Visual tracking in simulated salamander locomotion

This article presents a rst step towards our aim of building comprehensive models of neural systems embedded into biomechanical simulations for investigating the neuroethology of lower vertebrates. It investigates visual tracking in a model of the salamander which incorporates 1) a biomechanical body actuated by springs-and-damper muscles, 2) a spinal locomotor circuit simulated as a leaky-integrator neural network, and 3) a visionbased control circuit. A simple visuomotor experiment is presented in which the vision-based control circuit uses the signals from the retinas and from \water" sensors to modulate the type of gait produced by the locomotor circuit as well as the direction of motion. The simulated salamander is thus given the capacity to track and approach a randomly moving target both in water and on ground. Although our aim is to integrate realistic models of the visual system into the salamander model, only a very abstract visual system is implemented in this rst experiment. The primary motivations of this article are 1) to integrate a locomotor circuit evolved in previous work into a new 3D biomechanical model of the salamander, 2) to investigate the stability of pattern generation of the locomotor circuit against constantly varying inputs, and 3) to illustrate how the locomotor circuit can serve as basis for adaptive behavior.