Amblyopia is a developmental disorder of vision that affects 3-5% of children in the US. The goals of our work are to identify the neural mechanisms underlying the visual deficits and to evaluate specific hypotheses for the neural disorder. We study a nonhuman primate model for the human visual system so that we can directly assess the neural correlates of developmental visual disability without compromising the visual welfare of any child. The proposed work aims to evaluate the neural disorder of amblyopia with a series of matched behavioral and neurophysiological studies. Since amblyopia is predominantly a disorder of spatial vision, we plan to target the ventral visual cortical pathway. The framework for the research is to contrast two mechanistic hypotheses: 1) amblyopia is a disorder arising primarily at the first stages of cortical processing that is then passed along through subsequent levels of processing, essentially unmodified, or 2) amblyopia results from a cascade of deficits that emerge from a series of changes in cortical processing as signals traverse the ventral pathway. The planned experiments will directly evaluate neural activity as it relates to amblyopic performance deficits in ventral stream cortical areas V1, V2, and V4. We will use tasks ranging from low-level to higher-order to capture the range of individual losses in these three areas: Monocular and dichoptic contrast masking, second order contrast discrimination, naturalistic texture discrimination, and Gabor contour integration, as well as basic characterization of the first-order spatial deficit. The same stimuli will be employed for behavioral and neurophysiological testing in individual subjects. The recordings will be conducted in awake, behaving amblyopes with multi-electrode Utah arrays placed in the three ventral stream areas simultaneously. The goal is to record single and multi-unit activity simultaneously in foveal representations of the three target visual areas; we will also separately assess responses in the parafoveal visual field representation of V4. We will use population decoding and correlational analyses to compare behavioral performance and neural activity between the eyes of amblyopes, between amblyopes and controls, between different visual areas, and across specific visual tasks. The results will be used to evaluate and refine the current views on the neural disorder in amblyopia. In addition, we will learn about the neural mechanisms underlying form perception in normal individuals. Our research will ultimately inform efforts to treat and prevent amblyopia development in children.