Electrophysiological and behavioral studies are described to examine the neuronal basis for spatial analysis of electrosensory information in the optic tectum of the skate as related to production of a simple behavior. In a wide range of vertebrates the tectum has been found to organize spatial features of multisensory inputs and to direct oriented motor output. Local bioelectric fields associated with prey animals are sufficient alone to direct the close-range orientation and attack by skates on their prey. Such unconditioned orientation responses can be elicited by dipole E fields produced to simulate the bioelectric signals. The tectum in the little skate, Raja erinacea, receives a large input from ascending electrosensory fibers. Multiple and single unit studies will examine the organization of electrosensory information in the skate tectum and its relationship to other sensory modalities represented. The existence of spatial mapping of electrosensory as well as visual information will be examined and the relationship of such maps for different modalities determined. Quantitative measurements of such spatial representations will determine if space is represented uniformly in each modality. The receptive field properties of single cells will be studied along with the selectivity for specific sensory features (e.g. stimulus size, movement and direction). Finally, the responses of tectal cells to stimuli in more than one sensory modality will be measured. Behavioral studies of animals with partial or complete tectal abltaions will be used to assess the role of the tectum in the orienting responses to the E fields. The studies may provide insight into general principles of neuronal processing of spatial information by the vertebrate brain which have relevance for understanding the disruption of these processes in disease states. The evidence from many vertebrate classes indicates that the function of the optic tectum in organizing spatial information and directing orienting behavior is conserved throughout the vertebrates. The results of the studies proposed should, therefore, have relevance for understanding the tectum (superior colliculus) in humans.
