Fig. 1.
Feedback inhibition enhances the excitatory current profile representing an edge. A: dark gray square represents the edge of a 600 × 600 μm dark (−100% luminance) square against a gray background as it is flashed at different positions with respect to the cell dendritic field shown in the dashed circle. Stimulus position is shown at 5 key locations with respect to the dendritic field. Traces show the average excitatory currents for each position under control (n = 29) and with all inhibition blocked (γ-aminobutyric acid types A and C [GABAA and GABAC, respectively] and glycine, n = 5). Gray bar in each recording indicates the 1 s duration of the flash. Location intervals are spaced at 30 μm. The ratio of currents for 2 indicated stimulus positions is calculated. B: profile excitatory current measurements for 21 stimulus positions under control and with all inhibition blocked. Offset of square (relative to perfect centering at 0 μm) is indicated on the x-axis. Large gray square indicates locations where the dendritic field of the cell is located inside the square.