Microscopy tools to unveil brain activity during C. elegans foraging

Luis Alvarez1, Monika Scholz1

1 Center of Advanced European Studies and Research (caesar), Neural Information Flow, Bonn, Germany

During motor tasks, animals continually integrate information about the environment to make informed decisions. During foraging, the two motor tasks locomotion and feeding are temporally coordinated. We use the natural foraging behavior of the roundworm Caenorhabditis elegans to study motor coordination using two complementary approaches: high-throughput microscopy to study the behavior of many worms and high-speed 3D fluorescence microscopy to resolve the underlying brain activity.

To parallelize behavior imaging, we build a series of microscopes using a macro photography approach. Camera objectives adapted for close-up imaging of specimens providing high image quality and a custom-made LED illumination make the core of these cost-efficient macroscopes.

To gain insights into neural dynamics of the behaving worm, it is required to image neurons in 3D at high frame rates. Standard scanning microscopy techniques, while allowing sharp imaging of neural activity at different depths offer a limited time resolution, as they require point-by-point imaging. A suitable technique to achieve high-speed and confocal imaging is light-sheet microscopy because it allows imaging of a whole section at once. Recent advances (SCAPE microscopy; Voleti et al. (2019) Nat. Methods) have pushed the envelope of light-sheet microscopy to allow for a fast light sweeping throughout samples in 3D by using low-inertia galvanometric mirrors instead of microscope stages.

 We will show our advances at using our cost-efficient macroscopes to image worm populations and SCAPE microscopy to measure whole-brain activity in 3D during foraging behavior.