Jarlath Rodgers – “Investigating C. elegans Escape Responses with Biophotonics and Machine Vision”

Abstract

One of the fundamental goals in neuroscience is to describe how animals process information from their environment, integrate it with past experience and internal physiological states, and output an appropriate behavioral response. This goal has remained elusive, however, even in circuits as small as the adult nervous system of the nematode Caenorhabditis elegans, with just 302 neurons, and even in well-studied and apparently simple behaviors, such as the escape response. This thesis presents work towards achieving this goal by developing tools to quantify the behavioral complexity of the C. elegans escape from rapidly increasing temperature. We developed a system that tracks the behavior of individual freely behaving worms, and simultaneously targets infrared laser stimuli to small body regions. We showed that certain aspects of the escape response last for several minutes, and vary with experience, environment and immediate behavioral state. Equipped with these tools for applying precise stimuli and quantitatively measuring behavior, we characterized the worm’s response to repeated stimulation. Escape responses habituate over time, and high-content phenotyping revealed that different behavioral metrics reflect different rates of learning, which suggests multiple loci of plasticity for this simple form of learning.

To obtain these findings we were required to develop both new software for processing and interpreting behavioral tracking data, and techniques for the precise measurement of thermal stimuli and temperature-induced neuronal signals. We have already been able to apply these tools to collaborative projects, helping to describe neurons required for noxious thermal avoidance, and, by generating a large high-resolution dataset of stimulus-evoked deep turns, aiding in the discovery of a previously undescribed reorientation behavior. Taken together, this thesis demonstrates the utility of combining precise control of environmental stimuli with high-dimensional phenotyping for understanding how a small nervous system controls sensory behavior.

Ryu Lab