Showing papers by "Bernard Mazoyer published in 2011"

Brain activity at rest: A multiscale hierarchical functional organization

Abstract: Spontaneous brain activity was mapped with functional MRI (fMRI) in a sample of 180 subjects while in a conscious resting-state condition. With the use of independent component analysis (ICA) of each individual fMRI signal and classification of the ICA-defined components across subjects, a set of 23 resting-state networks (RNs) was identified. Functional connectivity between each pair of RNs was assessed using temporal correlation analyses in the 0.01- to 0.1-Hz frequency band, and the corresponding set of correlation coefficients was used to obtain a hierarchical clustering of the 23 RNs. At the highest hierarchical level, we found two anticorrelated systems in charge of intrinsic and extrinsic processing, respectively. At a lower level, the intrinsic system appears to be partitioned in three modules that subserve generation of spontaneous thoughts (M1a; default mode), inner maintenance and manipulation of information (M1b), and cognitive control and switching activity (M1c), respectively. The extrinsic system was found to be made of two distinct modules: one including primary somatosensory and auditory areas and the dorsal attentional network (M2a) and the other encompassing the visual areas (M2b). Functional connectivity analyses revealed that M1b played a central role in the functioning of the intrinsic system, whereas M1c seems to mediate exchange of information between the intrinsic and extrinsic systems.

Headache, migraine, and structural brain lesions and function: population based Epidemiology of Vascular Ageing-MRI study

Abstract: Objective To evaluate the association of overall and specific headaches with volume of white matter hyperintensities, brain infarcts, and cognition. Design Population based, cross sectional study. Setting Epidemiology of Vascular Ageing study, Nantes, France. Participants 780 participants (mean age 69, 58.5% women) with detailed headache assessment. Main outcome measures Brain scans were evaluated for volume of white matter hyperintensities (by fully automated imaging processing) and for classification of infarcts (by visual reading with a standardised assessment grid). Cognitive function was assessed by a battery of tests including the mini-mental state examination. Results 163 (20.9%) participants reported a history of severe headache and 116 had migraine, of whom 17 (14.7%) reported aura symptoms. An association was found between any history of severe headache and increasing volume of white matter hyperintensities. The adjusted odds ratio of being in the highest third for total volume of white matter hyperintensities was 2.0 (95% confidence interval 1.3 to 3.1, P for trend 0.002) for participants with any history of severe headache when compared with participants without severe headache being in the lowest third. The association pattern was similar for all headache types. Migraine with aura was the only headache type strongly associated with volume of deep white matter hyperintensities (highest third odds ratio 12.4, 1.6 to 99.4, P for trend 0.005) and with brain infarcts (3.4, 1.2 to 9.3). The location of infarcts was predominantly outside the cerebellum and brain stem. Evidence was lacking for cognitive impairment for any headache type with or without brain lesions. Conclusions In this population based study, any history of severe headache was associated with an increased volume of white matter hyperintensities. Migraine with aura was the only headache type associated with brain infarcts. Evidence that headache of any type by itself or in combination with brain lesions was associated with cognitive impairment was lacking.

Genome-wide association studies of cerebral white matter lesion burden: the CHARGE consortium.

Abstract: textObjective: White matter hyperintensities (WMHs) detectable by magnetic resonance imaging are part of the spectrum of vascular injury associated with aging of the brain and are thought to reflect ischemic damage to the small deep cerebral vessels. WMHs are associated with an increased risk of cognitive and motor dysfunction, dementia, depression, and stroke. Despite a significant heritability, few genetic loci influencing WMH burden have been identified. Methods: We performed a meta-analysis of genome-wide association studies (GWASs) for WMH burden in 9,361 stroke-free individuals of European descent from 7 community-based cohorts. Significant findings were tested for replication in 3,024 individuals from 2 additional cohorts. Results: We identified 6 novel risk-associated single nucleotide polymorphisms (SNPs) in 1 locus on chromosome 17q25 encompassing 6 known genes including WBP2, TRIM65, TRIM47, MRPL38, FBF1, and ACOX1. The most significant association was for rs3744028 (pdiscovery= 4.0 × 10-9; preplication= 1.3 × 10-7; pcombined= 4.0 × 10-15). Other SNPs in this region also reaching genome-wide significance were rs9894383 (p = 5.3 × 10-9), rs11869977 (p = 5.7 × 10-9), rs936393 (p = 6.8 × 10-9), rs3744017 (p = 7.3 × 10-9), and rs1055129 (p = 4.1 × 10-8). Variant alleles at these loci conferred a small increase in WMH burden (4-8% of the overall mean WMH burden in the sample). Interpretation: This large GWAS of WMH burden in community-based cohorts of individuals of European descent identifies a novel locus on chromosome 17. Further characterization of this locus may provide novel insights into the pathogenesis of cerebral WMH.

