Silence in the operating room. The surgeon slowly lowers a needle thinner than a human hair into the patient's brain. At its tip is not a point but a whole palisade of nine hundred sixty microscopic microphones. Each one listens to its own tiny patch of gray matter. This is how, for the first time in the world, the Neuropixels probe entered the brain of a living human — a device that had previously only worked in mice and monkeys.
Nine patients agreed to the trial. Some were having tumors removed, others were being treated for epilepsy, and still others were receiving a stimulator to combat Parkinson's disease. All of them were already scheduled for open-brain surgery, and the doctors obtained permission to insert the probe for a few minutes. The needle never broke and caused no complications. Instead, it recorded activity from several cortical layers at once, from the surface to the depths, and even from the hippocampus, where memories are born.
The probe captures signals with millisecond precision. It's like being able to pick out not the roar of the crowd but the individual voices of hundreds of fans from one section of a stadium. Surgeons used to settle for the general hum. Now they can hear what neurons deep in the brain are saying to each other — where silence once reigned.
The needle is already changing surgical plans. The surgeon sees on the screen exactly where an epileptic discharge originates and can remove only the diseased area without touching healthy tissue. And the stimulator for treating Parkinson's disease can now be aimed more precisely — directly at the nucleus that has fallen out of rhythm. Neuropixels doesn't just listen to the brain. It gives the doctor a map to guide the scalpel.
In the Neuropixels probe, 384 contacts fit on a needle 45 millimeters long, like 384 microphones arranged along a matchstick.
Similar needle-like probes with hundreds of contacts were described by Stanislaw Lem in 'Summa Technologiae'—though in his case, they were implanted in the brain not for minutes but forever.