Abstract
The nerve fibers are divided into three categories: projection, commissural, and association fibers. This study demonstrated a novel cortical mapping method based on these three fiber categories using MR tractography data. The MR fiber-track data were extracted using the diffusion-weighted 3T-MRI data from 19 individuals’ Human Connectome Project dataset. Anatomical MR images in each dataset were parcellated using FreeSurfer software and Brainnetome atlas. The 5 million extracted tracks per subject by MRtrix software were classified based on the basic cortical structure (cortical area in the left and right hemisphere, subcortical area), after the tracks validation procedure. The number of terminals for each categorized track per unit-sized cortical area (1 mm3) was defined as the track-density in that cortical area. Track-density ratio mapping with fiber types was achieved by mapping the density-dependent color intensity for each categorized tracks with a different primary color. The mapping results showed a highly localized, unique density ratio map determined by fiber types. Furthermore, the quantitative group data analysis based on the parcellation information revealed that the majority of nerve fibers in the brain are association fibers, particularly in temporal, inferior parietal, and occipital lobes, while the projection and commissural fibers were mainly located in the superior part of the brain. Hemispheric asymmetries in the fiber density were also observed, such as long association fiber in the Broca’s and Wernicke’s areas. We believe this new dimensional brain mapping information allows us to further understand brain anatomy, function.
Highlights
Neurons in the cerebral cortex are connected with three major brain regions, subcortical, inter-cortical, and intra-cortical regions
The dataset was obtained from the Human Connectome Project (HCP; Glasser et al, 2016b); 19 individual MRI datasets were selected without any criteria or prior knowledge about subjects
The voxel-based track-density ratio map (TDRM) that are on the left side are independent of the preceded brain parcellation information
Summary
Neurons in the cerebral cortex are connected with three major brain regions, subcortical, inter-cortical, and intra-cortical regions. Depending on these connected brain regions, the nerve fibers are broadly divided into three categories, i.e., projection, commissural, and association fibers. It can be presumed that the density of each categorized fiber in each cortical region is distinguishable. A novel brain mapping method can be considered based on the track-density distribution characteristic for each categorized fiber in the cerebral cortex using brain imaging data, such as the diffusionweighted MR-based tractography data (Basser et al, 1994, 2000)
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