Scientists Use 'Optogenetics' To Control Reward-seeking Behavior

Using a combination of genetic engineering and laser technology, researchers at the University of North Carolina at Chapel Hill have manipulated brain wiring responsible for reward-seeking behaviors, such as drug addiction. The work, conducted in rodent models, is the first to directly demonstrate the role of these specific connections in controlling behavior. The UNC study, published online on June 29, 2011, by the journal Nature, uses a cutting-edge technique called "optogenetics" to tweak the microcircuitry of the brain and then assess how those changes impact behavior. The findings suggest that therapeutics targeting the path between two critical brain regions, namely the amygdala and the nucleus accumbens, represent potential treatments for addiction and other neuropsychiatric diseases.

"For most clinical disorders we knew that one region or another in the brain was important, however until now we didn't have the tools to directly study the connections between those regions," said senior study author Garret D. Stuber, PhD, assistant professor in the departments of cell and molecular physiology, psychiatry and the Neuroscience Center in UNC School of Medicine. "Our ability to perform this level of sophistication in neural circuit manipulation will likely to lead to the discovery of molecular players perturbed during neuropsychiatric illnesses."

Because the brain is comprised of diverse regions, cell types and connections in a compact space, pinpointing which entity is responsible for what function can be quite tricky. In the past, researchers have tried to get a glimpse into the inner workings of the brain using electrical stimulation or drugs, but those techniques couldn't quickly and specifically change only one type of cell or one type of connection. But optogenetics, a technique that emerged six years ago, can.

In the technique, scientists transfer light-sensitive proteins called "opsins" – derived from algae or bacteria that need light to grow – into the mammalian brain cells they wish to study. Then they shine laser beams onto the genetically manipulated brain cells, either exciting or blocking their activity with millisecond precision.