AD-signature Cortical Thickness Research Articles

Neurodegenerative biomarkers of A‐T+ compared to A+T+ and A‐T‐ older adults

AbstractBackgroundPrimary age‐related tauopathy (PART) is a neuropathological entity with neurofibrillary tangles in the absence of beta‐amyloid plaques in the brain. Recent advances in neuroimaging made it possible to identify amyloid PET‐negative (A‐) tau PET‐positive (T+) condition as a possible candidate for PART in living human brains. We tried to investigate neurodegenerative biomarkers of A‐T+ older adults compared to those of A+T+ and A‐T‐ [corresponding to Alzheimer’s disease (AD) and no AD pathology, respectively] individuals.MethodA total of 156 older participants (64 cognitively normal, 43 mild cognitive impairment (MCI), and 49 dementia), were recruited from the Korean Brain Aging Study for the Early Diagnosis and Prediction of Alzheimer’s Disease (KBASE). All participants underwent comprehensive clinical evaluation and multimodal brain imaging including amyloid and tau PET, and MRI. Global PiB retention measured by 11C‐PiB‐PET and tau deposition in the regions corresponding to Braak stages measured by 18F‐AV‐1451 PET were used in this study. A+ was defined as global mean Aß deposition standardized uptake value ratio (SUVR) > 1.4 and T+ was defined as tau burden corresponding to Braak stages I/II, III/IV, or V/VI. Hippocampal volume, AD‐signature cortical thickness (AD‐CT), AD‐signature cerebral glucose metabolism (AD‐CM) and white matter hyperintensity (WMH) volume were also measured as neurodegenerative biomarkers. Multiple linear regression analysis controlling for age, gender, and APOE e4 positivity was used to investigate the group differences of neurodegenerative biomarkers.ResultOf the 156 participants, 31 were defined as A‐T‐, 53 as A+T‐, and 72 as A+T+. A‐T+ group had higher levels of hippocampal volume (B = 683.448, p<0.001), AD‐CT (B = 0.267, p<0.001) and AD‐CM (B = 0.174, p<0.001), but not WMH volume (B = ‐1.188, p = 0.651), compared to A+T+ group. When compared to A‐T‐ group, A‐T+ group did not show significant difference in any of the neurodegenerative biomarkers.ConclusionOur findings suggest that, in regard of neurodegeneration, older adults with A‐T+ condition, close to pathological PART, are less severe than those with A+T+, while they appear similar to those with A‐T‐.

Neurodegenerative biomarkers of A‐T+ compared to A+T+ and A‐T‐ older adults

AbstractBackgroundPrimary age‐related tauopathy (PART) is a neuropathological entity with neurofibrillary tangles in the absence of beta‐amyloid plaques in the brain. Recent advances in neuroimaging made it possible to identify amyloid PET‐negative (A‐) tau PET‐positive (T+) condition as a possible candidate for PART in living human brains. We tried to investigate neurodegenerative biomarkers of A‐T+ older adults compared to those of A+T+ and A‐T‐ [corresponding to Alzheimer’s disease (AD) and no AD pathology, respectively] individuals.MethodA total of 156 older participants (64 cognitively normal, 43 mild cognitive impairment (MCI), and 49 dementia), were recruited from the Korean Brain Aging Study for the Early Diagnosis and Prediction of Alzheimer’s Disease (KBASE). All participants underwent comprehensive clinical evaluation and multimodal brain imaging including amyloid and tau PET, and MRI. Global PiB retention measured by 11C‐PiB‐PET and tau deposition in the regions corresponding to Braak stages measured by 18F‐AV‐1451 PET were used in this study. A+ was defined as global mean Aβ deposition standardized uptake value ratio (SUVR) > 1.4 and T+ was defined as tau burden corresponding to Braak stages I/II, III/IV, or V/VI. Hippocampal volume, AD‐signature cortical thickness (AD‐CT), AD‐signature cerebral glucose metabolism (AD‐CM) and white matter hyperintensity (WMH) volume were also measured as neurodegenerative biomarkers. Multiple linear regression analysis controlling for age, gender, and APOE ε4 positivity was used to investigate the group differences of neurodegenerative biomarkers.ResultOf the 156 participants, 31 were defined as A‐T‐, 53 as A+T‐, and 72 as A+T+. A‐T+ group had higher levels of hippocampal volume (B = 683.448, p<0.001), AD‐CT (B = 0.267, p<0.001) and AD‐CM (B = 0.174, p<0.001), but not WMH volume (B = ‐1.188, p = 0.651), compared to A+T+ group. When compared to A‐T‐ group, A‐T+ group did not show significant difference in any of the neurodegenerative biomarkers.ConclusionOur findings suggest that, in regard of neurodegeneration, older adults with A‐T+ condition, close to pathological PART, are less severe than those with A+T+, while they appear similar to those with A‐T‐.

