Fig. 9. Visual processing in Pcdh- mutant retina. (A) Visual responses of RGCs in Pcdh- mutant retina to a flashing spot at photopic intensities. Background shading indicates periods of light On and Off. Each panel is a raster graph of firing from one neuron; each row is a repeat of the same stimulus; tick marks represent action potentials. Neurons vary greatly in whether they respond to light onset or offset, and whether firing is transient or sustained after the switch. (B) Direction-selective response of an RGC in Pcdh- mutant retina to a grating stimulus moving in eight different directions. Insets are histograms of spike times during one period of the grating (wavelength 664 µm, speed 664 µm/s). The polar plot reports the average firing rate as a function of direction. (C-H) Distribution of response parameters in mutant and control retinas. Each panel inspects a different characteristic of the visual response, and plots a cumulative histogram of that quantity for RGCs in mutant retinas (red curve, 115 cells, Chx10-Cre;Pcdh- ^fcon3/fcon3 or the peripheral region of the Pax6-Cre;Pcdh- ^fcon3/fcon3) and control retinas (black curve, 143 cells, genotype Pax6-Cre;Pcdh- ^+/fcon3 or Pcdh- ^fcon3/fcon3). The shaded range indicates 95% confidence interval. (C) Ratio of On and Off responses in mutant and control retinas. For each cell we computed an On-Off index from the experiment in A: (number of spikes fired during the on-phase of the spot)/(total number of spikes fired). (D) Size of the receptive field center, measured as the full width at half maximum of the receptive field profile b(x) (inset, see Eqn 2). (E) Speed of the response, measured as the time to peak of the temporal integration function a(t) (inset, see Eqn 2). (F) Average firing rate observed during stimulation with flickering gratings. (G,H) Threshold (G) and gain (H) of responses in a linear-nonlinear model (see Eqn 3).