Cognitive reserve, cortical plasticity and resistance to Alzheimer's disease

Resting-state neural dynamics changes in older adults with post-COVID syndrome and the modulatory effect of cognitive training and sex

Post-COVID syndrome manifests with numerous neurological and cognitive symptoms, the precise origins of which are still not fully understood. As females and older adults are more susceptible to developing this condition, our study aimed to investigate how post-COVID syndrome alters intrinsic brain dynamics in older adults and whether biological sex and cognitive training might modulate these effects, with a specific focus on older females. The participants, aged between 60 and 75 years, were divided into three experimental groups: healthy old female, post-COVID old female and post-COVID old male. They underwent an adaptive task-switching training protocol. We analysed multiscale entropy and spectral power density of resting-state EEG data collected before and after the training to assess neural signal complexity and oscillatory power, respectively. We found no difference between post-COVID females and males before training, indicating that post-COVID similarly affected both sexes. However, cognitive training was effective only in post-COVID females and not in males, by modulating local neural processing capacity. This improvement was further evidenced by comparing healthy and post-COVID females, wherein the latter group showed increased finer timescale entropy (1-30 ms) and higher frequency band power (11-40 Hz) before training, but these differences disappeared following cognitive training. Our results suggest that in older adults with post-COVID syndrome, there is a pronounced shift from more global to local neural processing, potentially contributing to accelerated neural aging in this condition. However, cognitive training seems to offer a promising intervention method for modulating these changes in brain dynamics, especially among females.

Effects of a dual intervention (motor and virtual reality-based cognitive) on cognition in patients with mild cognitive impairment: a single-blind, randomized controlled trial

BACKGROUND

The increase in cases of mild cognitive impairment (MCI) underlines the urgency of finding effective methods to slow its progression. Given the limited effectiveness of current pharmacological options to prevent or treat the early stages of this deterioration, non-pharmacological alternatives are especially relevant.

OBJECTIVE

To assess the effectiveness of a cognitive-motor intervention based on immersive virtual reality (VR) that simulates an activity of daily living (ADL) on cognitive functions and its impact on depression and the ability to perform such activities in patients with MCI.

METHODS

Thirty-four older adults (men, women) with MCI were randomized to the experimental group (n = 17; 75.41 ± 5.76) or control (n = 17; 77.35 ± 6.75) group. Both groups received motor training, through aerobic, balance and resistance activities in group. Subsequently, the experimental group received cognitive training based on VR, while the control group received traditional cognitive training. Cognitive functions, depression, and the ability to perform activities of daily living (ADLs) were assessed using the Spanish versions of the Montreal Cognitive Assessment (MoCA-S), the Short Geriatric Depression Scale (SGDS-S), and the of Instrumental Activities of Daily Living (IADL-S) before and after 6-week intervention (a total of twelve 40-minutes sessions).

RESULTS

Between groups comparison did not reveal significant differences in either cognitive function or geriatric depression. The intragroup effect of cognitive function and geriatric depression was significant in both groups (p < 0.001), with large effect sizes. There was no statistically significant improvement in any of the groups when evaluating their performance in ADLs (control, p = 0.28; experimental, p = 0.46) as expected. The completion rate in the experimental group was higher (82.35%) compared to the control group (70.59%). Likewise, participants in the experimental group reached a higher level of difficulty in the application and needed less time to complete the task at each level.

CONCLUSIONS

The application of a dual intervention, through motor training prior to a cognitive task based on Immersive VR was shown to be a beneficial non-pharmacological strategy to improve cognitive functions and reduce depression in patients with MCI. Similarly, the control group benefited from such dual intervention with statistically significant improvements.

TRIAL REGISTRATION

ClinicalTrials.gov NCT06313931; https://clinicaltrials.gov/study/NCT06313931 .

House dust mite-induced asthma exacerbates Alzheimer's disease changes in the brain of the AppNL-G-F mouse model of disease

Alzheimer's disease (AD) is an age-related neurodegenerative disorder characterized by the accumulation of amyloid-β (Aβ) plaques, neuroinflammation, and neuronal death. Besides aging, various comorbidities increase the risk of AD, including obesity, diabetes, and allergic asthma. Epidemiological studies have reported a 2.17-fold higher risk of dementia in asthmatic patients. However, the molecular mechanism(s) underlying this asthma-associated AD exacerbation is unknown. This study was designed to explore house dust mite (HDM)-induced asthma effects on AD-related brain changes using the AppNL-G-F transgenic mouse model of disease. Male and female 8-9 months old C57BL/6J wild type and AppNL-G-F mice were exposed to no treatment, saline sham, or HDM extract every alternate day for 16 weeks for comparison across genotypes and treatment. Mice were euthanized at the end of the experiment, and broncho-alveolar lavage fluid (BALF), blood, lungs, and brains were collected. BALF was used to quantify immune cell phenotype, cytokine levels, total protein content, lactate dehydrogenase (LDH) activity, and total IgE. Lungs were sectioned and stained with hematoxylin and eosin, Alcian blue, and Masson's trichrome. Serum levels of cytokines and soluble Aβ1-40/42 were quantified. Brains were sectioned and immunostained for Aβ, GFAP, CD68, and collagen IV. Finally, frozen hippocampi and temporal cortices were used to perform Aβ ELISAs and cytokine arrays, respectively. HDM exposure led to increased levels of inflammatory cells, cytokines, total protein content, LDH activity, and total IgE in the BALF, as well as increased pulmonary mucus and collagen staining in both sexes and genotypes. Levels of serum cytokines increased in all HDM-exposed groups. Serum from the AppNL-G-F HDM-induced asthma group also had significantly increased soluble Aβ1-42 levels in both sexes. In agreement with this peripheral change, hippocampi from asthma-induced male and female AppNL-G-F mice demonstrated elevated Aβ plaque load and increased soluble Aβ 1-40/42 and insoluble Aβ 1-40 levels. HDM exposure also increased astrogliosis and microgliosis in both sexes of AppNL-G-F mice, as indicated by GFAP and CD68 immunoreactivity, respectively. Additionally, HDM exposure elevated cortical levels of several cytokines in both sexes and genotypes. Finally, HDM-exposed groups also showed a disturbed blood-brain-barrier (BBB) integrity in the hippocampus of AppNL-G-F mice, as indicated by decreased collagen IV immunoreactivity. HDM exposure was responsible for an asthma-like condition in the lungs that exacerbated Aβ pathology, astrogliosis, microgliosis, and cytokine changes in the brains of male and female AppNL-G-F mice that correlated with reduced BBB integrity. Defining mechanisms of asthma effects on the brain may identify novel therapeutic targets for asthma and AD.

MIAMI-AD (Methylation in Aging and Methylation in AD): an integrative knowledgebase that facilitates explorations of DNA methylation across sex, aging, and Alzheimer's disease

Alzheimer's disease (AD) is a common neurodegenerative disorder with a significant impact on aging populations. DNA methylation (DNAm) alterations have been implicated in both the aging processes and the development of AD. Given that AD affects more women than men, it is also important to explore DNAm changes that occur specifically in each sex. We created MIAMI-AD, a comprehensive knowledgebase containing manually curated summary statistics from 98 published tables in 38 studies, all of which included at least 100 participants. MIAMI-AD enables easy browsing, querying, and downloading DNAm associations at multiple levels-at individual CpG, gene, genomic regions, or genome-wide, in one or multiple studies. Moreover, it also offers tools to perform integrative analyses, such as comparing DNAm associations across different phenotypes or tissues, as well as interactive visualizations. Using several use case examples, we demonstrated that MIAMI-AD facilitates our understanding of age-associated CpGs in AD and the sex-specific roles of DNAm in AD. This open-access resource is freely available to the research community, and all the underlying data can be downloaded. MIAMI-AD facilitates integrative explorations to better understand the interplay between DNAm across aging, sex, and AD. Database URL: https://miami-ad.org/.

