Neuralink, founded by Tesla creator Elon Musk, has launched clinical trials for brain-computer interfaces (BCIs) on humans for the first time this year. A BCI is a technology that implants a chip in the brain to capture neural signals and decode them with a computer. Neuralink has successfully implanted a chip in the brain, but later defects occurred when some electrodes and wires detached from the chip. Although there have been no clear side effects so far, this defect has raised controversies regarding the safety of BCIs.
Scientists have developed new technology to replace the method of implanting electrodes in the brain with BCIs. The U.S. BCI corporation Science Corporation announced results of an experiment on the 29th of last month, showcasing that living nerve cells implanted into the brains of mice could be controlled by external light. If research progresses, the implanted cells could develop into a BCI alternative technology that detects brain activity and sends it externally instead of using electrodes.
A BCI is a technology that directly connects the human brain and a computer. It can attach electrodes to the scalp or insert them deep into the brain to collect neural signals, decode them with a computer, and send them to other nerves. If a paralyzed patient uses a BCI, they can reconnect nerves and rehabilitate through a computer. It is also possible to control computers or robotic limbs according to human intent.
The problem is that implanting electrodes in the brain can cause side effects like inflammatory reactions and tissue damage. Max Hodak, the chief executive officer (CEO) of Science Corporation, noted that "implanting something in the brain can inevitably lead to brain damage" and that "the possibility of destroying tens of thousands of neurons also exists." He was aware of the potential side effects from implanting electrodes in the brain earlier due to his previous position as president of Neuralink.
Science Corporation is researching methods for living cells to detect neural signals and transmit them elsewhere instead of using electrodes. Unlike the existing method, which made it impossible to connect many areas of the brain using electrodes, theoretically, using living cells would allow for all brain areas to be linked to a computer.
Science Corporation conducted animal experiments to implant cells in the brain. They created a "micro well" with 100,000 tiny cylindrical holes, each 15 micrometers (1 micrometer equals one-millionth of a meter) deep, filled with and cultured nerve cells, and then implanted them into the brains of mice. The implanted cells were genetically modified to be controlled by external light.
As a result of the experiment, it was found that after 3 weeks of receiving the cell implant, the mice activated their brain nerves when exposed to light, regardless of vision. This indicates that even if genetically modified cells are implanted instead of electrodes, signals can be generated by connecting to an external device.
Science Corporation named this technology "bio-hybrid implant" and is developing it as a next-generation BCI device. They believe that using living cells for brain stimulation to treat neurological disorders or for transmitting neural signals for patients with nerve damage could enhance safety.
However, the low survival rate of the implanted nerve cells remains a challenge that needs to be addressed. Nearly half of the nerve cells that were implanted in the mice died after 3 weeks due to attacks from the immune system. If a method to sustain nerve cells over the long term can be found, a safe and effective cell-based BCI could be implemented. Beyond the relatively simple capability of nerve cells to detect light, methods to send signals externally also need to be discovered.
Hodak, the CEO, said, "The bio-hybrid implant technology is still in its early stages, but the impact it could have when commercialized is immense," adding that he expects it to play a significant role in future BCI technology.
Reference materials
bioRxiv (2024), DOI: https://doi.org/10.1101/2024.11.22.624907