My lab uses techniques from physics to address questions in systems neuroscience – how do interconnected networks of neurons process information and control behavior? As a model, we study the navigational behaviors of the Drosophila larva. Using a small brain of only about 10,000 neurons, how does the larva decode uncertain and often conflicting sensory cues to make the discrete decisions that allow it to achieve a navigational goal? Advances in genetics and protein engineering have made it possible to both measure and manipulate the activities of identified neurons using light microscopy. Larval Drosophila, whose transparent cuticle allows optical access to the entire brain, is an ideal system in which to exploit these tools of optical neurophysiology.
In order to move in a favorable direction, the larva executes a biased random walk strategy, alternating straight runs with reorienting turns, while using changes in sensory input to determine the frequency, magnitude, and direction of these turns. I will describe two ways my lab uses optical tools to understand the mechanisms underlying these turning decisions. First, I will demonstrate a novel two photon tracking microscope that allows us to optically record activity from individual neurons in freely behaving animals. Second, I will discuss a reverse correlation assay we developed that uses optical activation of targeted neurons to identify the computations by which the larva transforms activity in these neurons to navigational decisions, and I will share our results for multi-sensory integration and variance adaptation.