Plasticity of development of vision and of the mammalian central visual pathways

The major objective of my research program is to understand how the development of the pathways in the brain that process vision, and hence vision itself, are influenced by what an animal sees early in its life. From studies on animal species such as monkeys and kittens that have visual systems organized for accurate binocular depth perception (stereoscopic vision) like that of humans, it is known that there are so called "critical periods" in development during which abnormal or biased visual input can have a permanent effect on the development of the visual pathways which in turn result in visual impairments. The altered development of the visual pathways induced by an episode of abnormal early visual input is now thought to underlie the common (~3% of the population) developmental visual disorder called amblyopia ("lazy eye"), that is defined as poor vision that does not originate in the eye itself. The experiments I conduct explore the origins of this disorder through studies of how certain forms of abnormal input influence the vision of cats including their ability to perceive motion, to follow moving objects with their head and eyes and to strike at them with one of their paws. The majority of the experiments involve evaluations of the vision of the kittens by use of visual displays and tasks similar to those used to test the vision of amblyopic humans. A central theme of the experiments is the idea that not all visual input is treated equally during development; brief periods of normal binocular input where the two eyes see the same thing simultaneously, are weighted preferentially to prevent the development of amblyopia even when most visual input is grossly abnormal. I will examine whether the critical amount of binocular input is determined by the proportion of input that is normal or by an absolute amount of such input. In addition, I will examine whether division of the abnormal input into separate episodes will weaken its effectiveness.