optogenetics

:  the use of genetic engineering and optics to selectively monitor or control nerve cell activity; specifically :  the use of genetically manipulated cells which when exposed to certain wavelengths of light express either light-responsive fluorescent proteins capable of indicating neural activity or actuator proteins capable of activating specific neural pathways … scientists say optogenetics research is exciting because it gives them extraordinary control over specific brain circuits—and with it, new insights into an array of disorders, among them anxiety and Parkinson's disease.—Carl E. Schoonover et al., The New York Times, 17 May 2011