Modeling Peripheral Olfactory Coding in Drosophila Larvae

Abstract

The Drosophila larva possesses just 21 unique and identifiable pairs of olfactory sensory neurons (OSNs), enabling investigation of the contribution of individual OSN classes to the peripheral olfactory code. We combined electrophysiological and computational modeling to explore the nature of the peripheral olfactory code in situ. We recorded firing responses of 19/21 OSNs to a panel of 19 odors. This was achieved by creating larvae expressing just one functioning class of odorant receptor, and hence OSN. Odor response profiles of each OSN class were highly specific and unique. However many OSN-odor pairs yielded variable responses, some of which were statistically indistinguishable from background activity. We used these electrophysiological data, incorporating both responses and spontaneous firing activity, to develop a Bayesian decoding model of olfactory processing. The model was able to accurately predict odor identity from raw OSN responses; prediction accuracy ranged from 12%–77% (mean for all odors 45.2%) but was always significantly above chance (5.6%). However, there was no correlation between prediction accuracy for a given odor and the strength of responses of wild-type larvae to the same odor in a behavioral assay. We also used the model to predict the ability of the code to discriminate between pairs of odors. Some of these predictions were supported in a behavioral discrimination (masking) assay but others were not. We conclude that our model of the peripheral code represents basic features of odor detection and discrimination, yielding insights into the information available to higher processing structures in the brain.

Complex and non-redundant signals from individual odor receptors that underlie chemotaxis behavior in Drosophila melanogaster larvae

“…Further, the larval odor receptor repertoire has been comprehensively tested in terms of electrophysiological responsiveness to odors in the “empty neuron” system ( Dobritsa et al, 2003 ; Kreher et al, 2008 ). Calcium imaging studies and direct recordings from larval olfactory sensory neurons have led to similar conclusions about the receptive ranges of odor receptors, supporting assignment of ligands to the larval odor receptor repertoire ( Asahina et al, 2009 ; Hoare et al, 2011 ).…”

Drosophila adult and larval pheromones modulate larval food choice

“…The sequential perception of olfactory and gustatory cues is also necessary for adult discrimination of Drosophila sex pheromones [38][39][40]. We cannot currently explain why the simultaneous presentation of A-food patches of the two species dramatically reduced the general attractivity of food, particularly in D. simulans larvae.…”

Neural representation of calling songs and their behavioral relevance in the grasshopper auditory system

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