Cognition and Cognitive Reserve

Cognition is a mental process that provides the ability to think, know, and learn. Though cognitive skills are necessary to do daily tasks and activities, cognitive aging causes changes in various cognitive functions. Cognitive abilities that are preserved and strengthened by experience can be kept as a reserve and utilized when necessary. The concept of reserving cognition was found when people with Alzheimer's disease had differences in clinical manifestations and cognitive functions. The cognitive reserve builds resilience against cognitive decline and improves the quality of life. Also, several lines of studies have found that the plasticity between neurons has a significant impact on cognitive reserve and acts against cognitive decline. To extend the findings, the present study provides a comprehensive understanding of cognitive reserve and the variables that are involved in maintaining cognition. The study also considers reading as one of the cognitive proxies that develops and maintains cognitive reserve.

The association between posterior resting-state EEG alpha rhythms and functional MRI connectivity in older adults with subjective memory complaint

Resting-state eyes-closed electroencephalographic (rsEEG) alpha rhythms are dominant in posterior cortical areas in healthy adults and are abnormal in subjective memory complaint (SMC) persons with Alzheimer's disease amyloidosis. This exploratory study in 161 SMC participants tested the relationships between those rhythms and seed-based resting-state functional magnetic resonance imaging (rs-fMRI) connectivity between thalamus and visual cortical networks as a function of brain amyloid burden, revealed by positron emission tomography and cognitive reserve, measured by educational attainment. The SMC participants were divided into 4 groups according to 2 factors: Education (Edu+ and Edu-) and Amyloid burden (Amy+ and Amy-). There was a statistical interaction (p < 0.05) between the two factors, and the subgroup analysis using estimated marginal means showed a positive association between the mentioned rs-fMRI connectivity and the posterior rsEEG alpha rhythms in the SMC participants with low brain amyloidosis and high CR (Amy-/Edu+). These results suggest that in SMC persons, early Alzheimer's disease amyloidosis may contrast the beneficial effects of cognitive reserve on neurophysiological oscillatory mechanisms at alpha frequencies and connectivity between the thalamus and visual cortical networks.

GBA moderates cognitive reserve's effect on cognitive function in patients with Parkinson's disease

BACKGROUND

Cognitive reserve (CR) involves an individual's ability to maintain cognitive vitality over their lifespan. Glucocerebrosidase (GBA) gene mutations contribute to additional effects on cognitive function in Parkinson's disease (PD) patients, but the interplay between GBA mutations and CR remains unclear. We investigated the interactions among CR, GBA, and diseases, aiming to examine whether the CR established at different stages interacts with specific genotypes to affect cognitive function.

METHODS

Three hundred and eighteen participants' CR indicators (i.e., education, occupation, and social function) and comprehensive neuropsychological function (i.e., tests for executive function, attention/working memory, visuospatial function, memory, and language) were evaluated.

RESULTS

We found that CR established in a specific life stage influences the individual's cognitive function, particularly in PD, based on their distinct GBA rs9628662 genotypes. Attention/working memory and memory performance are affected by occupational complexity in midlife in PD patients with the GG genotype (q < 0.0001; q < 0.0001) and healthy adults with the T genotype (q = 0.0440; q < 0.0001). Language is influenced by early education and occupation, and the effects of occupation are also observed in PD patients with the GG genotype (q = 0.0040) and in healthy adults carrying the T genotype (q = 0.0040).

CONCLUSIONS

CR, established at different life stages, can be influenced by the GBA rs9628662 genotype, impacting later-life cognition. Validating genotypes and incorporating genotype information when assessing cognitive reserve effects is crucial and can enhance targeted cognitive training.