Memory self-efficacy and working memory

Dementia affects multiple aspects of cognitive functioning, including working memory and executive functioning. Memory self-efficacy (MSE) has previously been related to episodic memory performance and to executive functioning, but little research has examined the relations between MSE and working memory. United States older adults (N  = 197) were recruited via MTurk to complete an MSE questionnaire before completing a digit span working memory task. Hierarchical regression results revealed that the model accounted for a significant amount of variance in working memory performance after statistically controlling for several covariates, F(11, 179) = 4.94, p < .001, adjusted R2 = .19. MSE explained a large and unique portion of variance (B = 1.02, SE = 0.17, p < .001). Based on our findings, one's beliefs about their memory are positively associated with their working memory performance. These novel findings provide support for neuropsychologists to consider using MSE measures and utilizing MSE interventions.

Handicraft art leisure activities and cognitive reserve

ObjectiveOlder individuals face a higher likelihood of developing dementia. The rate of cognitive decline resulting from dementia is not equivalent for all, as some patients with dementia are able to function independently longer than others, despite having similar disease burden. The cognitive reserve (CR) theory provides one explanation for the differing rate of decline. CR suggests that there are factors-most notably, educational attainment and occupational attainment-that can protect against the cognitive decline. Although the beneficial effects of these notable CR factors are clear, not all are easily modifiable. Participation in leisure activities may represent a more easily modifiable factor. Some research hints at beneficial effects of leisure activities, although specific leisure activities have not been well examined. The present study examined the relations between handicraft art leisure activities (HALAs) and multiple cognitive domains. MethodArchival WAIS-IV and demographic data for 50 California retirement community residents were examined. ResultsHALA participation accounted for statistically significant variance in working memory performance (R2 = .40, β = .24%) over and above the established CR factors of age, depression, educational attainment, and occupational attainment. In addition, HALA participation was related to a better ability to perform abstract visual information tasks (Block Design subtest, r = .28, p = .05) and non-verbal reasoning tasks (Visual Puzzles subtest, r = .38, p = .008). ConclusionsHALA participation among older adults could contribute to the retention of cognitive function, supporting the role of HALA participation as a CR factor.

Electroacupuncture stimulation improves cognitive ability and regulates metabolic disorders in Alzheimer's disease model mice: new insights from brown adipose tissue thermogenesis

Background

Metabolic defects play a crucial role in Alzheimer's disease (AD) development. Brown adipose tissue (BAT) has been identified as a novel potential therapeutic target for AD due to its unique role in energy metabolism. Electroacupuncture (EA) shows promise in improving cognitive ability and brain glucose metabolism in AD, but its effects on peripheral and central metabolism are unclear.

Methods

In this study, SAMP8 mice (AD model) received EA stimulation at specific acupoints. Cognitive abilities were evaluated using the Morris water maze test, while neuronal morphology and tau pathology were assessed through Nissl staining and immunofluorescence staining, respectively. Metabolic variations and BAT thermogenesis were measured using ELISA, HE staining, Western blotting, and infrared thermal imaging.

Results

Compared to SAMR1 mice, SAMP8 mice showed impaired cognitive ability, neuronal damage, disrupted thermoregulation, and metabolic disorders with low BAT activity. Both the EA and DD groups improved cognitive ability and decreased tau phosphorylation (p<0.01 or p<0.05). However, only the EA group had a significant effect on metabolic disorders and BAT thermogenesis (p<0.01 or p<0.05), while the DD group did not.

Conclusion

These findings indicate that EA not only improves the cognitive ability of SAMP8 mice, but also effectively regulates peripheral and central metabolic disorders, with this effect being significantly related to the activation of BAT thermogenesis.

Visual Functions Are Associated with Biomarker Changes in Alzheimer's Disease

Background

While various biomarkers of Alzheimer's disease (AD) have been associated with general cognitive function, their association to visual-perceptive function across the AD spectrum warrant more attention due to its significant impact on quality of life. Thus, this study explores how AD biomarkers are associated with decline in this cognitive domain.

Objective

To explore associations between various fluid and imaging biomarkers and visual-based cognitive assessments in participants across the AD spectrum.

Methods

Data from participants (N = 1,460) in the Alzheimer's Disease Neuroimaging Initiative were analyzed, including fluid and imaging biomarkers. Along with the Mini-Mental State Examination (MMSE), three specific visual-based cognitive tests were investigated: Trail Making Test (TMT) A and TMT B, and the Boston Naming Test (BNT). Locally estimated scatterplot smoothing curves and Pearson correlation coefficients were used to examine associations.

Results

MMSE showed the strongest correlations with most biomarkers, followed by TMT-B. The p-tau181/Aβ1-42 ratio, along with the volume of the hippocampus and entorhinal cortex, had the strongest associations among the biomarkers.

Conclusions

Several biomarkers are associated with visual processing across the disease spectrum, emphasizing their potential in assessing disease severity and contributing to progression models of visual function and cognition.

MIAMI-AD (Methylation in Aging and Methylation in AD): an integrative knowledgebase that facilitates explorations of DNA methylation across sex, aging, and Alzheimer's disease

Alzheimer's disease (AD) is a common neurodegenerative disorder with a significant impact on aging populations. DNA methylation (DNAm) alterations have been implicated in both the aging processes and the development of AD. Given that AD affects more women than men, it is also important to explore DNAm changes that occur specifically in each sex. We created MIAMI-AD, a comprehensive knowledge base containing manually curated summary statistics from 97 published tables in 37 studies, all of which included at least 100 participants. MIAMI-AD enables easy browsing, querying, and downloading DNAm associations at multiple levels - at individual CpG, gene, genomic regions, or genome-wide, in one or multiple studies. Moreover, it also offers tools to perform integrative analyses, such as comparing DNAm associations across different phenotypes or tissues, as well as interactive visualizations. Using several use case examples, we demonstrated that MIAMI-AD facilitates our understanding of age-associated CpGs in AD and the sex-specific roles of DNAm in AD. This open-access resource is freely available to the research community, and all the underlying data can be downloaded. MIAMI-AD (https://miami-ad.org/) facilitates integrative explorations to better understand the interplay between DNAm across aging, sex, and AD.

Simulation of neuroplasticity in a CNN-based in-silico model of neurodegeneration of the visual system

The aim of this work was to enhance the biological feasibility of a deep convolutional neural network-based in-silico model of neurodegeneration of the visual system by equipping it with a mechanism to simulate neuroplasticity. Therefore, deep convolutional networks of multiple sizes were trained for object recognition tasks and progressively lesioned to simulate neurodegeneration of the visual cortex. More specifically, the injured parts of the network remained injured while we investigated how the added retraining steps were able to recover some of the model's object recognition baseline performance. The results showed with retraining, model object recognition abilities are subject to a smoother and more gradual decline with increasing injury levels than without retraining and, therefore, more similar to the longitudinal cognition impairments of patients diagnosed with Alzheimer's disease (AD). Moreover, with retraining, the injured model exhibits internal activation patterns similar to those of the healthy baseline model when compared to the injured model without retraining. Furthermore, we conducted this analysis on a network that had been extensively pruned, resulting in an optimized number of parameters or synapses. Our findings show that this network exhibited remarkably similar capability to recover task performance with decreasingly viable pathways through the network. In conclusion, adding a retraining step to the in-silico setup that simulates neuroplasticity improves the model's biological feasibility considerably and could prove valuable to test different rehabilitation approaches in-silico.

Design and Harmonization Approach for the Multi-Institutional Neurocognitive Discovery Study (MINDS) of Adult Congenital Heart Disease (ACHD) Neuroimaging Ancillary Study: A Technical Note

Dramatic advances in the management of congenital heart disease (CHD) have improved survival to adulthood from less than 10% in the 1960s to over 90% in the current era, such that adult CHD (ACHD) patients now outnumber their pediatric counterparts. ACHD patients demonstrate domain-specific neurocognitive deficits associated with reduced quality of life that include deficits in educational attainment and social interaction. Our hypothesis is that ACHD patients exhibit vascular brain injury and structural/physiological brain alterations that are predictive of specific neurocognitive deficits modified by behavioral and environmental enrichment proxies of cognitive reserve (e.g., level of education and lifestyle/social habits). This technical note describes an ancillary study to the National Heart, Lung, and Blood Institute (NHLBI)-funded Pediatric Heart Network (PHN) "Multi-Institutional Neurocognitive Discovery Study (MINDS) in Adult Congenital Heart Disease (ACHD)". Leveraging clinical, neuropsychological, and biospecimen data from the parent study, our study will provide structural-physiological correlates of neurocognitive outcomes, representing the first multi-center neuroimaging initiative to be performed in ACHD patients. Limitations of the study include recruitment challenges inherent to an ancillary study, implantable cardiac devices, and harmonization of neuroimaging biomarkers. Results from this research will help shape the care of ACHD patients and further our understanding of the interplay between brain injury and cognitive reserve.

