The brain cognitive reserve hypothesis: A review with emphasis on the contribution of nuclear medicine neuroimaging techniques

Are you more impulsive with age? Examining age, marital status, and gender on cognitive ageing

Understanding non-pathological cognitive aging processes remains a public health goal and research priority. Age-associated cognitive aging is a normal human process, however, individual differences may aid in the mitigation of cognitive aging. Assessing the role of certain protective factors (i.e., age, marital status, and gender) that influence age-related cognitive aging is imperative to slow down the progression of unwarranted cognitive aging. Participants aged over 18 (N = 123; 97 females and 26 males) recruited from Sydney, New South Wales, and Gold Coast, Queensland, completed an online neuropsychological test battery with computer-administered tasks, assessing impulsivity and working memory, which were entered as dependent variables. A 3(Age Group: 18-27 years; 28-61 years; 62+ years) x2(Marital Status: married; single) x2(Gender: male; female) Multivariate Analysis of Covariance (MANCOVA) design was used to examine the relationship between age, marital status, and gender (entered as independent variables) on cognitive aging. Participants' total scores from psychometrically sound measures assessing depressive symptomology, personal wellbeing, resilience, and social network engagement, were entered as covariates. No significant effects were found from the independent variables included in the MANCOVA. A significant covariate effect for resilience and depressive symptomology on impulsivity was found. A multiple regression analysis was performed on the significant covariates, and revealed increased resilience and depressive symptomology to significantly predict greater impulsivity.

Challenge Your Body, Challenge Your Mind: the Combined Effect of Fitness Level and Stress Appraisal on Stress Responses and Subsequent Cognitive Performance

BACKGROUND

Because of the health issues associated with high stress levels, it is important to find new strategies to regulate stress response. Previous research has examined the separate effects of fitness level and stress reappraisal on the stress response, but the combination of both factors is unknown. The goal of the study was to examine the combined effects of fitness and stress appraisal on stress responses and cognitive performance following a stressful event.

METHOD

On 2 separate days, 24 highly and poorly fit young men (Mage = 22.33, SD = 3.33) were exposed to a validated stress test and were induced to view their stress as facilitative or debilitative. Objective and subjective stress responses along with cognitive performance were evaluated before and immediately after the stress test.

RESULTS

Participants in the high-fit/negative appraisal condition reported lower anxiety scores than participants in the low-fit/negative appraisal condition (d = 1.04). Participants had higher levels of cortisol after the stress test (d = 0.31), but no difference in heart rate, cortisol, or cognitive performance emerged among the conditions.

CONCLUSION

Fitness level might have a larger impact on stress response than stress appraisal, and stress reappraisal manipulations require more than just reading a note and a self-talk statement.

Effectiveness of enhancing cognitive reserve in children, adolescents and young adults at genetic risk for psychosis: Study protocol for a randomized controlled trial

BACKGROUND

Offspring of patients diagnosed with bipolar disorder and schizophrenia (Off-BDSZ) have a high genetic risk of developing a mental illness. The aim of this project is to develop and investigate the efficacy of an intervention aimed at this population, based on the concept of cognitive reserve.

METHODS

This is a multicenter randomized trial with an experimental test-retest design study with control group. Two groups will be included: a community comparison group (CC) and a Off-BDSZ group. A total of 108 Off-BDSZ and 65 CC aged between 6 and 25 years will be recruited. Off-BDSZ participants will be randomized to receive either Cognitive Reserve EnhAncement ThErapy (CREATE) (n=54), or a supportive approach (n=54). The CC group will be assessed at baseline. The duration of the intervention will be 3 months, with 12 weekly group sessions. The primary outcome will be the improvement in CR measured according to change in the Cognitive Reserve Assessment Scale in Health (CRASH) and Cognitive Reserve scale for Adolescents (CORE-A). All participants will be blindly evaluated using clinical, cognitive and neuroimaging measures at baseline, at three months (after the psychological intervention), and at twelve-month follow-up after treatment completion.

DISCUSSION

The results will provide insight into whether the CREATE-Offspring version may enhance cognitive reserve (CR) in child, adolescent and young adult Off-BDSZ as well as advance knowledge about changes in clinical manifestations, neuropsychological performance and brain structure and function associated with improving CR. This novel and cost-effective intervention represents an advance in the framework of preventive interventions in mental health.