Cognitive Reserve proxies can modulate motor and non-motor basal ganglia circuits in early Parkinson's Disease

Parkinson's Disease (PD) is hallmarked by dysfunctional circuitry between the basal ganglia and dorsolateral-prefrontal cortex. Recently progress has been made in understanding factors contributing to differential susceptibility to pathology mitigating disease-related cognitive decline. Cognitive reserve, the brain processing resources accumulated throughout life while engaged in mentally stimulating activities, can play an important protective role in cognitive performance. We tested the hypothesis that Cognitive Reserve proxies may exert an impact on the basal ganglia and dorsolateral-prefrontal atrophy in early PD. Forty-five early patients with PD and 20 age-gender-matched healthy controls (HC) completed the Cognitive Reserve Index questionnaire to quantify Cognitive Reserve proxies by three indexes (CRI-Education, CRI-Working Activity, CRI-Leisure Time) and a structural MRI examination (3T). Morphometrical indexes for basal ganglia (bilateral putamen, caudate, pallidum volume) and dorsolateral-prefrontal cortex (cortical thickness) were computed. Significant differences between HC and PD were tested by direct comparisons in demographics, cognitive level, and cognitive reserve proxies indexes. Then two multiple regression analyses were performed to identify predictors of the basal ganglia and dorsolateral-prefrontal cortex structural integrity. Regression analysis revealed that basal ganglia volume was significantly predicted by CRI-Education (pFDR = 0.029), sex (pFDR = 0.029), and Total Intracranial Volume (pFDR < 0.001). Instead, the dorsolateral-prefrontal thickness was predicted by CRI-Leisure Time (pFDR = 0.030) and age (pFDR = 0.010). Cognitive Reserve proxies, especially education and leisure-time activities, can play a protective role on the structural integrity of the basal ganglia and dorsolateral-prefrontal cortex, respectively, critical regions hallmarking brain status of early phases of PD.

s-CRIq: the online short version of the Cognitive Reserve Index Questionnaire

BACKGROUND

The wide use of the term Cognitive Reserve (CR) is in need of a clear and shared definition of its concept and of the development of new tools, quick and easy to use and updated for the people of today. This study describes the online short CRIq (s-CRIq), the new shorter version of the CRIq, following an item analysis revision, and compares the data distribution of different samples.

METHODS

The s-CRIq was administered online to 435 people while another 440 filled out the s-CRIq in self-administration. A further 588 participants had been administered the original paper-and-pencil long CRIq and 344 the online long CRIq.

RESULTS

The major difference in the databases of s-CRIq versus the long versions is an increased score in education and in leisure activity. However, the density distributions of the total score of CRI in the 4 databases share 64% of their areas, and at least two of them share 84%.

CONCLUSION

The s-CRIq proved to be a simple and easy-to-administer tool. Similarly, to the original version, the s-CRIq is freely available on the web, and it is our hope that it will be of fruitful use for researchers and clinicians alike.

Systematic examination of methodological inconsistency in operationalizing cognitive reserve and its impact on identifying predictors of late-life cognition

BACKGROUND

Cognitive reserve (CR) is the ability to maintain cognitive performance despite brain pathology. CR is built through lifecourse experiences (e.g., education) and is a key construct in promoting healthy aging. However, the operationalization of CR and its estimated association with late-life cognition varies. The purpose of this study was to systematically examine the operationalization of CR and the relationship between its operationalization and late-life cognition.

METHODS

We performed a comprehensive review of experiences (proxies) used to operationalize CR. The review informed quantitative analyses using data from 1366 participants of the Memory and Aging Project to examine 1) relationships between proxies and 2) the relationship between operationalization and late-life cognition. We also conducted a factor analysis with all identified CR experiences to create a composite lifecourse CR score. Generalized linear mixed models examined the relationship between operationalizations and global cognition, with secondary outcomes of five domains of cognition to examine consistency.

RESULTS

Based on a review of 753 articles, we found the majority (92.3%) of the 28 commonly used proxies have weak to no correlation between one another. There was substantial variability in the association between operationalizations and late-life global cognition (median effect size: 0.99, IQR: 0.34 to 1.39). There was not strong consistency in the association between CR operationalizations and the five cognitive domains (mean consistency: 56.1%). The average estimate for the 28 operationalizations was 0.91 (SE = 0.48), compared to 2.48 (SE = 0.40) for the lifecourse score and it was associated with all five domains of cognition.

