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 role of pre-morbid intelligence and cognitive reserve in predicting cognitive efficiency in a sample of Italian elderly

BACKGROUND

Models of cognitive reserve in aging suggest that individual's life experience (education, working activity, and leisure) can exert a neuroprotective effect against cognitive decline and may represent an important contribution to successful aging.

AIM

The objective of the present study is to investigate the role of cognitive reserve, pre-morbid intelligence, age, and education level, in predicting cognitive efficiency in a sample of healthy aged individuals and with probable mild cognitive impairment.

METHODS

Two hundred and eight aging participants recruited from the provincial region of Bari (Apulia, Italy) took part in the study. A battery of standardized tests was administered to them to measure cognitive reserve, pre-morbid intelligence, and cognitive efficiency. Protocols for 10 participants were excluded since they did not meet inclusion criteria, and statistical analyses were conducted on data from the remaining 198 participants. A path analysis was used to test the following model: age, education level, and intelligence directly influence cognitive reserve and cognitive efficiency; cognitive reserve mediates the influence of age, education level, and intelligence on cognitive efficiency.

RESULTS

Cognitive reserve fully mediates the relationship between pre-morbid intelligence and education level and cognitive efficiency, while age maintains a direct effect on cognitive efficiency.

DISCUSSION

Cognitive reserve appears to exert a protective effect regarding cognitive decline in normal and pathological populations, thus masking, at least in the early phases of neurodegeneration, the decline of memory, orientation, attention, language, and reasoning skills.

CONCLUSIONS

The assessment of cognitive reserve may represent a useful evaluation supplement in neuropsychological screening protocols of cognitive decline.

Bilingualism in older Mexican-American immigrants is associated with higher scores on cognitive screening

Background

Bilingualism may protect against cognitive aging and delay the onset of dementia. However, studies comparing monolinguals and bilinguals on such metrics have produced inconsistent results complicated by confounding variables and methodological concerns.

Methods

We addressed this issue by comparing cognitive performance in a more culturally homogeneous cohort of older Spanish-speaking monolingual (n = 289) and Spanish-English bilingual (n = 339) Mexican-American immigrants from the Sacramento Longitudinal Study on Aging.

Results

After adjusting for demographic differences and depressive symptoms, both groups performed similarly at baseline on verbal memory but the bilingual group performed significantly better than the monolingual group on a cognitive screening test, the Modified Mini-Mental State Examination (3MS; p < 0.001). Group differences on the 3MS were driven by language/executive and language/praxis factors. Within the bilingual group, neither language of testing nor degree of bilingualism was significantly associated with 3MS or verbal memory scores. Amongst individuals who performed in the normal or better range on both tests at baseline and were followed for an average of 6 years, both monolinguals and bilinguals exhibited similar rates of cognitive decline on both measures.

Conclusions

These findings suggest that bilingualism is associated with modest benefits in cognitive screening performance in older individuals in cross-sectional analyses that persist across longitudinal analyses. The effects of bilingualism should be considered when cognitively screening is performed in aging immigrant populations.

Electronic supplementary material

The online version of this article (doi:10.1186/s12877-016-0368-1) contains supplementary material, which is available to authorized users.

Social Network Size and Cognitive Functioning in Middle-Aged Adults: Cross-Sectional and Longitudinal Associations

The objective of the present study was to examine relations between social network size and three cognitive abilities (episodic memory, semantic memory, visuospatial ability) in middle-aged adults. We analyzed cross-sectional data on social network size and cognitive functioning that were available for 804 participants aged 40–60 years. In addition, we examined 5- and 10-year follow-up measurements of cognitive functioning that were available for 604 and 255 participants, respectively. Cross-sectional analyses revealed a positive association between social network size and each of the three cognitive abilities. Baseline network size was positively related to 5-year changes in semantic memory, and to 10-year changes in semantic as well as episodic memory, but was unrelated to changes in visuospatial performance. A minor portion of the sample (n = 131) had 10-year follow-up data on network size. Cross-lagged panel correlations revealed that baseline network size was associated with follow-up measurement in cognitive functioning (episodic memory, semantic memory), whereas baseline cognitive performance was unrelated to future network size. Together, the results demonstrate a small but positive relation between network size and declarative memory abilities, in line with models proposing a cognitive reserve built up by factors such as the increased cognitive stimulation associated with a more extensive social network.

Premorbid exercise engagement and motor reserve in Parkinson's disease

BACKGROUND

Life-long experiences of cognitive activity could enhance cognitive reserve, which may lead individuals to show less cognitive deficits in Alzheimer's disease, despite similar pathological changes. We performed this study to test whether premorbid physical activity may enhance motor reserve in Parkinson's disease (PD) (i.e., less motor deficits despite similar degrees of dopamine depletion).

METHODS

We assessed engagement in premorbid leisure-time exercise among 102 drug naive PD patients who had been initially diagnosed at our hospital by dopamine transporter scanning. Patients were classified into tertile groups based on the frequency, duration, and intensity of the exercises in which they participated.

RESULTS

Among patients with mild to moderate reductions in striatal dopaminergic activity (above the median dopaminergic activity), the exercise group of the highest tertile showed significantly lower motor scores (i.e., fewer motor deficits, 15.53 ± 6.25), despite similar degrees of dopamine reduction, compared to the combined group of the middle and the lowest tertiles (21.57 ± 8.34, p = 0.01). Nonetheless, the highest tertile group showed a more rapid decline in motor function related to reductions in striatal dopaminergic activity than the other two groups (p = 0.002 with the middle tertile group and p = 0.001 with the lowest tertile group).

CONCLUSIONS

These results suggest that engagement in premorbid exercise acts as a proxy for an active reserve in the motor domain (i.e., motor reserve) in patients with PD.

Biology enters the scene-a new perspective on bilingualism, cognition, and dementia

The question of whether bilingualism can influence cognitive functions in healthy aging as well as in brain diseases is currently a topic of an intense debate. In a study published in this issue of the "Neurobiology of Ageing", Estanga et al. are breaking new ground by combining cognitive and biological approaches. Based on the data from the Guipuzkoa Alzheimer Project, they report that, compared with monolinguals, early bilinguals are not only characterized by a better cognitive performance in several domains and a lower prevalence of Alzheimer's disease but also by lower levels of t-tau in their cerebrospinal fluid. We suggest that sustained activation of noradrenergic signaling pathways associated with bilingualism could provide a possible mechanism linking results of this study with previous observations of delayed onset of dementia in bilinguals.

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.

Dual-task costs in aging are predicted by formal education

The capacity to manage different concurrent tasks at the same time decays in older adults. There is however a considerable amount of inter-individual variability in this capacity even in healthy aging. The purpose of this empirical study is to investigate which factors help explaining this variability. A dual-task paradigm was administered to 64 older adults and 31 younger controls. In this paradigm, a primary simple response time task had to be carried out either by itself (single-task condition) or while concurrently performing a secondary subtraction task (dual-task condition). Dual-task costs were operationalized by comparing dual-task and single-task conditions. Older adults showed higher dual-task interference than younger controls. Within the older group, the influence of age, general cognitive abilities, performance on the secondary task, and years of formal education was assessed with a multiple regression analysis. The results showed that years of formal education in older adults were the best predictor that significantly explained a portion of the variance in dual-task performance. These findings extend previous literature by showing that formal education provides an important dose of cognitive reserve, which is useful to successfully implement cognitive dual-task management despite aging.

Which types of mental work demands may be associated with reduced risk of dementia?

INTRODUCTION

Previous studies have demonstrated that an overall high level of mental work demands decreased dementia risk. In our study, we investigated whether this effect is driven by specific mental work demands and whether it is exposure dependent.