Cognitive-motor interventions based on virtual reality and instrumental activities of daily living (iADL): an overview

Non-invasive, non-pharmacological interventions utilizing virtual reality (VR) represent a promising approach to enhancing cognitive function in patients with degenerative cognitive disorders. Traditional "pen and paper" therapies often lack the practical engagement in everyday activities that older individuals encounter in their environment. These activities pose both cognitive and motor challenges, underscoring the necessity of understanding the outcomes of such combined interventions. This review aimed to assess the advantages of VR applications that integrate cognitive-motor tasks, simulating instrumental activities of daily living (iADLs). We systematically searched five databases-Scopus, Web of Science, Springer Link, IEEE Xplore, and PubMed, from their inception until January 31, 2023. Our review revealed that motor movements, coupled with VR-based cognitive-motor interventions, activate specific brain areas and foster improvements in general cognition, executive function, attention, and memory. VR applications that meld cognitive-motor tasks and simulate iADLs can offer significant benefits to older adults. Enhanced cognitive and motor performance can promote increased independence in daily activities, thereby contributing to improved quality of life.

Social enrichment on the job: Complex work with people improves episodic memory, promotes brain reserve, and reduces the risk of dementia

Individuals with more complex jobs experience better cognitive function in old age and a lower risk of dementia, yet complexity has multiple dimensions. Drawing on the Social Networks in Alzheimer Disease study, we examine the association between occupational complexity and cognition in a sample of older adults (N = 355). A standard deviation (SD) increase in complex work with people is associated with a 9% to 12% reduction in the probability of mild cognitive impairment or dementia, a 0.14-0.19 SD increase in episodic memory, and a 0.18-0.25 SD increase in brain reserve, defined as the gap (residual) between global cognitive function and magnetic resonance imaging (MRI) indicators of brain atrophy. In contrast, complexity with data or things is rarely associated with cognitive outcomes. We discuss the clinical and methodological implications of these findings, including the need to complement data-centered activities (e.g., Sudoku puzzles) with person-centered interventions that increase social complexity.

Race-Discordant School Attendance and Cognitive Function in Later Life

Early schooling plays an important role in shaping cognitive development. This study explored benefits of cognitive functioning in later life related to attending diverse schools in early life. Specifically, we explored the effects of having attended schools composed primarily of different race peers-race discordant schools (RDS)-among Black and White older adults. Using retrospective and prospective data from the Health and Retirement Study, we examined the association between RDS exposure and two measures of cognitive function (working memory, episodic memory) at age 55 and at age 70. We found that RDS exposed Blacks experienced significant benefits in cognitive function at age 55 and at age 70. In general, RDS exposed Whites did not experience cognitive benefits or deficits. Results suggest that exposure to more racially diverse school environments provides potentially beneficial effects for cognitive function, particularly in later phases of the life course.

Proteome-Wide Discovery of Cortical Proteins That May Provide Motor Resilience to Offset the Negative Effects of Pathologies in Older Adults

BACKGROUND

Motor resilience proteins have not been identified. This proteome-wide discovery study sought to identify proteins that may provide motor resilience.

METHODS

We studied the brains of older decedents with annual motor testing, postmortem brain pathologies, and proteome-wide data. Parkinsonism was assessed using 26 items of a modified United Parkinson Disease Rating Scale. We used linear mixed-effect models to isolate motor resilience, defined as the person-specific estimate of progressive parkinsonism after controlling for age, sex, and 10 brain pathologies. A total of 8 356 high-abundance proteins were quantified from dorsal lateral prefrontal cortex using tandem mass tag and liquid chromatography-mass spectrometry.

RESULTS

There were 391 older adults (70% female), mean age 80 years at baseline and 89 years at death. Five proteins were associated with motor resilience: A higher level of AP1B1 (Estimate -0.504, SE 0.121, p = 3.12 × 10-5) and GNG3 (Estimate -0.276, SE 0.068, p = 4.82 × 10-5) was associated with slower progressive parkinsonism. By contrast, a higher level of TTC38 (Estimate 0.140, SE 0.029, p = 1.87 × 10-6), CARKD (Estimate 0.413, SE 0.100, p = 3.50 × 10-5), and ABHD14B (Estimate 0.175, SE 0.044, p = 6.48 × 10-5) was associated with faster progressive parkinsonism. Together, these 5 proteins accounted for almost 25% of the variance of progressive parkinsonism above the 17% accounted for by 10 indices of brain pathologies.

DISCUSSION

Cortical proteins may provide more or less motor resilience in older adults. These proteins are high-value therapeutic targets for drug discovery that may lead to interventions that maintain motor function despite the accumulation of as yet untreatable brain pathologies.

Combined Effects of Diabetes and Education on Decline of Cognitive Performance in the Older Population: The Survey of Health, Ageing, and Retirement in Europe

AIMS

Diabetes management requires cognitive abilities. Unfortunately, diabetes is a risk factor for cognitive decline. However, the effects of diabetes in persons with reduced cognitive reserves are unclear. We aimed to examine whether the effects of diabetes and education on cognitive skills simply add up or deviate from simple additivity.

METHODS

We used data from waves 1 to 7 (except wave 3) of the Survey of Health, Ageing, and Retirement in Europe (SHARE) collected between 2004 and 2017. SHARE includes 140,000 persons aged ≥50 years from 28 European countries and Israel. Diabetes was assessed by self-report and education was coded according to the International Standard Classification of Education levels. Verbal fluency, immediate, and delayed memory were assessed using standard tests. Interaction between diabetes and education was estimated from interaction contrasts and from interaction terms in adjusted regression models.

RESULTS

At baseline, cognitive performance declined in the order "no diabetes/high education" > "diabetes/high education" > "no diabetes/low education" > "diabetes/low education" for all three tests - e.g., the first group named 21.4 ± 7.2, the fourth group 14.6 ± 6.1 animals in a minute in the test of verbal fluency. Interaction contrasts and regression coefficients of interaction terms were close to zero, showing that the effects of diabetes and education on cognitive performance added up without interaction both in cross-sectional and longitudinal analyses.

CONCLUSION

We have observed no interaction between education and diabetes on cognitive skills. Yet, people with diabetes and low education showed poor cognitive performance and should receive particular support in managing diabetes.

Systematic evaluation of the prevalence of cognitive impairment in elderly patients with diabetes in China

OBJECTIVE

To systematically evaluate the prevalence of cognitive impairment in elderly patients with diabetes in China.

METHODS

Computerized searches of the Chinese Biomedical, WanFang, Vip, Chinese National Knowledge Infrastructure, PubMed, Embase, and the Cochrane Library databases were used to collect research literature on cognitive impairment in older Chinese patients with diabetes from the time of database creation to May 5, 2021. A meta-analysis was performed using the Stata v14.0 software after two investigators independently screened the literature, extracted the information, and evaluated the bias risk of the included studies.

RESULTS

A total of 17 studies containing the records of 4380 elderly patients with diabetes were included. The meta-analysis results showed that the incidence of cognitive impairment in elderly patients with diabetes was 48% (95% confidence interval [0.40-0.55]). The results of the subgroup analysis showed that the incidence of cognitive impairment was higher in the elderly population with diabetes who were female, older, with a lower education level, no spouse, living alone, and with a monthly income of less than 2000 yuan.

