PROJECT SUMMARY The visual system encodes visual stimuli in a temporally dynamic fashion, where certain aspects of a stimulus are processed before others. A prime example of this trend is the spatial frequency (SF) tuning of individual neurons in the primary visual cortex (V1). These cells are initially tuned to prefer coarse stimuli of lower SF; however, throughout their brief responses their tuning profiles shift to preferring finer, high SF stimuli. This coarse-to-fine pattern of SF processing has been found in mice, cats, non-human primates and humans, suggesting it may be a fundamental property of spatial vision. Despite this, it is unclear whether this process develops postnatally in an experience-dependent fashion, like many other aspects of spatial vision. Furthermore, the neural circuits and mechanisms underlying coarse-to-fine SF processing are not well understood. To begin to understand the development of and neural circuitry behind coarse-to-fine SF processing, the investigator will study this temporally dynamic process throughout development of the mouse primary visual system. First, the investigator will characterize coarse-to-fine SF processing in V1 throughout early postnatal life and test the role of visual experience in driving this development. This will be done by using multichannel extracellular recordings in mice at key developmental ages as well as in dark-reared adult mice. Second, the extent to which coarse-to-fine SF processing is cortically derived will be determined by recording from the dorsal lateral geniculate nucleus (dLGN) and superior colliculus (SC) of adult mice. The role of descending cortical feedback will also be tested by chemically silencing the cortex while recording from these subcortical structures. Finally, the investigator will assess why cortical circuits develop coarse-to-fine SF processing by determining if this temporally dynamic process enables the efficient coding of natural images. Collectively, these results will provide novel and important information regarding the postnatal development of coarse-to- fine SF processing throughout the primary visual pathway and will begin to unveil how this process relates to coding complex natural images. Moreover, the research plan described within will provide the applicant with the additional technical, conceptual, computational and scientific training needed to be a competitive, independent scientist. Finally, the proposed research will take place in a stimulating scientific environment with all the resources required to see this project to completion. This collaborative scientific community is strongly supportive of the proposed research and its success.