The cloning and subsequent bioengineering of light-driven channels (e.g., channelrhodopsins) or pumps (e.g., halorhodopsin and archaerhodopsins) has opened a new avenue in the field of optogenetics. Optogenetics is a powerful method in neuroscience because these opsins can be expressed in specific subsets of neurons by genetic manipulation, allowing dynamic modulation of the discharge of these cells by light. In animal experiments, the effectiveness of brain manipulation is ultimately assessed by an animal's behavior. Because most rodent behavioral experiments assume free movement of the animals, a light delivery method that does not compromise their movement is desired.
We produced a miniaturized, multicode, multiband, and programmable light-emitting diode (LED) stimulator for wireless control of optogenetic experiments. The LED stimulator is capable of driving three independent LEDs upon reception of an infrared (IR) signal generated by a custom-made IR transmitter. Individual LED photopulse patterns are assigned to different codes of the IR signals (up to 256 codes). The photopulse patterns can be programmed in the on-board microcontroller by specifying the parameters of duration (>1 ms), frequency (<500 Hz), and pulse width (>1 ms). The IR signals were modulated at multiple carrier frequencies to establish multiband IR transmission. Using these devices, we could remotely control the moving direction of a Thy1-ChR2-YFP transgenic mouse by transcranially illuminating the corresponding hemisphere of the primary motor cortex. IR transmitter and LED stimulator will be particularly useful in experiments where free movement or patterned concurrent stimulation is desired.