Optogenetics

is a technique whereby excitable cells,

such as neurons,

can be controlled at will

by light.

To do this,

cells are genetically engineered

to produce ion channels

called opsins

that sit in the cells'

membranes

and open

in response

to a certain wavelength of light.

In classic optogenetics, scientists implant optical fibers near opsin-dotted neurons to deliver the light stimulation. Computer-programmed light pulses can then target these newly light-sensitive neurons in a particular region of the brain and control their activity like puppets on a string.