Episodic memory and executive functions in cognitively healthy individuals display distinct neuroanatomical correlates which are differentially modulated by aging

Small effects of olfactory identification and discrimination on global cognitive and executive performance over 1 year in aging people without a history of age-related cognitive impairment

Olfactory and cognitive performance share neural correlates profoundly affected by physiological aging. However, whether odor identification and discrimination scores predict global cognitive status and executive function in healthy older people with intact cognition is unclear. Therefore, in the present study, we set out to elucidate these links in a convenience sample of 204 independently living, cognitively intact healthy Czech adults aged 77.4 ± 8.7 (61-97 years) over two waves of data collection (one-year interval). We used the Czech versions of the Montreal Cognitive Assessment (MoCA) to evaluate global cognition, and the Prague Stroop Test (PST), Trail Making Test (TMT), and several verbal fluency (VF) tests to assess executive function. As a subsidiary aim, we aimed to examine the contribution of olfactory performance towards achieving a MoCA score above vs. below the published cut-off value. We found that the MoCA scores exhibited moderate associations with both odor identification and discrimination. Furthermore, odor identification significantly predicted PST C and C/D scores. Odor discrimination significantly predicted PST C/D, TMT B/A, and standardized composite VF scores. Our findings demonstrate that olfaction, on the one hand, and global cognition and executive function, on the other, are related even in healthy older people.

Insulin-like growth factor-1 and cognition in normoglycemia, prediabetes, and type 2 diabetes mellitus

BACKGROUND

The relationship between insulin-like growth factor-1 (IGF-1) and cognition has been studied in healthy individuals, but not extensively with regards to insulin resistance and type 2 diabetes mellitus (T2DM). In this retrospective observational study, we investigated relationships of IGF-1 with memory and executive function across people with normoglycemia, prediabetes, and T2DM.

METHODS

Data from the Midlife in the United States (MIDUS) study were used. Episodic memory and executive function were assessed using the Brief Test of Adult Cognition by Telephone approximately 21.42 ± 12.10 months prior to measuring IGF-1 levels from a fasting blood sample. Normoglycemia was identified as individuals without a physician diagnosis of diabetes and glycated hemoglobin (HbA1c) ≤5.6%. Prediabetes was identified as those without a physician diagnosis of diabetes and HbA1c between 5.7%-6.4%. T2DM was identified as anyone with a physician diagnosis of diabetes, or HbA1c ≥6.5%, or anyone using an oral hypoglycemic medication. The associations were assessed using linear regressions controlling for age, sex, education, body mass index, C-reactive protein, HbA1c or homeostatic model of insulin resistance, MIDUS wave, exercise, smoking status, sleep quality, alcohol intake, oral hypoglycemic use, and insulin use.

RESULTS

The study included 1400 participants, which consisted of 583 normoglycemic (48.4% female, mean age 51.0 ± 12.2 years), 512 prediabetes (58.4% female, mean age 57.3 ± 11.8 years), and 305 T2DM participants (53.8% female, mean age 57.6 ± 11.5 years). Peripheral IGF-1 concentrations were lower (F2,1397 = 28.29, p < 0.001) in people with prediabetes or T2DM, vs. normoglycemia. Participants with prediabetes or T2DM had lower episodic memory (F2,1397 = 9.21, p < 0.001) and executive function (F2,1397 = 20.29, p < 0.001) composite z-scores than people with normoglycemia. Higher IGF-1 concentrations were associated with better executive performance in individuals with prediabetes (β = 0.115 [0.028, 0.202], p = 0.010), but not in individuals with normoglycemia or T2DM. An interaction between IGF-1 and sex in predicting executive function was observed in the prediabetes group (β = -0.344, p = 0.042), where the relationship was weaker in females (β = 0.106 [-0.012, 0.224], p = 0.077) than males (β = 0.251 [0.123, 0.380], p < 0.001). No associations were seen between IGF-1 and memory.

CONCLUSION

The results suggest that peripheral IGF-1 concentrations may be related to executive function, and that the relationship may be sex-specific and dependent on diabetes status.

