Cognitive reserve protects against cognitive dysfunction in multiple sclerosis

Cognitive Vulnerability in Aging May Be Modulated by Education and Reserve in Healthy People

Aging is related to a deterioration of cognitive performance and to multiple alterations in the brain. Even before the beginning of a noticeable cognitive decline, the framework which holds cognitive function experiences these alterations. From a system-vulnerability point of view of cognition, the deterioration associated with age would be the collection of repercussions during a life. Brain function and structure are modified in a multidimensional way, which could concern different aspects like structural integrity, functional activity, connectivity, or glucose metabolism. From this point of view, the effects of aging could affect the most brain systems and their functional activity. In this study, we analyze the functional development of three cognitive domains in relation to aging, educational level, and cognitive reserve (CR). A total of 172 healthy subjects were divided into two age groups (young and old), and completed a battery of classic neuropsychological tests. The tests were organized and analyzed according to three cognitive domains: working memory and flexibility, visuoconstructive functions, and declarative memory. Subjects also completed a questionnaire on CR. Results showed that the performance in all cognitive domains decreased with age. In particular, tests related to working memory, flexibility, and visuoconstructive abilities were influenced by age. Nevertheless, this effect was attenuated by effects of education, mainly in visuoconstructive domain. Surprisingly, visual as well as verbal memory tests were not affected either by aging, education, or CR. Brain plasticity plays a prominent role in the aging process, but, as other studies have shown, the plasticity mechanism is quite different in healthy vs. pathological brains. Moreover, this plasticity brain mechanism could be modulated by education and CR. Specially, cognitive domains as working memory, some executive functions and the visuoconstructive abilities seem to be modulated by education. Therefore, it seems to be crucial, to propose mechanisms of maintenance of a healthy and enriched brain, since it promotes auto-regulatory mechanisms of well-aging.

A neuroimaging approach to capture cognitive reserve: Application to Alzheimer's disease

Cognitive reserve (CR) explains interindividual differences in the ability to maintain cognitive function in the presence of neuropathology. We developed a neuroimaging approach including a measure of brain atrophy and cognition to capture this construct. In a group of 511 Alzheimer's disease (AD) biomarker-positive subjects in different stages across the disease spectrum, we performed 3T magnetic resonance imaging and predicted gray matter (GM) volume in each voxel based on cognitive performance (i.e. a global cognitive composite score), adjusted for age, sex, disease stage, premorbid brain size (i.e. intracranial volume) and scanner type. We used standardized individual differences between predicted and observed GM volume (i.e. W-scores) as an operational measure of CR. To validate this method, we showed that education correlated with mean W-scores in whole-brain (r = -0.090, P < 0.05) and temporoparietal (r = -0.122, P < 0.01) masks, indicating that higher education was associated with more CR (i.e. greater atrophy than predicted from cognitive performance). In a voxel-wise analysis, this effect was most prominent in the right inferior and middle temporal and right superior lateral occipital cortex (P < 0.05, corrected for multiple comparisons). Furthermore, survival analyses among subjects in the pre-dementia stage revealed that the W-scores predicted conversion to more advanced disease stages (whole-brain: hazard ratio [HR] = 0.464, P < 0.05; temporoparietal: HR = 0.397, P < 0.001). Our neuroimaging approach captures CR with high anatomical detail and at an individual level. This standardized method is applicable to various brain diseases or CR proxies and can flexibly incorporate different neuroimaging modalities and cognitive parameters, making it a promising tool for scientific and clinical purposes. Hum Brain Mapp 38:4703-4715, 2017. © 2017 Wiley Periodicals, Inc.

Cognitive resilience in clinical and preclinical Alzheimer's disease: the Association of Amyloid and Tau Burden on cognitive performance

We explored the cross-sectional relationships between β-amyloid (Aβ) and inferior temporal tau deposition (IFT Tau) on cognitive performance and whether cognitive reserve (CR) modifies these associations. We studied 156 participants classified into groups of clinically normal (CN = 133), mild cognitive impairment (MCI = 17) and Alzheimer disease (AD = 6) dementia. AMNART IQ served as a proxy of CR and cognitive performance was assessed using the MMSE. In separate linear regression models predicting MMSE, we examined the interactions of CR x global Aβ and CR x IFT tau across all participants and within the CN group alone. In the whole sample, the interaction between CR and IFT tau was significant (p < 0.003), such that higher CR participants with elevated IFT tau had better MMSE scores compared with low CR participants with similar levels of IFT tau. The interaction between CR and Aβ status did not reach significance (p = 0.093). In CN only, no cross-sectional interactions among CR, Aβ, and IFT tau were observed on MMSE. These findings imply that CR may be protective against early AD processes and enable some individuals to remain cognitively stable despite elevated tau and Aβ burden.

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.

Cognitive impairment in MS: rehabilitation approaches

Cognitive deficits have been reported in 45%-70% of patients with multiple sclerosis (MS). Like other symptoms of MS, cognitive deficits are highly variable. Slowed information processing and memory and learning dysfunction are regarded as the most frequent cognitive deficits in MS. Both white and gray matter damages have been suggested to contribute to cognitive impairments in MS. There is no direct relationship between cognitive deficits and physical disability, disease duration or course of the disease. In addition to cognitive impairments, neuropsychiatric symptoms are observed in MS, the most common being alterations in mood state. Neurobehavioral deficits have multidimensional effects on the activities of daily living and quality of life. Consequently, attention should be paid to early diagnosis and treatment. Based on studies on cognitive retraining and more multimodal neuropsychological rehabilitation, both approaches show promise in the treatment of cognitive impairments and their harmful effects. This review introduces the frequency and characteristics of cognitive impairments, as well as main findings on the effects of neuropsychological rehabilitation in MS.

