wild type and Ptph-1:unc-103(gf) males mating with Plev-11:GCaMP6

Abstract: One goal of neurobiology is to explain how decision-making in neuromuscular circuits produce behaviors. However, two obstacles complicate such efforts: individual behavioral variability and the challenge of simultaneously assessing multiple neuronal activities during behavior. Here, we circumvent these obstacles by analyzing whole animal behavior from a library of C. elegans male mating recordings. The copulating males express the GCaMP calcium sensor in the muscles, allowing simultaneous recording of posture and muscle activities. Our library contains wild type and males with selective neuronal desensitization in serotonergic neurons, which include male-specific CP motor/inter-neurons and sensory ray neurons that modulate mating behavior. Incorporating deep-learning-enabled computer vision, we developed a software to automatically quantify posture and muscle activities. By modeling, the posture and muscle activity data are classified into stereotyped modules, with the behaviors represented by serial executions and transitions among the modules. Detailed analysis of the modules reveals previously unidentified sub-types of the male’s copulatory spicule prodding behavior. We find that wild type and serotonergic neurons-suppressed males had different usage preferences for those module sub-types, highlighting the requirement of serotonergic neurons in the coordinated function of some muscles. In the structure of the behavior, bi-module repeats coincide with most of the previously described copulation steps, suggesting a recursive “repeat until success/give up” program is used for each step during mating. On the other hand, the transition orders of the bi-module repeats reveal the sub-behavioral hierarchy males employ to locate and inseminate hermaphrodites.