Body modeling and model-based tracking for neuroethology

The accurate tracking of an animal's movements and postures through time ha s broad applicability to questions in neuroethology and animal behavior. In this paper we describe methods for precision body modeling and model-based tracking of non-rigid animal movements without the use of external markers . We describe the process of obtaining high-fidelity urethane casts of a mo del organism, the weakly electric knifefish Apteronotus albifrons, and the use of a stylus-type 3-D digitizer to create a polygonal model of the anima l from the cast. We describe the principles behind markerless model-based t racking software that allows the user to translate, rotate, and deform the polygon model to fit it to digitized video images of the animal. As an illu stration of these methods, we discuss how we have used model-based tracking in the study of prey capture in nocturnal weakly electric fish to estimate sensory input during behavior. These methods may be useful for bridging be tween the analytical approaches of quantitative neurobiology and the synthe tic approaches of integrative computer simulations and the building of biom imetic robots. (C) 2000 Elsevier Science B.V. All rights reserved.