ABSTRACT
Chronic electrophysiological recordings in rodents have significantly improved our understanding of neuronal dynamics and their behavioral relevance. However, current methods for chronically implanting probes present steep trade-offs between cost, ease of use, size, adaptability and long-term stability.
SUMMARY Introducing a lightweight, cost-effective probe implant system for chronic electrophysiology in rodents, optimized for ease of use, probe recovery, experimental versatility and compatibility with behavior.
This protocol introduces a novel chronic probe implant system for mice called the DREAM (Dynamic, Recoverable, Economical, Adaptable and Modular), designed to overcome the trade-offs associated with currently available options. The system provides a lightweight, modular and cost-effective solution with standardized hardware elements that can be combined and implanted in straightforward steps and explanted safely for recovery and multiple re-use of probes, significantly reducing experimental costs.
The DREAM implant system integrates three hardware modules: (1) a microdrive that can carry all standard silicon probes, allowing experimenters to adjust recording depth across a travel distance of up to 7mm; (2) a 3D-printable, open-source design for a wearable Faraday cage covered in copper mesh for electrical shielding, impact protection and connector placement, and (3) a miniaturized head-fixation system for improved animal welfare and ease of use. The corresponding surgery protocol was optimized for speed (total duration: 2 hours), probe safety and animal welfare.
The resulting implants had minimal impact on animals’ behavioral repertoire, were easily applicable in freely moving and head-fixed contexts and delivered clearly identifiable spike waveforms and healthy neuronal responses for weeks of data collection post-implant. Infections and other surgery complications were extremely rare.
As such, the DREAM implant system is a versatile, cost-effective solution for chronic electrophysiology in mice, enhancing animal well-being, and enabling more ethologically sound experiments. Its design simplifies experimental procedures across various research needs, increasing accessibility of chronic electrophysiology in rodents to a wide range of research labs.
Competing Interest Statement
TS, AN, and MNH are co-founders of 3Dneuro bv, which manufactures the open-source microdrives and Faraday crowns used in this protocol. FB and PT are part of the scientific advisory board of 3Dneuro. FB and PT do not receive any financial compensation for this position.
Footnotes
tim{at}3dneuro.com, robert.taylor{at}esi-frankfurt.de
We have added several new analyses and extended descriptions of the presented procedures and results. Specifically, we have extended the analyses of locomotion before and after implantation, which are now presented in the new Figure 2; we have extended the description of our new head fixation mechanism, including 2 new figure panels, and a link to a github repository with the corresponding STL files; we have added a supplemental figure depicting assembly steps for implanting two electrode drives; we have added examples of spike-sorted units across recording sessions; and we have added an extended comparison of the DREAM implant to other implant systems, particularly the implant system presented by Voroslakos et al. (2021), which is most similar to ours, with the main difference being a significant reduction (1.2 - 1.4g) in implant weight. To highlight the differences between implant systems, we have added precise weight estimates to the comparison in Table 1, as well as a precise breakdown of our implant weights compared to the Voroslakos et al. system in the new Table 2. We have also added a variety of supplemental figures that detail the components described in the main text, in the context of a surgical procedure, such as a step by step photoseries of implant building, as well as a surgical floorpan of component placement on the mouse skull.