We plan to continue the combined application of behavioral, neurophysiological and, more recently adopted, neuroanatomical approaches to the electrosensitive system of fish. This system offers the advantage of natural behavioral responses which still function in neurophysiological preparations and thus allows for the direct testing of a single unit's significance for the behavior under study. By applying modern anatomical methods (HRP and (3H)-3-Deoxyglucose) we plan to demonstrate neuronal structures and pathways whose existence so far can only be postulated on the basis of behavioral and neurophysiological observations. We want to focus on the following problems: 1) Species specific differences in processing of electroreceptive information. 2) The neuronal connection between torus semicircularis and medullary pacemaker in gymnotoid fish. This is the last unknown link in a chain of neuronal structures which control the jamming avoidance response. This response protects electrolocation performance against jamming signals. It is one of the few cases of a vertebrate behavior whose entire neuronal substrate will be known, from receptor to effector.