with complete agenesis of the corpus callosum [41]. However, it is noteworthy that resting state functional connectivity can be sensitive to multi-synaptic interactions, and hence, regions that are not directly connected structurally could still be functionally connected. These data suggest that if two regions have a direct structural connection, then they should also be functionally connected, but the opposite may not be true. Consequently, one could expect a strong functional connection between regions that are also directly connected structurally. In this work, our objective is to extend this concept from mesoscale connections between brain regions to rather microscale connections between different cortical layers in these regions. Attempts to do so have been scarce in the literature. Below, we present previous attempts in this direction. Layer-specific connections between the primary visual cortex layers II/III and middle temporal area layer IV were detected with high-resolution resting state fMRI through functional connectivity analysis [20]. The default mode network under resting state was clearly seen across six layers by seed-based functional connectivity analysis after removing depth-dependent physiological noise [42]. In addition, a recent study showed the existence of temporal correlation of resting state hemodynamic signals derived from optical imaging at sub-millimeter columnar scale in