Distinct neuroanatomical correlates of interference-related verbal episodic memory test in healthy older adults

Verbal learning test can include a trial of interference process that intrude initial learning and impose additional cognitive stress. However, it has been unclear whether the multiple memory processes underly different brain structural bases. We measured performances of word retrieval that represents distinct memory processes (initial learning, interference, and retention) and regional gray matter morphology from 230 cognitively unimpaired older adults. We identified three distinct multivariate pattern modes using canonical correlation analysis that map correspondence between memory and brain morphometry. The first mode comprised weights highly loaded on temporal lobe and overall performances. The second mode reflected subcortical volumes and initial learning performances. The third mode comprised thickness in the lateral prefrontal and parietal cortex and captured an ability to resist retroactive interference effect. While overall test performance reflected the temporal lobe and whole-gray matter volume, the interim trial of interference signifies neural correlates extending to subcortical and frontoparietal regions.

Genotypic effects of APOE-ε4 on resting-state connectivity in cognitively intact individuals support functional brain compensation

The investigation of resting-state functional connectivity (rsFC) in asymptomatic individuals at genetic risk for Alzheimer's disease (AD) enables discovering the earliest brain alterations in preclinical stages of the disease. The APOE-ε4 variant is the major genetic risk factor for AD, and previous studies have reported rsFC abnormalities in carriers of the ε4 allele. Yet, no study has assessed APOE-ε4 gene-dose effects on rsFC measures, and only a few studies included measures of cognitive performance to aid a clinical interpretation. We assessed the impact of APOE-ε4 on rsFC in a sample of 429 cognitively unimpaired individuals hosting a high number of ε4 homozygotes (n = 58), which enabled testing different models of genetic penetrance. We used independent component analysis and found a reduced rsFC as a function of the APOE-ε4 allelic load in the temporal default-mode and the medial temporal networks, while recessive effects were found in the extrastriate and limbic networks. Some of these results were replicated in a subsample with negative amyloid markers. Interaction with cognitive data suggests that such a network reorganization may support cognitive performance in the ε4-homozygotes. Our data indicate that APOE-ε4 shapes the functional architecture of the resting brain and favor the idea of a network-based functional compensation.

Longitudinal resting-state functional connectivity and regional brain atrophy-based biomarkers of preclinical cognitive impairment in healthy old adults

BACKGROUND

Intervention against age-related neurodegenerative diseases may be difficult once extensive structural and functional deteriorations have already occurred in the brain.

AIM

Investigating 6-year longitudinal changes and implications of regional brain atrophy and functional connectivity in the triple-network model as biomarkers of preclinical cognitive impairment in healthy aging.

METHODS

We acquired longitudinal cognitive scores and magnetic resonance imaging (MRI) data from 74 healthy old adults. Resting-state functional MRI (rs-fMRI) analysis was conducted using FSL6.0.1 to examine functional connectivity changes and regional brain morphometries were quantified using FreeSurfer5.3. Finally, we cross-validated and compared two support vector machine (SVM) regression models to predict future 6-year cognition score from the baseline regional brain atrophy and resting-state functional connectivity (rs-FC) measures.

RESULTS

After a 6-year follow-up, our results (P < 0.05-corrected) indicated significant connectivity reduction within all the three brain networks, significant differences in regional brain volumes and cortical thickness. We also observed significant improvement in episodic memory and significant decline in executive functions. Finally, comparing the two models, we observed that regional brain atrophy predictors were more efficient in approximating future 6-year cognitive scores (R = 0.756, P < 0.0001) than rs-FC predictors (R = 0.6, P < 0.0001).

CONCLUSION

This study used longitudinal data to keep subject variability low and to increase the validity of the results. We demonstrated significant changes in structural and functional MRI over 6 years. Our findings present a potential neuroimaging-based biomarker to detect cognitive impairment and prevent risks of neurodegenerative diseases in healthy old adults.

The associations of insomnia symptoms with daytime behavior and cognitive functioning in children with attention deficit hyperactivity disorder

STUDY OBJECTIVES

The current study aimed to examine the association of insomnia symptoms with daytime behavior and cognitive functioning in children with attention deficit hyperactivity disorder (ADHD).

METHODS

Thirty-six children with ADHD and insomnia symptoms, 27 children with ADHD without insomnia symptoms and 21 age-matched healthy controls were recruited in this study (age range: 6-12 years, 70% male). They were assessed by parent-report questionnaires on insomnia symptoms (Children's Sleep Habit Questionnaire) and ADHD symptoms (Strengths and Weaknesses of ADHD Symptoms and Normal Behavior Scale, SWAN), and completed a battery of cognitive tests including Continuous Performance Test (CPT) for sustained attention, Letter-digit test for processing speed, Digit Span forward test and N-back task for working memory, Tower of London (TOL) test for planning skills and Bergs Card Sorting Test (BCST) for set-shifting ability.

