Surface-based probabilistic tractography uncovers segregated white matter pathways underlying spatial and non-spatial control

Abstract

ABSTRACTThe frontal eye field (FEF) and the inferior frontal junction (IFJ) are regions that mediate orchestrating functions, with mounting neuroimaging evidence suggesting that they are specialized in the control of spatial versus non-spatial processing, respectively. We hypothesized that their unique patterns of structural connectivity (i.e., their connectivity fingerprints) underlie these specialized roles. To accurately infer the localization of FEF and IFJ in standard space, we carried out an activation likelihood estimation meta-analysis of fMRI paradigms targeting these regions. Using a surface-based probabilistic tractography approach, we tracked streamlines ipsilaterally from the inferred FEF and IFJ activation peaks to the dorsal and ventral visual streams on the native white matter surface parcellated using the atlas by Glasser et al. (2016). By contrasting FEF and IFJ connectivity likelihoods, we found predominant structural connectivity from FEF to regions of the dorsal visual stream (particularly in the left hemisphere) compared to the IFJ, and conversely, predominant structural connectivity from the IFJ to regions of the ventral visual stream compared to the FEF. Additionally, we analyzed the cortical terminations of the superior longitudinal fasciculus to the FEF and IFJ, implicating its first and third branches as segregated pathways mediating their communication to the posterior parietal cortex. The structural connectivity fingerprints of the FEF and IFJ support the view that the two visual stream architecture extends to the posterior lateral prefrontal cortex and provide converging anatomical evidence of their specialization in spatial versus non-spatial control.