@Bitking Because of conversation elsewhere, I reinvestigated these ideas again, and I again brought it up with Jeff. My first questions were on the L2/3 axonal projections:
These axons have one major bifurcation, where one path goes out of the cortex, so we are only talking about the path that stays in the cortex. The axons do not split up into lots of paths inside the cortex as shown on the right below.
The picture on the left looks right (except for missing the path out of cortex). But I can’t find evidence for the picture on the right. The axon doesn’t split up into a cloud to create this circle of influence. This cortical-cortical axon will create a cluster of synapses about 0.5mm away from the soma, then continue onward in one direction to do it again later. It’s more like a subway line than a hub.