Cognitive rehabilitation of working memory in juvenile multiple sclerosis-effects on cognitive functioning, functional MRI and network related connectivity

PURPOSE

To assess possible effects of working memory (WM) training on cognitive functionality, functional MRI and brain connectivity in patients with juvenile MS.

METHODS

Cognitive status, fMRI and inter-network connectivity were assessed in 5 cases with juvenile MS aged between 12 and 18 years. Afterwards they received a computerized WM training for four weeks. Primary cognitive outcome measures were WM (visual and verbal) and alertness. Activation patterns related to WM were assessed during fMRI using an N-Back task with increasing difficulty. Inter-network connectivity analyses were focused on fronto-parietal (left and right), default-mode (dorsal and ventral) and the anterior salience network. Cognitive functioning, fMRI and inter-network connectivity were reassessed directly after the training and again nine months following training.

RESULTS

Response to treatment was seen in two patients. These patients showed increased performance in WM and alertness after the training. These behavioural changes were accompanied by increased WM network activation and systematic changes in inter-network connectivity. The remaining participants were non-responders to treatment. Effects on cognitive performance were maintained up to nine months after training, whereas effects observed by fMRI disappeared.

CONCLUSIONS

Responders revealed training effects on all applied outcome measures. Disease activity and general intelligence may be factors associated with response to treatment.

Distraction adds to the cognitive burden in multiple sclerosis

Background:

Cognitive dysfunction in multiple sclerosis (MS) causes numerous limitations in activities of daily living.

Objectives:

To develop an improved method of cognitive assessment in people with MS using novel real-world distracters.

Methods:

A sample of 99 people with MS and 55 demographically matched healthy controls underwent testing with the Minimal Assessment of Cognitive Functioning in Multiple Sclerosis (MACFIMS) and a modified version of the computerized Symbol Digit Modalities Test (c-SDMT). Half of the subjects completed the c-SDMT with built-in real-world distracters and half without.

Results:

The mean time on the c-SDMT was significantly greater in MS subjects than healthy controls for both distracter ( p = 0.001) and non-distracter ( p < 0.001) versions. Significantly more MS subjects were impaired on the c-SDMT with distracters than the traditional SDMT (47.1% vs 30.3%, p = 0.04). There were no differences in impairment between the c-SDMT with and without distracters (47.1% vs 37.5%, p = 0.34). The distracter version had a sensitivity of 81% and specificity of 88% in detecting global cognitive impairment.

Conclusions:

The incorporation of distracters improves the sensitivity of a validated computerized version of the SDMT relative to the non-distracter and traditional versions and offers a quick and easy means of detecting cognitive impairment in people with MS.

Cognitive reserve in bipolar disorder: relation to cognition, psychosocial functioning and quality of life

OBJECTIVE

Cognitive reserve (CR) is a concept that was postulated as a protective factor for some clinical symptoms after the observation that there is not a direct relationship between the degree of brain damage and its clinical manifestation. This study aimed to explore the association between CR and the main outcomes in bipolar disorder (BD): cognitive functions, psychosocial functioning and perceived quality of life.

METHOD

A sample of 224 euthymic bipolar patients was assessed with a neuropsychological battery, the Functioning Assessment Short Test and the Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36). CR was calculated through three proxies: estimated premorbid Intelligent Quotient, educational level and occupational attainment. Relationships between CR and cognitive functions, psychosocial functioning and quality of life were assessed by multiple linear regression models.

RESULTS

Higher CR was associated with better cognitive functioning (P < 0.001 in processing speed, working memory, verbal and visual memory, and executive function; P = 0.026 in attention) and better psychosocial functioning (P = 0.008). For quality of life, CR was positively associated with the physical component of the SF-36 (P = 0.016) but negatively associated with the mental component (P = 0.004).

CONCLUSION

The results suggest that CR may play an important role in the course and prognosis of bipolar patients and it should be considered in both clinical and research settings related to BD.

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.

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.

The relationship between the rate of brain volume loss during first 24 months and disability progression over 24 and 48 months in relapsing MS

Clinical evidence in patients with relapsing-remitting multiple sclerosis suggests an association between MRI outcome measures and disability progression (DP). Post hoc analysis to investigate the association and potential predictive value of brain volume loss (BVL) with long-term DP in FREEDOMS. Patients were categorized into quartiles by SIENA-calculated percent brain volume change from baseline to month (M) 24. Patient characteristics at baseline were determined for each quartile, as were the proportions of patients at M24 and M48 reaching Expanded Disability Status Scale (EDSS) scores of ≥4.0 or ≥6.0 or DP confirmed at 3 months (CDP3) or 6 months (CDP6), and change in EDSS and Multiple Sclerosis Functional Composite. MS disease activity and severity as well as brain volume at baseline were predictive of subsequent BVL over 24 months. The quartiles of patients with greater BVL at 24 months were at highest risk (odds ratio, p value) for reaching EDSS ≥4 (2.8, p = 0.001) or ≥6 (5.73, p = 0.0005) and experienced more DP at M24 (CDP3 2.13, p = 0.002; CDP6 2.17, p = 0.003) and M48 (CDP3 1.98, p = 0.006; CDP6 1.87, p = 0.018) compared to the quartile of patients with the least amount of BVL. These findings confirm the clinical relevance of early brain volume changes for long-term DP.

