Flexible tentacle electrodes accurately record brain activity

Neurostimulators, also known as pacemakers, send electrical impulses to specific areas of the brain via special electrodes. It is estimated that around 200,000 people worldwide now benefit from this technology, including people suffering from Parkinson’s disease or pathological muscle spasms.

According to Mehmet Fatih Yanik, Professor of Neurotechnology at ETH Zurich, further research will significantly expand the application possibilities. Instead of just using them to stimulate the brain, the electrodes could also be used to precisely record brain activity and analyse it in order to detect abnormalities related to neurological or psychiatric disorders. In a second step, it would be possible to treat these abnormalities and disorders using electrical impulses.

To do this, Yanik and his team developed a new type of electrodes that can record brain activity in more detail and more precisely over a longer period of time. These electrodes consist of bundles of extremely thin and flexible gold fibers that conduct electricity and are encapsulated in a polymer.

Thanks to a process developed by ETH Zurich researchers, these beams can be introduced into the brain very slowly, which is why they do not cause any detectable damage to brain tissue. The research is published in the journal Nature Communications.

This is what distinguishes the new electrodes from competing technologies. Among these, perhaps the best known to the general public is that of Neuralink, a company owned by Elon Musk. In all of these systems, including Neuralink’s, the electrodes are considerably wider.

“The wider the probe, even if it is flexible, the greater the risk of damaging brain tissue,” Yanik explains. “Our electrodes are so thin that they can be threaded along the long processes that extend from nerve cells into the brain. They are about the same thickness as the processes of the nerve cells themselves.”

The research team tested the new electrodes on the brains of rats using four bundles of 64 fibers each. In principle, as Yanik explains, up to several hundred electrode fibers could be used to study the activity of an even larger number of brain cells. As part of the study, the electrodes were connected to a small recording device attached to each rat’s head, allowing them to move freely.

No influence on brain activity

During the experiments, the research team was able to confirm that the probes are biocompatible and have no influence on brain function. Since the electrodes are very close to the nerve cells, the signal quality is very good compared to other methods.

The probes are also suitable for long-term monitoring activities. The researchers record signals from the same cells in the animals’ brains for the entire duration of a ten-month experiment. Examinations have shown that no damage was done to brain tissue during this time. Another advantage: the beams can branch in different directions, meaning they can reach multiple areas of the brain.

Human testing to begin soon

In the study, the researchers used the new electrodes to track and analyze the activity of nerve cells in different areas of the rat brain over a period of several months. They were able to determine that nerve cells in different regions were “co-activated.”

Scientists believe that this large-scale synchronous interaction of brain cells plays a key role in processing complex information and forming memory. “This technology is of great interest for basic research that studies these functions and their alterations in neurological and psychiatric disorders,” Yanik explains.

The team has teamed up with researchers at University College London to test the diagnostic use of the new electrodes in the human brain. The project is focusing on epilepsy patients who do not respond to drug treatments. In these cases, neurosurgeons can remove a small part of the brain where the seizures started. The idea is to use the team’s method to pinpoint the exact area of ​​the brain affected before removing the tissue.

Brain-machine interfaces

There are also plans to use the new electrodes to stimulate human brain cells. “This could contribute to the development of more effective therapies for people with neurological and psychiatric disorders,” says Yanik. In cases of disorders such as depression, schizophrenia or OCD, specific brain disorders are often present, leading to problems with evaluating information and making decisions.

With these new electrodes, it might be possible to detect in advance the pathological signals generated by the brain’s neural networks, and then stimulate the brain in such a way as to alleviate these disorders.

Yanik also believes that this technology could lead to brain-machine interfaces for people with brain injuries. In this case, the electrodes could be used to read their intentions and thus, for example, control prosthetics or a voice output system.