Figure 8.

Light-stimulated Ca²⁺ responses are highly correlated to action potential firing frequency. A, Concurrent Ca²⁺ imaging trace and cell-attached patch recording for ipRGC stimulated with light (broad-spectrum, 6.9 × 10¹³ photons/s/cm² at 480 nm) for 4 min. Fura-2 images were acquired immediately before and then every 10 s during light stimulation. B, Expanded view of the same cell-attached recording shown in A. The fura-2 ratios numbered 1–4 in A were acquired at the time points denoted by matching numbers on the cell-attached recording (B). C, Relationship of fura-2 ratios to the number of spikes in 10 s interval preceding each ratio during the 4 min light exposure for the cell depicted in A and B. D, Plot of same relationship as in (C) using data from nine light-stimulated ipRGCs. Within-cell coefficients of determination (r²) for each of the nine cells are shown in inset box.