Reserve-building activities in multiple sclerosis patients and healthy controls: a descriptive study

BACKGROUND

Cognitive reserve has been implicated as a possible protective factor in multiple sclerosis (MS) but to date no study has compared reserve-building activities across disease course or to healthy controls. This study aims to describe differences in reserve-building activities across the MS disease course and healthy controls.

METHODS

Secondary analysis of a cross-sectional cohort study that included 276 healthy controls, and subjects with clinically isolated syndrome (CIS; n = 67), relapsing-remitting MS (RRMS; n = 358) and secondary progressive MS (PMS; n = 109). Past reserve-building activities were operationalized as occupational attainment and education. Current activities comprised 6 strenuous and 6 non-strenuous activities, including 5 reserve-building activities and television-watching. Multivariate Analysis of Variance models examined group differences in past and current activities, after adjusting for covariates.

RESULTS

There were group differences in past and current reserve-building activities. SPMS patients had lower past reserve-building activities than healthy controls. All forms of MS engaged in fewer strenuous current reserve-building pursuits than healthy controls. RRMS read less than healthy controls. SPMS engaged in fewer job-related non-strenuous activities. All MS groups watched more television than healthy controls.

CONCLUSIONS

MS patients show significantly fewer past and present reserve-building activities. Although it is difficult to establish causality without future prospective studies, lifestyle-modifying interventions should prioritize expanding MS patients' repertoire of strenuous and non-strenuous activities.

Cognitive reserve in multiple sclerosis: Protective effects of education

Background:

Recent data suggest that cognitive reserve modulates the adverse effects of multiple sclerosis (MS) pathology on cognitive functioning; however, the protective effects of education in MS are still unclear.

Objective:

To explore education as an indicator of cognitive reserve, while controlling for demographic, clinical and genetic features.

Methods:

A total of 419 MS patients and 159 healthy comparison (HC) subjects underwent a comprehensive neuropsychological (NP) assessment, and answered the Hospital Anxiety and Depression Scale. Based on the HC data, MS patients’ NP scores were adjusted for sex, age and education; and the estimated 5th percentile (or 95th percentile, when appropriate) was used to identify any deficits. Patients also performed the Mini-Mental State Examination (MMSE); and their human leucocyte antigen HLA-DRB1 and apolipoprotein E ( ApoE) genotypes were investigated.

Results:

Patients with higher education were less likely ( p < 0.05) to have cognitive deficits than those with lower education, even when controlling for other covariates. Other significant predictors of cognitive deficit were: age, Expanded Disability Status Scale (EDSS), Multiple Sclerosis Severity Scale (MSSS), and a progressive course. No significant association was found with the HLA-DRB1*15:01 or ApoE ε4 alleles.

Conclusions:

These results provide support to the use of education as a proxy of cognitive reserve in MS and stress the need to take into account education when approaching cognition in MS.

Cognitive deficits in pediatric-onset multiple sclerosis: what does the future hold?

Pediatric-onset multiple sclerosis is relatively rare and research regarding disease characteristics is in its infancy. Regardless, there are a growing number of studies finding early cognitive deficits in this population. There are some similarities in outcomes to those seen in the adult-onset multiple sclerosis population, but also several important differences. With specific regard to cognitive functioning in pediatric-onset multiple sclerosis, there is evidence of deficit in nearly a third of patients, with impairment primarily in areas of processing speed, visual-spatial processing and language. There are additional findings of fatigue and depression that impact functional outcomes requiring further attention in assessment and treatment considerations. This paper also explores other areas requiring increased focus, including treatment and outcomes, neuroimaging and additional disease-modifying factors (comorbidities, socioeconomic status, race and so on).

Is neuropsychological rehabilitation effective in multiple sclerosis?

Cognitive deficits are common symptoms in multiple sclerosis (MS), and evident even in the early stages of the disease. Cognitive functions most frequently affected are information processing, memory and learning, and attention. Deficits may have a multidimensional impact on quality of life by weakening the ability to work, impairing social functioning and increasing the strain of the caregiver. To date, no effective pharmacological treatment for cognitive decline has been established, although there is some evidence suggesting that disease-modifying therapies may help to preserve cognitive function. Neuropsychological rehabilitation aims at alleviation of the negative effects of cognitive impairments and has been found to be effective in patients with stroke and traumatic brain injury. This paper discusses the evidence on neuropsychological rehabilitation in MS based on a recent systematic literature review and suggests a model for alleviating the effects of cognitive impairments in MS. The preliminary research evidence on the effects of neuropsychological rehabilitation in MS is positive: rehabilitation may have favorable effects on patients' cognitive performance and coping with cognitive impairments. In clinical practice, the diagnostics and treatment of cognitive impairments should be improved. Neuropsychological rehabilitation should be an important part of a rehabilitation regimen in MS.