METHODS

Patients aged 75+ years were recruited from general practitioners and participated in up to seven assessment waves (every 1.5 years) of the longitudinal AgeCoDe study. Analyses of the impact of specific mental work demands on dementia risk were carried out via multivariate regression modeling (n = 2315).

RESULTS

We observed a significantly lower dementia risk in individuals with a higher level of "information processing" (HR, 0.888), "pattern detection" (HR, 0.878), "mathematics" (HR, 0.878), and "creativity" (HR, 0.878). Yet, exposure-dependent effects were only significant for "information processing" and "pattern detection."

DISCUSSION

Our longitudinal observations suggest that dementia risk may be reduced by some but not all types of mental work demands.

The conceptualization and measurement of cognitive reserve using common proxy indicators: Testing some tenable reflective and formative models

INTRODUCTION

The examination of cognitive reserve (CR) literature reveals a lack of consensus regarding conceptualization and pervasive problems with its measurement. This study aimed at examining the conceptual nature of CR through the analysis of reflective and formative models using eight proxies commonly employed in the CR literature. We hypothesized that all CR proxies would significantly contribute to a one-factor reflective model and that educational and occupational attainment would produce the strongest loadings on a single CR factor.

METHOD

The sample consisted of 149 participants (82 male/67 female), with 18.1 average years of education and ages of 45-99 years. Participants were assessed for eight proxies of CR (parent socioeconomic status, intellectual functioning, level of education, health literacy, occupational prestige, life leisure activities, physical activities, and spiritual and religious activities). Primary statistical analyses consisted of confirmatory factor analysis (CFA) to test reflective models and structural equation modeling (SEM) to evaluate multiple indicators multiple causes (MIMIC) models.

RESULTS

CFA did not produce compelling support for a unitary CR construct when using all eight of our CR proxy variables in a reflective model but fairly cogent evidence for a one-factor model with four variable proxies. A second three-factor reflective model based upon an exploratory principal components analysis of the eight proxies was tested using CFA. Though all eight indicators significantly loaded on their assigned factors, evidence in support of overall model fit was mixed. Based upon the results involving the three-factor reflective model, two alternative formative models were developed and evaluated. While some support was obtained for both, the model in which the formative influences were specified as latent variables appeared to best account for the contributions of all eight proxies to the CR construct.

CONCLUSION

While the findings provide partial support for our hypothesis regarding CR as a one-dimensional reflective construct, the results strongly suggest that the construct is more complex than what can be captured in a reflective model alone. There is a need for theory to better identify and differentiate formative from reflective indicators and to articulate the mechanisms by which CR develops and operates.

Middle age self-report risk score predicts cognitive functioning and dementia in 20-40 years

INTRODUCTION

On the basis of the proxy measures of cognitive reserve, we created a middle age self-report risk score for early prediction of dementia.

METHODS

We used a longitudinal population-based study of 2602 individuals with a replication sample (N = 1011). Risk score at a mean age of 47 years was based on questions on educational and occupational attainments. Cognitive status at a mean age of 74 was determined via two validated telephone instruments.

RESULTS

The prevalence of dementia was 10% after a mean follow-up of 28 years. Risk score was a good predictor of dementia: area under the curve = 0.77 (95% confidence interval, 0.74-0.80). The risk of dementia decreased as a function of risk score from 36% to 0%. The risk score was significantly associated with cognition after a mean follow-up of 39 years in the replication sample.

DISCUSSION

Self-report risk score predicted cognitive functioning and dementia risk 20-40 years later.

Education is associated with sub-regions of the hippocampus and the amygdala vulnerable to neuropathologies of Alzheimer's disease

We evaluated the correlation of educational attainment with structural volume and shape morphometry of the bilateral hippocampi and amygdalae in a sample of 110 non-demented, older adults at elevated sociodemographic risk for cognitive and functional declines. In both men and women, no significant education-volume correlation was detected for either structure. However, when performing shape analysis, we observed regionally specific associations with education after adjusting for age, intracranial volume, and race. By sub-dividing the hippocampus and the amygdala into compatible subregions, we found that education was positively associated with size variations in the CA1 and subiculum subregions of the hippocampus and the basolateral subregion of the amygdala (p < 0.05). In addition, we detected a greater left versus right asymmetric pattern in the shape-education correlation for the hippocampus but not the amygdala. This asymmetric association was largely observed in men versus women. These findings suggest that education in youth may exert direct and indirect influences on brain reserve in regions that are most vulnerable to the neuropathologies of aging, dementia, and specifically, Alzheimer disease.

Impact of literacy and years of education on the diagnosis of dementia: A population-based study

BACKGROUND

The effect of different educational indices on clinical diagnosis of dementia requires more investigation.

OBJECTIVE

We compared the differential influence of two educational indices (EIs): years of schooling and level of education (i.e., null/low literacy, can read and write, primary school, and secondary school) on global cognition, functional performance, and the probability of having a dementia diagnosis.

METHOD

A total of 3,816 participants were selected from the population-based study of older adults "Neurological Disorders in Central Spain" (NEDICES). The 37-item version of the Mini-Mental State Examination (MMSE-37) and the Pfeffer's questionnaire were applied to assess cognitive and functional performance, respectively. The diagnosis of dementia was performed by expert neurologists according to Diagnostic and Statistical Manual of Mental Disorders-Fourth Edition (DSM-IV) criteria. Logistic regression models adjusted for potential confounders were carried out to test the association between the two EIs and dementia diagnosis.

RESULTS

Both EIs were significantly associated with cognitive and functional scores, but individuals with null/low literacy performed significantly worse on MMSE-37 than literates when these groups were compared in terms of years of schooling. The two EIs were also related to an increased probability of dementia diagnosis in logistic models, but the association's strength was stronger for level of education than for years of schooling.

CONCLUSION

Literacy predicted cognitive performance over and above the years of schooling. Lower education increases the probability of having a dementia diagnosis but the impact of different EIs is not uniform.

Impact of duration of untreated psychosis and premorbid intelligence on cognitive functioning in patients with first-episode schizophrenia

BACKGROUND

The neurotoxic hypothesis suggests that psychosis is toxic to the brain leading to clinical consequences. In this study, we hypothesized that a longer duration of untreated psychosis (DUP) in first episode schizophrenia (FES) patients is associated with poorer cognitive functioning, and that higher premorbid intelligence buffers against DUP-related cognitive impairment.

METHOD

Eighty-one FES patients completed a neuropsychological battery, the Brief Assessment of Cognition in Schizophrenia (BACS). Composite scores of the BACS, which were normalized to a matched healthy control of seventy-three subjects, were used as an index of general cognition. A median split using the Wide Range Achievement Test-Reading Test scores was used to divide the patients into low versus high premorbid IQ groups. Hierarchical linear regression was performed to examine predictors of general cognition, including DUP.

RESULTS

Longer DUP was found to be a significant predictor of poorer general cognition. In addition, DUP predicted general cognition in the low premorbid IQ group but not in the high premorbid IQ group.

CONCLUSIONS

Our findings demonstrate that longer DUP in FES patients is associated with worse cognitive scores, and that this association is more pronounced in a subgroup of patients who have lower premorbid intelligence. Our results suggest the importance of earlier identification and management of patients with low premorbid IQ, given that their cognition may be more vulnerable to the toxicity of psychosis.

The relation of the number of languages spoken to performance in different cognitive abilities in old age

INTRODUCTION

Findings on the association of speaking different languages with cognitive functioning in old age are inconsistent and inconclusive so far. Therefore, the present study set out to investigate the relation of the number of languages spoken to cognitive performance and its interplay with several other markers of cognitive reserve in a large sample of older adults.

