Biology subjects

Duhamel, G.

Publications and source records attributed to Duhamel, G..

4 recordsLinked to original sources

bioRxiv2026

An Open Test--Retest Dataset of Rapid Myelin Mapping Acquisitions

Myelin supports rapid and efficient neural communication and is implicated in brain development, learning, aging, and neurological disease. Although numerous magnetic resonance imaging (MRI) approaches have been proposed to characterize myelin in vivo, they have rarely been evaluated together within the same participants and across repeated acquisitions. To address these gaps, we introduce the Myelin Imaging Reliability and ReprOducibility Resource (MIRROR), an openly available multimodal test--retest MRI dataset of diffusion MRI (dMRI), inhomogeneous magnetization transfer imaging (ihMT), quantitative susceptibility mapping (QSM), MP2RAGE, T1w/T2w ratio mapping, and transverse relaxometry in 22 healthy adults. We evaluated gray--white matter differentiation, intermetric correspondence, test--retest reliability, and participant specificity across 27 myelin-sensitive metrics. Gray--white matter differentiation was strong for dMRI derivatives, MP2RAGE-derived R1, T1w/T2w, and ihMT, while being substantially weaker for QSM measures. Intermetric spatial correlations were generally strongest within acquisition or modeling families. Test--retest reliability was generally high, particularly for dMRI-derived metrics, but was more variable among QSM-, ihMT-, and R2*-derived measures. Regional spatial profiles were also highly participant-specific, with discriminability approaching its upper bound for most metrics. All imaging data, derived maps, and processing code are openly released. MIRROR provides a benchmark for characterizing the measurement properties and practical tradeoffs of scalable myelin-sensitive MRI methods, supporting principled acquisition selection and accelerating methodological development and validation.

neuroscience↗

bioRxiv2026

Structural Characterization of Cardiac Purkinje Fibers Using Inhomogeneous Magnetization Transfer (ihMT): A proof of Concept MRI-Histology Approach

BACKGROUNDThe cardiac Purkinje network plays a critical role in maintaining synchronized activation of ventricles but remains challenging to image due to its fine and unique structure. Conventional MRI techniques lack sufficient contrast to distinguish the underlying structural composition of Purkinje Fibers (PF). PURPOSEThis study investigates the potential of inhomogeneous Magnetization Transfer (ihMT) as a novel contrast mechanism for visualizing and differentiating subregions of the PF. METHODSFive fixed ex-vivo sheep hearts (n = 5) containing free running PF were scanned with a 9.4T MRI using a 2D ihMT RARE sequence. ASSESSMENTihMTR maps were analyzed using manually defined regions-of-interest (ROIs) corresponding to free-running PF, insertion points, and myocardium. Histological analysis (light and polarized microscopy) was performed on matched sections to quantify collagen types I and III, adipocytes, Purkinje cells, and cardiomyocytes. RESULTSThree ihMT protocols, which produced high ihMTR values in free-running PF (9.25-10.83%) and strong absolute contrast relative to the myocardium (2.00-2.17%) and insertion points (2.99-3.40%) in one sample were selected and applied to all samples. Across all samples, mean ihMTR in free-running was consistently higher than in insertion points (11.5 {+/-} 1.5% vs. 9.0 {+/-} 2.9%). Histological analysis revealed a significantly greater collagen content in free-running regions compared with insertion points (72.4 {+/-} 15.9% vs. 31.1 {+/-} 13.1%; p = 0.001), along with higher adipocyte content at insertion points vs. free-running regions (12.3 {+/-} 6.1% vs. 3.8 {+/-} 2.7%, non-significant). Collagen type III was more prominent at insertion points but remained a minor component overall. CONCLUSIONihMT imaging can distinguish PF subregions based on microstructural differences, particularly collagen and adipocyte distribution. This study lays the groundwork for developing biophysical models to interpret ihMT signals in terms of tissue composition and microstructure, providing a foundation for future studies. SponsorThis study received financial support from the French Government by the National Research Agency (ANR; SYNATRA ANR-21-CE19-0014-01) and Region Nouvelle Aquitaine (convention N{degrees}AAPR2022-2021-16609210).

biophysics↗

bioRxiv2020

A Motion Correction Strategy for Multi-Contrast based 3D parametric imaging: Application to Inhomogeneous Magnetization Transfer (ihMT)

PurposeTo propose an efficient retrospective image-based method for motion correction of multi-contrast acquisitions with a low number of available images (MC-MoCo) and evaluate its use in 3D inhomogeneous Magnetization Transfer (ihMT) experiments in the human brain. MethodsA framework for motion correction, including image pre-processing enhancement and rigid registration to an iteratively improved target image, was developed. The proposed method was compared to Motion Correction with FMRIBs Linear Image Registration Tool (MCFLIRT) function in FSL over 13 subjects. Native (pre-correction) and residual (post-correction) motions were evaluated by means of markers positioned at well-defined anatomical regions over each image. ResultsBoth motion correction strategies significantly reduced inter-image misalignment, and the MC-MoCo method yielded significantly better results than MCFLIRT. ConclusionMC-MoCo is a high-performance method for motion correction of multi-contrast volumes as in 3D ihMT imaging.

neuroscience↗

bioRxiv2019

Global drivers of diversification in a marine species complex

Investigating historical gene flow in species complexes can indicate how environmental and reproductive barriers shape genome divergence before speciation. The processes influencing species diversification under environmental change remain one of the central focal points of evolutionary biology, particularly for marine organisms with high dispersal potential. We investigated genome-wide divergence, introgression patterns and inferred demographic history between species pairs of all extant rock lobster species (Jasus spp.), a complex with long larval duration, that has populated continental shelf and seamount habitats around the globe at approximately 40{degrees}S. Genetic differentiation patterns revealed the effects of the environment and geographic isolation. Species associated with the same habitat structure (either continental shelf or seamount/island) shared a common ancestry, even though the habitats were not adjacent. Differences in benthic temperature explained a significant proportion (41.3%) of the genetic differentiation. The Eastern Pacific species pair of J. caveorum and J. frontalis retained a signal of strict isolation following ancient migration, whereas species pairs from Australia and Africa and seamounts in the Indian and Atlantic oceans included events of introgression after secondary contact. Parameters estimated for time in isolation and gene flow were congruent with genetic differentiation metrics suggesting that the observed differentiation patterns are the product of migration and genetic drift. Our results reveal important effects of habitat and demographic processes on the divergence of species within the genus Jasus providing the first empirical study of genome-wide drivers of diversification that incorporates all extant species in a marine genus with long pelagic larval duration.

evolutionary biology↗