Brain-Machine Interfaces (BMIs) facilitate direct electrical communication between the brain and external electronic systems, allowing brain activity to directly control devices such as prosthetics or control nerve or muscle function. This is particularly helpful for those with paralysis or neurological disorders in regaining function. However, traditional BMIs are often restricted to assessing neural activity on the brain's surface. Monitoring single-neuron activity from deep brain areas usually requires invasive intracranial surgeries to embed probes, potentially leading to the risk of infection, inflammation, and damage to brain tissues. An innovative alternative involves utilizing the brain's vascular network to implant bio-probes into deep-brain regions. Researchers have now devised an ultra-small, ultra-flexible electronic neural implant that can be delivered via blood vessels and is capable of recording single-neuron activity from deep within rat brains.

Researchers at Stanford University (Stanford, CA, USA) have designed ultra-flexible micro-endovascular (MEV) probes that can be accurately delivered to deep-brain areas through the blood vessels. The researchers built a minute, flexible, mesh-like electronic recording device that can be mounted onto a flexible microcatheter and implanted into sub-100-micron scale blood vessels in the brain's inner areas. Once inserted, the device expands like a stent to record neuronal signals across the vascular wall without causing damage to the brain or its blood vessels.

To assess the potential of the MEV probe in vivo, the researchers implanted the injectable probe into the vascular system of rat brains. The MEV probe demonstrated the capability to measure local field potentials and single-neuron activity in the cortex and olfactory bulb. Furthermore, the implanted devices demonstrated long-term stability, did not cause significant changes to cerebral blood flow or rat behavior, and triggered a minimal immune response. According to the researchers, future versions of these devices could even offer customized therapies to patients by recording and decoding their neural activity, followed by delivery of the appropriate modulatory stimuli. 

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