Education modulates the impact of white matter lesions on the risk of mild cognitive impairment and dementia

OBJECTIVES

Conflicting results have been reported regarding the association between white matter lesions (WML) and cognitive impairment. We hypothesized that education, a marker of cognitive reserve (CR), could modulate the effects of WML on the risk of mild cognitive impairment (MCI) or dementia.

METHODS

We followed 500 healthy subjects from a cohort of community-dwelling persons aged 65 years and over (ESPRIT Project). At baseline, WML volume was measured using a semi-automatic method on T2-weighted MRI. Standardized cognitive and neurological evaluations were repeated after 2, 4, and 7 years. The sample was dichotomized according to education level into low (≤8 years) and high (>8 years) education groups. Cox proportional hazard models were constructed to study the association between WML and risk of MCI/dementia.

RESULTS

The interaction between education level and WML volume reached significance (p = 0.017). After adjustment for potential confounders, the association between severe WML and increased MCI/dementia risk was significant in the low education group (≤8 years) (p = 0.02, hazard ratio [HR]: 3.77 [1.29-10.99]), but not in the high education group (>8 years) (p = 0.82, HR: 1.07 [0.61-1.87]).

CONCLUSIONS

Severe WML significantly increases the risk of developing MCI/dementia over a 7-year period in low educated participants. Subjects with higher education levels were seen to be more likely to be resilient to the deleterious effects of severe WML. The CR hypothesis suggests several avenues for dementia prevention.

Does bilingualism contribute to cognitive reserve? Cognitive and neural perspectives

OBJECTIVE

Cognitive reserve refers to how individuals actively utilize neural resources to cope with neuropathology to maintain cognitive functioning. The present review aims to critically examine the literature addressing the relationship between bilingualism and cognitive reserve to elucidate whether bilingualism delays the onset of cognitive and behavioral manifestations of dementia. Potential neural mechanisms behind this relationship are discussed.

METHOD

PubMed and PsycINFO databases were searched (through January 2014) for original research articles in English or Spanish languages. The following search strings were used as keywords for study retrieval: "bilingual AND reserve," "reserve AND neural mechanisms," and "reserve AND multilingualism."

RESULTS

Growing scientific evidence suggests that lifelong bilingualism contributes to cognitive reserve and delays the onset of Alzheimer's disease symptoms, allowing bilingual individuals affected by Alzheimer's disease to live an independent and richer life for a longer time than their monolingual counterparts. Lifelong bilingualism is related to more efficient use of brain resources that help individuals maintain cognitive functioning in the presence of neuropathology. We propose multiple putative neural mechanisms through which lifelong bilinguals cope with neuropathology. The roles of immigration status, education, age of onset, proficiency, and frequency of language use on the relationship between cognitive reserve and bilingualism are considered.

CONCLUSIONS

Implications of these results for preventive practices and future research are discussed.

Cognitive reserve in multiple sclerosis

Cognitive impairment is common among persons with multiple sclerosis (MS), but some patients are able to withstand considerable disease burden (e.g. white matter lesions, cerebral atrophy) without cognitive impairment (cognitive inefficiency, memory decline). What protects these patients from cognitive impairment? We review the literature on cognitive reserve in MS, which shows that heritable (larger maximal lifetime brain growth) and environmental (greater intellectual enrichment) factors attenuate the negative effect of disease burden on cognitive status. That is, persons with larger maximal lifetime brain growth, greater vocabulary knowledge, and/or greater early life participation in cognitive leisure activities (e.g. reading, hobbies) are better able to cope with MS disease without cognitive impairment. We review evidence that benefits of intellectual enrichment on cognitive status may stem from more efficient patterns of brain function. We discuss clinical implications and highlight important unanswered questions for future research on reserve against cognitive impairment in MS.

Neuropsychological rehabilitation for multiple sclerosis

BACKGROUND

This is an update of the Cochrane review 'Neuropsychological rehabilitation for multiple sclerosis' (first published in The Cochrane Library 2011, Issue 11).Cognitive deficits are a common manifestation of multiple sclerosis (MS) and have a significant effect on the patient's quality of life. Alleviation of the harmful effects caused by these deficits should be a major goal of MS research and practice. 

OBJECTIVES

To assess the effects of neuropsychological/cognitive rehabilitation on health-related factors, such as cognitive performance and emotional well-being in patients with MS.

SEARCH METHODS

The Cochrane Multiple Sclerosis and Rare Diseases of the Central Nervous System Group Trials Search Co-ordinator searched their Specialised Register which, among other sources, contains trials from CENTRAL (The Cochrane Library 2013, Issue 2), MEDLINE, EMBASE, CINAHL, LILACS, PEDro and clinical trials registries (28 May 2013). We contacted authors of the studies for additional information.

SELECTION CRITERIA

Randomised controlled trials (RCTs) and quasi-randomised trials evaluating the effects of neuropsychological rehabilitation in MS compared to other interventions or no intervention.

DATA COLLECTION AND ANALYSIS

Two review authors individually judged the eligibility of the included studies, assessed risk of bias and extracted data. We combined results quantitatively in meta-analyses according to the intervention type: 1) cognitive training and 2) cognitive training combined with other neuropsychological rehabilitation methods.

