Figure 2. Amount of adapting inhibition can determine the type of adaptive field.

(A) Subunits in a model of a ganglion cell with a center-surround adaptive field (see Supplemental Experimental Procedures). Colored bars show different locations used for high contrast. Line thickness indicates the weight of each subunit onto the ganglion cell. (B) Both inhibitory and excitatory subunits are composed of spatiotemporal receptive fields, nonlinearities, and adaptive blocks (arrow in circle). Inhibition from inhibitory to excitatory subunits had a spatial weighting (w_I) equal to the spatial overlap between each excitatory and inhibitory subunit. The excitatory population was likewise spatially weighted (w_E) and then passed through a threshold to yield the model output. The average responses for two excitatory subunits are shown in response to a spot centered over the ganglion cell receptive field (colored bar in (A) matching the low contrast response). Markers in the top right corner of the two subunit responses correspond to their weighting w_E in the model output and their spatial location in (A). (C) Top, output of the model for three different locations of high contrast corresponding to the colored bars in (A) that match the low contrast responses. Bottom, example data PSTHs from fast Off adapting cells. (D) Adaptive indices from models with different maximal inhibitory weighting (w_max) (see Supplemental Experimental Procedures). The adaptive index is plotted for when the high contrast spot was located directly above or just neighboring the ganglion cell receptive field. Line colors correspond to the bars in (A). Green and purple icons represent the type of adaptive fields measured during L_early that correspond to that range of w_max.