The uncinate fasciculus as observed using diffusion spectrum imaging in the human brain.

Abstract

The definitive structure and comprehensive role of the uncinate fasciculus (UF) are still obscure. We aimed to map the human UF white matter tractography and investigate the asymmetry, connectivity, and segmentation of the UF. Subcomponents of the UF were analyzed in 9 normal subjects and a 30-subject diffusion spectrum imaging (DSI) template (CMU-30). DSI and microdissection were performed to explore the tractography of the UF. Both methods revealed that it connects the anterior part of the temporal lobe (superior temporal gyrus and temporal pole) with the inferior frontal cortex and the orbitofrontal cortex. The UF starts at the temporal gyrus, runs inferiorly to the inferior frontal occipital fasciculus and splits into two branches, terminating in the ventrolateral frontal cortex and the rostral middle frontal cortex. Our study showed that the cortical areas of termination in the frontal lobe of the UF are the pars triangularis and pars orbitalis. The relative volume of the UF in both hemispheres was calculated. An independent t test was used to determine variances in the value of tract volume between the left and right hemispheres. The volume and the length showed a significant statistical difference in the total volume of the UF. We suggest the UF is leftward asymmetry. The two parts of the UF were divided, but the conclusion is not consistent with the previous published articles which have shown that the UF is segmented into three parts. Our research facilitates a better understanding of the UF.