Fig. 8. Conceptual model of sensory integration for olfactory navigation in the Drosophila central brain.

Conceptual model of central olfactory navigation circuitry as suggested by this and previous studies. MBONs, LHONs, and FB tangential inputs promote wind navigation and encode odor information but not wind direction information. FB tangential inputs are a likely locus where learned and innate odor information may be integrated to drive behavior. In contrast, FB columnar inputs (PFNs) encode wind direction but not odor presence. h∆C neurons receive input both from directionally tuned PFNs at their dendrites and from odor-tuned FB tangential inputs at their axons. They encode a fly-specific wind direction signal that can be modulated ON by odor. Sparse activation of h∆C neurons can drive movement in a reproducible direction and activity in these neurons is required for sustained upwind orientation during odor. Our data support a model in which columnar and tangential inputs to the FB encode directional and non-directional information respectively, and where tangential input can gate the expression of directional information in local neurons outputs to specify navigational goals.