Table 3.

Percentage of maximum fluorescence change during a 2 msec action potential.

τon (msec)	% of maximum signal at 2 msec
1	86
2	63
3	49
4	39
5	33
6	28
7	25
8	22
9	20
10	18

Approximating an action potential as a 100 mV depolarization that lasts for 2 msec enables the estimation of the optical signal as a function of τ_on when fit to a single exponential decay (F_t = F_max(1 − e ^−t/τ) where F max is 100% and t is 2 msec).