Applying complementary techniques including functional imaging, post-imaging neuronal activity recordings with microelectrode arrays, and detailed histological mapping of axonal collaterals within neocortical gray matter in the rat’s neocortex, we have found a repeated structure-function gray matter neocortical motif. This motif, imaged after sensory point (small area) stimulation, or histologically after point injection of cortical tracers, is surprisingly large (up to 5 mm radius of both functional and their matching histological findings) and it therefore spreads beyond cytoarchitectonic borders to directly connect primary sensory-motor areas. The functional spread can be imaged/recorded in all major sensory areas, and the matching underpinning axonal spread can be mapped in the same areas and in various other non-sensory parts all over the neocortex. These findings suggest that every point in the neocortex is a source and recipient of a functional and histological spread.
Based on these findings we concluded that neocortical gray matter is functionally and structurally a continuous borderless neuronal tissue.
