The objective is to study the function of topographic maps in the visual system as they undergo growth, regeneration and plastic rearrangement. The retinotectal system of fishes is a valuable model system because it continues to grow in adulthood, and the optic nerve regenerates after injury, reforming a map of the visual field upon the primary visual center in the brain, the optic tectum. While much effort has been devoted to tracing the pathways between retina and tectum, and studying their patterns of development and regeneration, much less attention has been paid to the functional consequences of these processes. The proposed experiments will, therefore, examine the success with which the mechanisms governing map formation in the visual system lead to adaptive function. In particular, they aim to reveal the extent to which distorted or disordered maps formed during regeneration affect visuomotor behavior and psychophysical functions, such as acuity. Visual processing by the brain depends upon the integration of signals from the retina with signals from motor systems, as well as other sensory modalities. In some cases, this integration appears to be achieved by ordered mappings between the tectum and other brain structures. Part of this research will investigate the function of these connections, as well as their influence upon the reformation of the mapping of the retina onto the tectum after optic nerve damage. The capacity for neural regeneration and recorganization in fish is not shared by adult mammals. However, recent findings suggesting that central fiber tracts may be capable of more regeneration than previously thought, could account, at least in part, for recovery of function after brain injury. The proposed experments on rodents will assess the extent to which optic nerve fibers in the adult brain can regenerate and signal visual information. They will also lay the groundwork for testing various substances that have potential for promoting neural regeneration, thereby improving the prospects of restoring optic nerve function after injury or disease.