TRIAL REGISTRATION

Clinicaltrials.gov, NCT03722082. Registered on 26 October 2018.

Association of social participation and psychological resilience with adverse cognitive outcomes among older Chinese adults: A national longitudinal study

BACKGROUND

Limited epidemiological evidence exists regarding the association of social participation and psychological resilience with cognitive health. This study aimed to comprehensively investigate the effects of social participation and psychological resilience on adverse cognitive outcomes among older adults in China.

METHODS

We used two waves (2011 and 2014) of data from the Chinese Longitudinal Survey of Health and Longevity (CLHLS), and 9765 respondents were eligible for the subsequent screening for the present prospective analysis. The Cox proportional hazards model was utilized to examine the association of social participation and psychological resilience with cognitive impairment, cognitive decline and greater cognitive decline. The restricted cubic spline plots were applied to clarify the dose-response relationships between them.

RESULTS

Compared to those with low social participation, participants with high social participation had a lower hazard ratio (HR) of 0.72 (95 % confidence interval [CI]: 0.59-0.89) for cognitive impairment, 0.85 (95 % CI: 0.76-0.94) for cognitive decline and 0.78 (95 % CI: 0.67-0.90) for greater cognitive decline. Participants with high psychological resilience had an HR of 0.77 (95 % CI: 0.63-0.95) for cognitive impairment 0.85 (95 % CI: 0.76-0.94) for cognitive decline and 0.85 (95 % CI: 0.73-0.98) for greater cognitive decline compared with those with low psychological resilience. Similar effects were observed for social participation score and psychological resilience score. The dose-response analysis also showed that the risk of adverse cognitive outcomes decreased gradually with increasing social participation scores and psychological resilience scores. Additionally, the multiplicative interaction between social participation and psychological resilience was not significant.

LIMITATION

All information was collected by self-report, which may lead to biases in the process of information collection.

CONCLUSION

In this study, social participation and psychological resilience were independently associated with a lower risk of adverse cognitive outcomes, and therefore both need to be considered as broader measures to preserve cognitive health among older Chinese adults.

Predictors of 10-year functional independence trajectories in older adults with traumatic brain injury: A Model Systems study

BACKGROUND

Older adults have the highest traumatic brain injury (TBI)-related morbidity and mortality, and rates in older adults are increasing, chiefly due to falls.

OBJECTIVE

This study used hierarchical linear modeling (HLM) to examine baseline predictors of functional independence trajectories across 1, 2, 5, and 10 years after TBI in older adults.

METHODS

Participants comprised 2,459 individuals aged 60 or older at the time of TBI, enrolled in the longitudinal TBI Model Systems database, and had Functional Independence Measure Motor and Cognitive subscale scores and Glasgow Outcome Scale-Extended scores during at least 1 time point.

RESULTS

Functional independence trajectories generally declined over the 10 years after TBI. Individuals who were older, male, underrepresented minorities, had lower education, were unemployed at time of injury, had no history of substance use disorder, or had difficulties with learning, dressing, and going out of the home prior to the TBI, or longer time in posttraumatic amnesia had lower functional independence trajectories across at least one of the functional independence outcomes.

CONCLUSION

These predictors of functional independence in older adults with TBI may heighten awareness of these factors in treatment planning and long-term health monitoring and ultimately as a way to decrease morbidity and mortality.

