A Simple Computational Model for the Estimation of Time-to-collision

It is critical for animals to respond quickly and accurately to avoid looming objects. Recently computation of time-to-collision (TTC) with a looming object have received much attention. TTC can be specified by the optical variable tau ap thetas/thetas´, where thetas is the visual angle subtended by the looming object and thetas´ is the derivative of thetas over time. The neural mechanisms involved in the computation of tau have been described previously. In this article we describe a neural network model designed to explain the physiological response properties of those tau neurons. We found that 1/tau can be computed by using a weighted combination of 1/(thetas+B) and thetas where B is a constant. We then built a simple computational model by including an improved back propagation algorithm as a way of simulating the brain response patterns. The output of the model is consistent with the performance of the TTC computation