Figure 2. Silencing of neurons with specific colors of light.

A, Hyperpolarization and depolarization events induced in a representative cultured hippocampal neuron expressing both ChR2 and Halo, by a Poisson train (mean inter-pulse interval λ = 100 ms) of alternating pulses of yellow and blue light (10 ms duration), denoted by yellow and blue bars, respectively. Adapted from ref. (36). B, multicolor silencing of two neural populations, enabled by blue- and red-light drivable ion pumps of different genomic classes. Action potentials evoked by current injection into patch clamped cultured neurons transfected with the archaeal opsin Halo (i) were selectively silenced by the red light but not by blue light, and vice-versa in neurons expressing the fungal opsin Mac (ii). Gray boxes in the inset (iii) indicate periods of patch clamp current injection. Adapted from ref. (42).