Association between 10‐year cardiovascular mortality‐risk and neuroimaging biomarkers in the FINGER trial

AbstractBackgroundCardiovascular risk factors are associated with cognitive decline and dementia. Timely estimation and targeting of cardiovascular risk burden may contribute towards the prevention of cognitive decline. The cardiovascular risk scores of the European Society of Cardiology’s, SCORE (for adults up to 64 years) and SCORE‐OP (for older adults aged 65 years or more), are commonly used tool for estimation of 10‐year CVD mortality and may reflect the impact of cardiovascular risk burden on brain pathology if validated against neuroimaging biomarkers.MethodThis study investigated associations between (i) baseline SCORE/SCORE‐OP and baseline neuroimaging biomarkers (brain magnetic resonance imaging [MRI] and Pittsburgh Compound B‐positron emission tomography [PiB‐PET] measures) (ii) change in SCORE/SCORE‐OP and change in neuroimaging measures during the 2‐year Finnish Geriatric Intervention Study to Prevent Cognitive Impairment and Disability (FINGER). FINGER targeted at‐risk older adults, aged 60‐77 years, from the general population. Participants were randomized to either multidomain intervention (diet, exercise, cognitive training, and vascular risk management) or control group (general health advice). Neuroimaging (MRI and PiB‐PET) data from baseline and 2‐year visits were used. A total of 112 participants had repeated brain MRI measures (hippocampus, total grey matter, and white matter lesion volumes, and Alzheimer’s disease signature cortical thickness). Repeated PiB‐PET scans were available for 39 participants.ResultPreliminary results suggest that at baseline higher SCORE/SCORE‐OP, indicating increased risk of CVD mortality was significantly associated with lower hippocampus volume (estimate = ‐0.010; p = 0.004), lower total grey matter volume (estimate = ‐0.016; p = 0.007), higher white matter lesion volume (estimate = 0.048; p = 0.015), and lower AD signature cortical thickness (‐0.004; p = 0.048) but not with PiB‐PET. No significant associations were found for change in neuroimaging measures and baseline SCORE/SCORE‐OP or change in SCORE/SCORE‐OP during the 2‐year follow‐up.ConclusionCardiovascular risk scores need to be validated against different brain pathology markers in diverse populations. This will enable more precise identification and estimation of dementia risk profiles, guiding at‐risk persons to precise intervention strategies, good for both, heart, and brain.

Anosmia, mild cognitive impairment, and biomarkers of brain aging in older adults.

Olfactory impairment is a potential marker for prodromal dementia, but the underlying mechanisms are poorly understood. This population-based study included 4214 dementia-free participants (age ≥65 years). Olfaction was assessed using the 16-item Sniffin' Sticks identification test. In the subsamples, we measured plasma amyloid beta (Aβ)40, Aβ42, total tau, and neurofilament light chain (NfL; n = 1054); and quantified hippocampal, entorhinal cortex, and white matter hyperintensity (WMH) volumes, and Alzheimer's disease (AD)-signature cortical thickness (n = 917). Data were analyzed with logistic and linear regression models. In the total sample, mild cognitive impairment (MCI) was diagnosed in 1102 persons (26.2%; amnestic MCI, n = 931; non-amnestic MCI, n = 171). Olfactory impairment was significantly associated with increased likelihoods of MCI, amnestic MCI, and non-amnestic MCI. In the subsamples, anosmia was significantly associated with higher plasma total tau and NfL concentrations, smaller hippocampal and entorhinal cortex volumes, and greater WMH volume, and marginally with lower AD-signature cortical thickness. These results suggest that cerebral neurodegenerative and microvascular lesions are common neuropathologies linking anosmia with MCI in older adults.