RESULTS

Children with ADHD and insomnia symptoms had the highest scores on SWAN total, and inattention and hyperactivity subscales, followed by children with ADHD without insomnia and healthy controls (all ps < 0.05). After controlling for potential confounders, children with ADHD and insomnia symptoms showed poorer performance on CPT and Letter-digit test as compared to children with ADHD without insomnia and healthy controls (all ps < 0.05).

CONCLUSIONS

Insomnia symptoms are associated with more severe ADHD symptoms and cognitive impairments in children with ADHD, especially deficits on sustained attention and processing speed. Future longitudinal studies are needed to explore the long-term impacts of insomnia symptoms and the effects of sleep-focused intervention on cognitive functioning in children with ADHD.

Executive Functions in Alzheimer’s Disease: A Systematic Review

Background: In Alzheimer’s disease, in addition to memory, attention has been given to cognitive testing due to its interface and connection with memory. Objective: The aim of this study is to take a global view of executive functions and place the concept within the theoretical framework of Alzheimer’s disease dementia, verifying their role in the cognitive functioning of the human mind, as well as how they are compromised in this pathology. Methods: An initial search was carried out in databases such as PubMed, ScienceDirect, and Web of Science. The guiding question presented at the end of the introduction was elaborated from the PICO/PIO/PEO strategy. The selected articles, therefore, answered the guiding question, were made available in full, and published in the period from 2000 to 2020. Studies without specific methodology and which correlated with other diseases or other types of dementia were excluded. To meet the objective, an integrative literature review was adopted. Results: The results indicate that, although the tests to verify the performance of cognitive functions have their limitations, they bring some evidence that they have been compromised, especially when analyzed periodically during the development of dementia. Conclusion: It is concluded that there is an interference of executive functions in function of Alzheimer’s and that memory and attention are the most evident in this type of dementia.

Daytime Sleep Behaviors and Cognitive Performance in Middle- to Older-Aged Adults Living with and without HIV Infection

PURPOSE

We investigated whether daytime sleep behaviors (DSBs) such as frequent daytime sleepiness or napping are associated with worse cognitive performance, and whether HIV infection moderates this relationship.

METHODS

Among 502,507 participants in the UK Biobank study, we identified 562 people living with HIV infection (PLWH; M _age= 50.51±7.81; 25.09% female; 78.83% white) and extracted 562 uninfected controls who matched on age, sex, ethnic background, social-economic status, and comorbidities. DSB burden was assessed based on answers to two questions on DSBs. Participants who answered "sometimes" or "often/usually" to one of them were considered to have poor DSB burden, or otherwise were considered not having any. A composite cognition score was computed by averaging the available standardized individual test results from four neurocognitive tests: ie, a reaction time test for information processing speed, a pairs matching test for visual episodic memory, a fluid intelligence test for reasoning, and a prospective memory test. Mixed-effects models with adjustment for the variables used in extracting matched uninfected controls were performed to test the hypotheses.

RESULTS

Having poor DSB burden was associated with a 0.15 - standard deviation (SD) decrease in cognitive performance (p = 0.006). People living with HIV infection (PLWH) also performed worse on the cognitive tasks than uninfected controls, with an effect size similar to that of having poor DSB burden (p = 0.003). HIV infection significantly modified the negative association between DSB burden and cognition (p for interaction: 0.008). Specifically, the association between DSB burden and cognition was not statistically significant in uninfected controls, whereas PLWH who reported having poor DSB burden had a 0.28 - SD decrease in cognitive performance compared to PLWH who did not.

CONCLUSION

HIV infection significantly increased the adverse association between DSBs and cognitive performance. Further studies are needed to investigate the potential mechanisms that underlie this interaction effect and whether poor DSBs and worse cognitive performance are causally linked.

Cross-sectional and prospective associations between self-reported sleep characteristics and cognitive function in men and women: The Midlife in the United States study

Sleep behaviour is an important contributing factor in healthy human ageing and cognitive function. Previous studies have linked sleep deficiency with cognitive decline in older adults. However, there is need for more prospective investigations that focus on specific domains of cognitive function. The present study analysed cross-sectional and prospective associations between self-reported sleep and cognitive function in the Midlife in the United States (MIDUS) study. Weekday and weekend sleep duration and habitual sleep quality were obtained via questionnaire data. Brief Test of Adult Cognition by Telephone was conducted to assess overall cognitive function, as well as episodic memory and executive function. We found significant trend for both long weekday and weekend sleep (>8 hr) and lower episodic memory scores in the overall sample. Sex-specific cross-sectional analysis demonstrated men with longer weekend sleep duration have lower overall cognitive function scores, and a negative association between weekend sleep and episodic memory scores. Women demonstrated a positive association between weekend sleep duration and executive function scores. There was no prospective significance for overall or sex-specific analysis. Our present results suggest that sleep duration may contribute to cognitive function, and future studies should include objective sleep measurements and focus on the potential cognitive benefits of improving sleep to further elucidate this association.

