Meeting Abstract
The Drosophila larva is an important model system for understanding the interaction of neural circuits and body mechanics in directed locomotion. Its behaviour is often described as alternating between straight peristaltic crawling (runs) and lateral bending to reorient (turns), either for random exploration or to move up or down a sensory gradient (taxis) by making appropriate ‘decisions’ when to switch. Our analysis of larval motion suggests that there is actually a continuous underlying lateral oscillation and we show that a simple agent model that modulates its amplitude of oscillation according to the change in sensory input can reproduce a surprising range of the characteristics of taxis in larvae; importantly this depends on the closed-loop shaping of the sensory input by motion. To better understand the control of motion we have developed a mathematical model of larval segmental mechanics, and show that (in the absence of damping and driving) the mechanics of the body produces axial travelling waves, lateral oscillations, and unpredictable, chaotic deformations. Adding a simple reflexive neuromuscular circuit to this model to counter friction gives rise to forward and backward peristalsis and turning, even though the nervous system neither senses nor drives bending motions. Finally, by adding an additional reflex to enhance bending in response to sensory input, we can produce directed taxis that closely resembles the observed behaviour of larvae in a sensory gradient.
