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Toward Optogenetic Control of Social Interactions

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A multinational research team has developed a fully implantable, wireless device that enables optogenetic research in untethered animals. [Image: Northwestern University]

A wireless implant is letting scientists control the social behavior of mice with the switch of a light.

In a new study, scientists sent pulses of light into devices implanted in mice’s brains to target specific neurons. When two mice simultaneously received a similar light signal, they switched from independently roaming their cage to grooming and spending time with each other. By switching the light on and off, the scientists were able to program and deprogram the mice’s social interactions (Nat. Neurosci., doi: 10.1038/s41593-021-00849-x).

The study used optogenetics, in which light signals trigger neurons that have been genetically altered to be light sensitive. Optogenetics has been heralded as a revolutionary approach to neurobiology that will allow scientists to study in minute detail how the brain works.

“It’s a really magnificent and very useful tool in studying how neurons interact and how they build their circuits,” said Yevgenia Kozorovitskiy, co-author on the new study and neurobiologist at Northwestern University. “But also it’s not that terribly far off clinical applications.”

Light-sensitive neurons

To create light-sensitive neurons, the scientists genetically modified mice neurons to express a light-sensitive protein from a type of algae. After connecting the new wireless devices to specific altered neurons, the scientists could send a radio signal to the device to toggle an array of micro-LEDs on and off, the light from which triggered the neurons to fire in the mice’s brains.

Previously, scientists have used optogentics and similar devices to study brain activity in individual mice. But these devices were tethered with fiber optic wires, making it hard to test the behavior of mice in complex environments or to see how groups of mice would interact. To study mice’s unrestricted interactions, a group of material scientists, neurobiologists and engineers developed the new wireless system.

The device is about as thick as a sheet of paper and small enough to be implanted on a mouse’s head. Since it doesn’t have a battery, the device is paired with a radio-frequency coil on the outside of the cage that allows for the wireless power delivery. The coil also sends radio signals to the devices, allowing scientists to turn the micro-LEDs in the device on and off on the go and to operate separate devices simultaneously.

“We can study now the neural dynamics associated with interactions among multiple members of a socially interacting group of animals,” said John A. Rogers, a bioelectronics researcher at Northwestern University who led the technology development. “That essentially opens up a frontier in neuroscience, which will involve … how brains are interacting with one another across social groups.”

Mice and more

The group was surprised at how effective its first study was. After this proof-of-concept of the new device, the researchers plan to continue using it to probe how the signals affect social behavior, as well as possibly extending it to other species, such as voles, which are monogamous and generally more social than mice.

Eventually, the results could enable future studies of brain–behavior links in animals, which could offer insights into how some mental disorders are treated in humans. Already optogenetics is showing promise as a therapeutic approach for blindness and paralysis.  

“I’d be very surprised if you don’t see these types of approaches being used for treating brain disorders in the future,” Rogers said.

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