A Probe Thinner Than a Hair Recorded Single Neurons in a Living Human Brain

For the first time, researchers have recorded the activity of individual neurons in a living human brain while the person listened to spoken words, using a probe thinner than a human hair. The device, called Neuropixels, was reported in Nature on 2 November.

Neuropixels is a silicon shank about a centimetre long, studded with hundreds of electrode contacts. Pushed into brain tissue, it picks up the electrical spikes of many individual cells at once, rather than the blurred average that scalp electrodes record. The distinction matters: a summed signal tells you a region is busy, while single-unit recording tells you what the cells are doing.

The human work was done at the National Hospital for Neurology and Neurosurgery in London. A woman being treated for normal pressure hydrocephalus — a build-up of fluid that enlarges the brain's cavities and can disturb walking and thinking — was already scheduled for a shunt to drain it. Because her brain was going to be accessed anyway, she agreed to let surgeon Ahmed Toma insert a probe briefly, while researchers at the Francis Crick Institute watched the output in real time.

The team played a repeating list of words — blind spot, parking spot, piggy bank — and watched the traces shift with each sound. The question was how the brain represents the move from one stimulus to the next, and whether a word's familiarity, or how often it has been heard, changes the response.

Pierre Bourdillon, a neurosurgeon at the Rothschild Foundation Hospital in Paris, reached for an analogy: conventional recording is like planting one microphone at a busy crossroads and trying to follow individual conversations through the noise, whereas Neuropixels is closer to clipping a microphone to every person's collar. Neuroscience, he suggested, has only just reached the point where everyone can have one.

The hardware has scaled quickly. The first version, released in 2017 by the Howard Hughes Medical Institute's Janelia campus with the Belgian nanoelectronics institute imec, had 960 recording sites, of which 384 could be read at once. Version 2.0 in 2021 shrank the package and raised that to 5,120 sites and 1,536 readable channels. A 2025 study by the International Brain Laboratory ran 699 probes across 139 mice and 279 brain regions, logging more than 620,000 units and confirming some 75,700 cleanly isolated neurons. Roughly 1,700 laboratories now use the probes, in more than 20 species — zebra finches, bearded dragons and octopuses among them. At Stanford, neuroscientist Tirin Moore says his team now routinely records at least 100 primate neurons a day, against about 20 before the technology existed.

One caveat is worth keeping in view. Neuropixels is a research instrument, not a brain-computer interface and not a treatment. It may lay groundwork for both, but nothing in this experiment suggests the probe can yet treat disease.