METHOD

Two thousand eight hundred and twelve older adults served as sample for the present study. Psychometric tests on verbal abilities, basic processing speed, and cognitive flexibility were administered. In addition, individuals were interviewed on their different languages spoken on a regular basis, educational attainment, occupation, and engaging in different activities throughout adulthood.

RESULTS

Higher number of languages regularly spoken was significantly associated with better performance in verbal abilities and processing speed, but unrelated to cognitive flexibility. Regression analyses showed that the number of languages spoken predicted cognitive performance over and above leisure activities/physical demand of job/gainful activity as respective additional predictor, but not over and above educational attainment/cognitive level of job as respective additional predictor. There was no significant moderation of the association of the number of languages spoken with cognitive performance in any model.

CONCLUSIONS

Present data suggest that speaking different languages on a regular basis may additionally contribute to the build-up of cognitive reserve in old age. Yet, this may not be universal, but linked to verbal abilities and basic cognitive processing speed. Moreover, it may be dependent on other types of cognitive stimulation that individuals also engaged in during their life course.

Different reserve proxies confer overlapping and unique endurance to cortical thinning in healthy middle-aged adults

AIM

To investigate different proxies of brain and cognitive reserve as potential mediators of the effect of cortical thinning on cognition in healthy middle-aged adults.

METHODS

Eighty-two middle-aged individuals were included (mean(SD) age=45.1(3.9)years). Cortical thickness was calculated for multiple brain regions using FreeSurfer. Cognitive measures sensitive to early cognitive decline were selected, including Block Design from the Wechsler Adult Intelligence Scale-III (WAIS-III), Judgment of Line Orientation Test (JLOT), Color Trails Test (CTT), and first learning trial of TAVEC (the Spanish version of the California Verbal Learning Test, CVLT). Brain reserve was operationalized as total intracranial volume (TIV); and cognitive reserve was estimated by means of Years of Education, WAIS-III Vocabulary subtest, WAIS-III Information subtest, and a Cognitive Reserve Questionnaire (CRQ). Mediation effects were investigated with multiple linear regression and bootstrapping analysis.

RESULTS

Information and Vocabulary showed the greatest mediation capacity. All the observed mediations were positive indicating that higher levels of reserve attenuate the effect of reduced cortical thickness on cognition. Information, Vocabulary and TIV buffered the effect of frontal thinning on Block Design; Vocabulary and Years of Education buffered the effect of frontal thinning on JLOT; and CRQ buffered the effect of temporal thinning on CTT.

CONCLUSION

Higher reserve buffers the effect of cortical thinning on cognition in healthy middle-aged adults. The investigated proxies might be underpinned by slightly different neural networks. Advancing in the understanding of the influences of reserve in healthy middle-aged adults is crucial to facilitate early interventions.

Aging in two languages: Implications for public health

With the population aging and a dramatic increase in the number of senior citizens, public health systems will be increasingly burdened with the need to deal with the care and treatment of individuals with dementia. We review evidence demonstrating how a particular experience, bilingualism, has been shown to protect cognitive function in older age and delay onset of symptoms of dementia. This paper describes behavioral and brain studies that have compared monolingual and bilingual older adults on measures of cognitive function or brain structure and reviews evidence demonstrating a protective effect of bilingualism against symptoms of dementia. We conclude by presenting some data showing the potential savings in both human costs in terms of demented patients and economic considerations in terms of public money if symptoms of dementia could be postponed.

Influence of Educational Attainment on Cognition-Based Intervention Programs for Persons with Mild Alzheimer's Disease

OBJECTIVES

This research retrospectively analyzed the effect of education on cognitive interventions carried out in patients with mild Alzheimer's disease (AD).

METHODS

The total sample consisted of 75 patients with mild AD receiving treatment with cholinesterase inhibitors. The participants were divided into two groups: cognitive intervention (IG; n=45) and waiting list (WLG; n=30). Patients in the IG received either the Big Brain Academy (n=15) or the Integrated Psychostimulation Program (n=30) during 12 weeks. The influence of education on intervention effect was analyzed comparing mean change scores of the two study groups in the cognitive subscale of the Alzheimer's Disease Assessment Scale (ADAS-cog), stratified by educational level. The potential effect of age, sex, cognitive status, and type of intervention was examined using post hoc stratification analyses.

RESULTS

Higher education was associated with faster cognitive decline in the WLG (effect size=0.51; p<.01). However, cognitive evolution was not influenced by education in the IG (effect size=0.12; p=.42).

CONCLUSIONS

Our results suggest that cognitive intervention might delay accelerated cognitive decline in higher educated individuals with mild AD.

Breath-based meditation: A mechanism to restore the physiological and cognitive reserves for optimal human performance

Stress can be associated with many physiological changes resulting in significant decrements in human performance. Due to growing interests in alternative and complementary medicine by Westerners, many of the traditions and holistic yogic breathing practices today are being utilized as a measure for healthier lifestyles. These state-of-the-art practices can have a significant impact on common mental health conditions such as depression and generalized anxiety disorder. However, the potential of yogic breathing on optimizing human performance and overall well-being is not well known. Breathing techniques such as alternate nostril, Sudarshan Kriya and bhastrika utilizes rhythmic breathing to guide practitioners into a deep meditative state of relaxation and promote self-awareness. Furthermore, yogic breathing is physiologically stimulating and can be described as a natural “technological” solution to optimize human performance which can be categorized into: (1) cognitive function (i.e., mind, vigilance); and (2) physical performance (i.e., cardiorespiratory, metabolism, exercise, whole body). Based on previous studies, we postulate that daily practice of breathing meditation techniques play a significant role in preserving the compensatory mechanisms available to sustain physiological function. This preservation of physiological function may help to offset the time associated with reaching a threshold for clinical expression of chronic state (i.e., hypertension, depression, dementia) or acute state (i.e., massive hemorrhage, panic attic) of medical conditions. However, additional rigorous biomedical research is needed to evaluate the physiological mechanisms of various forms of meditation (i.e., breath-based, mantra, mindfulness) on human performance. These efforts will help to define how compensatory reserve mechanisms of cardiovascular and immune systems are modulated by breath-based meditation. While it has been suggested that breath-based meditation is easier for beginning practitioners when compared to other forms of meditation more research is needed to elucidate these observations. A breath-based meditation sequence such as Sudarshan Kriya has the potential to help develop an individual’s self-awareness and support better integration of the brain (i.e., mind) with other organ systems (i.e., body) for enhanced human performance.

Neuropsychological Practice Effects in the Context of Cognitive Decline: Contributions from Learning and Task Novelty

Although cognitive decline is typically associated with decreasing practice effects (PEs) (presumably due to declining memory), some studies show increased PEs with declines in cognition. One explanation for these inconsistencies is that PEs reflect not only memory, but also rebounds from adapting to task novelty (i.e., novelty effect), leading to increased PEs. We examined a theoretical model of relationships among novelty effects, memory, cognitive decline, and within-session PEs. Sixty-six older adults ranging from normal to severely impaired completed measures of memory, novelty effects, and two trials each of Wechsler Adult Intelligence Scale, 4 th Edition Symbol Search and Coding. Interrelationships among variables were examined using regression analyses. PEs for Symbol Search and Coding (a) were related to different proposed PE components (i.e., memory and novelty effects), such that novelty effect predicted Symbol Search PE (R2 =.239, p<.001) and memory predicted Coding PE (R2 =.089, p=.015), and (b) showed different patterns across stages of cognitive decline, such that the greatest cognitive decline was associated with smallest Coding PE (R2 =.125, p=.004), whereas intermediate cognitive decline was associated with the greatest Symbol Search PE (R2 =.097, p=.040). The relationship between cognitive decline and PE for Symbol Search was partially mediated by novelty effect among older adults with abnormal cognitive decline (model R2 =.286, p<.001). These findings (a) suggest that PE is not a unitary construct, (b) offer an explanation for contradictory findings in the literature, and (c) highlight the need for a better understanding of component processes of PE across different neuropsychological measures.

