Neuropixels Probes: How They Track Hundreds of Brain Cells and Are Revolutionizing Neuroscience

During neurosurgery in London, researchers inserted a Neuropixels probe thinner than a human hair into a patient’s brain while surgeons prepared to implant a shunt. The centimeter-long device recorded electrical activity from hundreds of neurons at once, offering an unusually detailed view of the living human brain. Neuropixels probes have already transformed electrophysiology in animals, and scientists are now adapting the technology for use in people.

In a brightly lit operating theater at the National Hospital of Neurology and Neurosurgery (NHNN) in central London, neurosurgeon Ahmed Thoma made an incision on the side of a woman’s head and drilled a small hole in her skull, exposing the pink, pulsating brain beneath.

Thoma was preparing to implant a shunt to drain excess cerebrospinal fluid. The routine procedure treats normal pressure hydrocephalus, a condition in which cerebrospinal fluid accumulates inside the skull. Patients at the NHNN also agreed to take part in an experiment involving the brief insertion of a centimeter-long Neuropixels probe into the brain.

The probe, which is thinner than a human hair, is designed to record the electrical activity of hundreds of neurons simultaneously. As Thoma and his team inserted it, Mihai Kolo, a research scientist at London’s Francis Crick Institute, monitored the colorful output from the recording site in real time.

After accounting for electrical noise from operating tables and other surgical equipment, Kolo played sequences of repeated terms such as “blind spot,” “parking lot” and “piggy bank.” The researchers were examining how the brain represents transitions between stimuli and how those representations are affected by frequency and habituation. Some words produced changes in the waveform, indicating a response from the neurons being recorded.

Scientists have long conducted experiments during neurosurgical procedures, which provide a rare opportunity to study the living—and often awake—human brain. Neuropixels probes could give researchers one of the clearest views yet of activity across large populations of human neurons.

Since their debut in 2017, Neuropixels probes have changed electrophysiology experiments in animals by allowing researchers to record electrical activity from hundreds or even tens of thousands of neurons at once. Over the past year, Kolo and colleagues at NHNN, which is part of University College London Hospital, have worked with neurosurgeons such as Thoma to record activity from human brains.

Recording many neurons at once

Other methods for studying activity in large populations of individual neurons include calcium imaging, which tracks the movement of calcium ions each time a neuron fires. These techniques can be too slow to capture the action potentials of specific neurons and generally require genetically encoded sensors, limiting their use in some organisms and preventing their routine use in humans.

Human researchers have primarily relied on devices placed on the brain’s surface to measure activity across groups of neurons, including electrocorticography. Tools such as the Utah array can record activity from relatively small numbers of individual neurons. The Utah array is a small device covered with tiny needles that penetrate about a millimeter into the brain and provide 96 recording channels.

Pierre Bourdillon, a neurosurgeon at the Adolphe de Rothschild Foundation Hospital in Paris, compares the advance made possible by Neuropixels with the difference between trying to decipher a conversation using a single microphone at a busy intersection and listening through individual microphones attached to each speaker’s collar.

“We’re just starting to get to the level of microphones to individuals,” he says. “For non-human animals, this revolution started about 10 to 15 years ago. We are now just beginning to see the first teams using this type of technology in humans.”

Simultaneous recording in animal brains

A short walk from NHNN, at the Cross Building, a former hospital converted into a research facility at University College London, neuroscientist Matteo Carandini is applying an advanced version of Neuropixels technology to animals with much smaller brains.

His team has used Neuropixels probes to record tens of thousands of neurons in mouse brains, sometimes for months at a time. On a sunny Monday afternoon in September, Carandini showed me the Neuropixels Opto system.¹ The system combines electrical recording with optogenetics, a method that uses light to activate or silence neurons.

Carandini was among the first neuroscientists to use Neuropixels, a device originally designed for rodent research. The project began with Tim Harris, a biomedical engineer who joined the Howard Hughes Medical Institute’s Janelia Research Campus in Ashburn, Virginia, in 2008. Harris was asked to identify and develop tools that researchers needed.

When Harris asked his colleagues, “What do you want to measure that you can’t?”, he learned that they lacked probes capable of supporting large-scale, long-term electrophysiology experiments. In living animals, such experiments require direct measurement of neurons’ electrical properties.

At the time, researchers mainly used arrays of twisted four-wire electrodes, which could be combined to record from dozens of channels, or silicon probes with roughly 32 recording sites. They wanted a more comprehensive picture of how cells work together to perform the brain’s functions, which required recording from more neurons at the same time.

After testing several designs, Harris contacted the Interuniversity Microelectronics Center (Imec), a research institute in Leuven, Belgium, that contributes to the development of advanced microchips. Varun Dutta, principal scientist at Imec’s Semiconductor Technology and Systems Center, agreed to work on the project.

Together, the researchers developed Neuropixels 1.0. The silicon probe has 960 recording sites along its hair-thin shank. Each channel is small enough to capture the action potentials of individual neurons, and 384 channels can be read out in parallel. The shank connects to a chip roughly the size of a nano-SIM card that contains the electronics needed to read, amplify and digitize the signals. The output travels through just two wires, a major improvement over devices that required a separate wire for every recording channel.

In a paper reporting the device,² Carandini and about 30 neuroscientists from multiple laboratories showed that two probes—each weighing about 250 milligrams—could be inserted into a mouse to record about 700 neurons simultaneously across five brain regions.

Four years later, the researchers introduced Neuropixels 2.0, a small, lightweight probe with four shanks and 5,120 recording sites, 1,536 of which can be read out at once.³ The 1.0 and 2.0 probes are available from Imec for approximately $1,700 and $1,800, respectively.

Carandini says Neuropixels probes have changed how neuroscience is conducted. His team uses them to study how the brain processes and uses sensory signals, tracking individual action potentials from thousands of neurons across multiple regions of a mouse brain that is only about a centimeter long.

Using Neuropixels, researchers have found that signals associated with particular sensory, cognitive and motor functions are more widely distributed across the brain than previously thought.⁴ The probes have also enabled scientists to study neural manifolds—the distinctive patterns of activity that emerge within populations of brain cells.

In several collaborations known as Brain Observatories, independent teams performed the same experiments using standardized methods and collected large Neuropixels datasets. In a 2025 study,⁵ more than a dozen laboratories in the United States and Europe, working as the International Brain Institute, recorded activity from more than 620,000 neurons across 279 regions in 139 mice. The resulting dataset provided a brain-wide map of neural activity linked to cognitive and motor functions including vision, movement and decision-making.

From rodents to humans

Approximately 1,700 laboratories around the world use Neuropixels probes in more than 24 species, including zebra finches, bearded dragons and octopuses. “I was completely surprised that the researchers used these in different species,” Harris says.

Scientists studying non-human primates were particularly enthusiastic. Existing tools either had too few recording channels or could reach only the brain’s superficial layers. Harris, Dutta and their colleagues worked with researchers to develop Neuropixels 1.0 NHP.⁶ The probe has a thicker shank to penetrate the tough membrane surrounding the non-human primate brain. It is also 4 centimeters long, allowing it to record from deeper structures. According to Dutta, each probe costs about $4,200.

Before Neuropixels, researchers could record from about 24 neurons in a non-human primate under favorable conditions, says Tyryn Moore, a neuroscientist at Stanford University in California who worked on the project. It is now routine to record from at least 100 neurons. Without these tools, primate neuroscience “would still be in the dark ages,” he says.

Moore and his colleagues plan to use the NHP probe to create high-resolution maps of neural activity in the macaque visual system as part of the Enigma Project, a brain-recording and deciphering initiative based at Stanford University.

Source: www.nature.com