Figure 5.

Comparison of measured activation thresholds of different cell types within four preparations. A, Thresholds of all activated cells from the preparation represented in Figure 4. Thresholds corresponding to example response curves shown in Figure 4 are marked with triangles. B–D, Measured thresholds for all cells from examined cell types in three additional retinal preparations. Values in parentheses indicate the fraction of cells lying over the array with measurable thresholds. Dashed vertical lines mark the conservative platinum charge density limit of 0.1 mC/cm² (see Discussion) based on the mean planar area of the electrodes used in each preparation. Gray regions indicate untested ranges of pulse amplitudes.