Life-long music practice and executive control in older adults: An event-related potential study

Recent research has indicated that music practice can influence cognitive processing across the lifespan. Although extensive musical experience may have a mitigating effect on cognitive decline in older adults, the nature of changes to brain functions underlying performance benefits remains underexplored. The present study was designed to investigate the underlying neural mechanisms that may support apparent beneficial effects of life-long musical practice on cognition. We recorded event-related potentials (ERPs) in older musicians (N=17; average age=69.2) and non-musicians (N=17; average age=69.9), matched for age and education, while they completed an executive control task (visual go/no-go). Whereas both groups showed similar response speed and accuracy on go trials, older musicians showed fewer no-go errors. ERP recordings revealed the typical N2/P3 complex, but the nature of these responses differed between groups in that (1) older musicians showed larger N2 and P3 effects ('no-go minus go' amplitude), with the N2 amplitude being correlated with behavioral accuracy for no-go trials and (2) the topography of the P3 response was more anterior in musicians. Moreover, P3 amplitude was correlated with measures of musical experience in musicians. In our discussion of these results, we propose that music practice may have conferred an executive control advantage for musicians in later life.

Childhood school performance, education and occupational complexity: a life-course study of dementia in the Kungsholmen Project

BACKGROUND

Cognitive reserve hypothesis predicts that intellectually demanding activities over the life course protect against dementia. We investigate if childhood school performance remains associated with dementia once education and occupational complexity are taken into account.

METHODS

A cohort of 440 individuals aged 75+ from the Kungsholmen Project was followed up for 9 years to detect dementia. To measure early-life contributors to reserve, we used grades at age 9-10 extracted from the school archives. Data on formal education and occupational complexity were collected at baseline and first follow-up. Dementia was ascertained through comprehensive clinical examination. Cox models estimated the relationship between life-course cognitive reserve measures and dementia.

RESULTS

Dementia risk was elevated [hazard ratio (HR): 1.54, 95% confidence interval (CI): 1.03 to 2.29] in individuals with low early-life school grades after adjustment for formal educational attainment and occupational complexity. Secondary education was associated with a lower risk of dementia (HR: 0.72, 95% CI: 0.50 to 1.03), although the effects of post-secondary and university degrees were indistinguishable from baseline. Occupational complexity with data and things was not related to dementia. However, an association was found between high occupational complexity with people and dementia, albeit only in women (HR: 0.39, 95% CI: 0.14 to 0.99). The pattern of results remained unchanged after adjustment for genetic susceptibility, comorbidities and depressive symptoms.

CONCLUSION

Low early-life school performance is associated with an elevated risk of dementia, independent of subsequent educational and occupational attainment.

Cognitive reserve and neuropsychological functioning in older HIV-infected people

Progress in treatments has led to HIV+ patients getting older. Age and HIV are risk factors for neurocognitive impairment (NCI). We explored the role of cognitive reserve (CR) on cognition in a group of virologically suppressed older HIV+ people. We performed a multicenter study, consecutively enrolling asymptomatic HIV+ subjects ≥60 years old during routine outpatient visits. A comprehensive neuropsychological battery was administered. Raw test scores were adjusted based on Italian normative data and transformed into z-scores; NCI was defined according to Frascati criteria. All participants underwent the Brief Intelligence Test (TIB) and the Cognitive Reserve Index (CRI) questionnaire as proxies for CR. Relationships between TIB, CRI, and NCI were investigated by logistic or linear regression analyses. Sixty patients (85 % males, median age 66, median education 12, 10 % HCV co-infected, 25 % with past acquired immunodeficiency syndrome (AIDS)-defining events, median CD4 cells count 581 cells/μL, median nadir CD4 cells count 109 cells/μL) were enrolled. Twenty-four patients (40 %) showed Asymptomatic Neurocognitive Impairment. At logistic regression analysis, only CRI (OR 0.94; 95 % CI 0.91-0.97; P = 0.001) and TIB (OR 0.80; 95 % CI 0.71-0.90; P < 0.001) were associated with a lower risk of NCI. Higher CRI and TIB were significantly correlated with a better performance (composite z-score) both globally and at individual cognitive domains. Our findings highlight the role of CR over clinical variables in maintaining cognitive integrity in a virologically suppressed older HIV-infected population. A lifestyle characterized by experiences of mental stimulation may help to cope aging and HIV-related neurodegeneration.

General Mathematical Ability Predicts PASAT Performance in MS Patients: Implications for Clinical Interpretation and Cognitive Reserve

OBJECTIVES

The Paced Auditory Serial Addition Test (PASAT) is used to assess cognitive status in multiple sclerosis (MS). Although the mathematical demands of the PASAT seem minor (single-digit arithmetic), cognitive psychology research links greater mathematical ability (e.g., algebra, calculus) to more rapid retrieval of single-digit math facts (e.g., 5+6=11). The present study evaluated the hypotheses that (a) mathematical ability is related to PASAT performance and (b) both the relationship between intelligence and PASAT performance as well as the relationship between education and PASAT performance are both mediated by mathematical ability.

METHODS

Forty-five MS patients were assessed using the Wechsler Test of Adult Reading, PASAT and Calculation Subtest of the Woodcock-Johnson-III. Regression based path analysis and bootstrapping were used to compute 95% confidence intervals and test for mediation.

RESULTS

Mathematical ability (a) was related to PASAT (β=.61; p<.001) and (b) fully mediated the relationship between Intelligence and PASAT (β=.76; 95% confidence interval (CI95)=.28, 1.45; direct effect of Intelligence, β=.42; CI95=-.39, 1.23) as well as the relationship between Education and PASAT (β=2.43, CI95=.81, 5.16, direct effect of Education, β=.83, CI95=-1.95, 3.61).

DISCUSSION

Mathematical ability represents a source of error in the clinical interpretation of cognitive decline using the PASAT. Domain-specific cognitive reserve is discussed.

An index predictive of cognitive outcome in retired professional American Football players with a history of sports concussion

OBJECTIVE

Various concussion characteristics and personal factors are associated with cognitive recovery in athletes. We developed an index based on concussion frequency, severity, and timeframe, as well as cognitive reserve (CR), and we assessed its predictive power regarding cognitive ability in retired professional football players.

METHOD

Data from 40 retired professional American football players were used in the current study. On average, participants had been retired from football for 20 years. Current neuropsychological performances, indicators of CR, concussion history, and play data were used to create an index for predicting cognitive outcome.

RESULTS

The sample displayed a range of concussions, concussion severities, seasons played, CR, and cognitive ability. Many of the participants demonstrated cognitive deficits. The index strongly predicted global cognitive ability (R(2) = .31). The index also predicted the number of areas of neuropsychological deficit, which varied as a function of the deficit classification system used (Heaton: R(2) = .15; Wechsler: R(2) = .28).

CONCLUSIONS

The current study demonstrated that a unique combination of CR, sports concussion, and game-related data can predict cognitive outcomes in participants who had been retired from professional American football for an average of 20 years. Such indices may prove to be useful for clinical decision making and research.

Right fronto-insular white matter tracts link cognitive reserve and pain in migraine patients

BACKGROUND

Structural white matter abnormalities in pain-modulating, regions are present in migraine. Whether they are associated with pain chronification and with cognitive reserve is unclear.

