Virtually all extrinsic afferents, including feedback cortico-cortical inputs to the cat’s primary visual cortex use glutamate and/or asparate as neurotransmitters and are thus presumably excitatory (Pérez-Cerdá et al., 1996). Indeed, electrical stimulation of areas 18 (V2) or 19 (V3) of the cat (Bullier et al., 1988) or the latero-medial (LM presumptive V2) area of the rat (Shao and Burkhalter, 1996) or area V2 of the mouse (De Pasquale and Sherman, 2011) result in the orthodromic, monosynaptic spike discharges or mono-synaptic depolarizations of neurons in their respective ipsilateral V1.