CONCLUSIONS

Inconsistent methodology is theorized as a major limitation of CR research and barrier to identification of impactful experiences for healthy cognitive aging. Based on the weak associations, it is not surprising that the relationship between CR and late-life cognition is dependent on the experience used to operationalize CR. Scores using multiple experiences across the lifecourse may help overcome such limitations. Adherence to a lifecourse approach and collaborative movement towards a consensus operationalization of CR are imperative shifts in the study of CR that can better inform research on risk factors related to cognitive decline and ultimately aid in the promotion of healthy aging.

[Neuropsychological Changes and Indication of Bariatric Surgery in Severely Obese Patients]

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Neuropsychological Profile, Cognitive Reserve and Emotional Distress in a Portuguese Sample of Severely Obese Patients

INTRODUCTION

Obesity is a significant risk factor for multiple comorbidities, and its relation to neurocognitive disfunction is particularly important in cognitive decline, especially in middle age. Due to their impact on neurodegeneration, we sought to explore neuropsychological profile, cognitive reserve and emotional distress in patients with severe obesity.

MATERIAL AND METHODS

We used a sociodemographic and clinical questionnaire, neuropsychological tests and a symptom self-reported scale of emotional distress. We evaluated the cognitive performance of 120 patients, aged between 18 and 65 years, in treatment for their severe obesity in Portugal, between May 2012 and December 2015.

RESULTS

Cognitive performance was below the mean for the Portuguese population, for immediate recall, visuoperception, resistance to interference and cognitive flexibility. Cognitive reserve was mostly low, especially in the older groups and groups with low professional status and increased associated with better cognitive outcomes. Emotional distress was shown to be higher in our sample compared with a normative sample. The risk factors evaluated were important in the worsening of cognitive functions. Cognitive performance decreased with age.

DISCUSSION

Severe obesity was associated with a poorer cognitive performance of the sample. The cognitive reserve was greater in the younger groups. There was a significant presence of emotional distress, especially among women.

CONCLUSION

Severe obesity is associated with an impairment in cognitive and emotional performance, aggravated by aging, cognitive reserve, and comorbidity. This study emphasizes the need for preventive actions, such as neuropsychological screening, in the detection of changes and the design of better interventions.

Cognitive Aging and Dementia: A Life Span Perspective

This article summarizes empirical findings and theoretical concepts in cognitive aging and late-life dementia research. Major emphases are placed on (1) person-to-person heterogeneity in trajectories of cognitive change over time, (2) how trajectories of child cognitive development determine peak levels of adult cognitive function from which aging-related cognitive declines occur, and (3) how lifelong trajectories of cognitive function relate to the timing of severe cognitive impairments characteristic of dementia. I consider conceptual issues surrounding categorical vs. dimensional models of late-life dementia, and how current diagnostic approaches affect inferences in the empirical study of disease progression. The incomplete current understanding of the biological foundations of aging-related cognitive declines and the continuous nature of many biomarkers commonly used in dementia diagnosis and classification together pose both opportunities and challenges in the current research landscape. Research moving forward will benefit from accurately measuring and analyzing continuous variation in longitudinal trajectories of cognitive function.

Pragmatic Language Disorder in Parkinson's Disease and the Potential Effect of Cognitive Reserve