METHODS

Prospective, cohort, six-month study of adult patients with episodic or chronic migraine, and controls. Cognitive reserve, quality of life, impact of pain on daily living, depression and anxiety were assessed. Participants underwent a diffusion-tensor MRI to establish the integrity of white matter tracts of three regions of interest (ROIs) implicated in pain modulation, emotion, cognition and resilience (anterior insula, anterior cingulate gyrus, and uncinate fasciculus).

RESULTS

Fifty-two individuals were enrolled: 19 episodic migraine patients, 18 chronic migraine patients, and 15 controls. The analysis of the fractional anisotropy in the ROIs showed that those patients with the poorest prognosis (i.e., those with chronic migraine despite therapy at six months--long-term chronic migraneurs) had a significantly lower fractional anisotropy in the right ROIs. Participants with higher cognitive reserve also had greater fractional anisotropy in the right anterior insula and both cingulate gyri. Multivariate analysis showed a significant association between cognitive reserve, migraine frequency, and fractional anisotropy in the right-sided regions of interest.

CONCLUSIONS

Long-term chronic migraine patients show abnormalities in anterior white matter tracts, particularly of the right hemisphere, involved in pain modulation emotion, cognition and resilience. Robustness in these areas is associated with a higher cognitive reserve, which in turn might result in a lower tendency to migraine chronification.

Cerebral correlates of cognitive reserve

Cognitive reserve is a hypothetical concept introduced to explain discrepancies between severity of clinical dementia syndromes and the extent of dementia pathology. We examined cognitive reserve in a research programme that followed up a non-clinical sample born in 1921 or 1936 and IQ-tested age 11 years in 1932 or 1947. Structural MRI exams were acquired in about 50% of the sample from whom a subsample were recruited into an additional fMRI study. Here, we summarise findings from seven inter-related studies. These support an understanding of cognitive reserve as a balance between positive life course activity-driven experiences and the negative effects of brain pathologies including cerebrovascular disease and total and regional brain volume loss. Hypothesised structural equation models illustrate the relative causal effects of these positive and negative contributions. Cognitive reserve is considered in the context of choice of interventions to prevent dementia and the opposing effects of cerebrovascular disease and Alzheimer like brain appearances.

Neuroimaging of hippocampal atrophy in early recognition of Alzheimer's disease--a critical appraisal after two decades of research

As a characteristic feature of Alzheimer's disease (AD) hippocampal atrophy (HA) can be demonstrated in the majority of patients by using neuroimaging techniques in particular magnetic resonance imaging (MRI). Hippocampal atrophy is associated with declarative memory deficits and can also be associated with changes of adjacent medial temporal substructures such as the parahippocampal gyrus or the the entorhinal cortex. Similar findings are present in patients with mild cognitive impairment (MCI) albeit to a lesser extent. While these finding facilitate the diagnostic process in patients with clinical suspicious AD, the metric properties of hippocampal atrophy for delineating healthy aging from MCI and mild AD still appear to be rather limited; as such it is not sufficient to establish the diagnosis of AD (and even more so of MCI). This limitation partly refers to methodological issues and partly to the fact that hippocampal tissue integrity is subject to various pathogenetic influences other than AD. Moreover,the effects of hippocampal atrophy on the behavioral level (e.g. cognitive deficits) are modulated by the individual's cognitive reserve. From a clinical standpoint these observations are in line with the hypothesis that the onset and course of AD is influenced by a number of peristatic factors which are partly conceptualized in the concepts of brain and/or cognitive reserve. These complex interactions have to be considered when using the presence of hippocampal atrophy in the routine diagnostic procedure of AD.

Cognitive Reserve and the Prevention of Dementia: the Role of Physical and Cognitive Activities

PURPOSE OF REVIEW

The article discusses the two most significant modifiable risk factors for dementia, namely, physical inactivity and lack of stimulating cognitive activity, and their effects on developing cognitive reserve.

RECENT FINDINGS

Both of these leisure-time activities were associated with significant reductions in the risk of dementia in longitudinal studies. In addition, physical activity, particularly aerobic exercise, is associated with less age-related gray and white matter loss and with less neurotoxic factors. On the other hand, cognitive training studies suggest that training for executive functions (e.g., working memory) improves prefrontal network efficiency, which provides support to brain functioning in the face of cognitive decline. While physical activity preserves neuronal structural integrity and brain volume (hardware), cognitive activity strengthens the functioning and plasticity of neural circuits (software), thus supporting cognitive reserve in different ways. Future research should examine whether lifestyle interventions incorporating these two domains can reduce incident dementia.

Neuromelanin marks the spot: identifying a locus coeruleus biomarker of cognitive reserve in healthy aging

Leading a mentally stimulating life may build up a reserve of neural and mental resources that preserve cognitive abilities in late life. Recent autopsy evidence links neuronal density in the locus coeruleus (LC), the brain's main source of norepinephrine, to slower cognitive decline before death, inspiring the idea that the noradrenergic system is a key component of reserve (Robertson, I. H. 2013. A noradrenergic theory of cognitive reserve: implications for Alzheimer's disease. Neurobiol. Aging. 34, 298-308). Here, we tested this hypothesis using neuromelanin-sensitive magnetic resonance imaging to visualize and measure LC signal intensity in healthy younger and older adults. Established proxies of reserve, including education, occupational attainment, and verbal intelligence, were linearly correlated with LC signal intensity in both age groups. Results indicated that LC signal intensity was significantly higher in older than younger adults and significantly lower in women than in men. Consistent with the LC-reserve hypothesis, both verbal intelligence and a composite reserve score were positively associated with LC signal intensity in older adults. LC signal intensity was also more strongly associated with attentional shifting ability in older adults with lower cognitive reserve. Together these findings link in vivo estimates of LC neuromelanin signal intensity to cognitive reserve in normal aging.

The relationship between cognitive reserve and the clinical stage of HIV infection

The objective of this study was to determine whether the effect of cognitive reserve (CR) on neuropsychological functioning differs according to the clinical stage of HIV infection. A sample of 34 HIV-positive individuals aged 23-49, with a minimum of 9 years of formal education, was assessed. Participants were grouped according to the Centers for Disease Control and Prevention's (CDC) clinical stages (A = 10, B = 16, C = 8). CR was calculated for each clinical stage group in accordance with estimates of premorbid IQ, years of education, and occupational attainment. The sum of these three variables was then transformed into z-scores. Individuals above the median were classified as having "High" CR (HCR), those below the median were classified as "Low" CR (LCR). Participants completed an evaluation of cognitive and executive functions based on selected, modified tasks from the HIV University of Miami Annotated Neuropsychological test in Spanish (HUMANS). Assessment included the following domains: attention, memory (visual, verbal, and working memory), executive functions (cognitive flexibility, switching), language (naming), and visual constructive skills (block design). HCR outperformed LCR in all cognitive domains. Comparison of HCR and LCR in each clinical stage revealed that the effect of CR was stronger in stage B than in stages A and C, suggesting that this effect does indeed vary among stages.

Amyloid positron emission tomography and cognitive reserve

Alzheimer’s disease (AD) is characterized by a non-linear progressive course and several aspects influence the relationship between cerebral amount of AD pathology and the clinical expression of the disease. Brain cognitive reserve (CR) refers to the hypothesized capacity of an adult brain to cope with brain damage in order to minimize symptomatology. CR phenomenon contributed to explain the disjunction between the degree of neurodegeneration and the clinical phenotype of AD. The possibility to track brain amyloidosis (Aβ) in vivo has huge relevance for AD diagnosis and new therapeutic approaches. The clinical repercussions of positron emission tomography (PET)-assessed Aβ load are certainly mediated by CR thus potentially hampering the prognostic meaning of amyloid PET in selected groups of patients. Similarly, amyloid PET and cerebrospinal fluid amyloidosis biomarkers have recently provided new evidence for CR. The present review discusses the concept of CR in the framework of available neuroimaging studies and specifically deals with the reciprocal influences between amyloid PET and CR in AD patients and with the potential consequent interventional strategies for AD.

