9500863 Kaas This U.S.-Brazil Cooperative Science Program award supports travel expenses, expendable research supplies and services, related to the visits of Drs. J. Kaas, the P.I. and his co-P.I.s, all from Vanderbilt University, Tennessee, to the lab of Dr. C. E. Rocha Miranda, Univ. Federal de Rio de Janeiro, Brazil. The purpose of the research is to develop a model of how simple, primitive mammalian brains are organized, in terms of functionally significant areas, nuclei and modules that are interconnected within cooperative systems. This model can be compared to those based on complex, advanced brains, such as those of higher primates, to determine changes associated with complexity and enhanced performance. The model will be based on data obtained from experimental studies on North and South American opossums. The brains of these Metatherian mammals have changed little in external appearance, judging from the brain endocasts of early mammals, since the major radiation of mammals some 65 mya, and they provide the clear advantage of availability near both the U.S.A. and Brazilian laboratories. Previous comparative studies provide direct evidence that the basic brain organization of opossums is less complex and more primitive than that of most extant mammals, and that further studies using a powerful range of modern techniques could provide valuable additional insights. The research will involve studies of the visual, auditory and somatosensory systems that involve the majority of neurons in neocortex, and address critical issues of motor system organization, where Metatherian mammals may be less complex than Eutherian mammals. Microelectrode recordings will be used to identify systematic representations of sensory surfaces in the brain and microstimulation methods will reveal movement centers. Brain subdivisions, identified with microelectrodes, will be further examined for histochemical, architectonic, and molecular distinctions, intern al microorder and patterns of connection with other systems. The research plan takes advantage of the extensive previous experience of researchers in the Brazilian laboratory in studies of the brains of opossums, and their unique experience in characterizing the response properties of neurons in sensory systems of opossums. The researchers in the U.S.A. laboratory also have relevant experience in brain studies in opossums, as well as an extensive background in comparative studies of brain organization. Investigators in the two laboratories have both overlapping and complementary experience with research procedures and techniques, and a joint interest in understanding brain organization in opossums. A merger of efforts will allow for greater progress in the field. ***
