Neuropathological and in vivo studies have revealed a tight relationship between tau pathology and cognitive impairment across the Alzheimer's disease spectrum. However, tau pathology is also ...intimately associated with neurodegeneration and amyloid pathology. The aim of the present study was therefore to assess whether grey matter atrophy and amyloid pathology contribute to the relationship between tau pathology, as measured with 18F-AV-1451-PET imaging, and cognitive deficits in Alzheimer's disease. We included 40 amyloid-positive patients meeting criteria for mild cognitive impairment due to Alzheimer's disease (n = 5) or probable Alzheimer's disease dementia (n = 35). Twelve patients additionally fulfilled the diagnostic criteria for posterior cortical atrophy and eight for logopenic variant primary progressive aphasia. All participants underwent 3 T magnetic resonance imaging, amyloid (11C-PiB) positron emission tomography and tau (18F-AV-1451) positron emission tomography, and episodic and semantic memory, language, executive and visuospatial functions assessment. Raw cognitive scores were converted to age-adjusted Z-scores (W-scores) and averaged to compute composite scores for each cognitive domain. Independent regressions were performed between 18F-AV-1451 binding and each cognitive domain, and we used the Biological Parametric Mapping toolbox to further control for local grey matter volumes, 11C-PiB uptake, or both. Partial correlations and causal mediation analyses (mediation R package) were then performed in brain regions showing an association between cognition and both 18F-AV-1451 uptake and grey matter volume. Our results showed that decreased cognitive performance in each domain was related to increased 18F-AV-1451 binding in specific brain regions conforming to established brain-behaviour relationships (i.e. episodic memory: medial temporal lobe and angular gyrus; semantic memory: left anterior temporal regions; language: left posterior superior temporal lobe and supramarginal gyrus; executive functions: bilateral frontoparietal regions; visuospatial functions: right more than left occipitotemporal regions). This pattern of regional associations remained essentially unchanged-although less spatially extended-when grey matter volume or 11C-PiB uptake maps were added as covariates. Mediation analyses revealed both direct and grey matter-mediated effects of 18F-AV-1451 uptake on cognitive performance. Together, these results show that tau pathology is related in a region-specific manner to cognitive impairment in Alzheimer's disease. These regional relationships are weakly related to amyloid burden, but are in part mediated by grey matter volumes. This suggests that tau pathology may lead to cognitive deficits through a variety of mechanisms, including, but not restricted to, grey matter loss. These results might have implications for future therapeutic trials targeting tau pathology.
OBJECTIVETo assess the relationships between fluid and imaging biomarkers of tau pathology and compare their diagnostic utility in a clinically heterogeneous sample.
METHODSFifty-three patients (28 ...with clinical Alzheimer disease AD and 25 with non-AD clinical neurodegenerative diagnoses) underwent β-amyloid (Aβ) and tau (FAV1451) PET and lumbar puncture. CSF biomarkers (Aβ42, total tau t-tau, and phosphorylated tau p-tau) were measured by multianalyte immunoassay (AlzBio3). Receiver operator characteristic analyses were performed to compare discrimination of Aβ-positive AD from non-AD conditions across biomarkers. Correlations between CSF biomarkers and PET standardized uptake value ratios (SUVR) were assessed using skipped Pearson correlation coefficients. Voxelwise analyses were run to assess regional CSF–PET associations.
RESULTSFAV1451-PET cortical SUVR and p-tau showed excellent discrimination between Aβ-positive AD and non-AD conditions (area under the curve 0.92–0.94; ≤0.83 for other CSF measures), and reached 83% classification agreement. In the full sample, cortical FAV1451 was associated with all CSF biomarkers, most strongly with p-tau (r = 0.75 vs 0.57 for t-tau and −0.49 for Aβ42). When restricted to Aβ-positive patients with AD, FAV1451 SUVR correlated modestly with p-tau and t-tau (both r = 0.46) but not Aβ42 (r = 0.02). On voxelwise analysis, FAV1451 correlated with CSF p-tau in temporoparietal cortices and with t-tau in medial prefrontal regions. Within AD, Mini-Mental State Examination scores were associated with FAV1451-PET, but not CSF biomarkers.
CONCLUSIONFAV1451-PET and CSF p-tau had comparable value for differential diagnosis. Correlations were robust in a heterogeneous clinical group but attenuated (although significant) in AD, suggesting that fluid and imaging biomarkers capture different aspects of tau pathology.
CLASSIFICATION OF EVIDENCEThis study provides Class III evidence that, in a clinical sample of patients with a variety of suspected neurodegenerative diseases, both CSF p-tau and FAV1451 distinguish AD from non-AD conditions.