The Effect of the APOE-ε4 Allele on the Cholinergic Circuitry for Subjects With Different Levels of Cognitive Impairment

Background: Cholinergic deficiency has been suggested to associate with the abnormal accumulation of Aβ and tau for patients with Alzheimer's disease (AD). However, no studies have investigated the effect of APOE-ε4 and group differences in modulating the cholinergic basal forebrain-amygdala network for subjects with different levels of cognitive impairment. We evaluated the effect of APOE-ε4 on the cholinergic structural association and the neurocognitive performance for subjects with different levels of cognitive impairment. Methods: We used the structural brain magnetic resonance imaging scans from the Alzheimer's Disease Neuroimaging Initiative dataset. The study included cognitively normal (CN, n = 167) subjects and subjects with significant memory concern (SMC, n = 96), early mild cognitive impairment (EMCI, n = 146), late cognitive impairment (LMCI, n = 138), and AD (n = 121). Subjects were further categorized according to the APOE-ε4 allele carrier status. The main effects of APOE-ε4 and group difference on the brain volumetric measurements were assessed. Regression analyses were conducted to evaluate the associations among cholinergic structural changes, APOE-ε4 status, and cognitive performance. Results: We found that APOE-ε4 carriers in the disease group showed higher brain atrophy than non-carriers in the cholinergic pathway, while there is no difference between carriers and non-carriers in the CN group. APOE-ε4 allele carriers in the disease groups also exhibited a stronger cholinergic structural correlation than non-carriers did, while there is no difference between the carriers and non-carriers in the CN subjects. Disease subjects exhibited a stronger structural correlation in the cholinergic pathway than CN subjects did. Moreover, APOE-ε4 allele carriers in the disease group exhibited a stronger correlation between the volumetric changes and cognitive performance than non-carriers did, while there is no difference between carriers and non-carriers in CN subjects. Disease subjects exhibited a stronger correlation between the volumetric changes and cognitive performance than CN subjects did. Conclusion: Our results confirmed the effect of APOE-ε4 on and group differences in the associations with the cholinergic structural changes that may reflect impaired brain function underlying neurocognitive degeneration in AD.

Association between composite scores of domain-specific cognitive functions and regional patterns of atrophy and functional connectivity in the Alzheimer's disease spectrum

•

Composite scores provide reliable metrics of domain function in multicenter cohort.

•

Visuo-spatial domain composite scores relate to anatomic changes in AD spectrum.

•

Domain scores relate to network-specific resting-state connectivity in AD spectrum.

Background

Cognitive decline has been found to be associated with gray matter atrophy and disruption of functional neural networks in Alzheimer’s disease (AD) in structural and functional imaging (fMRI) studies. Most previous studies have used single test scores of cognitive performance among monocentric cohorts. However, cognitive domain composite scores could be more reliable than single test scores due to the reduction of measurement error. Adopting a multicentric resting state fMRI (rs-fMRI) and cognitive domain approach, we provide a comprehensive description of the structural and functional correlates of the key cognitive domains of AD.

Method

We analyzed MRI, rs-fMRI and cognitive domain score data of 490 participants from an interim baseline release of the multicenter DELCODE study cohort, including 54 people with AD, 86 with Mild Cognitive Impairment (MCI), 175 with Subjective Cognitive Decline (SCD), and 175 Healthy Controls (HC) in the AD-spectrum. Resulting cognitive domain composite scores (executive, visuo-spatial, memory, working memory and language) from the DELCODE neuropsychological battery (DELCODE-NP), were previously derived using confirmatory factor analysis. Statistical analyses examined the differences between diagnostic groups, and the association of composite scores with regional atrophy and network-specific functional connectivity among the patient subgroup of SCD, MCI and AD.

Result

Cognitive performance, atrophy patterns and functional connectivity significantly differed between diagnostic groups in the AD-spectrum. Regional gray matter atrophy was positively associated with visuospatial and other cognitive impairments among the patient subgroup in the AD-spectrum. Except for the visual network, patterns of network-specific resting-state functional connectivity were positively associated with distinct cognitive impairments among the patient subgroup in the AD-spectrum.