Accuracy of Tau Positron Emission Tomography as a Prognostic Marker in Preclinical and Prodromal Alzheimer Disease

Tau positron emission tomography (PET) tracers have proven useful for the differential diagnosis of dementia, but their utility for predicting cognitive change is unclear. To examine the prognostic accuracy of baseline fluorine 18 (18F)-flortaucipir and [18F]RO948 (tau) PET in individuals across the Alzheimer disease (AD) clinical spectrum and to perform a head-to-head comparison against established magnetic resonance imaging (MRI) and amyloid PET markers. This prognostic study collected data from 8 cohorts in South Korea, Sweden, and the US from June 1, 2014, to February 28, 2021, with a mean (SD) follow-up of 1.9 (0.8) years. A total of 1431 participants were recruited from memory clinics, clinical trials, or cohort studies; 673 were cognitively unimpaired (CU group; 253 [37.6%] positive for amyloid-β [Aβ]), 443 had mild cognitive impairment (MCI group; 271 [61.2%] positive for Aβ), and 315 had a clinical diagnosis of AD dementia (315 [100%] positive for Aβ). [18F]Flortaucipir PET in the discovery cohort (n = 1135) or [18F]RO948 PET in the replication cohort (n = 296), T1-weighted MRI (n = 1431), and amyloid PET (n = 1329) at baseline and repeated Mini-Mental State Examination (MMSE) evaluation. Baseline [18F]flortaucipir/[18F]RO948 PET retention within a temporal region of interest, MRI-based AD-signature cortical thickness, and amyloid PET Centiloids were used to predict changes in MMSE using linear mixed-effects models adjusted for age, sex, education, and cohort. Mediation/interaction analyses tested whether associations between baseline tau PET and cognitive change were mediated by baseline MRI measures and whether age, sex, and APOE genotype modified these associations. Among 1431 participants, the mean (SD) age was 71.2 (8.8) years; 751 (52.5%) were male. Findings for [18F]flortaucipir PET predicted longitudinal changes in MMSE, and effect sizes were stronger than for AD-signature cortical thickness and amyloid PET across all participants (R2, 0.35 [tau PET] vs 0.24 [MRI] vs 0.17 [amyloid PET]; P < .001, bootstrapped for difference) in the Aβ-positive MCI group (R2, 0.25 [tau PET] vs 0.15 [MRI] vs 0.07 [amyloid PET]; P < .001, bootstrapped for difference) and in the Aβ-positive CU group (R2, 0.16 [tau PET] vs 0.08 [MRI] vs 0.08 [amyloid PET]; P < .001, bootstrapped for difference). These findings were replicated in the [18F]RO948 PET cohort. MRI mediated the association between [18F]flortaucipir PET and MMSE in the groups with AD dementia (33.4% [95% CI, 15.5%-60.0%] of the total effect) and Aβ-positive MCI (13.6% [95% CI, 0.0%-28.0%] of the total effect), but not the Aβ-positive CU group (3.7% [95% CI, -17.5% to 39.0%]; P = .71). Age (t = -2.28; P = .02), but not sex (t = 0.92; P = .36) or APOE genotype (t = 1.06; P = .29) modified the association between baseline [18F]flortaucipir PET and cognitive change, such that older individuals showed faster cognitive decline at similar tau PET levels. The findings of this prognostic study suggest that tau PET is a promising tool for predicting cognitive change that is superior to amyloid PET and MRI and may support the prognostic process in preclinical and prodromal stages of AD.

