Anatomical Segmentation and Connectivity of the Uncinate Fasciculus.

Abstract

Aim: The uncinate fasciculus (UF) is a major white matter tract that connects the frontal and temporal lobes, contributing significantly to higher-order cognitive and emotional functions. Despite its clinical relevance, the UF's internal segmentation and topographical organization remain incompletely understood. This study aims to provide a detailed anatomical segmentation of the UF and to identify its cortical and subcortical connections using complementary white matter dissection and diffusion-weighted imaging tractography techniques.

Material and methods: Human cadaveric hemispheres were used to perform fiber dissections of the UF using the Klingler technique. The tract was anatomically segmented based on its spatial relationships with surrounding structures. In parallel, high-resolution diffusion MRI data from healthy subjects were analyzed using deterministic tractography methods to reconstruct the UF and validate the anatomical segmentation.

Results: Dissection studies revealed three distinct segments of the UF-temporal, insular, and frontal-based on their anatomical trajectories. Tractography findings supported this segmentation and demonstrated specific patterns of connectivity: the temporal segment connected the anterior temporal lobe to the amygdala and insula; the insular segment traversed the limen insulae; and the frontal segment projected to Brodmann areas 10, 11, 47, as well as the anterior cingulate cortex. These findings were consistent across all subjects.

Conclusion: This study presents a novel three-segment model of the UF, integrating findings from both dissections and tractography. The identified connectivity patterns enhance our understanding of frontal-temporal network organization and provide valuable insights for neurosurgical approaches and neuropsychiatric research.