Proportional Changes in Cognitive Subdomains During Normal Brain Aging

Background: Neuroscience lacks a reliable method of screening the early stages of dementia. Objective: To improve the diagnostics of age-related cognitive functions by developing insight into the proportionality of age-related changes in cognitive subdomains. Materials and Methods: We composed a battery of psychophysiological tests and collected an open-access psychophysiological outcomes of brain atrophy (POBA) dataset by testing individuals without dementia. To extend the utility of machine learning (ML) classification in cognitive studies, we proposed estimates of the disproportional changes in cognitive functions: an index of simple reaction time to decision-making time (ISD), ISD with the accuracy performance (ISDA), and an index of performance in simple and complex visual-motor reaction with account for accuracy (ISCA). Studying the distribution of the values of the indices over age allowed us to verify whether diverse cognitive functions decline equally throughout life or there is a divergence in age-related cognitive changes. Results: Unsupervised ML clustering shows that the optimal number of homogeneous age groups is four. The sample is segregated into the following age-groups: Adolescents ∈ [0, 20), Young adults ∈ [20, 40), Midlife adults ∈ [40, 60) and Older adults ≥60 year of age. For ISD, ISDA, and ISCA values, only the median of the Adolescents group is different from that of the other three age-groups sharing a similar distribution pattern (p > 0.01). After neurodevelopment and maturation, the indices preserve almost constant values with a slight trend toward functional decline. The reaction to a moving object (RMO) test results (RMO_mean) follow another tendency. The Midlife adults group's median significantly differs from the remaining three age subsamples (p < 0.01). No general trend in age-related changes of this dependent variable is observed. For all the data (ISD, ISDA, ISCA, and RMO_mean), Levene's test reveals no significant changes of the variances in age-groups (p > 0.05). Homoscedasticity also supports our assumption about a linear dependency between the observed features and age. Conclusion: In healthy brain aging, there are proportional age-related changes in the time estimates of information processing speed and inhibitory control in task switching. Future studies should test patients with dementia to determine whether the changes of the aforementioned indicators follow different patterns.

Hippocampal resting-state functional connectivity with the mPFC and DLPFC moderates and mediates the association between education level and memory function in subjective cognitive decline

Objective:

This study aims to determine the relationship between education level, memory function, and hippocampus functional and structural alterations in subjective cognitive decline (SCD).

Methods:

Seventy-five participants with SCD were divided into high education (HE) and low education (LE) level groups. A Wechsler Memory Scale–Chinese Revision test and functional and structural MRI were performed within 1 week after participant recruitment. The bilateral hippocampus resting-state functional connectivity (rsFC), gray matter volume (GMV) of brain regions identified by rsFC analysis, and moderating and mediating effects were assessed.

Results:

Compared with the LE group, HE individuals showed 1) higher memory quotient (MQ) and Digit Span subscore, 2) decreased hippocampal rsFC with the right medial prefrontal cortex (mPFC) and dorsolateral prefrontal cortex (DLPFC), and 3) increased GMV in the right mPFC and DLPFC. The bilateral hippocampus–right DLPFC rsFC significantly associated with the MQ and the bilateral hippocampus–right mPFCrsFC with the Digit Span subscore in each group. The bilateral hippocampus–right DLPFC rsFC moderated the relationship between the education level and MQ. The bilateral hippocampus–right mPFC rsFC mediated the relationship between the education level and Digit Span subscore in all subjects.

Conclusion:

The hippocampal rsFC with the right mPFC and DLPFC contributes to the education level effect on memory function in SCD.

Pathobiological Subtypes of Alzheimer Disease

Alzheimer disease (AD), the most common form of dementia, is a heterogenous disorder with various pathobiological subtypes. In addition to the 4 major subtypes based on the distribution of tau pathology and brain atrophy (typical, limbic predominant, hippocampal sparing, and minimal atrophy [MA]), several other clinical variants showing distinct regional patterns of tau burden have been identified: nonamnestic, corticobasal syndromal, primary progressive aphasia, posterior cortical atrophy, behavioral/dysexecutive, and mild dementia variants. Among the subtypes, differences were found in age at onset, sex distribution, cognitive status, disease duration, APOE genotype, and biomarker levels. The patterns of key network destructions parallel the tau and atrophy patterns of the AD subgroups essentially. Interruption of key networks, in particular the default-mode network that is responsible for cognitive decline, is consistent in hetero-genous AD groups. AD pathology is often associated with co-pathologies: cerebrovascular lesions, Lewy pathology, and TDP-43 proteinopathies. These mixed pathologies essentially influence the clinical picture of AD and may accel-erate disease progression. Unraveling the heterogeneity among the AD spectrum entities is important for opening a window to pathogenic mechanisms affecting the brain and enabling precision medicine approaches as a basis for developing preventive and ultimately successful disease-modifying therapies for AD.

How repetitive traumatic injury alters long-term brain function

BACKGROUND

How recurrent traumatic brain injury (rTBI) alters brain function years after insult is largely unknown. This study aims to characterize the mechanistic cause for long-term brain deterioration following rTBI using a rat model.

