Spatial and Temporal Organization of Odor-evoked Responses in a Fly Olfactory Circuit: Inputs, Outputs and Idiosyncrasies

How is sensory information routed through different types of neurons within a circuit, and do equivalent circuits in different individuals follow similar organizational principles? We examined this issue in the fruit fly olfactory system. Odor-evoked signals from sensory neurons (ORNs) triggered neural responses that were patterned over space and time in cholinergic ePNs and GABAergic iPNs within the antennal lobe. The dendritic-axonal (I/O) response mapping was complex and diverse, and axonal organization was region-specific (mushroom body vs. lateral horn). In the lateral horn, feed-forward excitatory and inhibitory axonal projections matched 'odor tuning' in a stereotyped, dorsal-lateral locus, but mismatched in most other locations. In the temporal dimension, ORN, ePN and iPN odor-evoked responses had similar encoding features, such as information refinement over time and divergent ON and OFF responses. Notably, analogous spatial and temporal coding principles were observed in all flies, and the latter emerged from idiosyncratic neural processing approaches.