Conclusion

Consistent associations between cognitive domain scores and both regional atrophy and network-specific functional connectivity (except for the visual network), support the utility of a multicentric and cognitive domain approach towards explicating the relationship between imaging markers and cognition in the AD-spectrum.

The role of cognitive reserve in the relationship between metabolic syndrome and cognitive functioning

Metabolic syndrome (MetS) is a cluster of vascular risk factors that can impact cognition. Cognitive reserve (CR), specifically early operators of reserve (e.g., education), have not been explored in the relationship between MetS and cognition. Adults 45-90 years old (n = 149) underwent neuropsychological testing and evaluation for MetS. Exploratory and confirmatory factor analyses defined neuropsychological domains and created a CR score based on early operators of CR. Regression analyses examined the association among MetS, CR, and neuropsychological performance. CFA revealed two neuropsychological factors: Episodic Memory and Executive Functioning. Controlling for age and physical ability, MetS and CR were significant predictors of the Factors. With CR in the model, MetS became a non-significant predictor of Executive Functioning; CR and physical ability were the most significant predictors. CR and MetS significantly predicted Episodic Memory . The results are discussed in the context of neuroprotective factors and cognitive aging.

Effect of BDNF Val66Met on hippocampal subfields volumes and compensatory interaction with APOE-ε4 in middle-age cognitively unimpaired individuals from the ALFA study

Background

Current evidence supports the involvement of brain-derived neurotrophic factor (BDNF) Val66Met polymorphism, and the ε4 allele of APOE gene in hippocampal-dependent functions. Previous studies on the association of Val66Met with whole hippocampal volume included patients of a variety of disorders. However, it remains to be elucidated whether there is an impact of BDNF Val66Met polymorphism on the volumes of the hippocampal subfield volumes (HSv) in cognitively unimpaired (CU) individuals, and the interactive effect with the APOE-ε4 status.

Methods

BDNF Val66Met and APOE genotypes were determined in a sample of 430 CU late/middle-aged participants from the ALFA study (ALzheimer and FAmilies). Participants underwent a brain 3D-T1-weighted MRI scan, and volumes of the HSv were determined using Freesurfer (v6.0). The effects of the BDNF Val66Met genotype on the HSv were assessed using general linear models corrected by age, gender, education, number of APOE-ε4 alleles and total intracranial volume. We also investigated whether the association between APOE-ε4 allele and HSv were modified by BDNF Val66Met genotypes.

Results

BDNF Val66Met carriers showed larger bilateral volumes of the subiculum subfield. In addition, HSv reductions associated with APOE-ε4 allele were significantly moderated by BDNF Val66Met status. BDNF Met carriers who were also APOE-ε4 homozygous showed patterns of higher HSv than BDNF Val carriers.

Conclusion

To our knowledge, the present study is the first to show that carrying the BDNF Val66Met polymorphisms partially compensates the decreased on HSv associated with APOE-ε4 in middle-age cognitively unimpaired individuals.

Electronic supplementary material

The online version of this article (10.1007/s00429-020-02125-3) contains supplementary material, which is available to authorized users.

Fitness Level Influences White Matter Microstructure in Postmenopausal Women

Aerobic exercise has both neuroprotective and neurorehabilitative benefits. However, the underlying mechanisms are not fully understood and need to be investigated, especially in postmenopausal women, who are at increased risk of age-related disorders such as Alzheimer’s disease and stroke. To advance our understanding of the potential neurological benefits of aerobic exercise in aging women, we examined anatomical and functional responses that may differentiate women of varying cardiorespiratory fitness using neuroimaging and neurophysiology. A total of 35 healthy postmenopausal women were recruited (59 ± 3 years) and cardiorespiratory fitness estimated (22–70 mL/kg/min). Transcranial magnetic stimulation was used to assess -aminobutyric acid (GABA) and glutamate (Glu) receptor function in the primary motor cortex (M1), and magnetic resonance spectroscopy (MRS) was used to quantify GABA and Glu concentrations in M1. Magnetic resonance imaging was used to assess mean cortical thickness (MCT) of sensorimotor and frontal regions, while the microstructure of sensorimotor and other white matter tracts was evaluated through diffusion tensor imaging. Regression analysis revealed that higher fitness levels were associated with improved microstructure in pre-motor and sensory tracts, and the hippocampal cingulum. Fitness level was not associated with MCT, MRS, or neurophysiology measures. These data indicate that, in postmenopausal women, higher cardiorespiratory fitness is linked with preserved selective white matter microstructure, particularly in areas that influence sensorimotor control and memory.