CONCLUSION

Current evidence showed that the incidence of cognitive impairment in elderly patients with diabetes in China was 48%, with a higher incidence in the elderly population who were female, older, with a lower education level, a low income, no spouse, and living alone.

Cognitive reserve profiles are associated with outcome in schizophrenia

Cognitive reserve (CR), the brain's ability to cope with brain pathology to minimize symptoms, could explain the heterogeneity of outcomes in neuropsychiatric disorders, however it is still rarely investigated in schizophrenia. Indeed, this study aims to classify CR in this disorder and evaluate its impact on neurocognitive and socio-cognitive performance and daily functioning. A group of 106 patients diagnosed with schizophrenia was enrolled and assessed in these aereas: neurocognition, Theory of Mind (ToM) and daily functioning. A composite CR score was determined through an integration of the intelligence quotient and education and leisure activities. CR profiles were classified with a two-step cluster analysis and differences among clusters were determined with an analysis of variance (ANOVA). The cluster analysis was identified with three CR profiles characterized, respectively, by high, medium and low CR. ANOVA analysis showed significant differences on neurocognition, ToM and daily functioning between the clusters: people with higher CR reached significantly superior scores. This study suggests that greater general cognitive resources could act as a buffer against the effect of brain pathology, allowing patients to have a better cognitive performance, social outcome and quality of life.

Alzheimer's Disease: Efficacy of Mono- and Combination Therapy. A Systematic Review

IMPORTANCE

Alzheimer's disease (AD) is a complex neurodegenerative disorder and the most prevalent cause of dementia. In spite of the urgent need for more effective AD drug therapy strategies, evidence of the efficacy of combination therapy with existing drugs remains unclear.

OBJECTIVE

To assess the efficacy of combined drug therapy on cognition and progress in patients with AD in comparison to single agent drug therapy.

METHODS

The electronic databases MEDLINE and EMBASE were systematically searched to identify relevant publications. Only randomized controlled clinical trials were included, but no limits were applied to language or time published. Data were extracted from May 27th until December 29th, 2020.

RESULTS

Three trials found that a combination of ChEI with additional memantine provides a slight benefit for patients with moderate to severe AD over ChEI monotherapy and placebo. However, a further 4 trials could not replicate this effect. One trial reported benefits of add-on Gingko biloba in donepezil-treated patients with moderate AD (using a formula containing Gingko and other antioxidants) compared to donepezil with placebo. A further trial found no significant effect of combining EGb 761® and donepezil in patients with probable AD over donepezil with placebo. Approaches with idalopirdine, atorvastatin or vitamin supplementation in combination with ChEI have not proven effective and have not been retried since. Fluoxetine and ST101 have shown partial benefits in combination with ChEI over ChEI monotherapy and placebo. However, these effects must be replicated by further research.

CONCLUSION

Additional memantine in combination with ChEI might be of slight benefit in patients with moderate to severe AD, but evidence is ambiguous. Longer trials are needed. No major cognitive benefit is missed, if solely appropriate ChEI monotherapy is initiated.

Mixed Neuropathologies, Neural Motor Resilience and Target Discovery for Therapies of Late-Life Motor Impairment

By age 85, most adults manifest some degree of motor impairment. However, in most individuals a specific etiology for motor decline and treatment to modify its inexorable progression cannot be identified. Recent clinical-pathologic studies provide evidence that mixed-brain pathologies are commonly associated with late-life motor impairment. Yet, while nearly all older adults show some degree of accumulation of Alzheimer's disease and related dementias (ADRD) pathologies, the extent to which these pathologies contribute to motor decline varies widely from person to person. Slower or faster than expected motor decline in the presence of brain injury and/or pathology has been conceptualized as more or less "resilience" relative to the average person This suggests that other factors, such as lifestyles or other neurobiologic indices may offset or exacerbate the negative effects of pathologies via other molecular pathways. The mechanisms underlying neural motor resilience are just beginning to be illuminated. Unlike its cousin, cognitive resilience which is restricted to neural mechanisms above the neck, the motor system extends the total length of the CNS and beyond the CNS to reach muscle and musculoskeletal structures, all of which are crucial for motor function. Building on prior work, we propose that by isolating motor decline unrelated to neuropathologies and degeneration, investigators can identify genes and proteins that may provide neural motor resilience. Elucidating these molecular mechanisms will advance our understanding of the heterogeneity of late-life motor impairment. This approach will also provide high value therapeutic targets for drug discovery of therapies that may offset the negative motor consequences of CNS pathologies that are currently untreatable.

Sociodemographic, Lifestyle, Physical, and Psychosocial Determinants of Cognitive Reserve

BACKGROUND

Cognitive reserve aims to explain individual differences in the susceptibility to the functional impact of dementia in the presence of equal amount of neuropathological damage. It is thought to be shaped by a combination of innate individual differences and lifetime exposures. Which determinants are associated with cognitive reserve remains unknown.

OBJECTIVE

The objective of this study was to investigate the associations of sociodemographic, lifestyle, physical, and psychosocial determinants with cognitive reserve, and potential sex differences.

METHODS

This cross-sectional study included 4,309 participants from the Rotterdam Study (mean age 63.9±10.7) between 2006-2016. Participants completed five cognitive tests and a brain MRI-scan. Cognitive reserve was defined as a latent variable that captures variance common across five cognitive tests, while adjusting for demographic and MRI-inferred neuropathological factors. The associations of potential determinants and cognitive reserve, adjusted for relevant confounders, were assessed with structural equation models.

RESULTS

Current smoking (adjusted mean difference: -0.31, 95%confidence interval -0.42; -0.19), diabetes mellitus (-0.25, -0.40; -0.10) and depressive symptoms (-0.07/SD, -0.12; -0.03) were associated with a lower cognitive reserve whereas alcohol use (0.07/SD, 0.03; 0.12) was associated with higher cognitive reserve. Only smoking was associated with cognitive reserve in both men and women. Employment, alcohol use, diabetes, history of cancer, COPD, and depressive symptoms were only associated with cognitive reserve in women.

CONCLUSION

Our study found that current smoking, diabetes mellitus, and depressive symptoms were associated with a lower cognitive reserve, whereas more alcohol use was associated with a higher cognitive reserve, but with clear differences between men and women.

Why the cognitive "fountain of youth" may be upstream: Pathways to dementia risk and resilience through social connectedness

Research suggests social connectedness may help older adults with dementia maintain cognitive functionality and quality of life. However, little is known about its specific social and biological mechanisms. This paper proposes two pathways through social bridging (i.e., cognitive enrichment through expansive social networks) and bonding (i.e., neuroendocrine benefits of integration in cohesive social networks). We provide preliminary evidence for these pathways using neuroimaging, cognitive, and egocentric social network data from the Social Networks and Alzheimer's Disease (SNAD) study (N = 280). We found that network size, density, and presence of weak ties (i.e., social bridging) moderated the association between brain atrophy and cognitive function, while marriage/cohabitation (i.e., social bonding) moderated the association between perceived stress and cognitive function. We argue that social connectedness may have downstream implications for multiple pathophysiological processes in cognitive aging, even negating existing structural damage to the brain, making it a strong candidate for clinical or policy intervention.

Electrophysiological Proxy of Cognitive Reserve Index

Cognitive reserve (CR) postulates that individual differences in task performance can be attributed to differences in the brain’s ability to recruit additional networks or adopt alternative cognitive strategies. Variables that are descriptive of lifetime experience such as socioeconomic status, educational attainment, and leisure activity are common proxies of CR. CR is mostly studied using neuroimaging techniques such as functional MRI (fMRI) in which case individuals with a higher CR were observed to activate a smaller brain network compared to individuals with a lower CR, when performing a task equally effectively (higher efficiency), and electroencephalography (EEG) where a particular EEG component (P300) that reflects the attention and working memory load, has been targeted. Despite the contribution of multiple factors such as age, education (formal and informal), working, leisure, and household activities in CR formation, most neuroimaging studies, and those using EEG in particular, focus on formal education level only. The aim of the current EEG study is to investigate how the P300 component, evoked in response to an oddball paradigm, is associated with other components of CR besides education, such as working and leisure activity in older adults. We have used hereto a recently introduced CR index questionnaire (CRIq) that quantifies both professional and leisure activities in terms of their cognitive demand and number of years practiced, as well as a data-driven approach for EEG analysis. We observed complex relationships between CRIq subcomponents and P300 characteristics. These results are especially important given that, unlike previous studies, our measurements (P300 and CRIq) do not require active use of the same executive function and, thus, render our results free of a collinearity bias.