MAIN RESULTS

Twenty studies (986 participants; 966 MS participants and 20 healthy controls) fulfilled the inclusion criteria. The mean age of the participants was 44.6 years, mean length of education was 12.3 years and 70% of the participants were women. Most of the participants had a relapsing-remitting course of disease. The mean Expanded Disability Status Scale score was 3.2 and the mean duration of disease was 14.0 years.On the basis of these studies, we found low-level evidence that neuropsychological rehabilitation reduces cognitive symptoms in MS. Cognitive training was found to improve memory span (standardised mean difference (SMD) 0.54, 95% confidence interval (CI) 0.20 to 0.88, P = 0.002) and working memory (SMD 0.33, 95% CI 0.09 to 0.57, P = 0.006). Cognitive training combined with other neuropsychological rehabilitation methods was found to improve attention (SMD 0.15, 95% CI 0.01 to 0.28, P = 0.03), immediate verbal memory (SMD 0.31, 95% CI 0.08 to 0.54, P = 0.008) and delayed memory (SMD 0.22, 95% CI 0.02 to 0.42, P = 0.03). There was no evidence of an effect of neuropsychological rehabilitation on emotional functions.The overall quality, as well as the comparability of the included studies, was relatively low due to methodological limitations and heterogeneity of interventions and outcome measures. Although most of the pooled results in the meta-analyses yielded no significant findings, 18 of the 20 studies showed some evidence of positive effects when the studies were individually analysed.

AUTHORS' CONCLUSIONS

This review found low-level evidence for positive effects of neuropsychological rehabilitation in MS. The interventions and outcome measures included in the review were heterogeneous, which limited the comparability of the studies. New trials may therefore change the strength and direction of the evidence.

Efficiency, capacity, compensation, maintenance, plasticity: emerging concepts in cognitive reserve

Cognitive reserve (CR) is a concept meant to account for the frequent discrepancy between an individual's measured level of brain pathology and her expected cognitive performance. It is particularly important within the context of aging and dementia, but has wider applicability to all forms of brain damage. As such, it has intimate links to related compensatory and neuroprotective concepts, as well as to the related notion of brain reserve. In this article, we introduce the concept of cognitive reserve and explicate its potential cognitive and neural implementation. We conclude that cognitive reserve is compatible and complementary with many related concepts, but that each much draw sharper conceptual boundaries in order to truly explain preserved cognitive function in the face of aging or brain damage.

Cognitive reserve: implications for assessment and intervention

The concept of reserve is used to explain the observation that some individuals function better than others in the presence of brain pathology. This article reviews the concept of reserve from its theoretical basis to the implication of reserve for clinical practice. A distinction between brain reserve, referring to individual differences in the anatomic substrate, and cognitive reserve, referring to differences in the flexibility or adaptivity of cognitive networks, is useful. Epidemiologic evidence indicates that a set of life exposures including higher educational and occupational attainment, and engaging in leisure activities is associated with a lower risk of incident dementia, suggesting that these life exposures may enhance cognitive reserve. This provides a basis for controlled clinical studies that can test specific exposures that may enhance reserve. The concept of cognitive reserve also has important implications for clinical practice in terms of diagnosis and prognosis.

Assessing the validity of a computer-generated cognitive screening instrument for patients with multiple sclerosis

Background:

Neuropsychological testing requires considerable time, expense, and expertise to administer. These factors can limit patient access. Computerized cognitive testing has been proposed as an alternative.

Objectives:

The objective of this paper is to validate a brief, simple-to-use computer-generated cognitive assessment screening battery for multiple sclerosis (MS) patients that has minimal motor involvement.

Methods:

A sample of 96 MS patients and 98 healthy controls completed a computer-generated battery that included the Stroop, Symbol Digit Modalities Test (C-SDMT), a two- and four-second visual analog of the Paced Auditory Serial Addition Test (PVSAT-2, PVSAT-4), and simple and choice reaction time tests. The Minimal Assessment of Cognitive Function in MS was used to define cognitive impairment in the MS sample.

Results:

Each newly developed test successfully distinguished between cognitively impaired patients and healthy controls as well as cognitively intact patients. A combination of three computerized tests (C-SDMT, PVSAT-2, PVSAT-4) with a mean administration time of 10 minutes had a sensitivity of 82.5% and specificity of 87.5% in detecting cognitive impairment. Good test-retest reliability was obtained for each measure.

Conclusions:

Good sensitivity and specificity, brevity, ease of administration, and a limited motor component highlight the feasibility of introducing this computer-generated cognitive screening instrument in a busy MS clinic.

Cognitive reserve in ageing and Alzheimer's disease

The concept of cognitive reserve provides an explanation for differences between individuals in susceptibility to age-related brain changes or pathology related to Alzheimer's disease, whereby some people can tolerate more of these changes than others and maintain function. Epidemiological studies suggest that lifelong experiences, including educational and occupational attainment, and leisure activities in later life, can increase this reserve. For example, the risk of developing Alzheimer's disease is reduced in individuals with higher educational or occupational attainment. Reserve can conveniently be divided into two types: brain reserve, which refers to differences in the brain structure that may increase tolerance to pathology, and cognitive reserve, which refers to differences between individuals in how tasks are performed that might enable some people to be more resilient to brain changes than others. Greater understanding of the concept of cognitive reserve could lead to interventions to slow cognitive ageing or reduce the risk of dementia.

