Published on Fri Jun 25 2021

Non-synaptic interactions between olfactory receptor neurons, a possible key feature of odor processing in flies

Pannunzi, M., Nowotny, T.

Non-synaptic interactions (NSIs) between olfactory receptor neurons improve mixture ratio detection and plume structure sensing. NSIs decrease the dynamic range of co-housed ORNs, especially when they have similar sensitivity to an odorant.

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Abstract

When flies explore their environment, they encounter odors in complex, highly intermittent plumes. To navigate a plume and, for example, find food, they must solve several challenges, including reliably identifying mixtures of odorants and their intensities, and discriminating odorant mixtures emanating from a single source from odorants emitted from separate sources and just mixing in the air. Lateral inhibition in the antennal lobe is commonly understood to help solving these challenges. With a computational model of the Drosophila olfactory system, we analyze the utility of an alternative mechanism for solving them: Non-synaptic (``ephaptic'') interactions (NSIs) between olfactory receptor neurons that are stereotypically co-housed in the same sensilla. We found that NSIs improve mixture ratio detection and plume structure sensing and they do so more efficiently than the traditionally considered mechanism of lateral inhibition in the antennal lobe. However, we also found that NSIs decrease the dynamic range of co-housed ORNs, especially when they have similar sensitivity to an odorant. These results shed light, from a functional perspective, on the role of NSIs, which are normally avoided between neurons, for instance by myelination.