Figure 5.
Hypothesized homologous hodology of inter-areal connectivity. A, In primate neocortex, FF and FB streams have characteristic layers of origin and termination. B, In mouse visual cortex, FF and FB projections from an intermediate area (LM) arise from distinct IT subclasses that are intermingled within L2/3, as demonstrated by retrograde tracer injections into the upstream and downstream areas (adapted with permission from Ref. 111). Scale bar 50 μm. C, In rat secondary sensory cortices, a subclass of L6 neurons expressing latexin project back to the corresponding primary sensory region but not to thalamus, higher-order cortex, or contralateral cortex (adapted with permission from Ref. 82). Scale bar 200 μm. D, In mouse S1, two distinct subclasses of L2/3 neurons project to M1 and S2, both of which would be considered FF projections. Reconstructed neurons are adapted with permission from Ref. 66. Note the callosally projecting axons of both neurons (branches to the right), a defining feature of IT neurons.