WHAT IT IS
Optogenetics is a technique for precisely controlling the firing
of specific neurons. It relies on a group of microbial proteins that change their
properties in response to light of a specific wavelength. In the most widely used
optogenetic system, light-sensitive membrane channels (“channelrhodopsins”)
are introduced into a neuron. Cation channels will depolarize the membrane,
while anion channels will hyperpolarize it, effectively switching the neuron
“on” or “off” within milliseconds.
HOW IT WORKS
The gene for the protein is delivered by viral vectors. Cell
specificity is achieved either by including a cell-specific promoter in the gene
package, or, as in this paper, combining microinjection targeting with a genetic
“homing” system for the transgene. Light is introduced with a fine optical fiber
implanted into the target neurons.
HOW IT IS APPLIED
Optogenetics has been widely used throughout the brain to map neural circuits, by stimulating or inhibiting one type of neuron and recording the response in another. It has also been used to understand the inhibitory versus excitatory role of a specific neuronal
type within a circuit, and to explore temporal patterns of communication
between neurons. Therapeutic applications of optogenetics, for instance as a
type of deep brain stimulator, are being explored, but will require gene therapy
to deliver the proteins to the target neurons.