METHODS

Eighteen Sprague-Dawley wild-type rats underwent bilateral rTBI using a direct skull impact device or sham treatment, once per week for 5 weeks, and were euthanized 56 weeks after the first injury. Weekly rotarod performance measured motor deficits. Beam walk and grip strength were also assessed. Brain tissue were stained and volume was computed using Stereo Investigator's Cavalieri Estimator. The L5 cortical layer proximal to the injury site was microdissected and submitted for sequencing with count analyzed using R "DESeq2" and "GOStats." Brain-derived neurotrophic factor (BDNF) levels were determined using enzyme-linked immunosorbent assay.

RESULTS

Rotarod data demonstrated permanent deficits 1 year after rTBI. Decreased beam walk performance and grip strength was noted among rTBI rodents. Recurrent traumatic brain injury led to thinner cortex and thinner corpus callosum, enlarged ventricles, and differential expression of 72 genes (25 upregulated, 47 downregulated) including dysregulation of those associated with TBI (BDNF, NR4A1/2/3, Arc, and Egr) and downregulation in pathways associated with neuroprotection and neuroplasticity. Over the course of the study, BDNF levels decreased in both rTBI and sham rodents, and at each time point, the decrease in BDNF was more pronounced after rTBI.

CONCLUSION

Recurrent traumatic brain injury causes significant long-term alteration in brain health leading to permanent motor deficits, cortical and corpus callosum thinning, and expansion of the lateral ventricles. Gene expression and BDNF analysis suggest a significant drop in pathways associated with neuroplasticity and neuroprotection. Although rTBI may not cause immediate neurological abnormalities, continued brain deterioration occurs after the initial trauma in part due to a decline in genes associated with neuroplasticity and neuroprotection.

The basis of cellular and regional vulnerability in Alzheimer's disease

Alzheimer's disease (AD) differentially and specifically affects brain regions and neuronal cell types in a predictable pattern. Damage to the brain appears to spread and worsens with time, taking over more regions and activating multiple stressors that can converge to promote vulnerability of certain cell types. At the same time, other cell types and brain regions remain intact in the face of this onslaught of neuropathology. Although neuropathologic descriptions of AD have been extensively expanded and mapped over the last several decades, our understanding of the mechanisms underlying how certain regions and cell populations are specifically vulnerable or resistant has lagged behind. In this review, we detail what is known about the selectivity of local initiation of AD pathology in the hippocampus, its proposed spread via synaptic connections, and the diversity of clinical phenotypes and brain atrophy patterns that may arise from different fibrillar strains of pathologic proteins or genetic predispositions. We summarize accumulated and emerging knowledge of the cellular and molecular basis for neuroanatomic selectivity, consider potential disease-relevant differences between vulnerable and resistant neuronal cell types and isolate molecular markers to identify them.

Newly Generated and Non-Newly Generated "Immature" Neurons in the Mammalian Brain: A Possible Reservoir of Young Cells to Prevent Brain Aging and Disease?

Brain plasticity is important for translational purposes since most neurological disorders and brain aging problems remain substantially incurable. In the mammalian nervous system, neurons are mostly not renewed throughout life and cannot be replaced. In humans, the increasing life expectancy explains the increase in brain health problems, also producing heavy social and economic burden. An exception to the “static” brain is represented by stem cell niches leading to the production of new neurons. Such adult neurogenesis is dramatically reduced from fish to mammals, and in large-brained mammals with respect to rodents. Some examples of neurogenesis occurring outside the neurogenic niches have been reported, yet these new neurons actually do not integrate in the mature nervous tissue. Non-newly generated, “immature” neurons (nng-INs) are also present: Prenatally generated cells continuing to express molecules of immaturity (mostly shared with the newly born neurons). Of interest, nng-INs seem to show an inverse phylogenetic trend across mammals, being abundant in higher-order brain regions not served by neurogenesis and providing structural plasticity in rather stable areas. Both newly generated and nng-INs represent a potential reservoir of young cells (a “brain reserve”) that might be exploited for preventing the damage of aging and/or delay the onset/reduce the impact of neurological disorders.