PROJECT SUMMARY ABSTRACT Early infancy and childhood are periods of substantial neural and perceptual maturation. It is thought that much of the unfolding of visual function occurs hierarchically, from early stages of the visual pathway to decision processes and motor output. Nonetheless, the temporal correlation between behavioral and neural maturation is weak and the limiting factors on visual development still remain elusive. Recent findings suggest that functional changes in areas downstream of primary visual cortex (V1), such as V2 and V4 may give rise to progressively more complex visual abilities with age. However, the relationship between behavioral and neural development has only previously been assessed using metrics of basic spatial vision. Higher-order visual abilities like form perception, object identification, and figure-ground segregation develop later than basic spatial vision and likely depend on the function of areas beyond V1. In addition to changes at the level of individual neurons, it is possible that perceptual improvement during development may depend on the refinement of functional interactions between cortical neurons. This possibility has not previously been examined. To obtain a clearer picture of potential factors limiting visual function throughout development, I propose to characterize: a) perceptual and neuronal sensitivity to global form stimuli during development, and b) the pattern of correlated variability within neural populations in V1 and V4. For my first aim, I will use a recently developed, quick visual discrimination task to assess perceptual sensitivity to global form stimuli across development. In Aim 2, multi-electrode recordings will be made in V1 and V4 simultaneously after the first behavioral data collection phase for Aim 1. In Aim 2a, neuronal responses to radially modulated stimuli will be used to track the developmental time course of global form sensitivity in each visual area. In Aim 2b, I will establish whether the magnitude and pattern of correlated variability shifts with developmental time. For this investigation, I will use a limited set of interleaved, oriented grating stimuli to document any changes in correlated firing with age. I will then evaluate the ability of a standard decoder to correctly classify visual stimuli in the presence or absence of correlational structure in the data. Together, these experiments will provide important insight into the neural mechanisms underlying visual maturation and their relationship to perceptual improvement.