Playing Mahjong for 12 Weeks Improved Executive Function in Elderly People With Mild Cognitive Impairment: A Study of Implications for TBI-Induced Cognitive Deficits

Background: Mild cognitive impairment (MCI) is common among elderly people. So far, effective treatment that can stabilize or reverse the cognitive decline associated with MCI is lacking. Recent studies suggest that playing mahjong may improve attention and memory in elderly people. However, its effect on executive function remains unknown.

Methods: 56 elderly people (74.3 ± 4.3 years of age) with MCI from the First Social Welfare the First Nursing Home of Nanchong were randomized into mahjong and control groups (N = 28, each group). Subjects in the mahjong group played mahjong three times a week for 12 weeks, while people in the control group assumed normal daily activity. Executive function was evaluated using the Montreal Cognitive Assessment—Beijing (MoCA-B), the Shape Trail Test (STT), and the Functional Activities Questionnaire (FAQ) before the study and then at 6 and 12 weeks after mahjong administration.

Results: There were no baseline differences in MoCA-B, STT, and FAQ scoring between the two groups. The MoCA-B, STT, and FAQ scores, however, improved significantly in the mahjong group but not in the control group after the 12-week mahjong administration. Significant correlations were also found between STT and FAQ scores.

Conclusions: Playing Mahjong for 12 weeks improved the executive function of elderly people with MCI. Because Mahjong is a simple, low-cost entertainment activity, it could be widely applied to slow down or reverse the progression of cognitive decline in people with MCI, including those with traumatic brain injury.

Sadness, but not anger or fear, mediates the long-term leisure-cognition link: an emotion-specific approach

Past research has provided some evidence of positive relationships between leisure and cognitive functioning, but questions remain regarding their mechanisms. We argue that specific negative emotions may provide promising theoretical mechanisms for the leisure-cognition link. Guided by theories of leisure and emotion-specificity, we used a large-sample, longitudinal dataset of adult participants (N = 3536; 1940 females; M _age = 56.16) to examine the leisure-cognition link over about a decade and to test whether sadness, anger, or fear would be supported as emotion-specific mediators of the leisure-cognition link. Analyses were performed using observed variable path analyses and latent variable structural equation modelling. Controlling for demographics (age, gender, education level) and baseline cognitive functioning, leisure predicted better episodic memory and executive function a decade later. Moreover, both observed variable and latent variable mediational analyses supported sadness as a mediator of the link between leisure and episodic memory as well as executive function, such that leisure predicted reduced sadness, in turn predicting improved cognitive functioning. In contrast, neither fear nor anger were supported as mediators of the leisure-cognition link. Thus, the results support long-term links between leisure and cognitive functioning and also support sadness as an emotion-specific mediator of these relationships.

APOE-ε4 Shapes the Cerebral Organization in Cognitively Intact Individuals as Reflected by Structural Gray Matter Networks

Gray matter networks (GMn) provide essential information on the intrinsic organization of the brain and appear to be disrupted in Alzheimer’s disease (AD). Apolipoprotein E (APOE)-ε4 represents the major genetic risk factor for AD, yet the association between APOE-ε4 and GMn has remained unexplored. Here, we determine the impact of APOE-ε4 on GMn in a large sample of cognitively unimpaired individuals, which was enriched for the genetic risk of AD. We used independent component analysis to retrieve sources of structural covariance and analyzed APOE group differences within and between networks. Analyses were repeated in a subsample of amyloid-negative subjects. Compared with noncarriers and heterozygotes, APOE-ε4 homozygotes showed increased covariance in one network including primarily right-lateralized, parietal, inferior frontal, as well as inferior and middle temporal regions, which mirrored the formerly described AD-signature. This result was confirmed in a subsample of amyloid-negative individuals. APOE-ε4 carriers showed reduced covariance between two networks encompassing frontal and temporal regions, which constitute preferential target of amyloid deposition. Our data indicate that, in asymptomatic individuals, APOE-ε4 shapes the cerebral organization in a way that recapitulates focal morphometric alterations observed in AD patients, even in absence of amyloid pathology. This suggests that structural vulnerability in neuronal networks associated with APOE-ε4 may be an early event in AD pathogenesis, possibly upstream of amyloid deposition.