Exploitation of Marine Molecules to Manage Alzheimer's Disease

Neurodegenerative diseases are sociosanitary challenges of today, as a result of increased average life expectancy, with Alzheimer’s disease being one of the most prevalent. This pathology is characterized by brain impairment linked to a neurodegenerative process culminating in cognitive decline and behavioral disorders. Though the etiology of this pathology is still unknown, it is usually associated with the appearance of senile plaques and neurofibrillary tangles. The most used prophylaxis relies on anticholinesterase drugs and NMDA receptor antagonists, whose main action is to relieve symptoms and not to treat or prevent the disease. Currently, the scientific community is gathering efforts to disclose new natural compounds effective against Alzheimer’s disease and other neurodegenerative pathologies. Marine natural products have been shown to be promising candidates, and some have been proven to exert a high neuroprotection effect, constituting a large reservoir of potential drugs and nutraceutical agents. The present article attempts to describe the processes of extraction and isolation of bioactive compounds derived from sponges, algae, marine bacteria, invertebrates, crustaceans, and tunicates as drug candidates against AD, with a focus on the success of pharmacological activity in the process of finding new and effective drug compounds.

Cognitive reserve and Alzheimer's biological continuum: clues for prediction and prevention of dementia

Cognitive reserve is originally an epidemiological concept that encompasses individual abilities to cope with changes. It is considered the result of a balance between processes of cellular damage and repair, and its description raised much interest in predicting and preventing cognitive decline in aging and Alzheimer's disease (AD). In this study, we discussed the concept of cognitive reserve considering the recent definition of AD as a biological continuum and suggest that the protection of cognitive reserve may result from efficient synaptic plasticity mechanisms. Despite pathological changes of AD appearing very early during life, long before the onset of cognitive symptoms, different variables act together to keep repair mechanisms effective guaranteeing successful aging if environmental enrichment is maintained.

Integrating Three Characteristics of Executive Function in Non-Demented Aging: Trajectories, Classification, and Biomarker Predictors

OBJECTIVE

With longitudinal executive function (EF) data from the Victoria Longitudinal Study, we investigated three research goals pertaining to key characteristics of EF in non-demented aging: (a) examining variability in EF longitudinal trajectories, (b) establishing trajectory classes, and (c) identifying biomarker predictors discriminating these classes.

METHOD

We used a trajectory analyses sample (n = 781; M age = 71.42) for the first and second goals and a prediction analyses sample (n = 570; M age = 70.10) for the third goal. Eight neuropsychological EF measures were used as indicators of three EF dimensions: inhibition, updating, and shifting. Data-driven classification analyses were applied to the full trajectory distribution. Machine learning prediction analyses tested 15 predictors from genetic, functional, lifestyle, mobility, and demographic risk domains.

RESULTS

First, we observed: (a) significant variability in EF trajectories over a 40-year band of aging and (b) significantly variable patterns of EF decline. Second, a four-class EF trajectory model was observed, characterized with classes differentiated by an algorithm of level and slope information. Third, the highest group class was discriminated from lowest by several prediction factors: more education, more novel cognitive activity, lower pulse pressure, younger age, faster gait, lower body mass index, and better balance.

CONCLUSION

First, with longitudinal variability in EF aging, the data-driven approach showed that long-term trajectories can be differentiated into separable classes. Second, prediction analyses discriminated class membership by a combination of multiple biomarkers from demographic, lifestyle, functional, and mobility domains of risk for brain and cognitive aging decline.

Particulate Matter Exposure Exacerbates Amyloid-β Plaque Deposition and Gliosis in APP/PS1 Mice

BACKGROUND

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by the accumulation of amyloid-β (Aβ) plaques, neuroinflammation, and neuronal death. There are several well-established genetic and environmental factors hypothesized to contribute to AD progression including air pollution. However, the molecular mechanisms by which air pollution exacerbates AD are unclear.

OBJECTIVE

This study explored the effects of particulate matter exposure on AD-related brain changes using the APP/PS1 transgenic model of disease.

METHODS

Male C57BL/6;C3H wild type and APP/PS1 mice were exposed to either filtered air (FA) or particulate matter sized under 2.5μm (PM2.5) for 6 h/day, 5 days/week for 3 months and brains were collected. Immunohistochemistry for Aβ, GFAP, Iba1, and CD68 and western blot analysis for PS1, BACE, APP, GFAP, and Iba1 were performed. Aβ ELISAs and cytokine arrays were performed on frozen hippocampal and cortical lysates, respectively.

RESULTS

The Aβ plaque load was significantly increased in the hippocampus of PM2.5-exposed APP/PS1 mice compared to their respective FA controls. Additionally, in the PM2.5-exposed APP/PS1 group, increased astrocytosis and microgliosis were observed as indicated by elevated GFAP, Iba1, and CD68 immunoreactivities. PM2.5 exposure also led to an elevation in the levels of PS1 and BACE in APP/PS1 mice. The cytokines TNF-α, IL-6, IL-1β, IFN-γ, and MIP-3α were also elevated in the cortices of PM2.5-exposed APP/PS1 mice compared to FA controls.

CONCLUSION

Our data suggest that chronic particulate matter exposure exacerbates AD by increasing Aβ plaque load, gliosis, and the brain inflammatory status.

Strategy or symptom: Semantic clustering and risk of Alzheimer's disease-related impairment

Alzheimer's disease (AD) is the most common form of dementia, impacting global cognitive performance, including episodic memory. Semantic clustering is a learning strategy involving grouping words of similar meaning and can improve episodic memory performance, e.g., list learning. As the APOE ε4 allele is the most validated genetic risk factor for AD, we predicted that its presence would be associated with poorer list learning performance, and we hypothesized that semantic clustering moderates or mediates this association. The sample comprised 699 healthy older adults participating in the CHARIOT PRO Main Study, 169 of whom were APOE ε4 carriers. Participants' ability to form groups of related stimuli (assessed via a categorization task, CAT), and their use of semantic clustering during list learning, were investigated using the Neuropsychological Assessment Battery (NAB). CAT scores predicted the use of semantic clustering in, and performance on, the list learning task. CAT scores were not significantly lower in APOE ε4 carriers, suggesting that the ability to categorize was preserved. However, APOE ε4 carriers made less use of semantic clustering in list learning. Semantic clustering use partially mediated the relationship between CAT scores and list learning performance, and, in women only, moderated the impact of APOE ε4 on list learning performance. The results suggest that better categorization ability is associated with greater use of mnemonic strategies and better performance on memory tasks regardless of genetic risk, but that APOE ε4 carriers make less use of such strategies. Furthermore, female APOE ε4 carriers may benefit more than their non-carriers from using semantic clustering to aid list learning. Thus, semantic clustering may be a contributing factor of their "cognitive reserve", compensating for potential deficits in episodic memory.

