Ultra-Flexible Brain Probes Accurately Record Brain Activity Without Causing Tissue Damage

Neurostimulators, often referred to as brain pacemakers, transmit electrical impulses to specific brain regions through specialized electrodes. Around 200,000 individuals globally are currently reaping benefits from this technology, including those afflicted with Parkinson’s disease and pathological muscle spasms. Researchers have now developed a novel type of electrode that facilitates more detailed and precise brain activity recordings over prolonged periods. These electrodes, which mimic tentacles, are composed of ultra-thin gold and polymer fibers that are gentle on brain tissue and could assist individuals with neurological or psychiatric conditions in the future.

Developed by researchers at ETH Zurich (Zurich, Switzerland), these electrodes consist of bundles of highly flexible, electrically conductive gold fibers enveloped in a polymer. A technique pioneered by the researchers allows for the slow insertion of these bundles into the brain, causing no detectable tissue damage. The team conducted tests using these new electrodes on rat brains, deploying four bundles, each containing 64 fibers, although theoretically, hundreds of fibers could be employed to study even more brain cells. The study, published in Nature Communications, involved connecting the electrodes to compact recording devices on the rats, allowing for unrestricted movement.

The experiments validated the probes' biocompatibility and non-disruptive nature to brain function. Due to their proximity to nerve cells, these electrodes provide superior signal quality over other methods and are suitable for extended monitoring, as evidenced by successful recordings from the same brain cells throughout a ten-month study without any brain tissue damage. An added benefit is the electrodes' ability to branch out, allowing them to target multiple brain regions simultaneously.

During the study, researchers utilized these innovative electrodes to observe and analyze nerve cell activity across different brain areas over several months. They identified "co-activation" of nerve cells across various regions, which is believed to play a crucial role in complex information processing and memory formation. The next steps involve testing these electrodes for diagnostic purposes in humans, specifically targeting epilepsy patients unresponsive to medications. In such instances, neurosurgeons might remove brain sections responsible for seizures, and these electrodes could precisely identify the affected areas before surgery.

Plans are also underway to employ these electrodes for stimulating brain cells in humans, potentially enhancing treatments for neurological and psychiatric disorders such as depression, schizophrenia, or OCD, where specific brain regions often show functional impairments affecting information evaluation and decision-making. Researchers anticipate that these electrodes could pre-emptively identify and modulate the dysfunctional signals within neural networks, alleviating the symptoms. Additionally, this technology could lead to the development of brain-machine interfaces to aid individuals with brain injuries, using the electrodes to interpret their intentions for controlling devices like prosthetics or voice-output systems.

“The wider the probe, even if it is flexible, the greater the risk of damage to brain tissue,” said Mehmet Fatih Yanik, Professor of Neurotechnology at ETH Zurich. “Our electrodes are so fine that they can be threaded past the long processes that extend from the nerve cells in the brain. They are only around as thick as the nerve-cell processes themselves. The technology is of high interest for basic research that investigates these functions and their impairments in neurological and psychiatric disorders.”

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