The effects of aging on the cognitive and affective dimensions of theory of mind (ToM), and on the latter’s links with other cognitive processes, such as information processing speed, executive ...functions and episodic memory, are still unclear. We therefore investigated these effects in young (n=25), middle-aged (n=20) and older adults (n=25), using separate subjective and objective assessment tasks. Furthermore, a novel composite task probed participants’ abilities to infer both cognitive and affective mental states in an interpersonal context. Although age affected the objective ToM tests, results revealed a direct aging effect on the second-order ToM, but an indirect one on the first-order cognitive ToM, mediated mainly by age-related declines in executive functions. This study supports the notion of an age-related distinction between subjective and objective assessments of ToM, and confirms that ToM is a complex mental ability with several characteristics reliant to some extent on executive processes.
The brain mechanisms underlying the effect of intellectual enrichment may evolve along the normal aging Alzheimer's disease (AD) cognitive spectrum and may include both protective and compensatory ...mechanisms. We assessed the association between early intellectual enrichment (education, years) and average cortical florbetapir standardized uptake value ratio as well as performed voxel-wise analyses in a total of 140 participants, including cognitively normal older adults, mild cognitive impairment (MCI), and AD patients. Higher education was associated with lower cortical florbetapir positron emission tomography (florbetapir-PET) uptake, notably in the frontal lobe in normal older adults, but with higher uptake in frontal, temporal, and parietal regions in MCI after controlling for global cognitive status. No association was found in AD. In MCI, we observed an increased fluorodeoxyglucose positron emission tomography (FDG-PET) uptake with education within the regions of higher florbetapir-PET uptake, suggesting a compensatory increase. Early intellectual enrichment may be associated with protection and compensation for amyloid beta (Aβ) deposition later in life, before the onset of dementia. Previous investigations have been controversial as regard to the effects of intellectual enrichment variables on Aβ deposition; the present findings call for approaches aiming to evaluate mechanisms of resilience across disease stages.
The relationships between β-amyloid (Aβ), tau and neurodegeneration within Alzheimer's Disease pathogenesis are not fully understood. To explore these associations in vivo, we evaluated 30 Aβ ...PET-positive patients (mean±sd age 62.4±8.3) with mild probable AD and 12 Aβ PET-negative healthy controls (HC) (mean±sd age 77.3±6.9) as comparison. All participants underwent 3T MRI, 11C-PiB (Aβ) PET and 18F-AV1451 (tau) PET. Multimodal correlation analyses were run at both voxel- and region-of-interest levels. 11C-PiB retention in AD showed the most diffuse uptake pattern throughout association neocortex, whereas 18F-AV1451 and gray matter volume reduction (GMR) showed a progressive predilection for posterior cortices (p<0.05 Family-Wise Error-FWE-corrected). Voxel-level analysis identified negative correlations between 18F-AV1451 and gray matter peaking in medial and infero-occipital regions (p<0.01 False Discovery Rate-FDR-corrected). 18F-AV1451 and 11C-PiB were positively correlated in right parietal and medial/inferior occipital regions (p<0.001 uncorrected). 11C-PiB did not correlate with GMR at the voxel-level. Regionally, 18F-AV1451 was largely associated with local/adjacent GMR whereas frontal 11C-PiB correlated with GMR in posterior regions. These findings suggest that, in mild AD, tau aggregation drives local neurodegeneration, whereas the relationships between Aβ and neurodegeneration are not region specific and may be mediated by the interaction between Aβ and tau.
•Tau tangles show tight and local associations with gray matter volume.•Amyloid plaques show long-distance and indirect effects on gray matter volume.•Local relationships between tau and amyloid may evolve and vary by disease stage.•Amyloid accumulates homogeneously and uniformly across association cortices.•Tau accumulation begins locally and spreads to functionally connected regions.
OBJECTIVE:To improve our understanding of early β-amyloid (Aβ) accumulation processes using florbetapir-PET scan in 20- to 60-year-old individuals.
METHODS:Seventy-six cognitively normal individuals ...aged 20 to 60 years, 57 cognitively normal older individuals (61–84 years old), and 70 patients with mild cognitive impairment or probable Alzheimer disease (AD) underwent a florbetapir-PET scan. Images were spatially normalized and scaled using the whole cerebellum. The relationship with age was assessed on the mean neocortical standardized uptake value ratio (SUVR) and voxelwise in the younger group to assess early Aβ accumulation processes. To compare the topography of early-age-related vs AD-related changes, Aβ increase in patients vs cognitively normal older adults was also assessed.
RESULTS:A linear increase of Aβ deposition from 20 to 60 years old was found on the mean neocortical SUVR, and more specifically on the temporal neocortex. By contrast, increase in patients predominated in frontal and medial parietal areas. The temporal increase in healthy participants was still significant when including only the 20- to 50-year-old individuals and controlling for several possible methodologic confounds.