Is cognitive lifestyle associated with depressive thoughts and self-reported depressive symptoms in later life?

Key components of cognitive lifestyle are educational attainment, occupational complexity and engagement in cognitively stimulating leisure activities. Each of these factors is associated with experiencing fewer depressive symptoms in later life, but no study to date has examined the relationship between overall cognitive lifestyle and depressive symptoms. This task is made more complex because relatively few older participants in cross-sectional studies will be currently experiencing depression. However, many more will show evidence of a depressive thinking style that predisposes them towards depression. This study aimed to investigate the extent to which cognitive lifestyle and its individual components are associated with depressive thoughts and symptoms. Two hundred and six community-dwelling participants aged 65+ completed the depressive cognitions scale, the geriatric depression scale and the lifetime of experiences questionnaire, which assesses cognitive lifestyle. Correlational analysis indicated that each of the individual lifestyle factors—education, occupational complexity and activities in young adulthood, mid-life and later life—and the combined cognitive lifestyle score was positively associated with each other and negatively with depressive symptoms, while all except education were negatively associated with depressive thoughts. Depressive thoughts and symptoms were strongly correlated. Cognitive lifestyle score explained 4.6 % of the variance in depressive thoughts and 10.2 % of the variance in depressive symptoms. The association of greater participation in cognitive activities, especially in later life, with fewer depressive symptoms and thoughts suggests that preventive interventions aimed at increasing participation in cognitively stimulating leisure activity could be beneficial in decreasing the risk of experiencing depressive thoughts and symptoms in later life.

Is residual memory variance a valid method for quantifying cognitive reserve? A longitudinal application

Cognitive reserve describes the mismatch between brain integrity and cognitive performance. Older adults with high cognitive reserve are more resilient to age-related brain pathology. Traditionally, cognitive reserve is indexed indirectly via static proxy variables (e.g., years of education). More recently, cross-sectional studies have suggested that reserve can be expressed as residual variance in episodic memory performance that remains after accounting for demographic factors and brain pathology (whole brain, hippocampal, and white matter hyperintensity volumes). The present study extends these methods to a longitudinal framework in a community-based cohort of 244 older adults who underwent two comprehensive neuropsychological and structural magnetic resonance imaging sessions over 4.6 years. On average, residual memory variance decreased over time, consistent with the idea that cognitive reserve is depleted over time. Individual differences in change in residual memory variance predicted incident dementia, independent of baseline residual memory variance. Multiple-group latent difference score models revealed tighter coupling between brain and language changes among individuals with decreasing residual memory variance. These results suggest that changes in residual memory variance may capture a dynamic aspect of cognitive reserve and could be a useful way to summarize individual cognitive responses to brain changes. Change in residual memory variance among initially non-demented older adults was a better predictor of incident dementia than residual memory variance measured at one time-point.

Environment as 'Brain Training': A review of geographical and physical environmental influences on cognitive ageing

Global ageing demographics coupled with increased urbanisation pose major challenges to the provision of optimal living environments for older persons, particularly in relation to cognitive health. Although animal studies emphasize the benefits of enriched environments for cognition, and brain training interventions have shown that maintaining or improving cognitive vitality in older age is possible, our knowledge of the characteristics of our physical environment which are protective for cognitive ageing is lacking. The present review analyses different environmental characteristics (e.g. urban vs. rural settings, presence of green) in relation to cognitive performance in ageing. Studies of direct and indirect associations between physical environment and cognitive performance are reviewed in order to describe the evidence that our living contexts constitute a measurable factor in determining cognitive ageing.

Occupational Complexity and Cognitive Reserve in a Middle-Aged Cohort at Risk for Alzheimer's Disease

Higher occupational attainment has previously been associated with increased Alzheimer's disease (AD) neuropathology when individuals are matched for cognitive function, indicating occupation could provide cognitive reserve. We examined whether occupational complexity (OCC) associates with decreased hippocampal volume and increased whole-brain atrophy given comparable cognitive function in middle-aged adults at risk for AD. Participants (n = 323) underwent structural MRI, cognitive evaluation, and work history assessment. Three complexity ratings (work with data, people, and things) were obtained, averaged across up to 3 reported jobs, weighted by years per job, and summed to create a composite OCC rating. Greater OCC was associated with decreased hippocampal volume and increased whole-brain atrophy when matched for cognitive function; results remained substantively unchanged after adjusting for several demographic, AD risk, vascular, mental health, and socioeconomic characteristics. These findings suggest that, in people at risk for AD, OCC may confer resilience to the adverse effects of neuropathology on cognition.

The NEIL Memory Research Unit: psychosocial, biological, physiological and lifestyle factors associated with healthy ageing: study protocol

Background

Population ageing is a global phenomenon that has characterised demographic trends during the 20th and 21st century. The rapid growth in the proportion of older adults in the population, and resultant increase in the incidence of age-related cognitive decline, dementia and Alzheimer’s disease, brings significant social, economic and healthcare challenges. Decline in cognitive abilities represents the most profound threat to active and healthy ageing. Current evidence suggests that a significant proportion of cases of age-related cognitive decline and dementia may be preventable through the modification of risk factors including education, depressive symptomology, physical activity, social engagement and participation in cognitively stimulating activities. The NEIL Memory Research Unit cohort study was established to investigate factors related to brain health and the maintenance of cognitive function.

Methods

A cohort of 1000 normally ageing adults aged 50 years and over are being recruited to participate in comprehensive assessments at baseline, and at follow-up once every 2 years. The assessment protocol comprises a comprehensive neuropsychological battery, some basic physical measures, psychosocial scales, questionnaire measures related to a range of health, lifestyle and behavioural factors, and a measure of resting state activity using electroencephalography (EEG).

Discussion

The NEIL Memory Research Unit cohort study will address key questions about brain health and cognitive ageing in the population aged 50+, with a particular emphasis on the influence of potentially modifiable factors on cognitive outcomes. Analyses will be conducted with a focus on factors involved in the maintenance of cognitive function among older adults, and therefore will have the potential to contribute significant knowledge related to key questions within the field of cognitive ageing, and to inform the development of public health interventions aimed at preventing cognitive decline and promoting active and healthy ageing.

Impact of Education on Memory Deficits in Subclinical Depression

Elevated depressive symptoms are associated with cognitive deficits, while higher education protects against cognitive decline. This study was conducted to test if education level moderates the relationship between depressive symptoms and cognitive function. Seventy-three healthy, dementia-free adults aged 18-81 completed neuropsychological tests, as well as depression and anxiety questionnaires. Controlling for age, sex, and state anxiety, we found a significant interaction of depressive symptoms and education for immediate and delayed verbal memory, such that those with a higher education level performed well regardless of depressive symptomatology, whereas those with lower education and high depressive symptoms had worse performance. No effects were found for executive functioning or processing speed. Results suggest that education protects against verbal memory deficits in individuals with elevated depressive symptoms. Further research on cognitive reserve in depression-related cognitive deficits and decline is needed to understand the mechanisms behind this phenomenon.

Cognitive reserve and β-amyloid pathology in Parkinson disease

INTRODUCTION

Dementia in Parkinson disease (PD) is associated with abnormal accumulation of proteins, including β-amyloid, in cortical regions. High cognitive reserve capacity may protect cognition from β-amyloid and delay the onset of dementia. We tested the cognitive reserve theory in PD by determining whether educational attainment, a proxy for cognitive reserve, modifies the correlation between cortical β-amyloid accumulation and cognitive impairment.

