Scientists have figured out how to manipulate a monkey's behavior using a technology called optogenetics, in which genetically modified neurons are fired when exposed to light:
To control the electrical firing of a neuron, scientists use a virus to deliver a gene into brain cells. The gene is designed to produce a light-responsive protein (see "Brain Control"). Depending on the type of light-sensitive protein used, this genetic modification will either activate or silence a neuron in response to a specific color of light, delivered via optical fibers inserted into the brain.
They had previously accomplished this with mice, but success with primates brings the technology closer to human application:
"[Optogenetics] may also become useful in the far future for therapeutic purposes, because if you can activate or deactivate very specific cell types, you can actually target particularly circuitries that are important in different diseases with much more precision than is possible at this moment with drugs or [electrical] stimulation," says [study author Wim] Vanduffel. "But there is still a very long way to go before it gets there."
The Dish 