CONCLUSIONS:Florbetapir binding increases linearly from 20 to 60 years old in the temporal lobe. Pending replication, including with other PET tracers, this study suggests that the well-described medial frontal and parietal accumulation in late adulthood and AD might superimpose to a physiologic accumulation of Aβ, starting from young adulthood, in temporal lobes.
Conventional clinical trials are not usually designed to accommodate participants with posterior cortical atrophy, because inclusion criteria and outcomes are primarily focused on memory impairments. ......we advocate for the inclusion of posterior cortical atrophy and other common Alzheimer's disease phenotypes in future pharmacological trials targeting Alzheimer's disease pathology, using outcome measures that rely more on functional impairment (eg, the Alzheimer's Disease Cooperative Study–Activities of Daily Living for Mild Cognitive Impairment scale) so that the risk-benefit ratio assessment is not altered. Despite the impressive sample size of the study, and its meticulous approach, physicians must consider the inherent selection bias in the study design when making an aetiological investigation of a patient with posterior cortical atrophy. NV received research support from Fondation Bettencourt-Schueller, Fondation Servier, Union Nationale pour les Intérêts de la Médecine (UNIM), Fondation Claude Pompidou, Fondation Alzheimer and Fondation pour la Recherche sur l’Alzheimer; travel grant from the Movement Disorders Society, Merz-Pharma, UCB Pharma, and GE Healthcare SAS; is an unpaid local principal investigator or sub-investigator in NCT04241068 and NCT05310071 (aducanumab, Biogen), NCT05399888 (BIIB080, Biogen), NCT03352557 (gosuranemab, Biogen), NCT05463731 (remternetug, Eli-Lilly), NCT04592341 (gantenerumab, Roche), NCT03887455 (lecanemab, Eisai), NCT03828747 and NCT03289143 (semorinemab, Roche), NCT04619420 (JNJ-63733657, Janssen – Johnson & Johnson), NCT04374136 (AL001, Alector), NCT04592874 (AL002, Alector), NCT04867616 (bepranemab, UCB Pharma), NCT04777396 and NCT04777409 (semaglutide, Novo Nordisk), NCT05469360 (NIO752, Novartis), is an unpaid national coordinator for NCT05564169 (masitinib, ABScience), NCT (AD04, ADvantage Therapeutics GmbH); has given unpaid lectures in symposia organized by Eisai and the Servier Foundation; and has been an unpaid expert for Janssen and Johnson & Johnson, all outside of this work.
•We assessed the links between four quality of life (QoL) domains and brain integrity.•Physical health was the only QoL domain related to brain integrity.•Brain structure, but not brain function or ...amyloid was linked to physical health.•Structures involved belong to the pain pathway and the salience and empathy networks.•No association was found with the psychological, social and environmental QoL domains.
As the population ages, maintaining mental health and well-being of older adults is a public health priority. Beyond objective measures of health, self-perceived quality of life (QoL) is a good indicator of successful aging. In older adults, it has been shown that QoL is related to structural brain changes. However, QoL is a multi-faceted concept and little is known about the specific relationship of each QoL domain to brain structure, nor about the links with other aspects of brain integrity, including white matter microstructure, brain perfusion and amyloid deposition, which are particularly relevant in aging. Therefore, we aimed to better characterize the brain biomarkers associated with each QoL domain using a comprehensive multimodal neuroimaging approach in older adults.
One hundred and thirty-five cognitively unimpaired older adults (mean age ± SD: 69.4 ± 3.8 y) underwent structural and diffusion magnetic resonance imaging, together with early and late florbetapir positron emission tomography scans. QoL was assessed using the brief version of the World Health Organization's QoL instrument, which allows measuring four distinct domains of QoL: self-perceived physical health, psychological health, social relationships and environment. Multiple regression analyses were carried out to identify the independent global neuroimaging predictor(s) of each QoL domain, and voxel-wise analyses were then conducted with the significant predictor(s) to highlight the brain regions involved. Age, sex, education and the other QoL domains were entered as covariates in these analyses. Finally, forward stepwise multiple regressions were conducted to determine the specific items of the relevant QoL domain(s) that contributed the most to these brain associations.
Only physical health QoL was associated with global neuroimaging values, specifically gray matter volume and white matter mean kurtosis, with higher physical health QoL being associated with greater brain integrity. These relationships were still significant after correction for objective physical health and physical activity measures. No association was found with global brain perfusion or global amyloid deposition. Voxel-wise analyses revealed that the relationships with physical health QoL concerned the anterior insula and ventrolateral prefrontal cortex, and the corpus callosum, corona radiata, inferior frontal white matter and cingulum. Self-perceived daily living activities and self-perceived pain and discomfort were the items that contributed the most to these associations with gray matter volume and white matter mean kurtosis, respectively.
