Fig. 5.

Precision of single AP induction. (A Left) With high stimulation light intensity, TC often evoked several spikes in response to a single 2-ms light pulse during 1-Hz stimulation. (Right) Multiplet firing is observed mostly with TC and is reduced at lower stimulation intensity. (B) Multiplet firing is largely restricted to 1-Hz stimulation and rarely occurs at higher stimulation frequencies. (C Left) Example spike trains from neurons expressing TC or ET/TC stimulated with 60 2-ms pulses at 40 Hz with 42 mW/mm² light intensity. Plateau potentials were measured between baseline and the minimal membrane depolarization during the last 500 ms of the stimulation train (dashed lines). (Right) Summary of plateau potentials for 1- to 100-Hz stimulation (n = 9, 11, 14, 13, and 12 for wt, HR, TC, ET/TC, and ET/HR, respectively). (D) Plateau depolarization at 100 Hz was highly correlated with the product of photocurrent amplitude and channel closing speed.