Researchers at the University of California San Diego (UCSD) have developed a neural implant that transcends the limitations of current technologies, promising high-resolution insights into deep neural activity without the need for invasive procedures. Published in Nature Nanotechnology, the study marks a significant stride toward creating a minimally invasive brain-computer interface (BCI) that can unlock new insights into the brain’s workings.
The transparent and flexible neural implant, crafted from a thin polymer strip densely packed with graphene electrodes, has demonstrated its capabilities in transgenic mice, capturing intricate details of neural activity residing deep within the brain while residing on its surface. Led by study senior author Duygu Kuzum from the Department of Electrical and Computer Engineering at the UC San Diego Jacobs School of Engineering, the research team has successfully bridged the gap between surface recordings and deeper neural layers.
Kuzum expressed the importance of this breakthrough, stating, “We are expanding the spatial reach of neural recordings with this technology. Even though our implant resides on the brain’s surface, its design goes beyond the limits of physical sensing in that it can infer neural activity from deeper layers.”
The implant introduces a novel approach, overcoming the shortcomings of existing technologies. While conventional surface arrays lack the capacity to capture information beyond the outer layers of the brain, deeper penetrating needle-like arrays often cause inflammation and scarring. The new neural implant achieves a delicate balance, offering the best of both worlds.
Comprising a transparent polymer strip embedded with a high-density array of graphene electrodes, each measuring a mere 20 micrometers in diameter, the implant conforms seamlessly to the brain’s surface. In tests on transgenic mice, the researchers successfully recorded both electrical and calcium activity simultaneously. The technology enabled the correlation of surface electrical signals with calcium spikes in deeper layers, providing a basis for training neural networks to predict activity at various depths.
Mehrdad Ramezani, the study’s co-first author, emphasized the advantages of this predictive capability, stating, “Since electrical recordings do not have these limitations, our technology makes it possible to conduct longer duration experiments in which the subject is free to move around and perform complex behavioral tasks.”
The success of the neural implant is attributed to its innovative design features, including transparency, high electrode density, and integration with machine learning methods. The transparent graphene electrodes, a departure from traditional opaque materials, facilitate simultaneous electrical recordings and optical imaging during experiments, providing a clear field of view for researchers.
To achieve complete transparency, the researchers employed a unique fabrication technique involving super-thin, long graphene wires. Overcoming challenges posed by potential defects, they utilized a double-layer graphene approach doped with nitric acid, ensuring the creation of fully functional, thin, and long graphene wires with improved conductivity.
The research team, comprising experts from various disciplines, has applied for a National Institutes of Health (NIH) grant to scale up production and make the technology widely accessible. With plans to test the technology in different animal models, the ultimate goal for the researchers is human translation, offering unprecedented insights into the workings of the human brain.
