Turning behavior of freely-walking Drosophila in response to the timing of odor encounters

To survive, insects must use information from complex odor plumes to navigate to their source. In natural plumes, turbulence breaks up smooth odor regions into discrete packets, so navigators encounter brief bursts of odor interrupted by bouts of clean air. The timing of these encounters plays a critical role in navigation, modulating decisions to change orientation and walking speed. However, disambiguating the role of odor timing from other cues, such as spatial structure, is challenging due to natural correlations between plumes’ temporal and spatial features. Using optogenetics, we isolated the temporal features of odor signals, examining how signal frequency and duration shape the navigational decisions of freely-walking Drosophila. Analyzing the effect of these stimuli on flies’ turning behavior revealed a type of novelty detection: response to new (virtual) odor packets was larger when the most recent packet was sufficiently far in the past. Analysis also revealed behavioral changes over fast and slow timescales, allowing for responses to signal offset and sustained upwind bias across environments. These features are captured by a single mathematical model that predicts Drosophila orientation dynamics in the 45 temporally diverse environments tested. I will conclude by explaining how this combination of fast and slow timescales might emerge from known dynamical properties of neurons in the olfactory circuit, and how this enhances navigation towards odor sources in diverse environments.