Researchers in the United States have unveiled a wireless device that can "control the brain" using light and bypass the body's normal sensory pathways.

The soft, flexible implant, created by scientists at Northwestern University, sits beneath the scalp but above the skull. From there, it delivers precise patterns of light through bone to activate neurons across the cortex.

In laboratory experiments, the team used the device to send tiny, patterned bursts of light into the brains of genetically modified mice whose neurons respond to light. The mice quickly learned to interpret the sequences as meaningful signals, despite the absence of sight, sound or touch. They were then able to use the information to make decisions and perform behavioural tasks.

Researchers say the technology could one day provide sensory feedback for prosthetic limbs, create artificial stimuli for future vision or hearing devices, modulate pain perception without drugs, enhance stroke rehabilitation, or help control robotic limbs using brain activity. More concerningly, in theory, it could be used to control the mind by sending signals that directly turn electrical activity into experiences and commands.

"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 findings were published on Monday (8 December) in Nature Neuroscience.

John A. Rogers, who led the technology development, added: "Developing this device required rethinking how to deliver patterned stimulation to the brain in a format that is both minimally invasive and fully implantable. 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 behaviours 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."

The new study builds on earlier work in which the team introduced the first fully implantable, battery-free, programmable wireless device capable of influencing neurons with light. That 2021 research, also published in Nature Neuroscience, used a single micro-LED probe to affect social behaviour in mice - a leap forward from previous optogenetics experiments that required fibreoptic cables.

The updated system advances the technology by enabling richer communication with the brain. Instead of activating a single region of neurons, the new implant contains an array of up to 64 programmable micro-LEDs. With real-time control over each light source, researchers can generate complex sequences resembling the distributed neural activity that underlies natural perception.

About the size of a postage stamp and thinner than a credit card, the device is also less invasive than its predecessor. Rather than extending into the brain, it conforms to the skull's surface and shines light through bone.

To test the system, the researchers engineered mice with light-responsive cortical neurons, then trained them to associate a particular stimulation pattern with a reward at a specific port. During trials, the implant delivered signals across four cortical regions, effectively tapping a neural code directly onto the brain. The mice swiftly learned to recognise the target pattern among many alternatives and chose the correct port.

Now the team plans to explore how complex these artificial patterns can become - and how many distinct signals the brain is capable of learning. Future versions of the device may include more LEDs, denser arrays and wavelengths of light that can penetrate deeper into tissue.