Abstract: In a method for adjusting the voltage potential or pH of, or cause proton release from, cells, subcellular regions, or extracellular regions, a gene encoding for a light-driven proton pump is incorporated into at least one target cell or region, the proton pump operating in response to a specific wavelength of light. Expression of the gene is caused by exposing the target cell or region to the specific wavelength of light in a manner designed to cause the voltage potential adjustment, pH adjustment, or proton release. The proton pump may be a microbial rhodopsin, in particular derived from the halorubrum genus of archaeabacteria, or be derived from leptosphaeria maculans, P. triticirepentis, and S. scelorotorium. The voltage potential of the target cell or region may adjusted until it is hyperpolarized in order to achieve neural silencing. Light-activated proton pumps responsive to different wavelengths of light may be used together to achieve multi-color neural silencing.