A new breakthrough technology, co-developed by UCL scientists, that simultaneously records and manipulates neuron activity deep within the brain could transform our understanding of neural circuits and neurological conditions, such as Alzheimer's disease and schizophrenia.
The device, known as Neuropixels Opto and researched in mice, integrates two powerful but traditionally separate techniques – electrophysiology (the study of the electrical activity of living cells) and optogenetics (combining genetics and optics to control cells). They form a single probe, enabling unprecedented insight into how individual neurons in the brain function and interact.
Published in Nature Methods, the system allows researchers to monitor the electrical activity of hundreds of neurons while also selectively activating or silencing specific cells using light.
Developed by an international team, led by scientists at UCL and at the Allen Institute (Seattle, US), the research forms part of a £15 million project, funded by the Wellcome Trust, Allen Institute, and other partners, investigating Neuropixels probe technology.
Scientists believe Neuropixels Opto could transform our understanding of the brain by revealing how individual neurons interact within complex circuits to drive behaviour, perception and disease.
Co-author Professor Matteo Carandini (UCL Institute of Ophthalmology) said: "The brain processes information through complex patterns of electrical activity, with billions of neurons communicating via rapid electrical signals.
"Understanding how these signals give rise to behaviour, thought and disease requires tools that can both observe and influence neuronal activity.
"Until now, scientists have typically relied on separate approaches: electrophysiological probes to record neural activity, and optogenetics to control it. Combining the two has proved challenging, particularly in deeper brain regions, where delivering light without disrupting sensitive recordings is technically difficult.
"Neuropixels Opto overcomes these limitations by integrating both capabilities into a single device, enabling simultaneous measurement and manipulation of neural circuits."
A probe smaller than a human hair
At the centre of the technology is a silicon probe narrower than a human hair, equipped with hundreds of recording sites as well as microscopic light emitters.
These features allow the probe to capture detailed electrical signals from neurons distributed along its length while delivering precisely targeted light stimulation at multiple sites in the brain.
Professor Carandini, a Professor of Visual Neuroscience at UCL, added: "This makes it possible, for the first time, to directly test how specific neurons influence the activity of surrounding circuits - revealing causal relationships between neuronal activity and brain function.
"The ability to both record and control neuronal activity in the same experiment represents a significant advance for neuroscience."
Co-lead author, Dr Karolina Socha, a Research Fellow at UCL Institute of Ophthalmology, has started to use these probes to investigate the function of the cerebral cortex – responsible for many of the brain's most advanced capabilities. She says her studies in mice provide some surprising observations.
"By selectively activating or silencing specific types of neurons while monitoring the response of nearby cells, we can begin to map how different components of the brain work together to produce behaviour," she said.
"We were surprised to discover that the activity of neurons in the cortex can be remarkably localised. Up to now, we thought that neurons are so interconnected that there would be no way to activate some of them without activating many others. The new Neuropixels Opto probes revealed that these neurons can operate not only in concert but also rather independently."
This approach is expected to help address longstanding questions in neuroscience, including how information is processed across brain regions and how specific neural circuits contribute to perception, learning and decision-making.
Implications for studying brain disorders
The technology may also have important implications for understanding neurological and psychiatric conditions.
Many disorders, including schizophrenia, Alzheimer's disease and Parkinson's disease, are associated with disruptions in how neurons communicate. By providing a clearer picture of how neural circuits function in both healthy and diseased states, Neuropixels Opto could support the development of more targeted treatments.
The development of Neuropixels Opto involved a wide-ranging collaboration between institutions in the US, UK and Europe, alongside engineering partners.
The work forms part of a broader effort to develop advanced tools for studying the brain at scale, with the aim of making high-resolution, large-scale neural recording more accessible to researchers worldwide.
A step forward for neuroscience tools
Neuropixels are next-generation silicon probes that act like tiny electrodes, allowing scientists to record the electrical activity of hundreds of neurons simultaneously across different brain regions.
By packing around 1,000 closely spaced recording sites onto an ultra-thin probe, they make it possible to capture high-resolution signals from individual brain cells while monitoring large neural networks at the same time.
