A new brain device from Northwestern University is asking a daring question: what if information could reach your brain without ever passing through your eyes, ears, or skin?
In a study, scientists describe a soft, wireless implant that sends patterned bursts of light through the skull to activate neurons across the cortex. In mouse experiments, the animals learned to treat those light patterns as meaningful signals. They used them to make choices and finish tasks, even though no touch, sight, or sound cues were involved.
“Our brains are constantly turning electrical activity into experiences, and this technology gives us a way to tap into that process directly,” said Northwestern neurobiologist Yevgenia Kozorovitskiy, who led the experimental work. “This platform lets us create entirely new signals and see how the brain learns to use them. It brings us just a little bit closer to restoring lost senses after injuries or disease while offering a window into the basic principles that allow us to perceive the world.”
The approach could one day support new forms of sensory feedback for prosthetic limbs, future vision or hearing prostheses, pain control without opioids or systemic drugs, and stronger rehabilitation after stroke or injury. The team also sees paths toward controlling robotic limbs using brain signals, paired with artificial feedback sent back into the brain.
The device sits under the scalp but on top of the skull. It conforms to the skull’s surface like a thin patch. It then delivers precise, timed light pulses through bone to reach neurons in the cortex.
The system is fully implantable, wireless, and battery-free. It avoids the fiberoptic wires that often tether animals in optogenetics studies. Instead, a wirelessly powered control module runs the device, while an array of micro-LEDs provides the light.
“Developing this device required rethinking how to deliver patterned stimulation to the brain in a format that is both minimally invasive and fully implantable,” said Northwestern bioelectronics pioneer and lead technologist, John A. Rogers, to The Brighter Side of News.
“By integrating a soft, conformable array of micro-LEDs; each as small as a single strand of human hair; with a wirelessly powered control module, we created a system that can be programmed in real time while remaining completely beneath the skin, without any measurable effect on natural behaviors of the animals. It represents a significant step forward in building devices that can interface with the brain without the need for burdensome wires or bulky external hardware. It’s valuable both in the immediate term for basic neuroscience research and in the longer term for addressing health challenges in humans,” he continued.
The new device is roughly the size of a postage stamp and thinner than a credit card. Unlike earlier designs that extended into brain tissue through a small opening, this version avoids penetrating the brain. It shines light through the skull instead.
“Red light penetrates tissues quite well,” Kozorovitskiy said. “It reaches deep enough to activate neurons through the skull.”
The study builds on earlier work from the same researchers. In 2021, Kozorovitskiy and Rogers reported the first fully implantable, programmable, wireless, battery-free device that could control neurons with light. That earlier work used a single micro-LED probe and appeared in Nature Neuroscience. It allowed mice to move freely, while scientists influenced neurons linked to social behavior.
The new system expands what is possible. Instead of controlling one small area, it can stimulate multiple regions across the cortex. The implant includes a programmable array of up to 64 micro-LEDs. Researchers can control each one in real time.
That matters because real sensations do not light up one tiny spot. They activate networks across the cortex. The multi-region design aims to mimic that distributed activity more closely.
“In the first paper, we used a single micro-LED,” said Mingzheng Wu, the study’s first author and a postdoctoral fellow in the Rogers and Kozorovitskiy laboratories. “Now we’re using an array of 64 micro-LEDs to control the pattern of cortical activity. The number of patterns we can generate with various combinations of LEDs; frequency, intensity and temporal sequence; is nearly infinite.”
To test whether patterned stimulation could carry information, the team used mice engineered to have light-responsive cortical neurons. Then they trained the mice to connect a specific stimulation pattern with a reward. The task often involved visiting a particular port in a chamber.
In trials, the implant delivered a set pattern across four cortical regions. The team described it as tapping a code onto neural circuits. The mice learned to pick the target pattern from dozens of alternatives. When they recognized it, they chose the correct port and received a reward.
“By consistently selecting the correct port, the animal showed that it received the message,” Wu said. “They can’t use language to tell us what they sense, so they communicate through their behavior.”
The researchers now plan to test more complex patterns. They also want to learn how many distinct patterns the brain can reliably learn. Future versions could include more LEDs, tighter spacing, larger arrays that cover more cortex, and light wavelengths that penetrate deeper.
This study shows the brain can learn to use patterned stimulation as meaningful information, even when normal senses play no role. That opens a new direction for brain-machine interfaces that do more than read signals. It suggests devices could also deliver structured feedback into the brain.
In the nearer term, the platform gives neuroscientists a tool to study how the brain builds perception from patterns of activity. Researchers can create new signals and watch how the brain learns them, which may reveal basic rules of learning and perception.
Over time, the approach could support sensory feedback for prosthetic limbs, artificial signals for future vision or hearing prostheses, and new ways to modulate pain without opioids or systemic drugs. The work also points toward improved rehabilitation after stroke or injury, along with tighter control of robotic limbs that pairs movement commands with direct brain feedback.
Research findings are available online in the journal Nature Neuroscience.
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