Biology subjects

Parent, O.

Publications and source records attributed to Parent, O..

8 recordsLinked to original sources

bioRxiv2026

Regional distribution of white matter hyperintensity burden in coronary artery disease and links with coronary revascularization procedure

IntroductionCoronary artery disease (CAD) increases the risk of cerebrovascular events, yet early brain injury in this population remains poorly characterized. White matter hyperintensities (WMHs), a biomarker of cerebrovascular lesions, are prevalent in CAD and are linked to risk of stroke. Beyond total burden, spatial distribution of WMHs carries pathological significance and is critical for understanding CAD-related injury. While clinical outcomes including coronary revascularization procedure and myocardial infarction influence CAD prognosis, their impact on WMH burden remains unclear. MethodsThis study investigated regional WMH burden in CAD and its relationship with clinical characteristics. 82 adults over 50 years participated, including 44 individuals with CAD and 38 controls. WMHs were segmented from fluid attenuated inversion recovery and T1-weighted MRI and categorized as total, periventricular, deep, and superficial regions. History of myocardial infarction and coronary revascularization (coronary artery bypass grafting (CABG) and percutaneous coronary intervention (PCI)), was obtained from medical files. ResultsIndividuals with CAD exhibited higher total, periventricular, and deep WMH volumes than controls. Participants who underwent CABG had higher superficial WMH volumes than those with PCI, suggesting greater disease severity influences WMH burden. ConclusionCAD is characterized by a distinct pattern of cerebrovascular vulnerability, with revascularization procedures influencing WMH burden

neuroscience↗

bioRxiv2024

Cognitive-and lifestyle-related microstructural variation in the ageing human hippocampus

Ageing is a biological process associated with the natural degeneration of various regions of the brain. Alteration of neural tissue in the hippocampus with ageing typically results in cognitive decline that may serve as a risk factor for dementia and other neurodegenerative diseases. Modifiable lifestyle factors may help preserve hippocampal neural tissue (microstructure) and slow down neurodegeneration and thus promote healthy cognition in old age. In this study, we sought to identify potential modifiable lifestyle factors that may help preserve microstructure in the hippocampus. We used data from 494 subjects (36-100 years old) without clinical cognitive impairment from the Human Connectome Project-Aging study. We estimated hippocampal microstructure using myelin-sensitive (T1w/T2w ratio), inflammation-sensitive (MD) and fibre-sensitive (FA) MRI markers. Non-negative matrix factorization was used to integrate the signals of these images into a multivariate spatial signature of microstructure covariance across the hippocampus. The associations between hippocampal microstructural patterns and lifestyle factors & cognition were identified using partial least squares analysis. Our results reveal that the preservation of axon density and myelin in regions corresponding to subicular regions and CA1 to CA3 regions of the hippocampi of younger adults is associated with improved performance in executive function tasks, however, this is also associated with a decreased performance in memory tasks. We also show that microstructure is preserved across the hippocampus when there is normal hearing levels, physical fitness and normal insulin levels in younger adults of our study even in the presence of cardiovascular risk factors like high body mass index, blood pressure, triglycerides and blood glucose known to be associated with hippocampal neurodegeneration. This preservation is not observed in older adults when there are no normal levels of insulin, physical fitness and hearing. Taken together, our results suggest that certain lifestyle factors like normal hearing, physical fitness and normal insulin levels may help preserve hippocampal microstructure which may be useful in maintaining optimum performance on executive function tasks and potentially other modes of cognition.

neuroscience↗

bioRxiv2024

Joint signatures of morphological and microstructural inter-individual variation in the Alzheimer's spectrum

