Cone-driven flash responses isolated with ex vivo ERGs. Ex vivo ERG recordings from a WT adult mouse retina demonstrate the use of background light for isolating cone-evoked responses from the rod-dominated ERG. Constant (3 s) 505 nm light steps of increasing intensity (square steps) were delivered between 98 (maroon trace) and 150,526 photons µm⁻² s⁻¹ (brown trace). The background light step delivering 24,278 photons µm⁻² s⁻¹ (cyan trace) most effectively suppressed rod-evoked activity while minimizing response run-down and light adaptation between trials (inter-recording interval = 60 s). The extended time scale illustrates the slowed response recovery to the offset of background steps of increasing intensity. Arrow indicates the nose component and subsequent steady-state response reflecting prolonged rod response suppression (see Materials and methods). Inset: Cone-mediated photovoltages isolated by superimposed flashes (1–8 ms) of 520 nm light over steady background illumination (interstimulus interval = 500 ms). This stimulus protocol was used for measuring all cone-driven responses throughout this study aside from those collected from Gnat1^−/− retinas.