Neural Responses to Looming Objects in the Dragonfly

Abstract

Dragonflies have high visual acuity, which, when combined with a remarkably fast visual response, allows them to hunt with a high success rate. They do so by intercepting small flies in flight rather than by chasing from behind. Eight bilateral pairs of large Target‐ Selective Descending Neurons (TSDNs) of the dragonfly ventral nerve cord respond to small, contrasting objects, which presumably represent potential prey. These interneurons are part of the neuronal circuitry that triggers small changes in wing angle and position to control flight during prey interception. In flight, dragonflies extend their legs to catch the prey about 20 ms before contact. The current research investigates the role of the TSDNs in prey contact. Spiking traces from the nerve cord were recorded during the presentation of growing black circles projected on a screen, which simulate approaching the prey. Several loom sizes and speeds were used to cover a range of realistic and unrealistic rates of expansion. We investigated whether the interneurons predict the time to contact of the simulated looming stimuli. We hypothesize that TSDNs innervate circuitry that controls leg muscles for the purpose of catching prey in flight.