FIGURE 1 Predominant functional connectivity maps of FEF and IFJa across frequency bands and hemispheres for (A) oPEC and (B) iCOH metrics (two-sided Wilcoxon signed-rank test, p < 0.05, FDR-corrected for 33 ROIs). The results shown here are based on 2 s epoch segmentation.

Neuroimaging evidence suggests that the frontal eye field (FEF) and inferior frontal junction (IFJ) govern the encoding of spatial and nonspatial (such as feature- or object-based) representations, respectively, both during visual attention and working memory tasks. However, it is still unclear whether such contrasting functional segregation is also reflected in their underlying functional connectivity patterns. Here, we hypothesized that FEF has predominant functional coupling with spatiotopically organized regions in the dorsal ('where') visual stream whereas IFJ has predominant functional connectivity with the ventral ('what') visual stream. We applied seed-based functional connectivity analyses to temporally high-resolving resting-state magnetoencephalography (MEG) recordings. We parcellated the brain according to the multimodal Glasser atlas and tested, for various frequency bands, whether the spontaneous activity of each parcel in the ventral and dorsal visual pathway has predominant functional connectivity with FEF or IFJ. The results show that FEF has a robust power correlation with the dorsal visual pathway in beta and gamma bands. In contrast, anterior IFJ (IFJa) has a strong power coupling with the ventral visual stream in delta, beta and gamma oscillations. Moreover, while FEF is phase-coupled with the superior parietal lobe in the beta band, IFJa is phase-coupled with the middle and inferior temporal cortex in delta and gamma oscillations. We argue that these intrinsic connectivity fingerprints are congruent with each brain region's function. Therefore, we conclude that FEF and IFJ have dissociable connectivity patterns that fit their respective functional roles in spatial versus nonspatial top-down attention and working memory control.

Keywords: brain connectivity; magnetoencephalography; visual attention; visual pathways; working memory.

This research is supported by Ministero degli Affari Esteri e della Cooperazione Internazionale (to O.S.) and Fondazione Cassa Di Risparmio Di Trento E Rovereto (to D.B).

The data used in the current study provided and publicly made available by the 1200 Subjects Release of Human Connectome Project (Larson-Prior et al., 2013; Van Essen et al., 2013) in ConnectomeDB (db.humanconnectome.org; Hodge et al., 2016).