It is known that patients with Parkinson's Disease (PD) may show deficits in several areas of cognition, including speech and language abilities. One domain of particular interest is pragmatics, which refers to the capacity of using language in context for a successful communication. Several studies showed that some specific aspects of pragmatics - both in production and in comprehension - might be impaired in patients with PD. However, a clear picture of pragmatic abilities in PD is still missing, as most of the existing studies focused on specific aspects of the pragmatic competence rather than on sketching a complete pragmatic profile. Moreover, little is known on the potential role of protective factors in compensating the decline of communicative skills as the disease progresses. The present study has two aims: (1) to provide a complete picture of pragmatic abilities in patients with PD, by using a comprehensive battery (Assessment of Pragmatic Abilities and Cognitive Substrates, APACS) and by investigating the relationship with other aspects of cognitive functioning (e.g., working memory and Theory of Mind) and (2) to investigate whether Cognitive Reserve, i.e., the resilience to cognitive impairment provided by life experiences and activities, may compensate for the progressive pragmatic deficits in PD. We found that patients with PD, compared to healthy matched controls, had worse performance in discourse production and in the description of scenes, and that these impairments were tightly correlated with the severity of motor impairment, suggesting reduced intentionality of engaging in a communicative exchange. Patients with PD showed also an impairment in comprehending texts and humor, suggesting a problem in inferring from stories, which was related to general cognitive impairment. Notably, we did not find any significant difference between patients and controls in figurative language comprehension, a domain that is commonly impaired in other neurodegenerative diseases. This might be indicative of a specific profile of pragmatic impairment in patients with PD, worth of further investigation. Finally, Cognitive Reserve measures showed a high degree of association with pragmatic comprehension abilities, suggesting that the modification of life-styles could be a good candidate for compensating the possible problems in understanding the pragmatic aspects of language experienced by patients with PD.

Recent Advances in Preventing and Managing Postoperative Delirium

Postoperative delirium is a common and harrowing complication in older surgical patients. Those with cognitive impairment or dementia are at especially high risk for developing postoperative delirium; ominously, it is hypothesized that delirium can accelerate cognitive decline and the onset of dementia, or worsen the severity of dementia. Awareness of delirium has grown in recent years as various medical societies have launched initiatives to prevent postoperative delirium and alleviate its impact. Unfortunately, delirium pathophysiology is not well understood and this likely contributes to the current state of low-quality evidence that informs perioperative guidelines. Along these lines, recent prevention trials involving ketamine and dexmedetomidine have demonstrated inconsistent findings. Non-pharmacologic multicomponent initiatives, such as the Hospital Elder Life Program, have consistently reduced delirium incidence and burden across various hospital settings. However, a substantial portion of delirium occurrences are still not prevented, and effective prevention and management strategies are needed to complement such multicomponent non-pharmacologic therapies. In this narrative review, we examine the current understanding of delirium neurobiology and summarize the present state of prevention and management efforts.

Metabolic correlates of reserve and resilience in MCI due to Alzheimer's Disease (AD)

Background

We explored the presence of both reserve and resilience in late-converter mild cognitive impairment due to Alzheimer’s disease (MCI-AD) and in patients with slowly progressing amyloid-positive MCI by assessing the topography and extent of neurodegeneration with respect to both “aggressive” and typically progressing phenotypes and in the whole group of patients with MCI, grounding the stratification on education level.

Methods

We analyzed 94 patients with MCI-AD followed until conversion to dementia and 39 patients with MCI who had brain amyloidosis (AMY+ MCI), all with available baseline ¹⁸F-fluorodeoxyglucose positron emission tomography (FDG-PET) results. Using a data-driven approach based on conversion time, patients with MCI-AD were divided into typical AD and late-converter subgroups. Similarly, on the basis of annual rate of Mini Mental State Examination score reduction, AMY+ MCI group was divided, obtaining smoldering (first tertile) and aggressive (third tertile) subgroups. Finally, we divided the whole group (MCI-AD and AMY+ MCI) according to years of schooling, obtaining four subgroups: poorly educated (Low-EDUC; first quartile), patients with average education (Average-EDUC; second quartile), highly educated (High-EDUC; third quartile), and exceptionally educated (Except-EDUC; fourth quartile). FDG-PET of typical AD, late converters, and aggressive and smoldering AMY+ MCI subgroups, as well as education level-based subgroups, were compared with healthy volunteer control subjects (CTR) and within each group using a two-samples t test design (SPM8; p < 0.05 family-wise error-corrected).

