Functional imaging and quantification of multi-neuronal olfactory responses in C. elegans

Abstract

Many animals perceive odorant molecules by collecting information from ensembles of olfactory neurons. These neurons employ receptors that are tuned to recognize odorant molecules by chemical binding affinity. Olfactory systems are able, in principle, to detect and discriminate large numbers of odorants by using combinatorial coding strategies. Multineuronal imaging, combined with high-throughput stimulus delivery, allow for the comprehensive measurement of ensemble-level sensory representations. Here, we used microfluidics and multineuronal imaging to study olfactory representations at the sensory periphery of the nematode C. elegans. The collective activity of chemosensory neurons in C. elegans reveals high-dimensional representations of olfactory information across a broad space of odorant molecules. We reveal diverse tuning properties and dose-response curves across chemosensory neurons and across odorant molecules. We describe the unique contribution of each sensory neuron to an ensemble-level olfactory code, and show how the encoding of a set of natural stimuli, nematode pheromones, differs from the encoding of small volatile organic molecules. The integrated activity of the sensory periphery of C. elegans contains sufficient information to robustly encode the intensity and identity of a broad panel of odorants.