Optical imaging of intracellular Ca2+ influx as a correlate of neuronal excitation represents a standard technique for visualizing spatiotemporal activity of neuronal networks. However, the information-processing properties of single neurons and neuronal circuits likewise involve inhibition of neuronal membrane potential. Here, we report spatially resolved optical imaging of odor-evoked inhibitory patterns in the olfactory circuitry of Drosophila using a genetically encoded fluorescent Cl- sensor. In combination with the excitatory component reflected by intracellular Ca2+ dynamics, we present a comprehensive functional map of both odor-evoked neuronal activation and inhibition at different levels of olfactory processing. We demonstrate that odor-evoked inhibition carried by Cl- influx is present both in sensory neurons and second-order projection neurons, and is characterized by stereotypic, odor-specific patterns. Cl- mediated inhibition features distinct dynamics in different neuronal populations. Our data support a dual role of inhibitory neurons in the olfactory system: global gain control across the neuronal circuitry and glomerulus-specific inhibition to enhance neuronal information processing.
Odor-Induced Multi-Level Inhibitory Maps in Drosophila
Time-resolved false colored activity of averaged odor-evoked calcium (white-yellow-red) and chloride (white-green-blue) influx to different odors for a subset of glomeruli in olfactory input (upper panels) and output neurons (lower panels) of the Drosophila antennal lobe. Black bars indicate odor application.
Max Planck Institute for Chemical Ecology