Association between insomnia and cognitive performance, gray matter volume, and white matter microstructure in cognitively unimpaired adults

BACKGROUND

Mounting evidence links poor sleep quality with a higher risk of late-life dementia. However, the structural and cognitive correlates of insomnia are still not well understood. The study aims were to characterize the cognitive performance and brain structural pattern of cognitively unimpaired adults at increased risk for Alzheimer's disease (AD) with insomnia.

METHODS

This cross-sectional study included 1683 cognitively unimpaired middle/late-middle-aged adults from the ALFA (ALzheimer and FAmilies) study who underwent neuropsychological assessment, T1-weighted structural imaging (n = 366), and diffusion-weighted imaging (n = 334). The World Health Organization's World Mental Health Survey Initiative version of the Composite International Diagnostic Interview was used to define the presence or absence of insomnia. Multivariable regression models were used to evaluate differences in cognitive performance between individuals with and without insomnia, as well as potential interactions between insomnia and the APOE genotype. Voxel-based morphometry and tract-based spatial statistics were used to assess between-group differences and potential interactions between insomnia and the APOE genotype in gray matter volume and white matter diffusion metrics.

RESULTS

Insomnia was reported by 615 out of 1683 participants (36.5%), including 137 out of 366 (37.4%) with T1-weighted structural imaging available and 119 out of 334 (35.6%) with diffusion-weighted imaging. Individuals with insomnia (n = 615) performed worse in executive function tests than non-insomniacs and displayed lower gray matter volume in left orbitofrontal and right middle temporal cortex, bilateral precuneus, posterior cingulate cortex and thalamus, higher gray matter volume in the left caudate nucleus, and widespread reduction of mean and axial diffusivity in right hemisphere white matter tracts. Insomnia interacted with the APOE genotype, with APOE-ε4 carriers displaying lower gray matter volumes when insomnia was present, but higher volumes when insomnia was not present, in several gray matter regions, including the left angular gyrus, the bilateral superior frontal gyri, the thalami, and the right hippocampus.

CONCLUSIONS

Insomnia in cognitively unimpaired adults at increased risk for AD is associated to poorer performance in some executive functions and volume changes in cortical and subcortical gray matter, including key areas involved in Alzheimer's disease, as well as decreased white matter diffusivity.

Moderating effect of cognitive reserve on the association between grey matter atrophy and memory varies with age in older adults

BACKGROUND

Educational attainment and verbal intelligence, which indirectly reflect an individual's cognitive reserve (CR), is suggested to buffer the effect of late-life brain degradation on cognitive performance outcome. We aimed to explore how the relationship between whole grey matter volume (GMV) and episodic memory function is altered by CR proxy as well as age in healthy older adults.

METHODS

Elderly Verbal Learning Test (EVLT) and structural magnetic resonance imaging were administered to 110 community-residing older adults. Moderated moderation model tested whether the association between whole GMV and episodic memory was moderated by both CR and chronological age.

RESULTS

The results showed that the moderating effect of CR on Immediate Recall, Short-delay Recall, and Recognition scores of EVLT differed across age groups. The elderly with higher CR showed steeper GMV effect on EVLT at the Age-Younger condition, while such moderating effect was reversed in the Age-Older condition, suggesting an alleviated brain atrophy effect in higher CR elderly.

CONCLUSION

These findings suggest that although higher CR elderly may exhibit earlier GMV-related memory decline, the buffering effect of CR on the cognitive decline due to brain atrophy would become more evident in old-old elderly people who are likely to have accumulated more neuropathological changes. This study underscores chronological age as an important moderating factor in examining the moderating role of CR in late-life memory function.

White matter hyperintensities mediate gray matter volume and processing speed relationship in cognitively unimpaired participants

White matter hyperintensities (WMH) have been extensively associated with cognitive impairment and reductions in gray matter volume (GMv) independently. This study explored whether WMH lesion volume mediates the relationship between cerebral patterns of GMv and cognition in 521 (mean age 57.7 years) cognitively unimpaired middle‐aged individuals. Episodic memory (EM) was measured with the Memory Binding Test and executive functions (EF) using five WAIS‐IV subtests. WMH were automatically determined from T2 and FLAIR sequences and characterized using diffusion‐weighted imaging (DWI) parameters. WMH volume was entered as a mediator in a voxel‐wise mediation analysis relating GMv and cognitive performance (with both EM and EF composites and the individual tests independently). The mediation model was corrected by age, sex, education, number of Apolipoprotein E (APOE)‐ε4 alleles and total intracranial volume. We found that even at very low levels of WMH burden in the cohort (median volume of 3.2 mL), higher WMH lesion volume was significantly associated with a widespread pattern of lower GMv in temporal, frontal, and cerebellar areas. WMH mediated the relationship between GMv and EF, mainly driven by processing speed, but not EM. DWI parameters in these lesions were compatible with incipient demyelination and axonal loss. These findings lead to the reflection on the relevance of the control of cardiovascular risk factors in middle‐aged individuals as a valuable preventive strategy to reduce or delay cognitive decline.

