Since its emergence in 2005, a technique called optogenetics has made it much easier to link neural activity with behavior and to understand how neurons and brain regions connect to each other. Some scientists take neurons (animals) they are interested in, genetically engineer them to express a responsive protein, then expose them to the right kind of light. This technique can be used to selectively inhibit or excite a subset of neurons in moving, breathing, moving animals, shedding light on which neural networks inform animal behaviors and decisions.
Taking advantage of the work done in optogenetic material reduction, researchers have now used optogenetics to alter activity in parts of the brain that influence social interactions in mice. And they’ve worked out a disturbing level of control over the way rats behave.
A major limitation for early optogenetic studies was that the wires and optical fibers needed to beam light into the animal’s brain also got in the way of the animals, hindering their movements and potentially distorting results. New wireless devices were developed about five years ago, but they can only be placed near brain regions. They are also too small to accommodate many circuit components and receiver antennas, and they have to be pre-programmed. Pity the poor will be the leaders who have to deal with such limited tools.
Enter John Rogers, founding director of the new Center on Bio-Integrated Electronics at Northwestern University. His lab recently developed multilateral optogenetic devices that can be implanted into the heads or backs of animals as small as mice. The devices can receive instructions on different channels, so they allow the researchers to independently and at the same time modify the neuronal activity in the brain areas of one mouse or in different mice within the same enclosure. The machines are controlled wirelessly from a PC, and researchers can change instructions to them in real time as the experiment continues.
After confirming that the devices that are pressed do not have an impact or that they do not affect any of the tussues of the mouse go to the neurons that respond to some neurons fire areas of some mice. These areas are connected to gaming. The researchers then implanted their new device under the skin of a transgenic mouse.
The first experiments confirmed the results obtained in previous optogenetic experiments: the rats were affected by the reward of dopamine by flashing the light on the side of the enclosure where the system was programmed to make fire So far, so good. Next, since the researchers know that dopamine promotes social behavior, they wanted to see if light stimulation made the trained rats choose to hang out near the other mouse rather than the toy one. They do.
To put the system to use, the researchers tested an idea from a number of previous studies that suggested that mice that are mated together tend to have synchronized activity in a specific area of their brain. A new optogenetic device provides a way to create that synergy arbitrarily.
So the researchers generated a “synchronized interbrain task” by stimulating two mice with a 5-Hz (continuous) tonic burst for five minutes and a non-stimulating task by stimulating another pair of mice with a 25-Hz burst for five minutes. Almost twice as many synchronized mice chose to interact with each other—careful, sniffing, etc.—as synchronized mice did. When two mice were synchronized in a 5-Hz pair and a third mouse in a 25-Hz burst, the pair avoided the third out of sync. The researchers concluded that “enhanced interbrain connectivity shapes social interaction and social preference in rats.”
The home page of the Rogers Research Group is titled “science that brings solutions to society.” The lab has developed wearable wireless devices that track the vital signs of newborns in the NICU, record electrical activity in the brain, and detect and monitor symptoms of COVID-19. And that was just last year.
So before you let your mind go to dark places—about the stroke and the goose step and everyone staying forever in Facebook silos—just remember that Dr. Rogers is using his powers for good. Also, this work was done in genetically engineered mice.
Neuroscience, 2021. DOI: 10.1038/s41593-021-00849-x