked to greater baseline risk of objective MCI. Second, multinomial logistic regression revealed that (a) the presence of an APOE ε4 allele was associated with an increased risk of 4-year MCI status stability (chronicity), and (b) the COMT homozygous risk genotype (G/G or Val/Val) was associated with an increased risk of both MCI-to-MCI stability (chronicity) and emerging NIC-to-MCI conversion.

Discussion: Both chronicity and emergence of objectively classified early cognitive impairment may be genetically heterogeneous phenomena, with influences from a panel of both normal cognitive aging (COMT) and AD-related (APOE) polymorphisms.