A Head-Mounted Multi-Camera System for Electrophysiology and Behavior in Freely-Moving Mice.

Nicholas J Sattler,Michael Wehr

doi:10.3389/fnins.2020.592417

Abstract

Advances in the ability to monitor freely-moving mice may prove valuable for the study of behavior and its neural correlates. Here we present a head-mounted multi-camera system comprised of inexpensive miniature analog camera modules, and illustrate its use for investigating natural behaviors such as prey capture, courtship, sleep, jumping, and exploration. With a four-camera headset, monitoring the eyes, ears, whiskers, rhinarium, and binocular visual field can all be achieved simultaneously with high-density electrophysiology. With appropriate focus and positioning, all eye movements can be captured, including cyclotorsion. For studies of vision and eye movements, cyclotorsion provides the final degree of freedom required to reconstruct the visual scene in retinotopic coordinates or to investigate the vestibulo-ocular reflex in mice. Altogether, this system allows for comprehensive measurement of freely-moving mouse behavior, enabling a more holistic, and multimodal approach to investigate ethological behaviors and other processes of active perception.

Highlights

The first rodent head-mounted camera system was developed to monitor the behavior of freely-moving rats, with each attached camera weighing 800 mg (Wallace et al, 2013)
Integrating cameras with the headstage in this way allows electrophysiology, accelerometer, and video signals to be collected with a single mechanical attachment to the head, which simplifies experimental setup and reduces the overall weight
This design allows for stereotactic precision and reproducibility of camera views across animals and implants by combining the fixed dimensions of the implant with the stereotactic targeting of the electrodes

Summary

INTRODUCTION

Despite the insights that have been gained from research under head-fixed or eye-fixed conditions, there has been a growing appreciation that understanding brain function will require recording neural activity in freely-moving animals, especially during ethological behaviors (Datta et al, 2019; Parker et al, 2020). Every component comes with an associated cost of size, weight, positioning, balance, and cabling Each of these factors necessarily constrains the free movement of the animal, and the magnitude of their effects scale inversely with the animal’s size and strength. The first rodent head-mounted camera system was developed to monitor the behavior of freely-moving rats, with each attached camera weighing 800 mg (Wallace et al, 2013). A more recent breakthrough was the development of a head-mounted system for monitoring both behavior and electrophysiology in mice, with each attached camera weighing 500 mg (Meyer et al, 2018). We provide further examples of their implementation, and discuss general guidelines for designing a specific implementation of this system to best suit your experimental goals

RESULTS

DISCUSSION

METHODS

ETHICS STATEMENT