Effect of the electric field strength of a 250-ms sine wave on firing responses in three representative neurons. Shown are traces of the optical membrane potential at the indicated electric field strength (V/cm). The stimulating signal outline and frequency (kHz) are shown under the traces. Inset: the dependence of the maximum firing rate on the electric field strength in the neurons presented in (A)–(C). See also the main text and Figures S1 and S2.