METHODS

PD participants (N = 155) underwent MRI to quantify brain volume and [(11)C] PiB PET imaging to quantify fibrillar β-amyloid deposition. Mean cortical binding potentials (MCBP) were calculated for each participant, with higher scores indicating more fibrillar β-amyloid. Global cognitive function was assessed using the Clinical Dementia Rating (CDR) and Mini-Mental State Examination (MMSE). Multiple linear regression analysis was used to determine whether education modified the relationship between MCBP and cognitive function after controlling for brain volume.

RESULTS

MCBP interacted with educational attainment to predict scores on each of the cognitive outcome measures (ps ≤ 0.02). Post-hoc analysis revealed that the effect of MCBP on cognitive function changed once the level of education reached 16 years. For participants with less than 16 years of education (n = 68), higher MCBP correlated with worse cognitive function, with MCBP accounting for 8-30% of the variance in MMSE and CDR scores (ps ≤ 0.02). For participants with at least 16 years of education (n = 87), MCBP did not correlate with MMSE or CDR scores (R(2)s < 0.02, ps ≥ 0.17).

CONCLUSION

These findings provide support for the cognitive reserve theory in PD and suggest that education may protect PD patients' cognition against cortical β-amyloid pathology.

Exploring strategies to operationalize cognitive reserve: A systematic review of reviews

INTRODUCTION

The cognitive reserve hypothesis suggests that across the lifespan, higher education, regular participation in social or mentally stimulating activities, and complexity of occupation increase an individual's resistance to dementia. However, there is currently no consensus regarding how to assess or measure cognitive reserve.

METHOD

We performed a systematic review of reviews focused on the concept of cognitive reserve to examine key elements of the definition and highlight limitations. We searched Embase.com, MEDLINE (OvidSP), the Cochrane Library, Web of Science, Scopus, Google Scholar, and PubMed.

RESULTS

Five systematic reviews were identified. These incorporated findings from cohort, cross-sectional, and case-control studies, and the outcomes examined included Alzheimer's disease, vascular dementia, nonspecified dementia, all dementias, and cognitive decline or cognitive impairment. Education, occupation, and leisure or mentally stimulating activities were suggested to supply cognitive reserve and offer a protective effect against the risk of dementia. Premorbid IQ and socioeconomic status have not been investigated as thoroughly and showed inconsistent results. Two of the reviews showed that when combining different indicators in the analyses/definition, including education, occupation, mentally stimulating activities, and premorbid IQ, cognitive reserve had a protective effect against cognitive decline. However, other indicators may also supply the reserve, including dietary habits and genetic indicators, but research is lacking with regard to creating a full cognitive reserve model.

CONCLUSIONS

This review highlights the lack of consensus regarding a definition of cognitive reserve. Further research is required to clarify how the indicators already identified may provide cognitive reserve and offer a protective effect against dementia. Agreement on the indicators that constitute the cognitive reserve model is needed before testing possible interventions that may increase the reserve supply and improve cognition.

The relationship between cognitive reserve and functional ability is mediated by executive functioning in older adults

It has been noted in the literature that cognitive reserve (CR) predicts future functional ability (FA), but the association between CR and current FA is rather limited. This investigation aimed to explicate this relationship, and hypothesized it would be mediated by executive functioning (EF). To best understand the relationship between CR and FA, we recruited and tested independent community-dwelling older adults (OAs). Bivariate correlations and hierarchical regressions were completed to determine the association between CR and FA. Both individual CR measures and a composite CR score were used. Mediation analyses were completed to examine our hypothesis that EF would mediate the CR and FA relationship. All measures of CR were positively related to and predictive of FA. Although the highest zero-order correlation across the independent CR proxies was between income and FA (r = .417), education accounted for the greatest amount of variance in FA, 8.3% after controlling for age and Mini-Mental State Examination performance. Furthermore, the CR composite had a higher correlation (r = .447) and accounted for more variance than any of the independent proxies. Complete mediation was found between a CR composite and FA via an internally consistent D-KEFS composite score (Cronbach's α = .795). This suggests that as CR increases so does EF, which in turn improves FA. Thus, future investigations could determine the effect on FA in OAs by improving EF.

The influence of cognitive reserve on psychosocial and neuropsychological functioning in bipolar disorder

Cognitive reserve (CR) refers to the hypothesized capacity of an adult brain to cope with brain pathology in order to minimize symptomatology. CR was initially investigated in dementia and acute brain damage, but it is being applied to other neuropsychiatric conditions. The present study aims at examining the fit of this concept to a sample of euthymic bipolar patients compared with healthy controls in order to investigate the role of CR in predicting psychosocial and cognitive outcome in bipolar disorder (BD). The sample included 101 subjects: 52 patients meeting DSM-IV-TR criteria for BD type I or II and 49 healthy controls (HC) matched for age and gender. They were all assessed with a cognitive battery tapping into executive and memory functioning. CR was obtained using three different proxies: education-occupation, leisure activities and premorbid IQ. Psychosocial functioning was evaluated by means of the Functioning Assessment Short Test (FAST). MANCOVAs were performed to determine differences in cognitive and functioning variables. Linear regression analyses were carried out to predict neuropsychological and psychosocial outcomes. Euthymic bipolar patients showed worse neuropsychological performance and psychosocial functioning than HC. The linear regression models revealed that CR was significantly predictive of FAST score (β = -0.47, p < 0.0001), Executive Index (β = 0.62, p < 0.0001) and Visual Memory Index (β = 0.44, p = 0.0004), indicating that CR is a significant predictor of cognitive and psychosocial functioning in euthymic bipolar outpatients. Therefore, CR may contribute to functional outcome in BD and may be applied in research and clinical interventions to prevent cognitive and functional impairment.

Cognitive reserve modulates ERPs associated with verbal working memory in healthy younger and older adults

Although many epidemiological studies suggest the beneficial effects of higher cognitive reserve (CR) in reducing age-related cognitive decline and dementia risk, the neural basis of CR is poorly understood. To our knowledge, the present study represents the first electrophysiological investigation of the relationship between CR and neural reserve (i.e., neural efficiency and capacity). Specifically, we examined whether CR modulates event-related potentials associated with performance on a verbal recognition memory task with 3 set sizes (1, 4, or 7 letters) in healthy younger and older adults. Neural data showed that as task difficulty increased, the amplitude of the parietal P3b component during the probe phase decreased and its latency increased. Notably, the degree of these neural changes was negatively correlated with CR in both age groups, such that individuals with higher CR showed smaller changes in P3b amplitude and less slowing in P3b latency (i.e., smaller changes in the speed of neural processing) with increasing task difficulty, suggesting greater neural efficiency. These CR-related differences in neural efficiency may underlie reserve against neuropathology and age-related burden.

Age of dementia diagnosis in community dwelling bilingual and monolingual Hispanic Americans

Bilingualism has been reported to delay the age of retrospective report of first symptom in dementia. This study determined if the age of clinically diagnosed Alzheimer's disease and vascular dementia occurred later for bilingual than monolingual, immigrant and U.S. born, Hispanic Americans. It involved a secondary analysis of the subset of 81 bi/monolingual dementia cases identified at yearly follow-up (1998 through 2008) using neuropsychological test results and objective diagnostic criteria from the Sacramento Area Latino Study on Aging that involved a random sampling of community dwelling Hispanic Americans (N = 1789). Age of dementia diagnosis was analyzed in a 2 × 2 (bi/monolingualism × immigrant/U.S. born) ANOVA that space revealed both main effects and the interaction were non-significant. Mean age of dementia diagnosis was descriptively (but not significantly) higher in the monolingual (M = 81.10 years) than the bilingual (M = 79.31) group. Overall, bilingual dementia cases were significantly better educated than monolinguals, but U.S. born bilinguals and monolinguals did not differ significantly in education. Delays in dementia symptomatology pertaining to bilingualism are less likely to be found in studies: (a) that use age of clinical diagnosis vs. retrospective report of first dementia symptom as the dependent variable; and (b) involve clinical cases derived from community samples rather than referrals to specialist memory clinics.

