Fig. 1.

Schematic overview of optogenetics. (A) Genetic materials containing microbial opsin are introduced in viral vectors such as adeno-associated virus to transduce microbial opsins in laboratory mice. The vector is injected to target neuron cells and express opsins. (B) Creating transgenic mice through Cre recombinase is a novel approach to develop opsin-expressing mice. Through Cre-mediated recombination of loxP sites, microbial opsins can be expressed in specific cells that express Cre recombinase. (C) After expression of microbial opsins, light sources introduce light to specific sites in the laboratory animals. Some microbial opsins such as channelrhodopsin activate signals and others such as halorhodopsin inhibit signals. P, promoter; LED, light-emitting diode; OLED, organic LED.