Adiposity Is Positively Associated With AD-Signature Cortical Thickness in Older Adults

Mid-life obesity is associated with a higher risk for Alzheimer’s disease (AD). However, this association is attenuated or even reversed in late-life, when weight loss may be a preclinical sign of AD. While neuropathological changes likely occur alongside aging-related changes in body composition, this has not been largely investigated. We aimed to determine the association between adiposity and a specific pattern of reduced cortical thickness associated with AD risk and progression. Global and regional adiposity (via dual-energy x-ray absorptiometry) and AD-signature cortical thickness (via surface-based cortical analysis of 3T brain MRI scans) were measured in 35 middle-aged and older adults from the Wake Forest Alzheimer’s Disease Clinical Core (mean age: 69.4±7.8 years, 80% female, 91% White, 29% cognitively impaired). Partial correlations adjusted for age, sex, and cognitive status were examined overall and stratified by age (0.59, p≤0.05). No significant associations were observed in middle-aged adults. These findings suggest that AD-related cortical thinning may be accompanied by a global reduction in body fat among older adults.

Social support moderates the influence of Alzheimer’s disease–related neurodegeneration on cognitive decline

AbstractBackgroundSocial support (SS) have been associated with decreased rate of cognitive decline in Alzheimer’s disease (AD). However, it is still unclear whether SS can moderate the influence of AD‐related neurodegeneration on cognitive decline. We aimed to test the hypothetical moderation effect of SS on the relationship between AD‐related brain atrophy and cognitive decline.MethodTotal 200 participants from the Korean Brain Aging Study for Early Diagnosis &amp; Prediction of Alzheimer’s disease (KBASE), an ongoing prospective cohort study, were included for this analysis. Of the 200 participants, 130 were MCI and 70 were early AD. All participants underwent comprehensive clinical and neuropsychological assessment, multi‐modal neuroimaging including magnetic resonance imaging, and apolipoprotein E genotyping. AD‐signature cortical thickness (AD‐CT) was defined as a mean cortical thickness of several brain regions known to be sensitive to AD‐specific neurodegeneration. The Medical Outcome Study – Social Support Survey (MOS‐SSS), a 19‐iem brief, multi‐dimensional, self‐report social support survey, were administered to all participants to assess overall SS indices. Global cognitive performance was measured by the total score of the Consortium to Establish a Registry for Alzheimer’s Disease neuropsychological test battery (CERAD‐TS).ResultThere was a significant interaction between AD‐CT and SS on CERAD‐TS. Subgroup analyses demonstrated that the association between AD‐CT and CERAD‐TS was weaker in high SS group than in low SS group.ConclusionOur results suggest that SS may delay the progression of cognitive decline by moderating the influence of AD‐related neurodegeneration.

The impact of demographic, clinical, genetic, and imaging variables on tau PET status

PurposeA substantial proportion of amyloid-β (Aβ)+ patients with clinically diagnosed Alzheimer’s disease (AD) dementia and mild cognitive impairment (MCI) are tau PET–negative, while some clinically diagnosed non-AD neurodegenerative disorder (non-AD) patients or cognitively unimpaired (CU) subjects are tau PET–positive. We investigated which demographic, clinical, genetic, and imaging variables contributed to tau PET status.MethodsWe included 2338 participants (430 Aβ+ AD dementia, 381 Aβ+ MCI, 370 non-AD, and 1157 CU) who underwent [18F]flortaucipir (n = 1944) or [18F]RO948 (n = 719) PET. Tau PET positivity was determined in the entorhinal cortex, temporal meta-ROI, and Braak V-VI regions using previously established cutoffs. We performed bivariate binary logistic regression models with tau PET status (positive/negative) as dependent variable and age, sex, APOEε4, Aβ status (only in CU and non-AD analyses), MMSE, global white matter hyperintensities (WMH), and AD-signature cortical thickness as predictors. Additionally, we performed multivariable binary logistic regression models to account for all other predictors in the same model.ResultsTau PET positivity in the temporal meta-ROI was 88.6% for AD dementia, 46.5% for MCI, 9.5% for non-AD, and 6.1% for CU. Among Aβ+ participants with AD dementia and MCI, lower age, MMSE score, and AD-signature cortical thickness showed the strongest associations with tau PET positivity. In non-AD and CU participants, presence of Aβ was the strongest predictor of a positive tau PET scan.ConclusionWe identified several demographic, clinical, and neurobiological factors that are important to explain the variance in tau PET retention observed across the AD pathological continuum, non-AD neurodegenerative disorders, and cognitively unimpaired persons.

