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

For many animals, chemosensation is the primary sensory modality through which they perceive the world. To detect and identify a wide range of chemical compounds, animals employ a large number of chemosensory neurons, making olfactory responses inherently collective responses. Thus, multi-neuronal imaging methods are ideal for understanding the neuronal basis of odor coding. Here, we studied the ensemble-level representation of odor identity in the nematode C. elegans. We recorded from all chemosensory neurons in the animal simultaneously while presenting a broad panel of olfactory stimuli in a highly controlled manner using a microfluidics device. Observing the dynamics of these neurons has allowed us to build a quantitative and comprehensive picture of the way the olfactory system in C. elegans consolidates and represents high-dimensional sensory information. We found that collectively, the sensory neurons encode odor identity and intensity. We also described the roles of each of the individual sensory neurons in olfactory coding, finding diverse dose response and tuning properties across neuron classes.