Lifelong bilingualism and neural reserve against Alzheimer's disease: a review of findings and potential mechanisms

Alzheimer's disease (AD) is a progressive brain disorder that initially affects medial temporal lobe circuitry and memory functions. Current drug treatments have only modest effects on the symptomatic course of the disease. In contrast, a growing body of evidence suggests that lifelong bilingualism may delay the onset of clinical AD symptoms by several years. The purpose of the present review is to summarize evidence for bilingualism as a reserve variable against AD and discuss potential underlying neurocognitive mechanisms. Evidence is reviewed suggesting that bilingualism may delay clinical AD symptoms by protecting frontostriatal and frontoparietal executive control circuitry rather than medial temporal lobe memory circuitry. Cellular and molecular mechanisms that may contribute to bilingual cognitive reserve effects are discussed, including those that may affect neuronal metabolic functions, dynamic neuronal-glial interactions, vascular factors, myelin structure and neurochemical signaling. Future studies that may test some of these potential mechanisms of bilingual CR effects are proposed.

The smarter, the stronger: intelligence level correlates with brain resilience to systematic insults. Cortex. 2015;64:293-309. [PMID: 25569764 DOI: 10.1016/j.cortex.2014.11.005]

Neuroimaging evidences posit human intelligence as tightly coupled with several structural and functional brain properties, also suggesting its potential protective role against aging and neurodegenerative conditions. However, whether higher order cognition might in fact lead to a more resilient brain has not been quantitatively demonstrated yet. Here we document a relationship between individual intelligence quotient (IQ) and brain resilience to targeted and random attacks, as measured through resting-state fMRI graph-theoretical analysis in 102 healthy individuals. In this modeling context, enhanced brain robustness to targeted attacks (TA) in individuals with higher IQ is supported by an increased distributed processing capacity despite the systematic loss of the most important node(s) of the system. Moreover, brain resilience in individuals with higher IQ is supported by a set of neocortical regions mainly belonging to language and memory processing network(s), whereas regions related to emotional processing are mostly responsible for lower IQ individuals. Results suggest intelligence level among the predictors of post-lesional or neurodegenerative recovery, also promoting the evolutionary role of higher order cognition, and simultaneously suggesting a new framework for brain stimulation interventions aimed at counteract brain deterioration over time.

Educational attainment and hippocampal atrophy in the Alzheimer's disease neuroimaging initiative cohort

INTRODUCTION

Subjects with higher cognitive reserve (CR) may be at a lower risk for Alzheimer's disease (AD), but the neural mechanisms underlying this are not known. Hippocampal volume loss is an early event in AD that triggers cognitive decline.

MATERIALS AND METHODS

Regression analyses of the effects of education on MRI-measured baseline HV in 675 subjects (201 normal, 329 with mild cognitive impairment (MCI), and 146 subjects with mild AD), adjusting for age, gender, APOE ɛ4 status and intracranial volume (ICV). Subjects were derived from the Alzheimer's Disease Neuroimaging Initiative (ADNI), a large US national biomarker study.

RESULTS

The association between higher education and larger HV was significant in AD (P=0.014) but not in cognitively normal or MCI subjects. In AD, HV was about 8% larger in a person with 20 years of education relative to someone with 6 years of education. There was also a trend for the interaction between education and APOE ɛ4 to be significant in AD (P=0.056).

CONCLUSION

A potential protective association between higher education and lower hippocampal atrophy in patients with AD appears consistent with prior epidemiologic data linking higher education levels with lower rates of incident dementia. Longitudinal studies are warranted to confirm these findings.

Measurement equivalence of neuropsychological tests across education levels in older adults

OBJECTIVE

The objective was to determine whether neuropsychological tests provide an equivalent measure of the same psychological constructs in older adults with low versus higher levels of education.

METHOD

Confirmatory factor analysis was used to evaluate the fit of a three-factor model (Verbal Ability, Visuospatial Ability, Long-Term Retention) to scores from the neuropsychological battery of the Canadian Study of Health and Aging (CSHA). Measurement equivalence of the model across lower educated (LE; ≤8 years) and higher educated (HE; ≥9 years) participants was evaluated using invariance testing.

RESULTS

The measurement model demonstrated adequate fit across LE and HE samples but the loadings of the 11 tests onto the three factors could not be constrained equally across groups. Animal Fluency and the Token Test were identified as noninvariant tests of Verbal Ability that, when freed from constraints, produced a partial metric invariance model. Scalar invariance testing identified the Buschke Cued Recall Test and Block Design as measures with invariant factor loadings but noninvariant intercepts. Analyses were replicated in age- and sex-matched subsamples.

CONCLUSIONS

Metric and scalar invariance across HE and LE samples was achieved for seven of the 11 tests in the CSHA battery. Animal Fluency and the Token Test were noninvariant measures of Verbal Ability, suggesting that cognitive processes underlying performance on these tests may vary as a function of education. In addition, scores from Block Design and the Buschke Cued Recall Test were observed to differ in their scale of measurement between HE and LE examinees.

Cognitive reserve and the risk for Alzheimer's disease: a longitudinal study

This study investigates how cognitive reserve (CR) interacts with neurodegeneration (quantified by medial temporal atrophy, MTA) and macroscopic white matter lesions (WMLs) in delaying the conversion from amnestic mild cognitive impairment to Alzheimer's disease (AD). Forty-two amnestic mild cognitive impairment patients were consecutively recruited. They underwent magnetic resonance imaging and a comprehensive questionnaire to classify them as individuals with low or high CR. Patients were then clinically followed-up for 2 years. The patients' risk for conversion to AD because of CR was estimated by controlling for cognitive efficiency, MTA, and WMLs at baseline. Global cognition was the best predictor of conversion to AD in low CR patients. Conversely, in high CR patients only, WMLs (but not MTA) highly contributed in increasing the risk for conversion to AD. In conclusion, CR interacts with both patients' cognitive features and WMLs in modulating the impact of AD pathology. This seems relevant for clinical prognosis and therapeutic strategies.

Functional genetic variation in the serotonin 5-HTTLPR modulates brain damage in frontotemporal dementia

In frontotemporal dementia (FTD), nonmodifiable (genetic background) and modifiable (cognitive reserve [CR]) factors might interact in affecting frontotemporal damage. Serotoninergic dysfunction has been suggested as a key factor in FTD pathogenesis. 5-HTTLPR polymorphism on SCLA4 gene modulates the serotoninergic transmission. To evaluate the impact of 5-HTTLPR polymorphism on regional cerebral blood flow (rCBF) and its possible interaction with CR, 76 FTD patients with a 5-HTTLPR genotyping were recruited. All subjects underwent neuropsychological assessment and single-photon emission computed tomography imaging. Reserve index (RI) was computed from educational and occupational attainments, as proxy measure of CR. 5-HTTLPR analysis evidenced 14 S/S, 24 L/L, and 38 S/L carriers. No neuropsychological/behavioral differences were present. At the same disease stage, L/L carriers have a greater bilateral frontal rCBF decrease. Patients with higher RI had greater damage in right frontal and temporal regions. The additive effect of 5-HTTLPR polymorphism and RI was characterized by greater frontal rCBF deficit. 5-HTTLPR and CR act together to counteract brain pathology in FTD. Further studies are warranted to test the serotonin role in monogenic forms of FTD.