Yes you put in a "probe" (fiber optic), just like when you stimulate with an electrode. The difference is electricity stimulates everything, while the light can be targeted, not by what it illuminates but what responds* because...
Ahead of time, you either use viral tools or other genetic modifications to make specific cell types express the photorecrptor.
*there is an effect of light/heat that all cells are subject to, and good experiments try to control for this as best they can
Ahead of time, you either use viral tools or other genetic modifications to make specific cell types express the photorecrptor.
*there is an effect of light/heat that all cells are subject to, and good experiments try to control for this as best they can