The long arm of childhood intelligence on terminal decline: Evidence from the Lothian Birth Cohort 1921

The current study investigates the heterogeneity of cognitive trajectories at the end of life by assigning individuals into groups according to their cognitive trajectories prior to death. It also examines the role of childhood intelligence and education on these trajectories and group membership. Participants were drawn from the Lothian Birth Cohort of 1921 (LBC1921), a longitudinal study of individuals with a mean age of 79 years at study entry, and observed up to a maximum of five times to their early 90s. Growth mixture modeling was employed to identify groups of individuals with similar trajectories of global cognitive function measured with the Mini-Mental State Examination (MMSE) in relation to time to death, accounting for childhood intelligence, education, the time to death from study entry, and health conditions (hypertension, diabetes, and cardiovascular disease). Two distinct groups of individuals (classes) were identified: a smaller class (18% of the sample) of individuals whose MMSE scores dropped linearly with about 0.5 MMSE points per year closer to death and a larger group (82% of the sample) with stable MMSE across the study period. Only childhood intelligence was found to be associated with an increased probability of belonging to the stable class of cognitive functioning prior to death (odds ratio = 1.08, standard error = 0.02, p ≤ .001). These findings support a protective role of childhood intelligence, a marker of cognitive reserve, against the loss of cognitive function prior to death. Our results also suggest that terminal decline is not necessarily a normative process. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Misfolded proteins as a therapeutic target in Alzheimer's disease

For decades, Alzheimer's Disease (AD) was defined as a disorder of protein misfolding and aggregation. In particular, the extracellular peptide fragment: amyloid-β (Aβ), and the intracellular microtubule-associated protein: tau, were thought to initiate a neurodegenerative cascade which culminated in AD's progressive loss of memory and executive function. As such, both proteins became the focus of intense scrutiny, and served as the principal pathogenic target for hundreds of clinical trials. However, with varying efficacy, none of these investigations produced a disease-modifying therapy - offering patients with AD little recourse aside from transient, symptomatic medications. The near universal failure of clinical trials is unprecedented for a major research discipline. In part, this has motivated an increasing skepticism of the relevance of protein misfolding to AD's etiology. Several recent observations, principally the presence of significant protein pathologies in non-demented seniors, have lent credence to an apparent cursory role for Aβ and tau. Herein, we review both Aβ and tau, examining the processes from their biosynthesis to their pathogenesis and evaluate their vulnerability to medicinal intervention. We further attempt to reconcile the apparent failure of trials with the potential these targets hold. Ultimately, we seek to answer if protein misfolding is a viable platform in the pursuit of a disease-arresting strategy for AD.

Transcriptional Networks of Microglia in Alzheimer's Disease and Insights into Pathogenesis

Microglia, the main immune cells of the central nervous system, are increasingly implicated in Alzheimer's disease (AD). Manifold transcriptomic studies in the brain have not only highlighted microglia's role in AD pathogenesis, but also mapped crucial pathological processes and identified new therapeutic targets. An important component of many of these transcriptomic studies is the investigation of gene expression networks in AD brain, which has provided important new insights into how coordinated gene regulatory programs in microglia (and other cell types) underlie AD pathogenesis. Given the rapid technological advancements in transcriptional profiling, spanning from microarrays to single-cell RNA sequencing (scRNA-seq), tools used for mapping gene expression networks have evolved to keep pace with the unique features of each transcriptomic platform. In this article, we review the trajectory of transcriptomic network analyses in AD from brain to microglia, highlighting the corresponding methodological developments. Lastly, we discuss examples of how transcriptional network analysis provides new insights into AD mechanisms and pathogenesis.

Integrating Health Promotion Into Physical Therapy Practice to Improve Brain Health and Prevent Alzheimer Disease

BACKGROUND AND PURPOSE

Alzheimer disease is the most common cause of dementia, and brain pathology appears years before symptoms are evident. Primary prevention through health promotion can incorporate lifestyle improvement across the lifespan. Risk factor assessment and identifying markers of disease might also trigger preventive measures needed for high-risk individuals and groups.

SUMMARY OF KEY POINTS

Many potential risk factors are modifiable through exercise, and may be responsive to early intervention strategies to reduce the downward slope toward disability. Through the use of common clinical tests to identify cognitive and noncognitive functional markers of disease, detection and intervention can occur at earlier stages, including preclinical stages of disease. Physical activity and exercise interventions to address modifiable risk factors and impairments can play a pivotal role in the prevention and delay of functional decline, ultimately reducing the incidence of dementia. This article discusses prevention, prediction, plasticity, and participation in the context of preserving brain health and preventing Alzheimer disease and related dementias in aging adults.

RECOMMENDATIONS FOR CLINICAL PRACTICE

Rehabilitation professionals have opportunities to slow disease progression through research, practice, and education initiatives. From a clinical perspective, interventions that target brain health through lifestyle changes and exercise interventions show promise for preventing stroke and associated neurovascular diseases in addition to dementia. Physical therapists are well positioned to integrate primary health promotion into practice for the prevention of dementia and other neurological conditions in older adults.

Mapping the Proxies of Memory and Learning Function in Senior Adults with High-performing, Normal Aging and Neurocognitive Disorders

BACKGROUND

Memory and learning, as the core brain function, shows controversial results across studies focusing on aging and dementia. One of the reasons is because of the multi-faceted nature of memory and learning. However, there is still a dearth of comparable proxies with psychometric and morphometric portrait in clinical and non-clinical populations.

OBJECTIVE

We aim to investigate the proxies of memory and learning function with direct and derived measures and examine their associations with morphometric features in senior adults with different cognitive status.

METHODS

Based on two modality-driven tests, we assessed the component-specific memory and learning in the individuals with high performing (HP), normal aging, and neurocognitive disorders (NCD) (n = 488). Structural magnetic resonance imaging was used to measure the regional cortical thickness with surface-based morphometry analysis in a subsample (n = 52).

METHODS

Compared with HP elderly, the ones with normal aging and minor NCD showed declined recognition memory and working memory, whereas had better learning performance (derived scores). Meanwhile, major NCD patients showed more breakdowns of memory and learning function. The correlation between proxies of memory and learning and cortical thickness exhibited the overlapped and unique neural underpinnings.

CONCLUSIONS

The proxies of memory and learning could be characterized by component-specific constructs with psychometric and morphometric bases. Overall, the constructs of memory are more likely related to the pathological changes, and the constructs of learning tend to reflect the cognitive abilities of compensation.

Virtual reality-based cognitive-motor training for middle-aged adults at high Alzheimer's disease risk: A randomized controlled trial

Introduction

Ubiquity of Alzheimer's disease (AD) coupled with relatively ineffectual pharmacologic treatments has spurred interest in nonpharmacologic lifestyle interventions for prevention or risk reduction. However, evidence of neuroplasticity notwithstanding, there are few scientifically rigorous, ecologically relevant brain training studies focused on building cognitive reserve in middle age to protect against cognitive decline. This pilot study will examine the ability of virtual reality (VR) cognitive training to improve cognition and cerebral blood flow (CBF) in middle-aged individuals at high AD risk due to parental history.

Methods

The design is an assessor-blind, parallel group, randomized controlled trial of VR cognitive-motor training in middle-aged adults with AD family history. The experimental group will be trained with adaptive “real-world” VR tasks targeting sustained and selective attention, working memory, covert rule deduction, and planning, while walking on a treadmill. One active control group will perform the VR tasks without treadmill walking; another will walk on a treadmill while watching scientific documentaries (nonspecific cognitive stimulation). A passive (waitlist) control group will not receive training. Training sessions will be 45 minutes, twice/week for 12 weeks. Primary outcomes are global cognition and CBF (from arterial spin labeling [ASL]) at baseline, immediately after training (training gain), and 3 months post-training (maintenance gain). We aim to recruit 125 participants, including 20 passive controls and 35 in the other groups.

Discussion

Current pharmacologic therapies are for symptomatic AD patients, whereas nonpharmacologic training is administrable before symptom onset. Emerging evidence suggests that cognitive training improves cognitive function. However, a more ecologically valid cognitive-motor VR setting that better mimics complex daily activities may augment transfer of trained skills. VR training has benefited clinical cohorts, but benefit in asymptomatic high-risk individuals is unknown. If effective, this trial may help define a prophylactic regimen for AD, adaptable for home-based application in high-risk individuals.