Olfactory testing does not predict \u03b2-amyloid, MRI measures of neurodegeneration or vascular pathology in the British 1946 birth cohort

ObjectiveTo explore the value of olfactory identification deficits as a predictor of cerebral β-amyloid status and other markers of brain health in cognitively normal adults aged ~ 70 years.MethodsCross-sectional observational cohort study. 389 largely healthy and cognitively normal older adults were recruited from the MRC National Survey of Health and Development (1946 British Birth cohort) and investigated for olfactory identification deficits, as measured by the University of Pennsylvania Smell Identification Test. Outcome measures were imaging markers of brain health derived from 3 T MRI scanning (cortical thickness, entorhinal cortex thickness, white matter hyperintensity volumes); 18F florbetapir amyloid-PET scanning; and cognitive testing results. Participants were assessed at a single centre between March 2015 and January 2018.ResultsMean (± SD) age was 70.6 (± 0.7) years, 50.8% were female. 64.5% had hyposmia and 2.6% anosmia. Olfaction showed no association with β-amyloid status, hippocampal volume, entorhinal cortex thickness, AD signature cortical thickness, white matter hyperintensity volume, or cognition.Conclusion and relevanceIn the early 70s, olfactory function is not a reliable predictor of a range of imaging and cognitive measures of preclinical AD. Olfactory identification deficits are not likely to be a useful means of identifying asymptomatic amyloidosis. Further studies are required to assess if change in olfaction may be a proximity marker for the development of cognitive impairment.

Older Patients with Alzheimer's Disease-Related Cortical Atrophy Who Develop Post-Operative Delirium May Be at Increased Risk of Long-Term Cognitive Decline After Surgery.

Older surgical patients with Alzheimer's disease (AD) dementia and delirium are at increased risk for accelerated long-term cognitive decline. Investigate associations between a probabilistic marker of preclinical AD, delirium, and long-term cognitive decline. The Successful Aging after Elective Surgery cohort includes older adults (≥70 years) without dementia who underwent elective surgery. 140 patients underwent preoperative magnetic resonance imaging and had≥6 months cognitive follow-up. Cortical thickness was measured in 'AD-Signature' regions. Delirium was evaluated each postoperative day by the Confusion Assessment Method. Cognitive performance was assessed using a detailed neuropsychological battery at baseline; months 1, 2, and 6; and every 6 months thereafter until 36 months. Using either a General Cognitive Performance composite (GCP) or individual test scores as outcomes, we performed linear mixed effects models to examine main effects of AD-signature atrophy and the interaction of AD-signature atrophy and delirium on slopes of cognitive change from post-operative months 2-36. Reduced baseline AD-signature cortical thickness was associated with greater 36-month cognitive decline in GCP (standardized beta coefficient, β = -0.030, 95% confidence interval [-0.060, -0.001]). Patients who developed delirium who also had thinner AD signature cortex showed greater decline on a verbal learning test (β = -0.100 [-0.192, -0.007]). Patients with the greatest baseline AD-related cortical atrophy who develop delirium after elective surgery appear to experience the greatest long-term cognitive decline. Thus, atrophy suggestive of preclinical AD and the development of delirium may be high-risk indicators for long-term cognitive decline following surgery.

Brain amyloid, cortical thickness, and changes in activities of daily living.

