Temporal Integration of Olfactory and Wind Information in Plume Tracking Insects

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A major goal in modern science is to understand how brains function. Natural search behavior exemplifies this process, and thus serves as an excellent case study for discovering how brains operate. A classic example of natural search is chemical plume tracking, which is exhibited by animals ranging in scale from sperm, to sperm whales, allowing for comparative studies to discover general principles. The fundamental challenge organisms and researchers alike must overcome, is that natural plume dynamics are both highly complex, and difficult to observe. The complexity arises from turbulence in the wind, which breaks plumes into discrete packets interspersed with clean air. This structure results in an intermittent experience for the organisms, and the instantaneous olfactory experience at any given moment does not provide direct information about the location of the odor source. Instead, to make decisions, plume tracking animals must (a) integrate information across time and (b) across sensory modalities. To overcome the obstacles that have historically hampered efforts to uncover the detailed behavioral and neural mechanisms that underlie this process, we have developed a novel approach for spatially controlling the remote activation of olfactory receptor neurons to create a virtual odor plume that is independent of the wind. We will use this new approach to determine the behavioral mechanisms of how flies temporally integrate information from olfactory stimuli, and wind stimuli, independent of one another. Future work will: (1) investigate how wind and odor cues are integrated together, in particular when wind changes direction; (2) discover how flies respond to heterogeneous mixtures of odors, as would be found downstream of groups of physical odor sources. Once the behavior is characterized, we will begin pursuing a circuit level understanding of wind-olfactory sensory integration. Our experiments will provide the necessary data to build a deeper theoretical understanding of how organisms integrate sensory information in general. Beyond broadening our understanding of how brains function, our insights may inspire new strategies for controlling agricultural pests and human parasites such as mosquitoes.