READY YOUR TINFOIL HATS—mind control is not as far-fetched an idea as it may seem. In Jeffrey M. Friedman’s laboratory, it happens all the time, though the subjects are mice, not people.

Friedman and his colleagues have demonstrated a radio-operated remote control for the appetite and glucose metabolism of mice—a sophisticated technique to wirelessly alter neurons in the animals’ brains. At the flick of a switch, they are able to make mice hungry—or suppress their appetite—while the mice go about their lives normally. It’s a tool they are using to unravel the neurological basis of eating, and it is likely to have applications for studies of other hard-wired behaviors.

Friedman, Marilyn M. Simpson Professor, has been working on the technique for several years with Sarah Stanley, a former postdoc in his lab who now is assistant professor at the Icahn School of Medicine at Mount Sinai, and collaborators at Rensselaer Polytechnic Institute. Aware of the limitations of existing methods for triggering brain cells in living animals, the group set out to invent a new way. An ideal approach, they reasoned, would be as noninvasive and non-damaging as possible. And it should work quickly and repeatedly.

Although there are other ways to deliver signals to neurons, each has its limitations. In deep-brain stimulation, for example, scientists thread a wire through the brain to place an electrode next to the target cells. But the implant can damage nearby cells and tissues in ways that interfere with normal behavior. Optogenetics, which works similarly but uses fiber optics and a pulse of light rather than electricity, has the same issue. A third strategy—using drugs to activate genetically modified cells bred into mice—is less invasive, but drugs are slow to take effect and wear off.

The solution that Friedman’s group hit upon, referred to as radiogenetics or magnetogenetics, avoids these problems. With their method, published last year in Nature, biologists can turn neurons on or off in a live animal at will—quickly, repeatedly, and without implants—by engineering the cells to make them receptive to radio waves or a magnetic field.

“In effect, we created a perceptual illusion that the animal had a drop in blood sugar.”

“We’ve combined molecules already used in cells for other purposes in a manner that allows an invisible force to take control of an instinct as primal as hunger,” Friedman says.

The method links five very different biological tools, which can look whimsically convoluted, like a Rube Goldberg contraption on a molecular scale. It relies on a green fluorescent protein borrowed from jellyfish, a peculiar antibody derived from camels, squishy bags of iron particles, and the cellular equivalent of a door made from a membrane-piercing protein—all delivered and installed by a genetically engineered virus. The remote control for this contraption is a modified welding tool (though a store-bought magnet also works).

The researchers’ first challenge was to find something in a neuron that could serve as an antenna to detect the incoming radio signal or magnetic field. The logical choice was ferritin, a protein that stores iron in cells in balloon-like particles just a dozen nanometers wide. Iron is essential to cells but can also be toxic, so it is sequestered in ferritin particles until it is needed.