Responses to melanopsin-isolating steps and gradual irradiance ramps in retina.

<p>A: Trial bin count examples of two cells responding to a 71% contrast step (blue bar at 0 to 20 seconds) presented during protocol 1 (background log 12.75 melanopsin photons/cm²/s to step log 13.5 photons/cm²/s) before (i) and during (ii) synaptic blockade. Before and after graphs are scaled to same axis to show changes in baseline activity upon synaptic blockade. B: Example raster plots and PSTH to a 50ms rod favouring yellow flash from dark (flash intensity log 11.45 rod photons/cm²/s) under normal conditions (aCSF) and under synaptic blockade (5 minutes after application of L-AP4 + NBQX) in a cell that was identified to respond to our melanopsin-isolating stimulus. C: Averaged plots for firing rate over time of consistent (n = 31) melanopsin-step responsive cells (mean±SEM) before (left) and during (right) synaptic blockade. D: Mean response onset and offset latencies for individual melanopsin-step responsive cells in the presence (purple symbols) and absence (green) of synaptic blockade. E: Under protocol 2, retinal cells responding to a melanopsin-step (n = 22/ 314 cellls; 71% contrast) do so over a range of background irradiances on both the upward and downward phases of the ramp (Repeated measures 2-way ANOVA, step vs baseline firing rate x irradiance; main effects of irradiance (p<0.001), step vs baseline (p<0.001) and interaction (p<0.05); Bonferroni post-hoc comparisons marked on figure as ** and *** p<0.01 for ND2 upward ramp and ND1.5 for downward; n = 22 cells). F: Retinal melanopsin-step responsive cells also tracked the gradual change in irradiance during protocol 2, revealed as a change in firing rate (mean± SEM) as a function of ramp progression.