Neuropixels: Hi-Def Brain Probes

A new type of electrode for recording brain cell activity is set to revolutionize our understanding of decision making in the brain.

The findings of a global collaborative effort are published today in the journal Nature. The paper describes a new recording probe, Neuropixels, 10mm long and thinner than the width of a human hair. Each Neuropixels probe uses technology identical to that found in your smart phone to enable recording from 384 channels that line the shank of the electrode. 

Watch: An interview recorded LIVE with Dr Tim Harris, probe inventor

Seeing neuronal activity in hi-def. 
The Neuropixels probes enable observation of the activity of hundreds of neurons simultaneously at a level of resolution previously unachievable.

The densely packed recording channels allow researchers to see brain activity in higher resolution because they can now pick out activity in the small processes, like dendrites or axons, that they may have missed with the current wire electrodes in use, which are limited to dozens of recording sites.  

The Neuropixels probe. Courtesy of imec.

The design is also a big improvement on the current technology, in that the headstage, the part of the set-up that amplifies the millivolt signals recorded from the neurons so they can be seen on a screen, is directly connected to the electrode. Also, the recorded analog signal is digitized at the level of the headstage. This limits the amount of signal interference from external electrical sources, electrical noise which is a frustration for any electrophysiologist. 

Improving the fidelity of the electrical signal improves the resolution of the electrical activity recorded. Meaning the researchers are not only able to record from more neurons in one go, they also get cleaner signals from the neurons as well. 

Deep brain activity

The long 10mm shank means scientists can delve deeper into the brain and record from the multiple brain areas that the shank passes through, simultaneously. The set-up allows researchers to record up to 384 channels at any one time from the 960 channels available. This means researchers can group their recording sites around areas of interest. 

The product of international collaboration

The probes were developed by an international team who received $5.5 million from the Howard Hughes Medical Institute (HHMI), the Allen Institute for Brain Science, the Gatsby Charitable Foundation and Wellcome. Scientists at HHMI’s Janelia Research Campus, the Allen Institute and University College London (UCL) worked together with engineers at nanotechnology company imec to build and test the probes.

Lead author Dr Timothy Harris, Senior Fellow at HHMI’s Janelia Research Campus, was speaking with Wellcome about the power of the Neuropixels probes: “Every action and decision you take involves the interactions of millions of neurons spread across your brain. This new technology enables us to detect the activity of large numbers of neurons from multiple brain regions with much less difficulty. I believe they will be transformational and will greatly accelerate the pace of neuroscience research”.

Prof. Matteo Carandini, Wellcome Investigator and joint head of the Cortex lab at UCL, was also speaking to Wellcome about the impact the probes will have on the field of neuroscience: “To understand the brain we need to understand how a lot of neurons spread all over the brain work together. Until recently, it was possible to measure the activity of individual neurons within a specific spot in the brain or to reveal larger, regional patterns of activity—but not to do both at the same time. These probes are a game changer. If you place them appropriately, you can really study how different parts of the brain work together at the neuronal level.”

In their paper, the researchers describe how the Neuropixels work. They also present data obtained from 700 well-isolated single neurons from five brain structures in a mouse. The researchers have also shown that the probes can be used in long-duration experiments with freely moving animals, in experiments with mice lasting up to 150 days. Long-term experiments enable researchers to study changes in the brain resulting from development, experience and learning, as well as the effects of neurodegenerative processes in disease. 

This video from Wellcome describes the power of the Neuropixel probes and how they are being utilized by the International Brain Lab to increase our understanding of the brain. Credit: Wellcome

Neuropixels at the heart of a large coordinated neuroscience effort

In September, the International Brain Laboratory was launched. The research groups involved in this coordinated approach, to understand decision making, have been working with the prototype Neuropixels probes and helping guide their development. 

Learn more: International Brain Laboratory Launches

The different groups will use Neuropixels probes to study many different areas in the brain of a mouse, as it forages for food. The collaboration will involve data sharing between the groups involved, to enhance understanding of neural activity and to build a functional map of neuronal activity throughout the brain as the animal performs a foraging task.

Collaboration is at the heart of the development of these probes which were developed and tested between labs in America, UK and the nanofabrication company, imec, in Belgium. The probes will shortly be made available to researchers across the world at cost-price. The authors hope this will encourage uptake of these probes among academic researchers and contribute to advancing our understanding of the brain. The probes are already enabling a concerted and collaborative effort in the form of the International Brain Lab.