Results

Late converters were characterized by relatively preserved metabolism in the right middle temporal gyrus (Brodmann area [BA] 21) and in the left orbitofrontal cortex (BA 47) with respect to typical AD. When compared with CTR, the High-EDUC subgroup demonstrated a more extended bilateral hypometabolism in the posterior parietal cortex, posterior cingulate cortex, and precuneus than the Low- and Average-EDUC subgroups expressing the same level of cognitive impairment. The Except-EDUC subgroup showed a cluster of significant hypometabolism including only the left posterior parietal cortex (larger than the Low- and Average-EDUC subgroups but not further extended with respect to the High-EDUC subgroup).

Conclusions

Middle and inferior temporal gyri may represent sites of resilience rather than a hallmark of a more aggressive pattern (when hypometabolic). These findings thus support the existence of a relatively homogeneous AD progression pattern of hypometabolism despite AD heterogeneity and interference of cognitive reserve. In fact, cortical regions whose “metabolic resistance” was associated with slower clinical progression had different localization with respect to the regions affected by education-related reserve.

Electronic supplementary material

The online version of this article (10.1186/s13195-018-0366-y) contains supplementary material, which is available to authorized users.

Reserve and Reserve-building activities research: key challenges and future directions

Background

The concept of Cognitive Reserve has great appeal and has led to an interesting and important body of research. We believe, however, that it is unnecessarily limited by ‘habits’ of measurement, nomenclature, and intra-disciplinary thinking.

Main body

A broader, more comprehensive way of conceptualizing Reserve is proposed that invokes a broader measurement approach, nomenclature that uses specific terms embedded in a theoretical model, and crosses disciplines.

Conclusion

Building on this comprehensive conceptualization, we will discuss fruitful directions for future research.

Educational inequalities in aging-related declines in fluid cognition and the onset of cognitive pathology

BACKGROUND

Education has been robustly associated with cognitive reserve and dementia, but not with the rate of cognitive aging, resulting in some confusion about the mechanisms of cognitive aging. This study uses longitudinal data to differentiate between trajectories indicative of healthy versus pathological cognitive aging.

METHODS

Participants included 9,401 Health and Retirement Study respondents aged 55 and older who completed cognitive testing regularly over 17.3 years until most recently in 2012. Individual-specific random change-point modeling was used to identify age of incident pathological decline; acceleration is interpreted as indicating likely onset of pathological decline when it is significant and negative.

RESULTS

These methods detect incident dementia diagnoses with specificity/sensitivity of 89.3%/44.3%, 5.6 years prior to diagnosis. Each year of education was associated with 0.09 (95% CI, 0.087-0.096; P<0.001) standard deviation higher baseline cognition and delayed onset of cognitive pathology (HR, 0.98; 95% CI, 0.96-0.99; P=0.006).

CONCLUSION

Longitudinal random change-point modeling was able to reliably identify incident dementia. Accounting for incident cognitive pathology, we find that education predicts cognitive capability and delayed onset pathological declines.

Cognitive Consequences of Aging with HIV: Implications for Neuroplasticity and Rehabilitation

Combination active antiretroviral therapy prevents HIV from replicating and ravaging the immune system, thus allowing people to age with this disease. Unfortunately, the synergistic effects of HIV and aging can predispose many to become more at-risk of developing cognitive deficits which can interfere with medical management, everyday functioning, and quality of life. The purpose of this article is to describe the role of cognitive reserve and neuroplasticity on cognitive functioning in those aging with this disease. Specifically, the role of environment and the health of these individuals can compromise cognitive functioning. Fortunately, some cognitive interventions such as prevention and management of co-morbidities, cognitive remediation therapy, and neurotropic medications may be of value in preventing and rehabilitating the cognitive consequences of aging with HIV. Novel approaches such as cognitive prescriptions, transcranial direct stimulation, and binaural beat therapy may also be considered as possible techniques for cognitive rehabilitation.