Mitochondrial Regulatory Pathways in the Pathogenesis of Alzheimer's Disease

Alzheimer's disease (AD) is an age-associated neurodegenerative brain disorder with progressive cognitive decline that leads to terminal dementia and death. For decades, amyloid-beta (Aβ) and neurofibrillary tangle (NFT) aggregation hypotheses have dominated studies on the pathogenesis and identification of potential therapeutic targets in AD. Little attention has been paid to the mitochondrial molecular/biochemical pathways leading to AD. Mitochondria play a critical role in cell viability and death including neurons and neuroglia, not only because they regulate energy and oxygen metabolism but also because they regulate cell death pathways. Mitochondrial impairment and oxidative stress are implicated in the pathogenesis of AD. Interestingly, current therapeutics provide symptomatic benefits to AD patients resulting in the use of preventive trials on presymptomatic subjects. This review article elucidates the pathophysiology of AD and emphasizes the need to explore the mitochondrial pathways to provide solutions to unanswered questions in the prevention and treatment of AD.

Positive Social Interactions in a Lifespan Perspective with a Focus on Opioidergic and Oxytocinergic Systems: Implications for Neuroprotection

In recent years, a growing interest has emerged in the beneficial effects of positive social interactions on health. The present work aims to review animal and human studies linking social interactions and health throughout the lifespan, with a focus on current knowledge of the possible mediating role of opioids and oxytocin. During the prenatal period, a positive social environment contributes to regulating maternal stress response and protecting the fetus from exposure to maternal active glucocorticoids. Throughout development, positive social contact with the caregiver acts as a “hidden regulator” and promotes infant neuroaffective development. Postnatal social neuroprotection interventions involving caregiver–infant physical contact seem to be crucial for rescuing preterm infants at risk for neurodevelopmental disorders. Attachment figures and friendships in adulthood continue to have a protective role for health and brain functioning, counteracting brain aging. In humans, implementation of meditative practices that promote compassionate motivation and prosocial behavior appears beneficial for health in adolescents and adults. Human and animal studies suggest the oxytocinergic and opioidergic systems are important mediators of the effects of social interactions. However, most of the studies focus on a specific phase of life (i.e., adulthood). Future studies should focus on the role of opioids and oxytocin in positive social interactions adopting a lifespan perspective.

Religious Orders Study and Rush Memory and Aging Project

BACKGROUND

The Religious Orders Study and Rush Memory and Aging Project are both ongoing longitudinal clinical-pathologic cohort studies of aging and Alzheimer's disease (AD).

OBJECTIVES

To summarize progress over the past five years and its implications for understanding neurodegenerative diseases.

METHODS

Participants in both studies are older adults who enroll without dementia and agree to detailed longitudinal clinical evaluations and organ donation. The last review summarized findings through the end of 2011. Here we summarize progress and study findings over the past five years and discuss new directions for how these studies can inform on aging and AD in the future.

RESULTS

We summarize 1) findings on the relation of neurobiology to clinical AD; 2) neurobiologic pathways linking risk factors to clinical AD; 3) non-cognitive AD phenotypes including motor function and decision making; 4) the development of a novel drug discovery platform.

CONCLUSION

Complexity at multiple levels needs to be understood and overcome to develop effective treatments and preventions for cognitive decline and AD dementia.

Investigating the Usability and Acute Effects of a Bedside Video Console to Prefrontal Cortical Activity Alterations: A Preclinical Study in Healthy Elderly

Elderly people at risk of developing cognitive decline; e.g., following surgery, may benefit from structured, challenging, and repetitive cognitive video training. This study assessed usability and acute effects of a newly developed bedside console (COPHYCON). Fifteen healthy elderly individuals performed a one-time 80-min intervention, including cognitive video games aimed at improving awareness and selective attention. Perceived usefulness and perceived ease of use (Technology Acceptance Model) were assessed together with measures of the achieved game level, reaction times, (in-) correct responses during ALERT and SELECT game play. Further, prefrontal cortical involvement of the regional cerebral hemoglobin saturation (rS02%) assessed with functional near infrared spectroscopy (fNIRS) (n = 5) and EEG power (n = 10) was analyzed. All participants completed the study without any adverse events. Perceived usefulness and perceived ease of use (TAM scores range 1-7) of the system varied between 3.9 and 6.3. The game levels reached for awareness varied between 9 and 11 (initial score 8-10), for reaction speed between 439 and 469 ms, and for correct responses between 74.1 and 78.8%. The highest level for the selective attention games was 2 (initial score 1), where reaction speed varied between 439 and 469 ms, correct responses between 96.2 and 98.5%, respectively. The decrease of rS02% in the right prefrontal cortex during gameplay was significantly (p < 0.001) lower, compared to the left prefrontal cortex. Four participants yielded significant lower rS02% measures after exergaming with the ALERT games (p < 0.000), but not with the SELECT games. EEG recordings of theta power significantly decreased in the averaged ~0.25-0.75 time interval for the left prefrontal cortex sensor across the cognitive game levels between the ALERT 1 and SELECT 1, as well as between SELECT 1 and 2 games. Participants rated the usability of the COPHYCON training positively. Further results indicate that video gaming may be an effective measure to affect prefrontal cortical functioning in elderly. The results warrant a clinical explorative study investigating the feasibility of the COPHYCON in a clinical setting.

Differential Roles of Environmental Enrichment in Alzheimer's Type of Neurodegeneration and Physiological Aging

Impairment of hippocampal adult neurogenesis in aging or degenerating brain is a well-known phenomenon caused by the shortage of brain stem cell pool, alterations in the local microenvironment within the neurogenic niches, or deregulation of stem cell development. Environmental enrichment (EE) has been proposed as a potent tool to restore brain functions, to prevent aging-associated neurodegeneration, and to cure neuronal deficits seen in neurodevelopmental and neurodegenerative disorders. Here, we report our data on the effects of environmental enrichment on hippocampal neurogenesis in vivo and neurosphere-forming capacity of hippocampal stem/progenitor cells in vitro. Two models - Alzheimer's type of neurodegeneration and physiological brain aging - were chosen for the comparative analysis of EE effects. We found that environmental enrichment greatly affects the expression of markers specific for stem cells, progenitor cells and differentiated neurons (Pax6, Ngn2, NeuroD1, NeuN) in the hippocampus of young adult rats or rats with Alzheimer's disease (AD) model but less efficiently in aged animals. Application of time-lag mathematical model for the analysis of impedance traces obtained in real-time monitoring of cell proliferation in vitro revealed that EE could restore neurosphere-forming capacity of hippocampal stem/progenitor cells more efficiently in young adult animals (fourfold greater in the control group comparing to the AD model group) but not in the aged rats (no positive effect of environmental enrichment at all). In accordance with the results obtained in vivo, EE was almost ineffective in the recovery of hippocampal neurogenic reserve in vitro in aged, but not in amyloid-treated or young adult, rats. Therefore, EE-based neuroprotective strategies effective in Aβ-affected brain could not be directly extrapolated to aged brain.

The BDNF Val66Met polymorphism moderates the effect of cognitive reserve on 36-month cognitive change in healthy older adults

Introduction

Cognitive reserve (CR) and BDNF Val66Met are independently associated with the rate of cognitive decline in preclinical Alzheimer's disease. This study was designed to investigate the interactive effects of these variables on 36-month cognitive change in cognitively intact older adults.

Methods

Data for this investigation were obtained from 445 community-residing participants of the Tasmanian Healthy Brain Project, who underwent genetic screening and annual assessment of neuropsychological, health, and psychosocial function.

Results

Our main result was that BDNF Val66Met moderated the relationship between baseline CR and change in executive function performance, in that CR-related differences in function decreased across the follow-up period in BDNF Val homozygotes, but became more pronounced in BDNF Met carriers. Similar effects were not observed within the other memory- and language-related cognitive domains.

Discussion

Inheritance of BDNF Met may be associated with a detrimental influence on the relationship between CR and cognitive change in cognitively intact older adults, but this effect may be restricted to the executive function domain.

Social class, dementia and the fourth age

Research addressing social class and dementia has largely focused on measures of socioeconomic status as causal risk factors for dementia and in observed differences in diagnosis, treatment and care. This large body of work has produced important insights but also contains numerous problems and weaknesses. Research needs to take account of the ways in which ageing and social class have been transformed in tandem with the economic, social and cultural coordinates of late modernity. These changes have particular consequences for individual identities and social relations. With this in mind this article adopts a critical gaze on research that considers interactions between dementia and social class in three key areas: (i) epidemiological approaches to inequalities in risk (ii) the role of social class in diagnosis and treatment and (iii) class in the framing of care and access to care. Following this, the article considers studies of dementia and social class that focus on lay understandings and biographical accounts. Sociological insights in this field come from the view that dementia and social class are embedded in social relations. Thus, forms of distinction based on class relations may still play an important role in the lived experience of dementia.

