Mechanism underlying the inhibitory sidebands in the receptive field of simple striate cells of the cat: pure on/off antagonism only or true inhibition?

The intrinsic organization of the receptive fields of simple striate cells revealed by moving stimuli is much more complex than could have been suspected from the use of stationary ones. There is, in fact, a small excitatory region centrally located in these receptive fields and an inhibitory region encompassing the whole excitatory component. These inhibitory regions or "inhibitory sidebands", were identified by stimulating the cells with bars of light against an artificial background discharge produced by repeated asynchronous stimulation of the excitatory component of the cell's receptive field. For a long time these inhibitory sidebands have been accounted for on the basis of the receptive field ON/OFF antagonism. These inhibitory regions, instead, are activated by both stationary and moving stimuli. Therefore, besides the antagonistic component a non-antagonistic one, purely inhibitory, greatly contributes to their origin.