Physiology of the receptive-field surround. A: Flashing-spot stimulation of a transient ON-OFF RGC showing the position of three of the 10 spots relative to the ON (red) and OFF (black) dendritic arbors. B: Spike raster plots from the cell shown in A to 10 spots of 50–1,000-µm diameter. C: Area-response plots from seven cells to the same stimuli as B, error bars = s.e.m. D–F: Excitatory conductance, Ge ± s.e.m., averaged from 10 cells in response to a 100-µm spot (D), a 200-µm spot (E), and an 800-µm spot (F). G–I: Inhibitory conductance, Gi ± s.e.m., averaged from 10 cells in response to a 100-µm spot (G), a 200-µm spot (H), and an 800-µm spot (I).