ObjectiveTo examine the association of baseline elevated brain amyloid and neurodegeneration with changes in activities of daily living in participants without dementia (ND; i.e., cognitively unimpaired and participants with mild cognitive impairment) at baseline in the population‐based Mayo Clinic Study of Aging.MethodsWe included 1747 ND participants with 11C‐PiB PET and MR imaging in the study, with data on activities of daily living (as assessed by the Functional Activities Questionnaire (FAQ) and the Clinical Dementia Rating scale Sum of Boxes for functional domains (CDR‐SOB (functional)), with a median (range) of 4.3 (0.0–12.7) years of follow‐up. Abnormal (elevated; A+) 11C‐PiB‐PET retention ratio was defined as standardized uptake value ratio ≥ 1.48, and abnormal (reduced) AD signature cortical thickness as ≤ 2.68 mm (neurodegeneration; N+). Associations were examined with mixed effects models, adjusting for age, sex, education, apolipoprotein E ε4 allele carrier status, and global cognitive z‐score.ResultsMean age (SD) was 71.4 years (10.1), 46.7% were females, 195 (11.2%) had A+N‐, 442 (25.3%) had A‐N+, and 339 (19.4%) had A+N+ biomarkers. The A+N+ group had the largest annualized change in the FAQ score from baseline (difference in annual change A+N+ vs. A‐N‐; ß (SE): 0.80 (0.07)); associations were substantially attenuated when a time‐varying global cognitive composite was included in the model (A+N+ vs. A‐N‐; ß (SE): 0.31 (0.05)). CDR‐SOB (functional) findings partly agreed with FAQ score findings.InterpretationThe longitudinal increase in functional limitations is greater for individuals with abnormal neuroimaging biomarkers, especially for those with both elevated brain amyloid and neurodegeneration.

Cholinergic White Matter Lesions, AD-Signature Cortical Thickness, and Change in Cognition: The Northern Manhattan Study.

How cerebrovascular disease and neurodegeneration affect each other to impact cognition is not yet known. We aimed to test whether Alzheimer's disease-signature (AD) cortical thickness mediates the association between cholinergic white matter lesion load and change in domain-specific cognition. Clinically stroke-free participants from the Northern Manhattan Study with both regional white matter hyperintensity volume (WMHV) and gray matter measurements were included (N = 894). Tract-specific WMHVs were quantified through FSL using the Johns Hopkins University white matter tract atlas. We used Freesurfer 5.1 to estimate regional cortical thickness. We fit structural equation models, including multiple indicator latent change score models, to examine associations between white matter hyperintensity volume (WMHV) in cholinergic tracts, AD-signature region cortical thickness (CT), and domain-specific cognition. Our sample (N = 894) had a mean (SD) age = 70 (9) years, years of education = 10 (5), 63% women, and 67% Hispanics/Latinos. Greater cholinergic WMHV was significantly related to worse processing speed at baseline (standardized β = -0.17, SE = 0.05, p = .001) and over time (standardized β = -0.28, SE = 0.09, p = .003), with a significant indirect effect of AD-signature region CT (baseline: standardized β = -0.02, SE = 0.01, p = .023; change: standardized β = -0.03, SE = 0.02, p = .040). Cholinergic tract WMHV is associated with worse processing speed, both directly and indirectly through its effect on AD-signature region CT.

Blood biomarkers as surrogate endpoints of treatment responses to aerobic exercise and cognitive training (ACT) in amnestic mild cognitive impairment: the blood biomarkers study protocol of a randomized controlled trial (the ACT Trial)