Antihypertensive Treatment and Change in Blood Pressure Are Associated With the Progression of White Matter Lesion Volumes The Three-City (3C)–Dijon Magnetic Resonance Imaging Study

Abstract: Background—Blood pressure (BP) is recognized as a major risk factor for white matter lesions (WMLs), but longitudinal data are scarce, and there is insufficient evidence for the benefit of antihypertensive therapy on WML progression. We studied the relationship between BP change and WML volume progression over time in a sample of 1319 elderly individuals who had 2 cerebral magnetic resonance imaging examinations 4 years apart. We also examined the impact of antihypertensive treatment on WML progression. Methods and Results—Subjects were participants from the Three-City (3C)–Dijon Magnetic Resonance Imaging Study, a prospective population-based cohort of elderly ≥65 years of age. WML volumes and their progression were estimated with the use of a fully automatic procedure. We performed ANCOVA models first to assess the association between BP change and WML progression and second to estimate the relation between antihypertensive treatment and WML load progression. Baseline and change in BP were significant p...

Longitudinal neuroimaging correlates of subjective memory impairment: 4-year prospective community study.

Abstract: Background Complaints about memory are common in older people but their relationship with underlying brain changes is controversial. Aims To investigate the relationship between subjective memory impairment and previous or subsequent changes in white matter lesions and brain volumes. Method In a community cohort study of 1336 people without dementia, 4-year changes in brain magnetic resonance imaging measures were investigated as correlates of subjective memory impairment at baseline and follow-up. Results Subjective memory impairment at baseline was associated with subsequent change in hippocampal volume and at follow-up impairment was associated with previous change in hippocampal, cerebrospinal fluid and grey matter volume and with subcortical white matter lesion increases. All associations with volume changes were U-shaped with significant quadratic terms – associations between least decline and subjective memory impairment were potentially explained by lower baseline hippocampal volumes in the groups with least volume change. Associations between hippocampal volume change and subjective memory impairment at follow-up were independent of cognitive decline and depressive symptoms, they were stronger in participants with the apolipoprotein E (APOE) ϵ4 allele and in those without baseline subjective memory impairment. Conclusions Complaints of poor memory by older people, particularly when new, may be a realistic subjective appraisal of recent brain changes independent of observed cognitive decline.

Frequency and Location of Dilated Virchow-Robin Spaces in Elderly People: A Population-Based 3D MR Imaging Study

Abstract: BACKGROUND AND PURPOSE: dVRS have been previously associated with aging and cerebrovascular diseases. However, little is known about their prevalence and topographic distribution in the general elderly population. MATERIALS AND METHODS: dVRS were evaluated by using high-resolution 3D MR imaging in 1826 subjects enrolled in the 3C-Dijon MR imaging study. On T1-weighted MR imaging, dVRS were detected according to 3D imaging criteria and rated by using 4-level severity scores based in the BG or in the WM. The number and anatomic location of large dVRS (≥3 mm) were recorded. RESULTS: dVRS were observed in the BG or WM in every subject. The severity of dVRS was significantly associated with higher age in both the BG and WM, whereas sex was related to the severity of dVRS only in the BG. Large dVRS were detected in 33.2% of participants. Status cribrosum was found in 1.3% of participants. dVRS were also highly prevalent within the hippocampus (44.5%) and hypothalamus (11.6%). CONCLUSIONS: dVRS are always detected in the BG or WM in elderly people, and large dVRS are also prevalent. The topographic distribution of dVRS is not uniform within the brain and may depend on anatomic or pathologic characteristics interacting with aging and sex.

