(586b) Multifunctional Microfluidic Clamp for Simultaneous Behavior Phenotyping, Neural Imaging, and Chemical Stimulation of C. Elegans

Monitoring an animal’s brain activity during a course of action provides valuable information about how the brain functions. However, it is challenging to obtain such information for brain activity of the popular model organism, C. elegans, due to technical challenges of imaging the microscopic-sized animal. Commonly, fully immobilized animals are used for recording neuron activities at single-cell resolution, which eliminates any readout of concurrent behavior during functional imaging. On the other hand, neural imaging of a freely moving C. elegans requires active tracking and advanced equipment, which are often incompatible with microfluidic operations that enable controlled manipulation of the animal’s environment.

To address this need, we engineered and optimized a microfluidic method that selectively keeps the head portion of the animal stationary while allowing fluid exchanges for simultaneous recording of neural activity and behavior. The method takes advantage of microfluidic geometry and flow pressure balances to keep the neurons of interest stationary at the site of fluid exchanges while permitting movement in the other end for behavior readout. The 3D tapering geometry effectively creates a pressure drop that acts as a clamp on the animal’s body, and this is maintained robustly at wide ranges of pressure balances.

We show the device geometry can be tuned to observe a wide range of interpretable behaviors, such as forward and backward swimming, coiling, and egg-laying that correlate with the sensory stimuli, suggesting perception of the chemical environment. By examining the neuronal activities in conjunction with the corresponding behavior, we can verify and elucidate the mechanics of neuronal circuitries regarding individualistic and sexual dimorphic differences in chemosensory preferences. Furthermore, this system is directly applicable to volumetric whole-brain imaging and can also be used to understand the biomechanics and motor coordination in locomotion. We anticipate the platform will facilitate neural analysis and behavior phenotyping of C. elegans and other small organisms, particularly swimmers such as hydra, zebrafish, and tunicate.