Repix: reliable, reusable, versatile chronic Neuropixels implants using minimal components

Abstract

Neuropixels probes represent the state-of-the-art for high-yield electrophysiology in neuroscience: the simultaneous recording of hundreds of neurons is now routinely carried out in head-restrained animals. In contrast, neural recording in unrestrained animals, as well as recording and tracking neurons over days, remains challenging, though it is possible using chronic implants. A major challenge is the availability of simple methods that can be implemented with limited or no prior experience with Neuropixels probes, while achieving reliable, reusable, versatile high-density electrophysiology. Here we developed, deployed, and evaluated the real-world performance of Repix, a chronic implantation system that permits the repeated re-use of Neuropixels probes. The lightweight system allows implanted animals to express a full range of natural behaviors, including social behaviors. We show that Repix allows the recording of hundreds of neurons across many months, up to a year, with implants across cortical and subcortical brain regions. Probes can be reused repeatedly with stable yield. Repix has been used by 16 researchers in 10 laboratories to date, and we evaluated the real-world performance of Repix in a variety of chronic recording paradigms in both mice and rats with a combined 209 implantations. We found that the key advantage of Repix is robustness and simplicity. Adopters of Repix became proficient at five procedures on average, regardless of prior experience with in vivo electrophysiology. With the companion protocol alongside this article, the performance and user-friendliness of Repix should facilitate a wide uptake of chronic Neuropixels recordings.

Large scale, simultaneous, chronic neural recordings from multiple brain areas

“…Chronic surgical procedures are rarely standardized across labs. However certain principles, such as the use of viscous cement to carefully create a well around the implant, leaving the shank open to air, are relatively constant across published work (Bimbard et al, 2023; Horan et al, 2024; Jones, 2023; Juavinett et al, 2019; Luo et al, 2020; van Daal et al, 2021). When implanting a single probe, or multiple probes attached to the same fixture, surgeries are reported to take 4-5 hours (van Daal et al, 2021), which would render implanting multiple probes on independent fixtures impractical and time consuming.…”

“…Our fixture tripled the number of probes simultaneously implanted in comparison to the state-of-the-art work in mouse (van Daal et al, 2021; Jones, 2023; Bimbard et al, 2023; Horan et al, 2024) and doubled the capacity in freely moving settings. Moreover, our new method for encapsulating the probes reduced the implant time to ∼1 hour/probe, a ∼3-fold improvement relative to (4 hours) published work (van Daal et al, 2021).…”

“…Despite using an independent fixture for each probe, our implant (NP1: 1.2g, NP2: 0.57g – probe included) is lighter than existing designs (Luo et al, 2020; van Daal et al, 2021; Bimbard et al, 2023; Horan et al, 2024) and allows implanting multiple probes in freely moving animals, without severely impacting naturalistic behaviors (Figure 5a,c).…”

“…Indeed, most labs consider Neuropixels a precious resource and have a sufficiently limited supply that re-using probes is a necessity. An alternative approach to irreversible cementing is to secure the probe(s) to a fixture, usually 3D-printed, that is attached to the skull (Juavinett et al, 2019; Luo et al, 2020; van Daal et al, 2021; Jones, 2023; Bimbard et al, 2023; Horan et al, 2024). There are a wide range of implant strategies; existing fixtures have been used to implant 1-2 probes in mice and 1-3 in rats.…”

“…Bimbard et al (2024) reports 55 out of 63 successful explants and 30 re-uses. Horan et al (2024) reports 127 explants out of 175 insertions with 36 re-uses. It remains unclear, however, whether using probes for many months impacts re-usability or extraction success since these metrics are inconsistently reported across studies.…”