Quantifying Mechanosensory Responses with Optogenetics in the Drosophila Larva.

The Drosophila melanogaster larvae are small, crawling animals with a brain composed of roughly 10,000 neurons. In response to unfavorable changes in odor and light, larvae modulate their turn rate and turn size, but in response to a sudden onset of vibration larvae engage a much richer behavioral repertoire: turns, but also pauses (startle response) and reverse crawl (strong avoidance response), which we never see in response to light or odor. The rate at which each decision is activated depends on the vibration’s frequency and strength. The same sensory neurons that mediate response to vibration also mediate larval anemotaxis, navigation in response to wind. Although these behaviors have been studied using natural mechanosensory stimuli, relatively little work has been done to reproduce similar responses through optogenetic stimulation.

Here, we optogenetically deliver vibrational stimuli through the activation of mechanosensory chordotonal neurons, quantify responses across a range of temporal patterns, and compare them to responses to natural vibration. We address the extent to which optogenetic activation of mechanosensory neurons can recover the behavioral repertoire to natural stimuli and whether distinct activation patterns can drive known behaviors.