Figure 10. Modulation of RGC and cortical responses by pulse width and irradiance.

At the level of the RGCs, the number of elicited action potentials increases with irradiance (a) and with pulse width (b). Error bars, s.e.m. At the cortical level, (c) devices with 70 μm pixels (blue) elicit a VEP response at 0.25 mW/mm², which increases up to 1 mW/mm² and saturates beyond that level. The 140 μm pixels (black) have lower thresholds and do not saturate at high irradiance. (d) VEP amplitude increases with pulse duration between 1 and 10 ms, and saturates with longer pulses (with 2 and 4 mW/mm² irradiance for 140 μm and 70 μm pixel devices, respectively). Error bars, s.d. Adapted from [46, 106].