The connectivity fingerprints of the frontal eye field and the inferior frontal junction

Within the prefrontal cortex, the frontal eye field (FEF) and the inferior frontal junction (IFJ) are crucial regions that mediate attention, working memory, and cognitive control functions. I comprehensively reviewed the neuroimaging evidence on these regions, suggesting that they are specialized in the control of spatial versus non-spatial visual processing, respectively, and hypothesized that their connectivity fingerprints might underlie these roles. To accurately infer the localization of these regions in standard space, I carried out an activation likelihood estimation (ALE) fMRI meta-analysis using tasks that reliably engage these regions. Prosaccade and antisaccade tasks were included in the FEF sample, whereas oddball/attention, n-back, Stroop and task-switching experiments were included in the IFJ sample (n = 35 and 32, respectively). The ALE technique revealed the strongest convergence of activations at the junctions of the superior precentral sulcus and superior frontal sulcus for the FEF, and the inferior precentral sulcus and inferior frontal sulcus for the IFJ. I employed the resulting ALE peaks to perform a meta-analytic connectivity modeling analysis to uncover their whole-brain fMRI coactivations and decoded these patterns to infer significant associations with behavioral domains. The ALE peaks from a subsample of the previous meta-analysis were used to analyze 3T diffusion MRI data released by the Human Connectome Project from 56 unrelated subjects. Using a surface-based probabilistic tractography approach, I tracked streamlines ipsilaterally from the FEF and IFJ to regions of the dorsal and ventral visual streams on the native white matter surface parcellated using the atlas by Glasser et al. (2016). By contrasting their connectivity likelihood, I 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. These results were replicated when accounting for the distance between FEF, IFJ, and the target regions. The connectivity fingerprints of the FEF and IFJ provide converging evidence of their specialization in the control of spatial vs non-spatial processing, which is mediated by long-range white matter association pathways. The results presented in this dissertation overall support the view that the two-visual stream architecture extends to the human prefrontal cortex, as was originally hypothesized in the macaque based on tract tracing and neurophysiological evidence.