A new wireless device – lighter than a U.S. dime and shaped like a tiny chef’s hat – can track the brainwaves of animals as they move in natural habitats, opening doors to understanding complex behaviors that are impossible to study in the lab.

In a paper published Sept. 10 in Nature Methods, researchers provide a proof-of-concept for the device, which includes flexible probes that can track groups of neurons for months, as well as different modules to manipulate brain activity or log an animal’s locomotion and orientation, vocalizations and eye movements. The device, called the Wireless, Interactive, Lightweight Datalogger (WILD), will allow researchers to study how the brain responds to changes in a natural environment and group social contexts for the first time.

“What’s exciting is that these devices open new questions that we and other researchers can now tackle,” said co-senior author Azahara Oliva, assistant professor of neurobiology and behavior in the College of Arts and Sciences (A&S). “Before you could either record neural activity with high resolution in the lab or you could record behavior in nature – now we can do both.”

The researchers tested the device, spearheaded by first author and research associate Zifang Zhao, on groups of mice outside the lab, recording their brain activity as they navigated a natural field setting – and interacted with each other – for more than two weeks at a time.

“One of the biggest frontiers in neuroscience is studying how groups of animals, from mice to humans, coordinate behavior among them: How do animals form a colony, coordinate to take care of young, defend territory or build a nest? To study this, we need to have animals freely interacting,” said co-senior author Antonio Fernandez-Ruiz, associate professor of neurobiology and behavior and Nancy and Peter Meinig Family Investigator in the Life Sciences (A&S). “Our technology enables precisely these kinds of novel experiments that were not possible with existing approaches.”

Using pulses of light and electricity, researchers can use the device to manipulate mechanisms in the brain and study the results; they can even program the device to send signals when it detects specific brain patterns or animal behaviors. WILD can record continuously for three to nine hours, depending on battery size, and much longer if researchers program it to conserve energy when the animals are dormant. Collaborators are already using the technology to study birds, bats and monkeys.  

In field experiments just north of Cornell’s campus, WILD has provided a much richer picture of what happens in the brain when mice navigate their surroundings, with the first ever recordings of “place cells” activating as mice move through and internalize a large field enclosure.

“This paper is the proof-of-concept that we were able to identify these place cells outside the laboratory,” Fernandez-Ruiz said. “We’re seeing that the cells have to some degree shared properties to the ones that have been observed in the lab, but to a large extent have many differences that we’re further investigating in follow-up studies.”

Previous efforts to study complex behaviors in free-moving animals involved either tethers or heavy, expensive wireless devices that impeded natural movement – and neither strategy could be used in a natural setting where the technology is subject to humidity and moisture.

The WILD device, by contrast, can withstand the elements and can be built modularly at low cost, with the ability to customize the device with different modules. The research team has made all materials open source.

“If we do it that way, the entire field moves forward,” Oliva said. “And if everyone moves forward, it pushes you to think further and keep developing and adding to it.”

Oliva and Fernandez-Ruiz, who share a lab at Cornell, will use the device to study: group coordination to complete complex tasks; the effect of seasons on the brain; the dynamics of neurodivergence in social settings; and the long-term impact of psychedelics on the brain. They will also continue developing modules that can add more data and insights – tracking an animal’s physiological state, for example, such as heartrate, temperature and glucose levels.

Fernandez-Ruiz said the device’s development was made possible by resources that are unique to the university, especially the Cornell NanoScale Facility and AI for Science Institute. The interdisciplinary makeup of the lab, with expertise in neuroscience, engineering and computer science, also accelerated development, moving a rudimentary prototype to field experiments in just two years.

“This type of work is very collective,” Fernandez-Ruiz said. “When I was a student, you were typically working alone in a room without windows, in darkness, in silence. But here we are outside in nature, working together with a large group of people with different backgrounds but similar goals – it’s very enriching, very rewarding.”

Additional co-authors include doctoral students Hongyu Chang, Praveen Paudel, Jaehyo Park and Can Liu; and undergraduate Maria Aurelio ’27.

Support for the study came from the National Institutes of Health, the Whitehall Foundation, the David and Lucille Packard Foundation, the Alfred P. Sloan Foundation, the Simons Foundation, the Pershing Square Foundation, the Pew Charitable Trusts and the Mong Family Foundation.