Alzheimers disease (AD) is primarily characterized by the accumulation of amyloid and tau pathologies. However, alterations in the detailed organization and composition of neural tissue also contribute to the diseases early stages. Here, we sought to explore whether hippocampal and cortical microstructural changes, such as myelin alterations and inflammation-mediated increases in iron, could serve as indices of AD-related pathophysiology. In this study, we included 158 participants across the AD spectrum: from individuals without cognitive impairment, at high risk for AD, in the prodromal phase with mild cognitive impairment, and suffering from clinical dementia. We measured atrophy using structural magnetic resonance imaging (MRI) and estimated myelin and iron content using quantitative MRI (qMRI) metrics derived from T1 and T2* relaxation, times respectively. We integrated these contrasts to estimate a joint multivariate signature of tissue alterations across the cortex and hippocampus using non-negative matrix factorization. The relevance of these signatures to AD-spectrum measures of medical history, lifestyle, and cognition were further explored using partial least squares correlation. Our results reveal lower disease-related cortical thickness over large areas of the cortex while T2* provided specific variation across the brain (lower in dorsomedial and superior temporal areas, superior frontal cortex, and premotor cortex, and higher in the occipital lobe). Additionally, we observed longer T1 and T2* times in the hippocampus associated with specific lifestyle risk factors like past smoking, high blood pressure, high cholesterol levels, and higher anxiety. These patterns were significantly related to older age, associated with AD progression, being female, and being an APOE-{square}4 carrier. Taken together, our results suggest that qMRI metrics could serve as a valuable non-invasive tool for exploring the role of myelin and inflammation in AD-related pathophysiology and could be sensitive to modifiable risk factors related to lifestyle and medical history. Future studies may use these signatures to investigate their relationship in investigations related to lifestyle interventions or novel therapeutics.

neuroscience↗

bioRxiv2023

Assessment of white matter hyperintensity severity using multimodal MRI in Alzheimer's Disease

White matter hyperintensities (WMHs) are clinically significant MRI abnormalities often detected in the elderly and early stages of Alzheimers Disease. They are indicative of vascular pathology but represent a mixture of microstructural tissue alterations that is highly variable between individuals. To better understand these alterations, we leveraged the signal of different MRI contrasts sampled within WMHs, which have differential sensitivity to microstructural properties. Subsequently, we sought to examine the asso of these WMH signal measures to clinically-relevant measures such as cortical and global brain atrophy, cognitive function, diagnostic and demographic differences, and Alzheimers Disease-relevant cardiovascular risk factors. Our sample of 118 subjects was composed of healthy controls (n=30), high-risk of Alzheimers Disease due to familial history (n=47), mild cognitive impairment (n=32), and clinical Alzheimers Disease (n=9) as a means of ascertaining a spectrum of impairment. We sampled the median signal within WMHs on weighted MRI images that are commonly acquired (T1-weighted [T1w], T2-weighted [T2w], T1w/T2w ratio, Fluid-Attenuated Inversion Recovery [FLAIR]), and the relaxation times from quantitative T1 (qT1) and T2* (qT2*) images. Main analyses were performed with a periventricular/deep/superficial white matter parcellation and were repeated with a lobar white matter parcellation. We demonstrated that the correlations between WMH signal measures were variable, suggesting that they are likely influenced by different microstructural properties. We observed that the WMH qT2* and FLAIR measures displayed different age- and disease-related trends compared to normal-appearing white matter, highlighting sensitivity to WMH-specific tissue deterioration. Further, WMH qT2* particularly in periventricular and occipital white matter regions was consistently associated with several of our clinical variables of interest using both parcellation schemes in univariate analyses, and further showed high contributions to a pattern of brain variables that was associated with age and cognitive variables in multivariate Partial Least Squares Correlation analyses. qT1 and FLAIR measures showed consistent clinical relationships in multivariate analyses only, while T1w, T2w, and T1w/T2w ratio measures were not consistently associated with clinical variables. We observed that the qT2* signal was sensitive to clinically-relevant microstructural tissue alterations specific to WMHs. Combining volumetric and signal measures of WMH, particularly qT2* and to a lesser extent qT1 and FLAIR, should be considered to more precisely characterize the severity of WMHs in vivo. These findings may have implications in determining the reversibility of WMHs and potential efficacy of cardio- and cerebrovascular treatments.

neuroscience↗

bioRxiv2022

The impact of study design choices on significance and generalizability of canonical correlation analysis in neuroimaging studies

This technical note describes the effects of different data reduction methods and sample sizes for neuroimaging studies in the context of canonical correlation analysis (CCA). CCA is a multivariate statistical technique which has gained increasing popularity in neuroimaging research in recent years. Here, we investigate the parcellation methods impact on elucidating neuroanatomical relationships (based on cortical thickness) with known risk factors related to Alzheimers disease risk using data from the UK Biobank. The cortical thickness values were parcellated using four common methods in neuroimaging (atlas-based parcellation, spectral clustering, principal component analysis, and independent component analysis) and results from CCA were compared. The results show that the choice of parcellation technique impacts the strength and significance of the correlation between the brain and behaviours. Principal component analysis and independent component analysis result in the strongest correlations. Additionally, we show that regardless of parcellation technique, smaller sample sizes of participants result in inflated correlation strength and significance.

