Courvoisier, S. | bioRxiv Science

bioRxiv2025

Regional BOLD variability reflects microstructural maturation and neuronal ensheathment in the preterm infant cortex

BOLD variability reflects meaningful brain activity, yet its structural and biological correlates during early development remain unknown. We aimed to investigate how BOLD variability evolves in very preterm (VPT) infants, its relationship with cortical microstructure and gene expression, and how it differs from full-term (FT) newborns at term-equivalent age (TEA). Using resting-state fMRI and multi-shell diffusion imaging, acquired in 54 VPT (longitudinally at 33-weeks GA and at TEA) and 24 FT newborns, we evaluated regional differences in cortical BOLD variability and microstructural maturation, and compared to patterns of gene expression in the fetal cortex, using the BrainSpan dataset. BOLD variability increased in primary sensory-sensorimotor and proto-DMN regions, accompanied by decreased cortical diffusivity. Gene expression analysis revealed concurrent upregulation of genes mediating gliogenesis and neuronal ensheathment. Compared to FT newborns, VPT at TEA showed decreased BOLD variability and increased cortical diffusivity. BOLD variability reflects cortical microstructure, mediated by upregulation of gliogenesis and neuronal ensheathment. Interruption of these processes by preterm birth identifies putative mechanisms of preterm brain injury.

neuroscience↗

bioRxiv2020

Whole-Brain High-Resolution Metabolite Mapping with 3D Compressed-Sensing-SENSE-LowRank 1H FID-MRSI

There is a growing interest in the neuroscience community to map the distribution of brain metabolites in vivo. Magnetic resonance spectroscopic imaging (MRSI) is often limited by either a poor spatial resolution and/or a long acquisition time which severely limits its applications for clinical or research purposes. Building on a recently developed technique of acquisition-reconstruction for 2D MRSI, we combined fast Cartesian 1H-FID-MRSI acquisition sequence, compressed-sensing acceleration, and low-rank total-generalized-variation constrained reconstruction to produce 3D high-resolution whole-brain MRSI with a significant acquisition time reduction. We first evaluated the acceleration performance using retrospective undersampling of a fully-sampled dataset. Second, a 20 min accelerated MRSI acquisition was performed on the brain of three healthy volunteers resulting in metabolite maps with 5 mm isotropic resolution. The metabolite maps exhibited the detailed neurochemical composition of all brain regions and revealed parts of the underlying brain anatomy. The latter assessment used previous reported knowledge and a brain atlas-based analysis to show consistency of the concentration contrasts and ratio across all brain regions. These results acquired on a clinical 3 Tesla MRI successful combinae of the 3D 1H-FID-MRSI with a constrained reconstruction to produce detailed mapping of metabolite concentrations at high-resolution over the whole brain, with an acquisition time suitable for clinical or research settings.

neuroscience↗