Fluctuation-Driven Neural Dynamics Reproduce Drosophila Locomotor Patterns.

The neural mechanisms determining the timing of even simple actions, such as when to walk or rest, are largely mysterious. One intriguing, but untested, hypothesis posits a role for ongoing activity fluctuations in neurons of central action selection circuits that drive animal behavior from moment to moment. To examine how fluctuating activity can contribute to action timing, we paired high-resolution measurements of freely walking Drosophila melanogaster with data-driven neural network modeling and dynamical systems analysis. We generated fluctuation-driven network models whose outputs-locomotor bouts-matched those measured from sensory-deprived Drosophila. From these models, we identified those that could also reproduce a second, unrelated dataset: the complex time-course of odor-evoked walking for genetically diverse Drosophila strains. Dynamical models that best reproduced both Drosophila basal and odor-evoked locomotor patterns exhibited specific characteristics. First, ongoing fluctuations were required. In a stochastic resonance-like manner, these fluctuations allowed neural activity to escape stable equilibria and to exceed a threshold for locomotion. Second, odor-induced shifts of equilibria in these models caused a depression in locomotor frequency following olfactory stimulation. Our models predict that activity fluctuations in action selection circuits cause behavioral output to more closely match sensory drive and may therefore enhance navigation in complex sensory environments. Together these data reveal how simple neural dynamics, when coupled with activity fluctuations, can give rise to complex patterns of animal behavior

Cellular level analysis of the locomotor neural circuits in Drosophila melanogaster

To investigate the neural mechanisms of insect locomotion, we aimed to generate genetic reagents to manipulate the specific cell types in the thoracic ganglion of Drosophila melanogaster. By using the split-Gal4 technique, we have generated ~1000 lines which can drive reporters or modulators in the specific cell types. We used these split-GAL4 lines to analyze the anatomy of individual cell types. Furthermore, we have screened their functions in locomotion by optogenetic activation. We observed a wide range of activation phenotypes, including the initiation and stopping of locomotion. These genetic resources will enable us to analyze the anatomy and function of insect locomotor circuits at the cellular level