Figure 4: Categorization of RGCs responses to wide-field stimuli.

Of 93 channels (n=2 ChR2-expressing retinas) which responded to high-intensity blue light (after application of blockers). (a) In 66 units, the response was abolished with application of blockers and intense response was restored with high-intensity light stimulation (as in Fig. 2a). (b) A total of 15 units did not respond to lower light stimuli (0.08–0.17 mW mm⁻²) with and without blockers, but responded to intense blue light. (c) In 12 units, a shorter and weaker response was still observed after application of blockers and a more robust response was later observed to high-intensity light. These responses may indicate a higher concentration of ChR2 channels, or a higher underlying excitability of these cells. ↓-low (0.1–0.15 mW mm⁻²), ↑-high intensities (~2.6 mW mm⁻²).