An adaptable, reusable, and light implant for chronic Neuropixels probes

Abstract

Understanding neural processes such as memory formation, learning, or aging requires tracking the activity of neural populations across short and long time scales. Such longitudinal recordings can be achieved with chronically implanted Neuropixels probes. An ideal chronic implant should (1) allow stable recordings of neurons for weeks; (2) be light enough for use in small animals like mice; (3) allow reuse of the probes after explantation. In this initial preprint, we present the "Apollo Implant", an open-source and editable device that meets all these criteria and accommodates up to two Neuropixels 1.0 or 2.0 probes. The assembled implant comprises two modules: a recoverable "payload" module, and a "docking" module that is cemented to the skull. The design is readily adjustable: the distance between probes, angle of insertion, and depth of penetration can all be easily changed. We tested the implant across multiple labs, and in head-fixed and freely moving animals. The number of neurons recorded across days was stable, even after repeated implantations of the same probe. The Apollo implant thus provides an inexpensive, lightweight, and flexible solution for reusable chronic Neuropixels recordings.

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

“…We found that users preferred to use new probes whenever possible and only reused probes later in their experimental journey. The total number of reuses of single probes ( 5) is comparable to the best reported 20 , and we found no meaningful detriment to the recording quality in repeated reuse.…”

“…As the Neuropixels recording technology evolved and matured, researchers developed solutions to chronically implanting Neuropixels probes. They have a common design principle using payload and docking modules and have been effectively used for some combination of recording from Neuropixels 1.0; Neuropixels 2.0; in mice or rats; with the ability to reuse probes 3,17,19,20,[23][24][25][26] . Repix combines all these qualities to ensure longterm recordings in an aluminum system that is strong enough for rats and light enough for mice; which can accommodate any probe type; in assays that span rodent behaviors, including freely-moving, head-fixed, and social behaviors; where probes can be reused; all in a solution with a minimal number of components that can be adapted for individual use cases.…”

“…The second drawback is that the current Repix design does not allow two probes to be simultaneously inserted using the same posts. Dual probe implants in mice are the standard feature of Apollo or similar systems 19,20,24 , and a recent report showed a 3.4g fixture with 6 probes chronically implanted 25 . The resources accompanying this article include two versions of dual-probe Repix prototypes (Supplemental Material: CAD/Cassette/Prototypes/DualProbe.step).…”

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

“…In addition to designing a novel fixture, it was essential to optimize the surgical procedures for multi-probe implants. Chronic surgical procedures are rarely standardized across labs, however certain principles, such as the use of viscous cement to seal the implant leaving the shank open to air, are relatively constant across published work (Bimbard et al, 2023;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.…”

“…Recoverability is possible and is reported for many of the designs; however, the reliability of the process remains largely uncharacterized (Bimbard et al, 2023;Jones, 2023;Juavinett et al, 2019;Luo et al, 2020;van Daal et al, 2021). In detail, Juavinett et al 2019 report 4 explants out of 10 with 2 re-uses.…”