Connectivity-based parcellation of the anterior limb of the internal capsule

The anterior limb of the internal capsule (ALIC) is an important locus of frontal-subcortical fiber tracts involved in cognitive and limbic feedback loops. However, the structural organization of its component fiber tracts remains unclear. Therefore, although the ALIC is a promising target for various neurosurgical procedures for psychiatric disorders, more precise understanding of its organization is required to optimize target localization. Using diffusion tensor imaging (DTI) collected on healthy subjects by the Human Connectome Project (HCP), we generated parcellations of the ALIC by dividing it according to structural connectivity to various frontal regions. We then compared individuals' parcellations to evaluate the ALIC's structural consistency. All 40 included subjects demonstrated a posterior-superior to anterior-inferior axis of tract organization in the ALIC. Nonetheless, subdivisions of the ALIC were found to vary substantially, as voxels in the average parcellation were accurately assigned for a mean of only 66.2% of subjects. There were, however, some loci of consistency, most notably in the region maximally connected to orbitofrontal cortex. These findings clarify the highly variable organization of the ALIC and may represent a tool for patient-specific targeting of neuromodulation. Hum Brain Mapp 38:6107-6117, 2017. © 2017 Wiley Periodicals, Inc.