Better self-perceived physical health, encompassing daily living activities and pain and discomfort, was the only QoL domain related to brain structural integrity including higher global gray matter volume and global white matter microstructural integrity in cognitively unimpaired older adults. The relationships involved brain structures belonging to the salience network, the pain pathway and the empathy network. While previous studies showed a link between objective measures of physical health, our findings specifically highlight the relevance of monitoring and promoting self-perceived physical health in the older population. Longitudinal studies are needed to assess the direction and causality of the relationships between QoL and brain integrity.
Subjective cognitive decline (SCD) defines a heterogeneous population, part of which having Alzheimer's disease (AD). We aimed at characterizing SCD populations according to whether or not they ...referred to a memory clinic, by assessing the factors associated with increased AD risk.
Seventy-eight cognitively unimpaired older adults from the IMAP+ study (Caen) were included, amongst which 28 healthy controls (HC) and 50 SCD recruited from the community (SCD-community; n = 23) or from a memory clinic (SCD-clinic; n = 27). Participants underwent cognitive, psychoaffective, structural MRI, FDG-PET, and amyloid-PET assessments. They were followed up over a mean period of 2.4 ± 0.8 years. The groups were compared in terms of baseline and follow-up levels of SCD (self- and informant-reported), cognition, subclinical anxiety and depression, and atrophy progression over time. We also investigated SCD substrates within each SCD group through the correlations between self-reported SCD and other psychometric and brain measures.
Compared to HC, both SCD groups showed similar cognitive performances but higher informant-reported SCD and anxiety. Compared to SCD-community, SCD-clinic showed higher informant-reported SCD, depression score, and atrophy progression over time but similar brain amyloid load. A significant increase over time was found for depression in the SCD-community and for self-reported praxis-domestic activities SCD factor in the SCD-clinic. Higher self-reported SCD correlated with (i) lower grey matter volume and higher anxiety in SCD-community, (ii) greater informant-reported SCD in SCD-clinic, and (iii) lower glucose metabolism in both SCD groups.
Higher subclinical depression and informant-reported SCD specifically characterize the SCD group that refers to a memory clinic. The same group appears as a frailer population than SCD-community as they show greater atrophy progression over time. Yet, both the SCD groups were quite similar otherwise including for brain amyloid load and the SCD-community showed increased depression score over time. Altogether, our findings highlight the relevance of assessing psychoaffective factors and informant-reported SCD in SCD populations and point to both differences and similarities in SCD populations referring or not to a memory clinic.
Oculomotor behavior can provide insight into the integrity of widespread cortical networks, which may contribute to the differential diagnosis between Alzheimer's disease and frontotemporal dementia. ...Three groups of patients with Alzheimer's disease, behavioral variant of frontotemporal dementia (bvFTD) and semantic variant of primary progressive aphasia (svPPA) and a sample of cognitively unimpaired elders underwent an eye-tracking evaluation. All participants in the discovery sample, including controls, had a biomarker-supported diagnosis. Oculomotor correlates of neuropsychology and brain metabolism evaluated with 18F-FDG PET were explored. Machine-learning classification algorithms were trained for the differentiation between Alzheimer's disease, bvFTD and controls. A total of 93 subjects (33 Alzheimer's disease, 24 bvFTD, seven svPPA, and 29 controls) were included in the study. Alzheimer's disease was the most impaired group in all tests and displayed specific abnormalities in some visually-guided saccade parameters, as pursuit error and horizontal prosaccade latency, which are theoretically closely linked to posterior brain regions. BvFTD patients showed deficits especially in the most cognitively demanding tasks, the antisaccade and memory saccade tests, which require a fine control from frontal lobe regions. SvPPA patients performed similarly to controls in most parameters except for a lower number of correct memory saccades. Pursuit error was significantly correlated with cognitive measures of constructional praxis and executive function and metabolism in right posterior middle temporal gyrus. The classification algorithms yielded an area under the curve of 97.5% for the differentiation of Alzheimer's disease vs. controls, 96.7% for bvFTD vs. controls, and 92.5% for Alzheimer's disease vs. bvFTD. In conclusion, patients with Alzheimer's disease, bvFTD and svPPA exhibit differentiating oculomotor patterns which reflect the characteristic neuroanatomical distribution of pathology of each disease, and therefore its assessment can be useful in their diagnostic work-up. Machine learning approaches can facilitate the applicability of eye-tracking in clinical practice.
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