BackgroundAlzheimer’s disease (AD) is an epidemic with tremendous public health impacts because there are currently no disease-modifying therapeutics. Randomized controlled trials (RCTs) for prevention of AD dementia often use clinical endpoints that take years to manifest (e.g., cognition) or surrogate endpoints that are costly or invasive (e.g., magnetic resonance imaging [MRI]). Blood biomarkers represent a clinically applicable alternative surrogate endpoint for RCTs that would be both cost-effective and minimally invasive, but little is known about their value as surrogate endpoints for treatment responses in the prevention of AD dementia.MethodsThe objective of this study is to investigate blood neuropathological, neurodegenerative, and neurotrophic biomarkers as surrogate endpoints for treatment responses to three interventions in older adults with amnestic mild cognitive impairment (aMCI, a prodromal stage of AD): aerobic exercise, cognitive training, and combined aerobic exercise and cognitive training (ACT). We chose these three sets of biomarkers for their unique mechanistic associations with AD pathology, neurodegeneration and neurogenesis. This study is built on the ACT Trial (1R01AG055469), a single-blinded, multi-site, 2 × 2 factorial phase II RCT that examines the synergistic effects of a 6-month ACT intervention on cognition and MRI biomarkers (AD-signature cortical thickness and hippocampal volume) (n = 128). In this ACT Trial blood biomarkers study, we will enroll 120 ACT Trial participants with aMCI and measure blood biomarkers at baseline and at 3, 6, 12, and 18 months. The goals are to (1) determine the effect of interventions on blood biomarkers over 6 months, (2) evaluate blood biomarkers as surrogate endpoints for predicting cognitive responses to interventions over 18 months, and (3, exploratory) examine blood biomarkers as surrogate endpoints for predicting brain MRI biomarker responses to interventions over 18 months.DiscussionThis study aims to identify new blood biomarkers that can track cognitive decline or AD-related brain atrophy among patients with aMCI subjected to a regimen of aerobic exercise and cognitive training. Findings from this study will drive the further use of blood biomarkers in developing effective prevention and treatment strategies for AD dementia.Trial registrationClinicalTrials.gov, NCT03313895. Registered on 18 October 2017.

The Role of MRI Biomarkers and Their Interactions with Cognitive Status and APOE ε4 in Nondemented Elderly Subjects

Purpose: (1) To investigate atrophy patterns of hippocampal subfield volume and Alzheimer’s disease (AD)-signature cortical thickness in mild cognitive impairment (MCI) patients; (2) to explore the association between the neuropsychological (NP) and the brain structure in the MCI and older normal cognition group; (3) to determine whether these associations were modified by the apolipoprotein E (APOE) ε4 gene and cognitive status. Methods: The FreeSurfer software was used for automated segmentation of hippocampal subfields and AD-signature cortical thickness for 22 MCI patients and 23 cognitive normal controls (NC). The volume, cortical thickness, and the neuropsychological scale were compared with two-sample t tests. Linear regression models were used to determine the association between the NP and the brain structure. Results: Compared with the NC group, MCI patients showed a decreased volume of the left presubiculum, subiculum and right CA2_3 and CA4_DG (p < 0.05, FDR corrected). The volume of these regions was positively correlated with NP scores. Of note, these associations depended on the cognitive status but not on the APOE ε4 status. The left subiculum and presubiculum volume were positively correlated with the Montreal Cognitive Assessment (MoCA) scores only in the MCI patients. Conclusion: Atrophy of the hippocampal subfields may be a powerful biomarker for MCI in the Chinese population.

Is the Alzheimer's disease cortical thickness signature a biological marker for memory?

Recent work suggests that analysis of the cortical thickness in key brain regions can be used to identify individuals at greatest risk for development of Alzheimer's disease (AD). It is unclear to what extent this "signature" is a biological marker of normal memory function - the primary cognitive domain affected by AD. We examined the relationship between the AD signature biomarker and memory functioning in a group of neurologically healthy young and older adults. Cortical thickness measurements and neuropsychological evaluations were obtained in 110 adults (age range 21-78, mean = 46) drawn from the Brain Resource International Database. The cohort was divided into young adult (n = 64, age 21-50) and older adult (n = 46, age 51-78) groups. Cortical thickness analysis was performed with FreeSurfer, and the average cortical thickness extracted from the eight regions that comprise the AD signature. Mean AD-signature cortical thickness was positively associated with performance on the delayed free recall trial of a list learning task and this relationship did not differ between younger and older adults. Mean AD-signature cortical thickness was not associated with performance on a test of psychomotor speed, as a control task, in either group. The results suggest that the AD signature cortical thickness is a marker for memory functioning across the adult lifespan.