Occupational attainment as a marker of cognitive reserve in multiple sclerosis

Cognitive dysfunction affects half of MS patients. Although brain atrophy generally yields the most robust MRI correlations with cognition, significant variance in cognition between individual MS patients remains unexplained. Recently, markers of cognitive reserve such as premorbid intelligence have emerged as important predictors of neuropsychological performance in MS. In the present study, we aimed to extend the cognitive reserve construct by examining the potential contribution of occupational attainment to cognitive decline in MS patients. Brain atrophy, estimated premorbid IQ, and occupational attainment were assessed in 72 MS patients. The Minimal Assessment of Cognitive Functioning in MS was used to evaluate indices of information processing speed, memory, and executive function. Results showed that occupational attainment was a significant predictor of information processing speed, memory, and executive function in hierarchical linear regressions after accounting for brain atrophy and premorbid IQ. These data suggest that MS patients with low occupational attainment fare worse cognitively than those with high occupational attainment after controlling for brain atrophy and premorbid IQ. Occupation, like premorbid IQ, therefore may make an independent contribution to cognitive outcome in MS. Information regarding an individual's occupation is easily acquired and may serve as a useful proxy for cognitive reserve in clinical settings.

Functional magnetic resonance imaging movers and shakers: does subject-movement cause sampling bias?

Head movement during functional magnetic resonance imaging (fMRI) degrades data quality. The effects of small movements can be ameliorated during data postprocessing, but data associated with severe movement is frequently discarded. In discarding these data, it is often assumed that head-movement is a source of random error, and that data can be discarded from subjects with severe movement without biasing the sample. We tested this assumption by examining whether head movement was related to task difficulty and cognitive status among persons with multiple sclerosis (MS). Thirty-four persons with MS were scanned while performing a working memory task with three levels of difficulty (the N-back task). Maximum movement (angle, shift) was estimated for each difficulty level. Cognitive status was assessed by combining performance on a working memory and processing speed task. An interaction was found between task difficulty and cognitive status (high vs. low cognitive ability): there was a linear increase in movement as task difficulty increased that was larger among subjects with lower cognitive ability. Analyses of the signal-to-noise ratio (SNR) confirmed that increases in movement degraded data quality. Similar, though far smaller, effects were found in a cohort of healthy control (HC) subjects. Therefore, discarding data with severe movement artifact may bias MS samples such that only those with less-severe cognitive impairment are included in the analyses. However, even if such data are not discarded outright, subjects who move more (MS and HC) will contribute less to the group-level results because of degraded SNR.

Cognitive reserve in secondary progressive multiple sclerosis

Background: Consistent with the cognitive reserve hypothesis, lifetime intellectual enrichment protects MS patients from cognitive impairment. As studies have focused predominately on patients with relapsing–remitting courses, it is unknown whether lifetime enrichment is protective against cognitive impairment in patients with secondary-progressive MS (SPMS), a more advanced disease course.

Objective: Examine whether greater lifetime intellectual enrichment moderates/reduces the deleterious effect of SPMS on memory and cognitive efficiency.

Methods: Twenty-five SPMS patients and 25 healthy controls (HC) completed neuropsychological tasks, yielding two composite scores: memory and cognitive efficiency. An estimate of lifetime enrichment was created from educational attainment and vocabulary knowledge. Regression analyses predicted memory and cognitive efficiency, with age, sex, intellectual enrichment and group (SPMS, HC) controlled in step one, and the interaction between intellectual enrichment and group evaluated within step two.

Results: Interactions emerged between intellectual enrichment and group when predicting memory ( R2Δ=0.081, p = 0.041) and cognitive efficiency ( R2Δ=0.064, p = 0.024), such that SPMS patients exhibited deficits relative to HCs at lower levels of enrichment, but these SPMS-related cognitive deficits were absent at higher levels of enrichment.

Conclusion: Intellectual enrichment protects SPMS patients from cognitive impairment, thereby extending the cognitive reserve hypothesis to this more advanced MS disease course.

Neuropsychological rehabilitation for multiple sclerosis

BACKGROUND

Cognitive deficits are a common manifestation in multiple sclerosis (MS) and have a wide effect on the patient's quality of life. Alleviation of the harmful effects caused by these deficits should be a major goal of MS research and practice.

OBJECTIVES

The aim of this review was to evaluate the effects of neuropsychological/cognitive rehabilitation in MS by conducting a systematic review.

SEARCH METHODS

A systematic literature search was carried out on reports drawn from Cochrane MS Group Specialised Register (To October 2010), Evidence-based medicine (EBM) reviews (To September 2010), MEDLINE (January 1950 to September 2010), EMBASE (1974 to September 2010), PsycINFO (January 1806 to September 2010), WEB OF SCIENCE (WOS) (January 1986 to September 2010), CINAHL (1982 to September 2010), and identified from the references in these reports.

SELECTION CRITERIA

Randomised Controlled Trials (RCTs) and quasi-randomised trials evaluating the effects of neuropsychological rehabilitation in MS compared to other interventions or no intervention at all and employing neuropsychological rehabilitation methods and outcome measures were included.

DATA COLLECTION AND ANALYSIS

Two review authors individually judged the relevance, risk of bias, and content of the included studies. Results were combined quantitatively with meta-analyses according to the intervention type: 1) Cognitive training and 2) Cognitive training combined with other neuropsychological rehabilitation methods. In addition, narrative presentation was used in reporting the results of those studies which were inappropriate to be included in the meta-analysis.

