The image below shows the Hermann Now let's suppose that a If we want the VI cell's preferred As we have seen before, we can use a grid displayed as a 15x15 pixel image. simple cell in V1 receives stimulus to be a vertical bar of light transfer function to derive the V1 cell's We can think of each individual pixel as synaptic inputs from 25 LGN positioned in the center of the a single neuron in LON (so here we have neurons within a receptive receptive field, then we can place a membrane potential as a weighted sum of its inputs, That is, we multiply each 'x' by each 30x30-900 LGN neurons). The shading field occupying a 5x5 patch vertical column of POSITIVE weights w' and add up the products plus the bias of each pixel corresponds to the LGN of the image. The 25 each equal to 0.2) in the field's term, b neuron's firing rate, with dark vs, light numbers below are the 25 center, flanked by vertical columns of shading indicating low vs. high firing LGN firing rates in a V1 cell's NEGATIVE weights teach equal to - If we set the bias term to b=0 rates, respectively. Let's assume that eceptive field. 05] in the surround the lowest possible firing rate is O Hz X=0 (no spikes] and the highest is 100 Hz W= .02 * The Vi cell will have a "resting membrane potential" of 0 when there is no input. (100 spikes per second). x=1 WE -.05 * The V1 cell membrane potential will become positive (greater than zero) when the cell is excited by its inputs; this happens oodoo when the 5x5 image in the cell's receptive field is similar to the cell's preferred stimulus a vertical bar of light in the center with darkness flanking in the surround). 25 The V1 cell membrane potential will b + xiWi become negative (less than zero) when the cell is inhibited by its inputs. This happens 1=1 when the image in the cell's receptive field is similar to the cell's antipreferred stimulus (a 100 V1 SIMPLE CELL vertical bar of darkness in the center with 90 20 40 60 8 100 light flanking in the surround). LGN CELL FIRING RATES If the numerical values to the left of each pixel show the firing rate ('x' value) of each input to the V1 cell, and the synaptic weights ('w' values) are those indicated by the colors of the triangles, then what is the membrane potential of the V1 simple cell? Assume b=0