9511430 Pallas The overall goal of this research is to determine how different areas of the cerebral cortex become specialized to process different types of sensory information, and how functionally specialized brain circuitry is created from non-specialized brain tissue during development and evolution. The hypothesis being tested is that the sensory inputs received by cortex during development play a critical role in organizing specific circuits in cortex. To test this hypothesis, auditory cortex will be studied in three groups of animals; one group which has had sensory input to auditory cortex removed at birth, another group which, by a minor surgical procedure, has had visual input diverted into the auditory pathway at birth, and a third group which consists of normal, unmanipulated animals. How the circuitry of auditory cortex is affected by these manipulations of sensory experience will then be examined. Using the rewiring manipulation, it has been shown previously that auditory cortex can be "turned into" visual cortex by supplying it with visual input from birth. The question yet to be investigated is whether this occurs because the early visual inputs have changed the circuitry of auditory cortex, or because auditory cortex is so similar to visual cortex that it it has an intrinsic capability for processing visual input appropriately. Preliminary results suggest that the visual inputs do induce changes in circuitry. The circuitry of auditory cortex, then, will be examined using anatomical methods to determine exactly what these changes are and how they produce the functional changes that have been observed. Knowledge of how sensory input influences cortical circuitry during development will provide information about how evolutionary changes in sensory organs might ultimately be accommodated by the central nervous system. This research, therefore, will provide fundamental information about both cortical developmental mechanisms and the evolution o f complex structures in the central nervous system.
