“Neurogranules” to record neural activity from thousands of locations

Today's brain implants are bulky and can typically only register neural activity from one or two locations. Now the researchers have shown in mice that a network of tiny "neurogranules" can be used to wirelessly register and stimulate neurons in multiple locations.

Researchers have been experimenting for decades brain-computer interfaces (BCI) able to register and stimulate groups of neurons. In recent years, however, there has been a growing interest in using them to treat diseases such as epilepsy, Parkinson's or various psychiatric disorders.

Great progress

New research conducted by a team from Brown University has made great strides on the latter problem by developing tiny implants measuring less than 0,1 cubic millimeters. Implants can both register and stimulate neural activity. These “neurogranules” can be combined to create a network of systems that can be controlled and powered wirelessly.

"One of the great challenges in the field of brain-computer interfaces is finding ways to probe as many points in the brain as possible," he says in a press release Arto Nurmikko, who led the research. “Until now, most of the BCIs have been monolithic devices, a bit like little mats of needles. Our team's idea is to break that monolith into tiny sensors that can be distributed across the cerebral cortex. "

How the new approach works

Each of the tiny chips is equipped with electrodes to pick up electrical signals from brain tissue, circuitry to amplify the signal, and a tiny coil of wire that sends and receives wireless signals. The chips are attached to the surface of the brain, and a thin relay coil that helps improve wireless energy transfer to the neurogrants is placed over the area where they are placed.

A thin patch containing another coil is then attached to the outside of the scalp above the relay coil. Works as a mini tower for mobile phones, using a specially designed network protocol to individually connect to each of the neurogranules. It also transmits wireless energy to the neurogranules to make them work.

The study of neural activity

In an article in Nature Electronics, the team showed they could implant 48 of the tiny chips in a mouse's brain. He then used them to record and stimulate neural activity. Although both capabilities will ultimately be integrated into one device, for the purpose of the study some neurogranules were designed to record while others were built to stimulate.

The researchers say the fidelity of the recordings has room for improvement, but they were able to collect spontaneous brain signals and detect when the brain was stimulated using a conventional implant. They also showed that they could direct a single neurogranule to stimulate neural activity, which they were able to detect with conventional recording devices.

The team states that their current configuration could support up to 770 neurogranules, but they plan to scale the system up to thousands of neurogranules. It will be possible with further miniaturization. The chip design should go through the manufacturing process at 65 nanometers which it currently uses at one at 22 nanometers.

There is still much work to be done to improve the quality of the neural activity records that implants are capable of and to verify their safety in humans. But the ability to coordinate many small plants in a network is an interesting advance, with great potential for both research and medicine.