Double-opponent cell
= Double-opponent cell
A color-responsive <neuron> with opposite chromatic tuning in different spatial subregions. A simple filter is $r=(c_L-c_M)_{\rm center}-(c_L-c_M)_{\rm surround}$. It cancels a spatially uniform opponent signal but responds when the regions differ. Such filtering can support chromatic boundaries without by itself solving every illumination ambiguity.