MAIN RESULTS

Fourteen studies (770 MS patients) fulfilled the inclusion criteria. On the basis of these studies, low level evidence was found that neuropsychological rehabilitation reduces cognitive symptoms in MS. Cognitive training was found to improve memory span (standardised mean difference 0.54 (95% confidence interval 0.2 to 0.88, P = 0.002)), working memory (standardised mean difference 0.33 (95% confidence interval 0.09 to 0.57, P = 0.006)), and immediate visual memory (standardised mean difference 0.32 (95% confidence interval 0.04 to 0.6, P = 0.02)). There was no evidence of an effect of cognitive training combined with other neuropsychological rehabilitation methods on cognitive or emotional functions. The overall quality as well as the comparability of the included studies were relatively low due to methodological limitations and heterogeneity of outcome measures. Although most of the pooled results in the meta-analyses yielded no significant findings, twelve of the fourteen studies showed some evidence of positive effects when the studies were individually analysed.

AUTHORS' CONCLUSIONS

The review indicates low level evidence for the positive effects of neuropsychological rehabilitation in MS. Interventions included in the review were heterogeneous. Consequently, clinical inferences can basically be drawn from single studies. Therefore, new trials may change the strength and direction of the evidence. To further strengthen the evidence, well-designed high quality studies are needed. In this systematic review, recommendations are given for improving the quality of future studies on the effects of neuropsychological rehabilitation in MS.

Cognitive reserve moderates the association between heart failure and cognitive impairment

BACKGROUND

Cognitive impairment in persons with heart failure is common. Theories of cognitive reserve suggest that premorbid factors, such as intellectual ability, may provide a buffer against cognitive impairment due to neuropathological insult. No study has examined the influence of cognitive reserve on cognitive functioning in older adults with heart failure.

AIM

This study examined whether cognitive reserve moderates the relationship between heart failure severity and cognitive function.

METHODS

A total of 157 persons with heart failure (69.26 ± 9.26 years; 39% female) completed neuropsychological testing and a brief fitness assessment. Cognitive reserve was operationalized using estimated premorbid intellect on the American National Adult Reading Test (AMNART).

RESULTS

A moderation analysis was performed using hierarchical regression models for each cognitive domain. An interaction term between the AMNART and 2-Minute Step Test was created and entered into the final block of the model, with demographic, psychosocial, and heart failure severity entered in the previous blocks. The interaction term was significant for attention, t(155) = -2.54, p = .012, executive function, t(155) = -3.30, p = .001, and language, t(155) = -2.83, p = .005, domains.

CONCLUSION

The current findings suggest that cognitive reserve moderates the association between heart failure severity and cognitive function in multiple cognitive domains. Further work is needed to clarify the mechanisms by which cognitive reserve attenuates cognitive impairment in this population.

Cognitive functioning in multiple sclerosis

In this article, the nature and course of cognitive dysfunction in MS are reviewed, particularly in the context of recent advances in our understanding of the diffuse nature of neuropathology in MS, and in the context of specific factors that may confer risk or protection for the development of cognitive impairment. In addition, assessment and screening approaches of MS-related cognitive dysfunction are discussed. MS is a condition not only restricted to the adult population, and this article includes a brief description of cognition in pediatric-onset MS. Finally, promising intervention approaches to treat cognitive problems in MS are summarized.

Successful cognitive aging in persons living with HIV infection

The number of older adults living with human immunodeficiency virus (HIV) infection is growing and this subpopulation of the epidemic is at heightened risk for a variety of poor health outcomes including HIV-associated neurocognitive disorders. The current study sought to examine the factors associated with freedom from neurocognitive impairment in older HIV-infected adults. Participants included 74 middle-aged and older (mean age 51 years), HIV-infected individuals with a mean estimated duration of infection of 17 years who underwent comprehensive neuropsychological, psychiatric, and medical evaluations. Successful cognitive aging (SCA) was operationally defined as the absence of neurocognitive deficits as determined by a battery of well-validated cognitive tests and self-endorsed cognitive complaints. Thirty-two percent of the cohort met these criteria. Compared to the group that did not meet these criteria, successful cognitive agers had significantly lower lifetime rates of major depressive disorder and current affective distress (e.g., depression, anxiety). Moreover, the SCA group evidenced better everyday functioning outcomes, including medication adherence, lower self-reported rates of declines in activities of daily living, and superior abilities related to medication management and dealing with healthcare providers. SCA was not related to demographic composition, HIV disease or treatment factors, medical comorbidities, or histories of substance use disorders. Findings from this preliminary study suggest that approximately one-third of older persons with HIV were free of cognitive impairments, which is associated with more favorable emotional, psychosocial, and everyday functioning.

Intellectual enrichment lessens the effect of brain atrophy on learning and memory in multiple sclerosis

OBJECTIVE

Learning and memory impairments are prevalent among persons with multiple sclerosis (MS); however, such deficits are only weakly associated with MS disease severity (brain atrophy). The cognitive reserve hypothesis states that greater lifetime intellectual enrichment lessens the negative impact of brain disease on cognition, thereby helping to explain the incomplete relationship between brain disease and cognitive status in neurologic populations. The literature on cognitive reserve has focused mainly on Alzheimer disease. The current research examines whether greater intellectual enrichment lessens the negative effect of brain atrophy on learning and memory in patients with MS.

