Optokinetic response in D. Melanogaster reveals the nature of common repellent odorants.

Animals ability to orient and navigate relies on selecting an appropriate motor response based on the perception and integration of the environmental information. This is the case, for instance, of the optokinetic response (OKR) in Drosophila melanogaster, where optic flow visual stimulation modulates the walking or flying patterns. Despite a large body of literature on the OKR, theres still a limited understanding of the impact on OKR of concomitant, potentially conflicting, inputs. To evaluate the impact of this multimodal integration, we combined in D. melanogaster, while flying in a tethered condition, the optic flow stimulation leading to OKR with the simultaneous presentation of olfactory cues, based on repellent or masking compounds typically used against noxious insect species. First, this approach al lowed us to directly quantify the effect of several substances and their concentration, on the dynamics of the flies OKR in response to moving gratings by evaluating the number of saccades and the velocity of its slow phase. Subsequently, this analysis was capable of easily revealing the actual effect, i.e. masking vs repellent, of the compound tested. In conclusion, we show that D. melanogaster, a cost-affordable species, represents a viable option for studying the effects of several compounds on the navigational abilities of insects.