Imaging Paradigm for Studying Brain-Wide Activity Patterns in a Drosophila Neural Circuit

Abstract

Behavior is the result of patterned activity in motor neurons produced by the action of central neural circuits. Abnormalities in these circuits lead to behavioral disorders in a way that is poorly understood because the circuits themselves are complex and highly distributed. The circuits of the fruitfly nervous system are like those found in humans, but the fly nervous system is small enough that brain-wide circuit analysis at subcellular resolution is conceivable with cutting edge microscopy. We are developing a custom dual-view selective plane illumination microscope (diSPIM) for brain-wide imaging in order to characterize the fruit fly neural circuit that drives the ecdysis sequence. This sequence is a hormonally-induced behavioral program that is executed to shed the old exoskeleton. It consists of distinct phases of activity and is governed by ∼300 neurons that express the Ecdysis Triggering Hormone receptor (ETHR).We hypothesize that patterned activity within these neurons drives downstream motor neuron activity to generate the ecdysis sequence. We will use the diSPIM together with recently developed genetic targeting techniques to simultaneously measure Ca2+ activity in ETHR-expressing neurons and motor neurons and create spatiotemporal maps of their activity with subcellular spatial resolution and ∼1 Hz temporal resolution. Collectively, these maps will be used to generate a predictive model of the circuit underlying the ecdysis sequence. Currently, we are constructing and characterizing the diSPIM, testing analysis methods using data collected by conventional confocal microscopy, and generating fly lines that will allow us to simultaneously interrogate the Ca2+ activity in two different populations of neurons.