The classification of spatial, chromatic, and intensity features of simple visual stimuli by a network of retinal ganglion cells

We are investigating the representation of simple visual objects by groups of retinal ganglion cells and are simultaneously recording the responses of ganglion cells in the isolated turtle retina with 15 out of an array of 100 penetrating microelectrodes. Stimulation is with circular spots of light of various intensities, diameters and colors. We have trained a three layer artificial neural network to estimate the stimulus parameters and have challenged it to classify the color, size and intensity of test stimuli. Individual ganglion cells are poor encoders of stimulus features, but the 15 cells in our sample allow one to classify intensity, color and spot diameter to within 0.6 log units, 61 nm, and 0.68 mm, respectively.