A huge step forward for electrophysiology
CMOS technology is everywhere—in your camera, your phone, and your computer. It’s the fabrication process that allows Intel and AMD to pack billions of transistors into the chips that power billions of devices across the planet. Now, you can use it to record spikes at an unprecedented scale. Each Neuropixels probe packs 960 recording sites onto a shank that’s 10-mm long and 70 microns wide—a density that’s only possible thanks to CMOS manufacturing. Having closely spaced electrodes along such a long range allows you to detect single units from deep within the brain, while simultaneously measuring activity in the cortex.
Record hundreds of units per probe
One Neuropixels probe can be inserted through multiple brain regions, thanks to its long length and high site density. By inserting multiple probes in the same brain, it’s possible to study how diverse cortical and subcortical structures interact in real time. With their fully integrated, compact package, Neuropixels make it easier than ever before to study neural population dynamics throughout the brain.
The story behind the probe
The dominant tools for extracellular electrophysiology haven’t undergone a fundamental change in decades. Tetrodes and silicon probes, the most popular types of electrodes, are based on technology that has been around since the early 90s. Both have seen incremental increases in channel counts in recent years, with 128-tetrode hyperdrives and 512-channel silicon probes becoming more common. But in order to get an order-of-magnitude increase in the number of channels that can be recorded simultaneously, we need to move to a new type of technology.
Tim Harris of HHMI’s Janelia Research Campus saw an opportunity to collaborate with imec, a world-leading nanoelectronics research center, in order to apply CMOS manufacturing to build new electrodes. Three other funding agencies, the Allen Institute, Wellcome Trust, and the Gatsby Charitable Foundation, signed on to the project, in the hopes that it would lead to a breakthrough electrode technology. Their goal was to create a fully integrated, easy-to-use device that would be competitive with existing silicon probes in terms of pricing. Furthermore, the product needed to be compatible with both acute and chronic recordings. Over the past 5 years, scientists around the world have tested several iterations of Neuropixels probes to arrive at the final version, which went on sale in late 2018 (see below for ordering info).
Rigorously tested in many brain areas
Neuropixels are capable of isolating single units all over the brain. This figure, adapted from Jun et al. (2017), shows the average unit yield from acute insertions of a single probe into a wide variety of structures in the mouse brain. Much of the data for this paper was collected with the Open Ephys GUI.
Neuropixels and Open Ephys
As part of their role in testing these probes, the Allen Institute developed a Neuropixels plugin for the Open Ephys GUI. Open Ephys is one of two pieces of software that are currently capable of acquiring data from Neuropixels (the other being SpikeGLX, maintained at Janelia). Open Ephys can stream data from any type of Neuropixels hardware, allowing you to take advantage of all the existing GUI plugins, or develop your own. The Allen Institute has used Open Ephys to collect over 100 TB of Neuropixels data and counting.
Up to four Neuropixels probes can interface with a single basestation module, which communicates with a PC via a standard PXIe interface card. Up to four basestations can live inside the same PXIe chassis, allowing you to stream data from 16 probes to a single computer.
For recordings with two or more probes simultaneously, we recommend using the Multi-Probe Micromanipulator from New Scale Technologies. It was developed in collaboration with the Allen Institute in order to be the easiest way to flexibly mount Neuropixels probes and precisely insert them into the brain.
Neuropixels probes are being distributed by imec, the research center that developed them in collaboration with scientists at the Allen Institute, HHMI Janelia, and UCL. To obtain probes, you’ll have to fill out the form available at neuropixels.org. There’s a minimum order size of 20 probes in 2018, with the first 30 orders filled by lottery. In 2019, imec expects to ship 2,400 probes, with the minimum order quantity reduced to five.