Scientists use optogenetics to control reward-seeking behavior

June 30, 2011
Nerve Cells

Nerve cells in the nucleus accumbens (red) receive input from amygdala fibers (green). Optogenetic stimulation of these nerve fibers produces a rewarding effect in mice (credit: Stuber lab/UNC-Chapel Hill)

Researchers at the University of North Carolina at Chapel Hill have manipulated brain wiring responsible for reward-seeking behaviors in mice, using optogenetic stimulation targeting the path between two critical brain regions, the amygdala and the nucleus accumbens.

The finding represents potential treatments for addiction and other neuropsychiatric diseases, according to the researchers.

With the optogenetic technique, scientists transfer light-sensitive proteins called “opsins” — proteins 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.

They used this technique to excite (activate) the connections between the amygdala and the nucleus accumbens, essentially “rewarding” the rodents with laser stimulation when they poked their nose into a hole in their cage. They found that mice genetically treated with light-sensitive opsins  quickly learned to “nose-poke” to receive stimulation of the neural pathway. In comparison, genetically untouched control mice never caught on to the task.

The researchers are now exploring how changes to this segment of brain wiring can either make an animal sensitized to or oblivious to rewards.

The researchers said their approach presents a useful tool for studying basic brain function, and could one day provide a powerful alternative to electrical stimulation or pharmacotherapy for neuropsychiatric illnesses like Parkinson’s disease.

Ref.: Antonello Bonci, Excitatory transmission from the amygdala to nucleus accumbens facilitates reward seeking, Nature, 2011; [DOI: 10.1038/nature10194]