The flowchart of the fiber shape analysis methods. (a) Whole-brain white matter fiber tractography; (b) U-shape fibers; (c) Reconstructed gray matter/white matter surface with gyral region color-coded by brown and sulcal region color-coded by other colors; (d) Sulcal fundi (white curves); (e) U-shape fiber bundles extracted from sulcal fundi. Step 1: fiber clustering; Step 2: Sulcal fundi extraction; Step 3: Fiber bundles extraction around sulcal fundi.
Diffusion tensor imaging (DTI), high angular resolution diffusion imaging (HARDI), and diffusion spectrum imaging (DSI) have been widely used in the neuroimaging field to examine the macro-scale fiber connection patterns in the cerebral cortex. However, the topographic and geometric relationships between diffusion imaging derived streamline fiber connection patterns and cortical folding patterns remain largely unknown. This paper specifically identifies and characterizes the U-shapes of diffusion imaging derived streamline fibers via a novel fiber clustering framework and examines their co-localization patterns with cortical sulci based on DTI, HARDI, and DSI datasets of human, chimpanzee and macaque brains. We verified the presence of these U-shaped streamline fibers that connect neighboring gyri by coursing around cortical sulci such as the central sulcus, pre-central sulcus, post-central sulcus, superior temporal sulcus, inferior frontal sulcus, and intra-parietal sulcus. This study also verified the existence of U-shape fibers across data modalities (DTI/HARDI/DSI) and primate species (macaque, chimpanzee and human), and suggests that the common pattern of U-shape fibers coursing around sulci is evolutionarily-preserved in cortical architectures.