Meeting Abstract
A major challenge to understanding terrestrial locomotion in complex natural terrain is the lack of tools to perform controlled, systematic experiments in the laboratory. Recent progress was made by creating complex 3-D terrain arenas of obstacles such as grass-like beams with controlled and variable geometry and stiffness. However, these terrain arenas only allow experiments at relatively small temporal and spatial scales (~10 stride cycles, ~10 body length) with low resolution observations (~5% pixels representing the animal). Here, we create the first terrain treadmill to enable high resolution observations of locomotion in complex 3-D terrains over a long time and a large distance, analogous to treadmills for studying continuous running and walking on flat, rigid ground. Our terrain treadmill consists of two rigidly attached concentric spheres. The animal moves through modular terrain on the inner sphere, while the transparent outer sphere allows its position to be tracked in real time. This is then used to rotate the spheres opposite to the animal via closed-loop control to keep it on top. To demonstrate the usefulness of our device, we tested its performance in eliciting sustained locomotion of the discoid cockroach through cluttered pillar obstacles. In a single, continuous trial, the animal moved through pillars for 25 minutes (2500 stride cycles) over 100 m (2000 body length). For 99.7% of the experiment, the terrain treadmill contained the animal within a 5 cm2 region even at locomotion speeds of up to 10 body length/s, enabling high resolution observations (25% pixels representing the animal). Our terrain treadmill not only increased limits of experiment duration (by 250×), distance (by 200×), and resolution (by 5×), but is also opening doors to studying sensorimotor control in complex terrains.
