Project Summary Amblyopia is a developmental disorder of vision that affects 3-5% of children in the US. The goals of our work are to more fully characterize the disorder and identify the neural mechanisms underlying the visual losses experienced by amblyopic individuals. Amblyopia is now known to include far more diverse visual losses than simple acuity, including abnormalities in binocular vision, global form perception, visuomotor coordination and even some higher order cognitive functions. These deficiencies are typically not ameliorated by standard amblyopia treatment. There is no clear understanding of the neural basis for the full range of amblyopic deficits. We study a nonhuman primate model for the human visual system for this work so that we can directly assess the neural correlates of developmental visual disability without compromising the visual welfare of any child. The studies we propose in this renewal application build directly on our findings from previous project periods to move us closer to developing a full understanding of the nature of amblyopic vision loss. The proposed work strives to directly assess the neural mechanisms underlying amblyopia in awake, behaving nonhuman primates while they perform behavioral tasks that exemplify amblyopic losses in global form perception, natural image processing and visual attention. Since amblyopia is predominantly a disorder of spatial vision we plan to target the ventral cortical visual pathway. We plan to study higher-order visual functions that have been linked to neural activity in area V4 in primates. In Aim 1, we plan to use two assays of form perception: Glass pattern perception and radial frequency discrimination, to study both global form perception and shape discrimination losses. In Aim 2, we will evaluate the extent to which compromised discrimination of natural image statistics, which we have identified in amblyopia, affects the processing of natural images. In Aim 3, we will directly evaluate whether there is a neural deficit in attentional processing in amblyopia. The neural recordings will be conducted using multi-electrode “Utah” arrays placed in the near-foveal representation of area V4. We will use population decoding and correlational analyses to compare behavioral performance and neural activity between the eyes of amblyopes for the specific visual conditions we plan to study. The results will be used to evaluate and refine current thinking on the neural disorder underlying amblyopia. Our research will ultimately inform efforts to treat and prevent amblyopia development in children.