Cognitive reserve moderates the association between functional network anti-correlations and memory in MCI

Cognitive reserve (CR) shows protective effects on cognitive function in older adults. Here, we focused on the effects of CR at the functional network level. We assessed in patients with amnestic mild cognitive impairment (aMCI) whether higher CR moderates the association between low internetwork cross-talk on memory performance. In 2 independent aMCI samples (n = 76 and 93) and healthy controls (HC, n = 36), CR was assessed via years of education and intelligence (IQ). We focused on the anti-correlation between the dorsal attention network (DAN) and an anterior and posterior default mode network (DMN), assessed via sliding time window analysis of resting-state functional magnetic resonance imaging (fMRI). The DMN-DAN anti-correlation was numerically but not significantly lower in aMCI compared to HC. However, in aMCI, lower anterior DMN-DAN anti-correlation was associated with lower memory performance. This association was moderated by CR proxies, where the association between the internetwork anti-correlation and memory performance was alleviated at higher levels of education or IQ. In conclusion, lower DAN-DMN cross-talk is associated with lower memory in aMCI, where such effects are buffered by higher CR.

The impact of cognitive reserve in the outcome of first-episode psychoses: 2-year follow-up study

The concept of cognitive reserve (CR) suggests that the premorbid intelligence quotient (IQ), years of education and leisure activities provide more efficient cognitive networks and therefore allow a better management of some conditions associated to cognitive impairment. Fifty-two DSM-IV diagnosed FEP subjects were matched with 41 healthy controls by age, gender and parental socio-economic status. All subjects were assessed clinically, neuropsychologically and functionally at baseline and after a two-year follow-up. To assess CR at baseline, three proxies have been integrated: premorbid IQ, years of education-occupation and leisure activities. Higher CR was associated with better cognitive, functional and clinical outcomes at baseline. The CR proxy was able to predict working memory, attention, executive functioning, verbal memory and global composite cognitive score accounting for 48.9%, 19.1%, 16.9%, 10.8% and 14.9% respectively of the variance at two-year follow-up. CR was also significantly predictive of PANSS negative scale score (12.5%), FAST global score (13.4%) and GAF (13%) at two-year follow-up. In addition, CR behaved as a mediator of working memory (B=4.123) and executive function (B=3.298) at baseline and of working memory (B=5.034) at 2-year follow-up. An additional analysis was performed, in order to test whether this mediation could be attributed mainly to the premorbid IQ. We obtained that this measure was not enough by itself to explain this mediation. CR may contribute to neuropsychological and functional outcome. Specific programs addressed to improve cognition and functioning conducted at the early stages of the illness may be helpful in order to prevent cognitive and functional decline.

Impaired neurogenesis of the dentate gyrus is associated with pattern separation deficits: A computational study

The separation of input patterns received from the entorhinal cortex (EC) by the dentate gyrus (DG) is a well-known critical step of information processing in the hippocampus. Although the role of interneurons in separation pattern efficiency of the DG has been theoretically known, the balance of neurogenesis of excitatory neurons and interneurons as well as its potential role in information processing in the DG is not fully understood. In this work, we study separation efficiency of the DG for different rates of neurogenesis of interneurons and excitatory neurons using a novel computational model in which we assume an increase in the synaptic efficacy between excitatory neurons and interneurons and then its decay over time. Information processing in the EC and DG was simulated as information flow in a two layer feed-forward neural network. The neurogenesis rate was modeled as the percentage of new born neurons added to the neuronal population in each time bin. The results show an important role of an optimal neurogenesis rate of interneurons and excitatory neurons in the DG in efficient separation of inputs from the EC in pattern separation tasks. The model predicts that any deviation of the optimal values of neurogenesis rates leads to different decreased levels of the separation deficits of the DG which influences its function to encode memory.

Alzheimer Disease and Its Growing Epidemic: Risk Factors, Biomarkers, and the Urgent Need for Therapeutics

Alzheimer disease (AD) represents one of the greatest medical challenges of this century; the condition is becoming increasingly prevalent worldwide and no effective treatments have been developed for this terminal disease. Because the disease manifests at a late stage after a long period of clinically silent neurodegeneration, knowledge of the modifiable risk factors and the implementation of biomarkers is crucial in the primary prevention of the disease and presymptomatic detection of AD, respectively. This article discusses the growing epidemic of AD and antecedent risk factors in the disease process. Disease biomarkers are discussed, and the implications that this may have for the treatment of this currently incurable disease.

An approach for estimating item sensitivity to within-person change over time: An illustration using the Alzheimer's Disease Assessment Scale-Cognitive subscale (ADAS-Cog)

When assessments are primarily used to measure change over time, it is important to evaluate items according to their sensitivity to change, specifically. Items that demonstrate good sensitivity to between-person differences at baseline may not show good sensitivity to change over time, and vice versa. In this study, we applied a longitudinal factor model of change to a widely used cognitive test designed to assess global cognitive status in dementia, and contrasted the relative sensitivity of items to change. Statistically nested models were estimated introducing distinct latent factors related to initial status differences between test-takers and within-person latent change across successive time points of measurement. Models were estimated using all available longitudinal item-level data from the Alzheimer's Disease Assessment Scale-Cognitive subscale, including participants representing the full-spectrum of disease status who were enrolled in the multisite Alzheimer's Disease Neuroimaging Initiative. Five of the 13 Alzheimer's Disease Assessment Scale-Cognitive items demonstrated noticeably higher loadings with respect to sensitivity to change. Attending to performance change on only these 5 items yielded a clearer picture of cognitive decline more consistent with theoretical expectations in comparison to the full 13-item scale. Items that show good psychometric properties in cross-sectional studies are not necessarily the best items at measuring change over time, such as cognitive decline. Applications of the methodological approach described and illustrated in this study can advance our understanding regarding the types of items that best detect fine-grained early pathological changes in cognition. (PsycINFO Database Record

Brain-derived neurotropic factor polymorphisms, traumatic stress, mild traumatic brain injury, and combat exposure contribute to postdeployment traumatic stress

BACKGROUND

In addition to experiencing traumatic events while deployed in a combat environment, there are other factors that contribute to the development of posttraumatic stress disorder (PTSD) in military service members. This study explored the contribution of genetics, childhood environment, prior trauma, psychological, cognitive, and deployment factors to the development of traumatic stress following deployment.

METHODS

Both pre- and postdeployment data on 231 of 458 soldiers were analyzed. Postdeployment assessments occurred within 30 days from returning stateside and included a battery of psychological health, medical history, and demographic questionnaires; neurocognitive tests; and blood serum for the D2 dopamine receptor (DRD2), apolipoprotein E (APOE), and brain-derived neurotropic factor (BDNF) genes.

RESULTS

Soldiers who screened positive for traumatic stress at postdeployment had significantly higher scores in depression (d = 1.91), anxiety (d = 1.61), poor sleep quality (d = 0.92), postconcussion symptoms (d = 2.21), alcohol use (d = 0.63), traumatic life events (d = 0.42), and combat exposure (d = 0.91). BDNF Val66 Met genotype was significantly associated with risk for sustaining a mild traumatic brain injury (mTBI) and screening positive for traumatic stress. Predeployment traumatic stress, greater combat exposure and sustaining an mTBI while deployed, and the BDNF Met/Met genotype accounted for 22% of the variance of postdeployment PTSD scores (R (2)  = 0.22, P < 0.001). However, predeployment traumatic stress, alone, accounted for 17% of the postdeployment PTSD scores.

CONCLUSION

These findings suggest predeployment traumatic stress, genetic, and environmental factors have unique contributions to the development of combat-related traumatic stress in military service members.