To confirm these results with a much larger sample size, we recorded STOCs without imaging Ca2+ sparks. In the cell shown in Fig. 2 B, 991 events from an ∼30-min recording were detected and analyzed. Strikingly, STOCs varied by a factor of 10 in amplitude but decayed with time constants that differ by less than a factor of 2 (Fig. 2, B and C), suggesting that the decay of STOCs is not dependent on the amplitude of STOCs. Given the large variation in the STOC amplitude, we ranked STOCs by their amplitude and grouped them by quartile. On average, τ values for STOC decay were 22 ± 1.4, 23 ± 1.5, 25 ± 1.1, and 31 ± 1.5 ms (n = 8 cells) from the smallest quartile to the largest (Fig. 2 C). Among the first three quartiles in which mean STOC amplitudes varied by threefold, no statistically significant difference in decay rate was detected. Although the decay in the largest quartile was somewhat longer than the first three groups, it still fell within the range of the mean open
