Internal connectivity of the mouse mesocortical ring and functional implications

The mammalian mesocortex (MCx) was redefined recently as a complete ring intercalated between the allo- and iso-cortex, attending to the consistent expression of 46 selective gene markers. The MCx exhibits various other characteristics such as low myelin content of its fibers, a property directly related to its function and susceptibility to degenerative disorders. Irrespective of its shared molecular profile, the MCx ring differentiates into different sectors with singular molecular and cytoarchitectonic characteristics, such as the posterior orbitary cortex, the cingulate cortex, and the insula. In the present study, using anterograde connectivity experiments published in an Allen Institute for Brain Science public database ( https://brain-map.org/our-research/connectivity ), we analyzed the internal connectivity of the mesocortical ring. We observed that its different sectors are multiply interconnected, possibly achieving integrative functions. The medial posterior orbitary cortex stands out; it appears to play a higher hierarchical role within the MCx ring by sending and receiving projections from all mesocortical sectors.