An Inexpensive, High-Precision, Modular Spherical Treadmill Setup Optimized for Drosophila Experiments

Abstract

To pursue a more mechanistic understanding of the neural control of behavior, many neuroethologists study animal behavior in controlled laboratory environments. One popular approach is to measure the movements of restrained animals while presenting controlled sensory stimulation. This approach is especially powerful when applied to genetic model organisms, such as Drosophila melanogaster, where modern genetic tools enable unprecedented access to the nervous system for activity monitoring or targeted manipulation. While there is a long history of measuring the behavior of body- and head-fixed insects walking on an air-supported ball, the methods typically require complex setups with many custom components. Here we present a compact, simplified setup for these experiments that achieves high-performance at low cost. The simplified setup integrates existing hardware and software solutions with new component designs. We replaced expensive optomechanical and custom machined components with off-the-shelf and 3D-printed parts, and built the system around a low-cost camera that achieves 180 Hz imaging and an inexpensive tablet computer to present view-angle-corrected stimuli updated through a local network. We quantify the performance of the integrated system and characterize the visually guided behavior of flies in response to a range of visual stimuli. In this paper, we thoroughly document the improved system; the accompanying repository incorporates CAD files, parts lists, source code, and detailed instructions. We detail a complete ~$300 system, including a cold-anesthesia tethering stage, that is ideal for hands-on teaching laboratories. This represents a nearly 50-fold cost reduction as compared to a typical system used in research laboratories, yet is fully featured and yields excellent performance. We report the current state of this system, which started with a 1-day teaching lab for which we built seven parallel setups and continues toward a setup in our lab for larger-scale analysis of visual-motor behavior in flies. Because of the simplicity, compactness, and low cost of this system, we believe that high-performance measurements of tethered insect behavior should now be widely accessible and suitable for integration into many systems. This access enables broad opportunities for comparative work across labs, species, and behavioral paradigms.

A high-speed, modular display system for diverse neuroscience applications

“…Multiple closed-loop modes are implemented for customizable virtual reality (VR) experiments, where visual scenes of arbitrary complexity can be flexibly controlled to provide interactive visual feedback. A common VR experiment for flies uses rotational closed loop, in which a single behavioral measurement (flight: turning measured as 'L-R' Left-Right wingbeat amplitudes 47 ; walking: rotation of air-supported ball 42,48 ) is fed back to control the rotational velocity of the rendered virtual environment. Stripe fixation is a paradigmatic example, in which flies control the azimuthal position of a vertical bar, and preferentially orient their flight towards it 47 .…”

A novel approach to quantifying inter-individual distance in insects

“…Furthermore, observation and analysis of social behaviour can be used to teach students about the main principles of neuroscience. In an educational setting there is a need for low-cost experimental setups that can easily be produced in a larger number to allow each student firsthand experience [53].…”

“…While these setups open up an impressive range of possible applications, they are technically very elaborate and often expensive. Behavioural setups that can be produced at low cost are important for small labs and education purposes [53]. Our new approach to quantify inter-individual distance in Drosophila will therefore be a convenient and easily accessible tool to unveil the basic mechanisms of forming and maintaining of groups.…”

An optogenetics device with smartphone video capture to introduce neurotechnology and systems neuroscience to high school students

“…Adding carrot juice to fly food could therefore be a possible low-cost, easily accessible alternative but this has yet to be tested. Next, while we have found tethering under a stereoscope to be sufficient for a trained student, a newly designed, inexpensive fly tethering apparatus could be incorporated into the workshop to enable a novice to consistently tether flies [21]. Third, our device currently runs in open loop.…”

“…However, many cuttingedge neuroscience/neurotechnology experiments are costly [18]. In recognizing this need, there have been concerted outreach efforts from higher education, the nonprofit research sector, and the private sector to develop low-cost versions of cutting-edge devices that enable high school students to employ neurotechnologies and engage in hands-on activities to learn neuroscience concepts [8,[19][20][21][22][23][24][25][26][27].…”