Meeting Abstract
The halteres of flies are reduced hindwings possessing several fields of mechanosensory campaniform sensilla at their bases. Halteres beat at the same frequency as wings, and this motion makes them susceptible to gyroscopic forces and deformations during body rotations. Theoretical and experimental evidence suggests that the campaniform sensilla send information about these forces to motoneurons for use in flight control. We modeled the haltere of a crane fly using finite element analyses and verified two critical emergent deformations that arise from gyroscopic forces: (1) a lateral deflection of the haltere and (2) a previously unreported torsional deformation that arises when the haltere is represented as a distributed mass. Using this structural model, combined with experimentally determined neural encoding of strain by campaniform sensilla, we predict spatial and temporal patterns of neuronal firing at the base of the haltere. Our results show that there is a significant spike timing difference of sensilla around the circumference of the haltere. Along the dorsal and ventral surfaces, the timing differences are below the experimentally determined estimates of the jitter of spike time arrival (approximately 0.2 ms). However, along the lateral margins we see timing difference arising from gyroscopic forces on the order of 5 to 10 ms for an orthogonal body rotation of 10 rad/s. The mechanics of the haltere can significantly change this spike timing. These results suggest that spike timing differences of campaniform sensilla, in addition to directional selectivity, can contribute to gyroscopic force sensing.
