Prey-catching and predator avoidance 2: modeling the medullary hemifield deficit

We provide a biological and behavioral analysis of our schema-theoretic model of prey-catching and predator-avoidance. Based on lesion data, our model is structured on the principles of segregation of coordinate systems and participation of maps intermediate between sensory and motor schemas: The motor schemas are driven by specific internal maps which between them constitute a distributed internal representation of the world. These maps collectively provide the transition from topographically-coded sensory information to frequency-coded inputs to the diverse motor schemas that drive muscle activity. We simulate data on approach and avoidance behavior of the frog or toad under normal conditions and under lesion of different brain centers. The model postulates the construction of motor actions through the interaction of different motor schemas via a process of competition and cooperation wherein there is no need for a unique schema to win the competition (although that might well be the result) since two or more schemas may simultaneously be active and cooperate to yield a more complicated motor pattern. The model generates different motor zones for prey-catching behavior which match those observed experimentally in normal conditions and in the medullary hemifield deficit, and offers predictions for new experiments on both approach and avoidance behaviors.