METHODS

Forty-four persons with MS completed neuropsychological measures of verbal learning and memory, and a vocabulary-based estimate of lifetime intellectual enrichment. Brain atrophy was estimated with third ventricle width measured from 3-T magnetization-prepared rapid gradient echo MRIs. Hierarchical regression was used to predict learning and memory with brain atrophy, intellectual enrichment, and the interaction between brain atrophy and intellectual enrichment.

RESULTS

Brain atrophy predicted worse learning and memory, and intellectual enrichment predicted better learning; however, these effects were moderated by interactions between brain atrophy and intellectual enrichment. Specifically, higher intellectual enrichment lessened the negative impact of brain atrophy on both learning and memory.

CONCLUSION

These findings help to explain the incomplete relationship between multiple sclerosis disease severity and cognition, as the effect of disease on cognition is attenuated among patients with higher intellectual enrichment. As such, intellectual enrichment is supported as a protective factor against disease-related cognitive impairment in persons with multiple sclerosis.

Intellectual enrichment is linked to cerebral efficiency in multiple sclerosis: functional magnetic resonance imaging evidence for cognitive reserve

The cognitive reserve hypothesis helps to explain the incomplete relationship between brain disease and cognitive status in people with neurologic diseases, including Alzheimer's; disease and multiple sclerosis. Lifetime intellectual enrichment (estimated with education or vocabulary knowledge) lessens the negative impact of brain disease on cognition, such that people with greater enrichment are able to withstand more severe neuropathology before suffering cognitive impairment or dementia. The current research is the first to investigate directly the relationship between intellectual enrichment and an index of cerebral activity (the blood oxygen level dependent signal) in a neurologic sample. Multiple sclerosis patients completed a vocabulary-based estimate of lifetime intellectual enrichment. Disease severity was estimated with brain atrophy. Cognitive status was measured with the Symbol Digit Modalities Test. Cerebral activity (functional magnetic resonance imaging blood oxygen level dependent signal) and behavioural performance (accuracy, reaction time) were recorded during the visual N-Back working memory task (three levels of demand: 0-, 1-, 2-Back). All patients produced perfect/nearly perfect accuracy during lower demands (0- and 1-Back), and reaction time was unrelated to intellectual enrichment; however, voxelwise partial correlations controlling for brain atrophy revealed strong positive correlations between intellectual enrichment and cerebral activity within the brain's; default network (e.g. anterior and posterior cingulate corticies), indicating that patients with greater enrichment were able to maintain resting state activity during cognitive processing better. In turn, intellectual enrichment was negatively associated with prefrontal recruitment, suggesting that patients with lesser enrichment required more cerebral resources to perform the same cognitive task as patients with greater enrichment. This same pattern of enrichment-related cerebral activity was observed when cognitive demands increased (2-Back), and intellectual enrichment was negatively associated with reaction time. Principle components analysis revealed a single cognitive reserve network across tasks (greater default network, lesser prefrontal recruitment). Expression of this network almost fully mediated the positive relationship between intellectual enrichment and cognitive status (Symbol Digit Modalities Test). Also, expression of this network was positively associated with brain atrophy when controlling for cognitive status, indicating that patients with greater expression of this network can withstand more severe brain disease before exhibiting cognition similar to patients with lesser network expression. Of note, similar functional magnetic resonance imaging research with healthy adults has not found an association between intelligence and cerebral efficiency. The unique relationship between intellectual enrichment and cerebral efficiency in neurologic patients is consistent with the cognitive reserve hypothesis, which does not posit that enrichment leads to gains in neurocognitive functioning per se; rather, enrichment protects against neurocognitive decline secondarily to disease.

White matter hyperintensities and cognition: testing the reserve hypothesis

OBJECTIVE

White matter hyperintensities (WMH), visualized on T2-weighted MRI, are thought to reflect small-vessel vascular disease. Much like other markers of brain disease, the association between WMH and cognition is imperfect. The concept of reserve may account for this imperfect relationship. The purpose of this study was to test the reserve hypothesis in the association between WMH severity and cognition. We hypothesized that individuals with higher amounts of reserve would be able to tolerate greater amounts of pathology than those with lower reserve.

METHODS

Neurologically healthy older adults (n=717) from a community-based study received structural MRI, neuropsychological assessment, and evaluation of reserve. WMH volume was quantified algorithmically. We derived latent constructs representing four neuropsychological domains, a measure of cognitive reserve, and a measure of brain reserve. Measures of cognitive and brain reserve consisted of psychosocial (e.g., education) and anthropometric (e.g., craniometry) variables, respectively.

RESULTS

Increased WMH volume was associated with poorer cognition and higher cognitive and brain reserve were associated with better cognition. Controlling for speed/executive function or for language function, those with higher estimates of cognitive reserve had significantly greater degrees of WMH volume, particularly among women. Controlling for cognitive functioning across all domains, individuals with higher estimates of brain reserve had significantly greater WMH volume.

CONCLUSIONS

For any given level of cognitive function, those with higher reserve had more pathology in the form of WMH, suggesting that they are better able to cope with pathology than those with lower reserve. Both brain reserve and cognitive reserve appear to mitigate the impact of pathology on cognition.