Abstract
A multi-electrode system that can address widely-separated targets at multiple sites across multiple brain regions with independent implant angling is needed to investigate neural function and signaling in systems and circuits of small animals. Here, we present the systemDrive: a novel multi-site, multi-region microdrive that is capable of moving microwire electrode bundles into targets along independent and non-parallel drive trajectories. Our design decouples the stereotaxic surgical placement of individual guide cannulas for each trajectory from the placement of a flexible drive structure. This separation enables placement of many microwire multitrodes along widely-spaced and independent drive axes with user-set electrode trajectories and depths from a single microdrive body, and achieves stereotaxic precision with each. The system leverages tight tube-cannula tolerances and geometric constraints on flexible drive axes to ensure concentric alignment of electrode bundles within guide cannulas. Additionally, the headmount and microdrive both have an open-center design to allow for the placement of additional sensing modalities. This design is the first, in the context of small rodent chronic research, to provide the capability to finely position microwires through multiple widely distributed cell groups, each with stereotaxic precision, along arbitrary and non-parallel trajectories that are not restricted to emanate from a single source. We demonstrate the use of the systemDrive in male Long Evans rats to observe simultaneous single- and multi- unit activity from multiple widely-separated sleep-wake regulatory brainstem cell groups, along with cortical and hippocampal activity, during free behavior over multiple many-day continuous recording periods.
Significance Statement The novel design of the systemDrive overcomes current microdrive limitations by providing the ability to finely position microwires through multiple widely-distributed cell groups, each with stereotaxic precision, along arbitrary and non-parallel trajectories that are not restricted to emanate from a single source. This allows for targeting of a larger set of brain regions, including deep brainstem areas, as the electrodes do not emerge from a single area, initial driving points can be placed at set distances from targets, and electrodes can be placed along trajectories designed to minimize collateral damage to sensitive brain structures. This technology enables easier simultaneous monitoring and analysis of neural activity in multiple widely-spaced brain regions that comprise a fully interconnected neural circuit.
Footnotes
The authors report no conflicts of interest for this work.
Word supported under NIH funding through grant R01EB019804.
This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International license, which permits unrestricted use, distribution and reproduction in any medium provided that the original work is properly attributed.
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