Investigating the Neural Control of Social Behavior in <i>Drosophila melanogaster</i> Using a Low-Cost Optogenetics System

Optogenetics offers a powerful tool for students to explore how neural circuits generate behavior. Here we introduce a lab module using Drosophila to help students understand the principles of optogenetics through the study of social behaviors such as aggression and courtship. In this activity, students used the red-shifted opsin CsChrimson to activate P1 neurons—key regulators of male courtship and aggression. They observed that P1 activation elicits courtship in the absence of appropriate sensory cues and induces a persistent internal state that enhances aggression or courtship depending on social context, illustrating how a single neuronal population can regulate opponent behaviors and internal states. We implemented this module using FlyRig, an inexpensive, modular, open-source system we developed that provides precise light stimulation and synchronized video recordings suitable for automated tracking and classification tools. This lab module introduces students to the principles of optogenetics, experimental design, and quantitative behavior analysis, and provides a framework for exploring the neural basis of social behaviors and the internal states that drive them. Assessment of student experiences supports the utility of this lab activity in enhancing understanding of conceptual and experimental methods for studying neural control of behavior with optogenetics, as well as the usability of the FlyRig system for behavioral experiments.