Spatiotemporal Relationship of Brain Pathways during Human Fetal Development Using High-Angular Resolution Diffusion...

Area of Science:

• Neuroscience
• Developmental Biology
• Medical Imaging

Background:

• Understanding the intricate development of white matter tracts in the human fetal brain is crucial for insights into neurodevelopmental disorders.
• Transient fetal zones represent critical regions for the formation and organization of neural pathways.

Purpose of the Study:

• To identify major fiber pathways and their spatiotemporal relationships within transient fetal zones in the developing human fetal brain.
• To correlate findings from postmortem high-angular resolution diffusion MR imaging (HARDI) with histological data.

Main Methods:

• Postmortem diffusion-weighted imaging (DWI) was performed on 9 human fetal brains (18-34 PCW).
• High-angular resolution diffusion MR imaging (HARDI) data were reconstructed using the Q-ball algorithm and deterministic streamline tractography.
• Fiber pathways were identified and localized using both diffusion-weighted images and histological sections.

Main Results:

• Massive projection fibers were identified by 18 PCW, while most association fibers emerged later.
• Characteristic laminar distribution and sagittal plane geometry of fiber tracts were observed throughout development.
• Protracted prenatal development of the corpus callosum and association fibers was noted.
• Radial coherence predominated in the telencephalon during the early prenatal period (24 PCW).

Conclusions:

• Correlation between histology and HARDI enabled the detection of sequential development of fiber systems (projection, callosal, association).
• The study elucidated the spatial relationships of these fiber systems with transient fetal zones.
• Geometric properties and developmental trajectories of major white matter tracts were characterized.