Relationship between neuropsychological behavior and brain white matter in first-episode psychosis

We addressed the relationship between white matter architecture, represented by MRI fractional anisotropy (FA), and cognition in individuals with first-episode psychosis (FEP) by applying for a new methodology that allows whole brain parcellation of core and peripheral white matter in a biologically meaningful fashion. Regionally specific correlations were found in FEP between three specific domains of cognition (processing speed, attention/working memory, and executive functioning) and FA at the deep (cerebral peduncles, sagittal striatum, uncinate, internal/external capsule, cingulum) and peripheral white matter (adjacent to inferior temporal, angular, supramarginal, insula, occipital, rectus gyrus).

APOE-ε4 risk variant for Alzheimer's disease modifies the association between cognitive performance and cerebral morphology in healthy middle-aged individuals

The APOE-ε4 genotype is the highest genetic risk factor for Alzheimer's disease (AD). In cognitively unimpaired individuals, it has been related to altered brain morphology, function and earlier amyloid beta accumulation. However, its impact on cognitive performance is less evident. Here, we examine the impact of APOE-ε4 allele load in modulating the association between cognitive functioning and brain morphology in middle-aged healthy individuals. A high-resolution structural MRI scan was acquired and episodic memory (EM) as well as executive functions (EFs) were assessed in a sample of 527 middle-aged unimpaired individuals hosting a substantial representation of ε4-homozygous (N = 64). We adopted a voxel-wise unbiased method to assess whether the number of APOE-ε4 alleles significantly modified the associations between gray matter volumes (GMv) and performance in both cognitive domains. Even though the APOE-ε4 allele load did not exert a direct impact on any cognitive measures, it reversed the relationships between GMv and cognitive performance in a highly symmetrical topological pattern. For EM, interactions mapped onto the inferior temporal gyrus and the dorsal anterior cingulate cortex. Regarding EFs, significant interactions were observed for processing speed, working memory, and visuospatial attention in distinct brain regions. These results suggest that APOE-ε4 carriers display a structure-function association corresponding to an older age than their chronological one. Our findings additionally indicate that APOE-ε4 carriers may rely on the integrity of multiple compensatory brain systems in order to preserve their cognitive abilities, possibly due to an incipient neurodegeneration. Overall this study provides novel insights on the mechanisms through which APOE-ε4 posits an increased AD risk.

Episodic memory and executive functions in cognitively healthy individuals display distinct neuroanatomical correlates which are differentially modulated by aging

The neuroanatomical bases of episodic memory (EM) and executive functions (EFs) have been widely addressed in patients with brain damage and in individuals with neurologic disorders. These studies reported that larger brain structures support better outcomes in both cognitive domains, thereby supporting the “bigger is better” account. However, relatively few studies have explored the cerebral morphological properties underlying EM and EFs in cognitively healthy individuals and current findings indicate no unitary theoretical explanation for the structure–function relationship. Moreover, existing studies have typically restricted the analyses to a priori defined regions of interest. Here we conducted unbiased voxel‐wise analysis of the associations between regional gray as well as white matter volumes (GMv; WMv) and performance in both cognitive domains in a sample of 463 cognitively intact individuals. We found that efficiency in EM was predicted by lower GMv in brain areas belonging to the default‐mode network (DMN). By contrast, EFs performance was predicted by larger GMv in a distributed set of regions, which overlapped with the executive control network (ECN). Volume of white matter bundles supporting both cross‐cortical and interhemispheric connections was positively related to processing speed. Furthermore, aging modulated the relationship between regional volumes and cognitive performance in several areas including the hippocampus and frontal cortex. Our data extend the critical role of the DMN and ECN by showing that variability in their morphological properties, and not only their activation patterns, affects EM and EFs, respectively. Moreover, our finding that aging reverts these associations supports previously advanced theories of cognitive neurodevelopment.