bioinformatics↗

bioRxiv2022

Menopause, Brain Anatomy, Cognition and Alzheimer's Disease

The menopause transition has been repeatedly associated with decreased cognitive performance and increased incidence of Alzheimers Disease (AD), particularly when it is induced surgically 1,2 or takes place at a younger age 3,4. However, there are very few studies that use neuroimaging techniques to examine the effects of these variables in aggregate and in a large sample. Here, we use data from thousands of participants from the UK Biobank to assess the relationship between menopausal status, menopause type (surgical or natural), and age at menopause with cognition, AD, and neuroanatomical measures derived from magnetic resonance imaging. We find that for brain and cognitive measures, menopausal status, menopause type and age at surgical menopause do not impact the brain; but that there is a positive correlation between anatomy, cognition and age at non-surgical menopause. These results do not align with previous reports in the literature with smaller samples. However, we confirm that both early and surgical menopause are associated with a higher risk of developing AD, indicating that early and abrupt ovarian hormone deprivation might contribute to the development of the disorder.

neuroscience↗

bioRxiv2022

Variation in subcortical anatomy: relating interspecies differences, heritability, and brain-behavior relationships

There has been an immense research focus on the topic of cortical reorganization in human evolution, but much less is known regarding the reorganization of subcortical circuits which are intimate working partners of the cortex. Here, by combining advanced image analysis techniques with comparative neuroimaging data, we systematically map organizational differences in striatal, pallidal and thalamic anatomy between humans and chimpanzees. We relate interspecies differences, a proxy for evolutionary changes, to genetics and behavioral correlates. We show that highly heritable morphological measures are significantly expanded across species, in contrast to previous findings in the cortex. The identified morphological-cognitive latent variables were associated with striatal expansion, and affective latent variables were associated with more evolutionarily-conserved areas in the thalamus and globus pallidus. These findings provide new insight into the architecture of these subcortical hubs and can provide greater information on the role of these structures in health and illness.

neuroscience↗

bioRxiv2022

High spatial overlap but diverging age-related trajectories of cortical MRI markers aiming to represent intracortical myelin and microstructure

Cortical thickness (CT), gray-white matter contrast (GWC), boundary sharpness coefficient (BSC), and T1-weighted/T2-weighted ratio (T1w/T2w) are cortical metrics derived from standard T1- and T2-weighted magnetic resonance imaging (MRI) images that are often interpreted as representing or being influenced by intracortical myelin content. However, there is little empirical evidence to justify these interpretations nor have the homologies or differences between these measures been examined. We examined differences and similarities in group mean and age-related trends with the underlying hypothesis that different measures sensitive to similar changes in underlying myelo- and microstructural processes should be highly related. We further probe their sensitivity to cellular organization using the BigBrain, a high-resolution digitized volume stemming from a whole human brain histologically stained for cell bodies with the Merker stain. The measures were generated on both the MRI-derived images of 127 healthy subjects, aged 18 to 81, and on the BigBrain volume using cortical surfaces that were generated with the CIVET 2.1.0 pipeline. Comparing MRI markers between themselves, our results revealed generally high overlap in spatial distribution (i.e., group mean), but mostly divergent age trajectories in the shape, direction, and spatial distribution of the linear age effect. Significant spatial relationships were found between the BSC and GWC and their BigBrain equivalent, as well as a correlation approaching significance between the BigBrain intensities and the T1w/T2w ratio in gray matter (GM) both sampled at half cortical depth. We conclude that the microstructural properties at the source of spatial distributions of MRI cortical markers (e.g. GM myelin) can be different from microstructural changes that affect these markers in aging. While our findings highlight a discrepancy in the interpretation of the biological underpinnings of the cortical markers, they also highlight their potential complementarity, as they are largely independent in aging. Our BigBrain results indicate a general trend of GM T1w signal and myelin being spatially related to the density of cells, which is possibly more pronounced in superficial cortical layers. Highlights- Different MRI cortical markers aim to represent myelin and microstructure - These markers show high spatial overlap, but mostly divergent age trajectories - It is unlikely that myelin changes are the source of the age effect for all markers - Trend of MRI signal being related to cell density in more superficial cortical layers

neuroscience↗