Multiple indices of diffusion identifies white matter damage in mild cognitive impairment and Alzheimer's disease.

Abstract: The study of multiple indices of diffusion, including axial (DA), radial (DR) and mean diffusion (MD), as well as fractional anisotropy (FA), enables WM damage in Alzheimer's disease (AD) to be assessed in detail. Here, tract-based spatial statistics (TBSS) were performed on scans of 40 healthy elders, 19 non-amnestic MCI (MCIna) subjects, 14 amnestic MCI (MCIa) subjects and 9 AD patients. Significantly higher DA was found in MCIna subjects compared to healthy elders in the right posterior cingulum/precuneus. Significantly higher DA was also found in MCIa subjects compared to healthy elders in the left prefrontal cortex, particularly in the forceps minor and uncinate fasciculus. In the MCIa versus MCIna comparison, significantly higher DA was found in large areas of the left prefrontal cortex. For AD patients, the overlap of FA and DR changes and the overlap of FA and MD changes were seen in temporal, parietal and frontal lobes, as well as the corpus callosum and fornix. Analysis of differences between the AD versus MCIna, and AD versus MCIa contrasts, highlighted regions that are increasingly compromised in more severe disease stages. Microstructural damage independent of gross tissue loss was widespread in later disease stages. Our findings suggest a scheme where WM damage begins in the core memory network of the temporal lobe, cingulum and prefrontal regions, and spreads beyond these regions in later stages. DA and MD indices were most sensitive at detecting early changes in MCIa.

Using diffusion tensor imaging and mixed-effects models to investigate primary and secondary white matter degeneration in Alzheimer's disease and mild cognitive impairment.

Abstract: White matter (WM) degeneration in Alzheimer's disease (AD) and mild cognitive impairment (MCI) may be a key indicator of early damage in AD. Here, we analyzed WM diffusion tensor data using Tract-Based Spatial Statistics in conjunction with mixed-effects models. Four indices of diffusion were assessed in 61 healthy control, 19 non-amnestic MCIs, 14 amnestic MCIs, and 9 AD patients. The aim of the study was to use advanced mixed-effects models to investigate the retrogenesis hypothesis of AD, which suggests that tracts that are late to myelinate in ontogenetic development are the earliest to be affected in AD. Our results show that a number of late-myelinating pathways, including the parahippocampal region and the inferior longitudinal fasciculus, were predominantly affected by changes in WM volume. Conversely, early-myelinating pathways were found to be affected by a combination of both WM and gray matter (GM) atrophy. A model of the entire WM structure of the brain returned GM models for two indices of diffusion, suggesting that more complex regional landscapes of diffusion lie hidden beneath a global analysis of the entire brain. Our results warn against an explanation of white matter damage that points simply to one of two mechanisms: secondary degeneration or direct damage of myelin. We suggest that tracts may be affected by both mechanisms, with the balance depending on whether tracts are early or late-myelinating. A greater understanding of the pattern of WM changes in AD may prove useful for the early detection of AD.

ORIGINAL RESEARCH Frequency and Location of Dilated Virchow-Robin Spaces in Elderly People: A Population-Based 3D MR Imaging Study

Abstract: RESULTS: dVRS were observed in the BG or WM in every subject. The severity of dVRS was significantly associated with higher age in both the BG and WM, whereas sex was related to the severity of dVRS only in the BG. Large dVRS were detected in 33.2% of participants. Status cribrosum was found in 1.3% of participants. dVRS were also highly prevalent within the hippocampus (44.5%) and hypothalamus (11.6%). CONCLUSIONS: dVRS are always detected in the BG or WM in elderly people, and large dVRS are also prevalent. The topographic distribution of dVRS is not uniform within the brain and may depend on anatomic or pathologic characteristics interacting with aging and sex. ABBREVIATIONS: BG basal ganglia; 3C 3 city; CADASIL cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy; CMA cortical medullary arteries; dVRS dilated Virchow-Robin spaces; INSERM French Institute of Health and Medical Research; LSA lenticulostriate arteries; UMR Mixed Unit of Research; WM white matter