Wireless ‘WILD’ Device Records and Steers Brain Activity in Freely Roaming Mice

For decades, neuroscientists have faced an uncomfortable trade-off: the equipment that lets them eavesdrop on the brain has too often prevented animals from behaving like themselves. Tethered recording systems, for all their fidelity, anchor a mouse to a cable, restricting the very movements, social encounters and exploratory drives that researchers hope to understand. A team at Cornell University has now unveiled a device designed to dissolve that compromise. Called WILD, for Wireless, Interactive, Lightweight Datalogger, the platform combines neural recording, optogenetic stimulation, motion tracking, ultrasonic audio capture and a head-mounted camera in a single package small enough for a mouse to wear while chasing, sniffing and fighting with its cage mates, both in the laboratory and outdoors.

The engineering challenge behind WILD is formidable. A mouse weighs roughly 25 grams, and any head-mounted payload above a few grams measurably alters its natural behavior. Earlier wireless loggers managed to record neural activity but sacrificed bandwidth, battery life or the ability to stimulate the brain in response to what the animal was doing. WILD addresses these constraints through a modular architecture built around a high-efficiency power system that accepts a wide input range of 1.6 to 5.5 volts and generates isolated supplies for its analog and digital subsystems. At its core sits a Cortex-M4 microcontroller paired with a Bluetooth Low Energy radio, a microSD card for onboard storage, and acquisition circuits that include a neural amplifier, a nine-axis inertial measurement unit, a camera and an ultrasonic microphone.

The device’s wireless performance is a key part of its appeal. Using the onboard antenna, WILD maintains stable communication with a host laptop at distances of up to 70 meters, a range that opens the door to experiments in large arenas and outdoor enclosures rather than cramped laboratory mazes. Clock synchronization between the device and the host computer is handled through a careful calibration procedure: the crystal oscillator is first tuned, then time-of-flight estimation aligns the device clock with the PC, and continuous refinement keeps the estimated clock error near zero, at 0.0 plus or minus 4.3 milliseconds. Once calibrated, the device no longer needs a persistent wireless link, which means researchers can record from more animals simultaneously than the typical seven-device Bluetooth connection limit would otherwise allow.

On the recording side, WILD supports flexible polymer neural probes as well as standard 64-channel silicon probes, achieving noise levels comparable to benchtop tethered systems. In head-to-head comparisons with the widely used Intan RHD2000 platform, the root-mean-square noise of WILD channels was statistically indistinguishable, and local field potential spectra recorded during sleep matched those of tethered hardware. Single units recorded through flexible probes remained stable over nine days, with spike waveforms and firing rates consistent across the transition from tethered to wireless operation. The platform also scales up: the authors demonstrated 128-channel recordings at 20,000 samples per second in rats exploring an outdoor enclosure, along with a roughly 12-hour low-rate recording session, illustrating the device’s flexibility across species and experimental timescales.

Perhaps the most consequential feature of WILD is its onboard signal processing. The device embeds a neural signal processor that detects band-limited signatures of brain activity, from delta and theta oscillations to gamma rhythms and hippocampal sharp-wave ripples, with a processing delay of just 5.56 microseconds. A Hilbert-transform-based detection mode reduces latency further, and receiver operating characteristic analysis shows the onboard ripple detector performs nearly as well as a curated offline detector, with area under the curve values above 0.97. This speed and accuracy make genuine closed-loop experiments possible: the device can detect a specific neural event or behavioral motif in real time and trigger optogenetic stimulation within the tight temporal window that causal neuroscience demands.

Closed-loop capability extends beyond neural events to behavior itself. WILD runs compact TinyML machine learning models that classify social behaviors, such as sniffing, chasing, fighting and tail rattling, directly on the device, allowing stimulation to be contingent on what the animal is actually doing rather than on an experimenter’s judgment from a video feed. The inertial measurement unit feeds a gravity-constrained model that predicts locomotion speed, acceleration and head angular velocity with high fidelity against ground-truth tracking, meaning the logger can reconstruct movement even when overhead cameras are unavailable. In validation tests, stimulation could be targeted to precise theta phases, with the distribution of real-time stimulation phases clustering within the requested 30 to 45 degree window across more than 15,000 events.

To demonstrate what the platform makes possible, the Cornell team deployed WILD on groups of socially interacting mice. In male-male and male-female encounters, the devices simultaneously captured hippocampal activity, pupil dynamics from the integrated eye camera, ultrasonic vocalizations and movement trajectories. The data revealed physiological signatures tied to specific social behaviors: pupil diameter contracted when a mouse looked at a partner and dilated during approach, while ultrasonic call rates soared during male-female interactions compared with male-male ones, with over 3,000 calls detected in a single set of sessions. The entropy of a male’s vocal repertoire increased with distance from his partner, suggesting that mice deploy more varied calls when farther apart, a finding that would have been difficult to obtain without head-mounted microphones tracking each individual’s output.

The team also took WILD outside. In an outdoor enclosure tracked by ultra-wideband positioning, multiple mice wearing the devices were recorded simultaneously across night-long sessions, yielding more than 1,600 identified place cells whose firing fields could be mapped in a naturalistic environment. Place cells, the hippocampal neurons that encode location, have historically been studied in sterile laboratory arenas; recording them as animals navigate real terrain under open sky brings neuroscience closer to the conditions in which these circuits evolved. The wireless condition also changed the animals’ behavior in measurable ways: tethered mice showed reduced spatial coverage and altered speed distributions during social interactions, while wirelessly recorded animals behaved much like unimplanted controls, confirming that the cable itself, not the implant, was distorting natural behavior.

The implications reach well beyond social neuroscience. Because WILD is open source, with design files, source code, compiled binaries and a full manual released under a GPL-3.0 license on GitHub, and datasets deposited on Zenodo, laboratories anywhere can adopt, modify and extend the platform without proprietary barriers. The authors suggest applications ranging from studies of memory consolidation during sleep, where sharp-wave ripples play a central role, to investigations of navigation, vocal communication and psychiatric-relevant behaviors in semi-natural environments. By fusing multimodal sensing, onboard artificial intelligence and bidirectional brain interfacing in a package light enough for a mouse to forget, WILD signals a shift in systems neuroscience: from observing the brain under constrained conditions to interrogating it, and even steering it, in the wild.

Subject of Research: A wireless modular neuro-behavioral recording and closed-loop optogenetic platform for small animals

Article Title: A wireless modular platform for neuro-behavioral recording and closed-loop manipulation in small animals

Article References: Zhao, Z., Chang, H., Paudel, P., Park, J., Liu, C., Aurelio, M. Q., Oliva, A., & Fernandez-Ruiz, A. (2026). A wireless modular platform for neuro-behavioral recording and closed-loop manipulation in small animals. Nature Methods. https://doi.org/10.1038/s41592-026-03220-9

Image Credits: AI Generated

DOI: 10.1038/s41592-026-03220-9

Keywords: wireless neurorecording, optogenetics, closed-loop stimulation, freely behaving mice, hippocampal sharp-wave ripples, social behavior, TinyML, neuroethology, place cells, ultrasonic vocalizations, brain-computer interface, Nature Methods