SUMMARY The goals and specific aims of the present Administrative Supplement application are unchanged with respect to the parent R01 award. Here we request additional funds for unanticipated expenses within the original scope of the project. In the original application we proposed to investigate the anatomical and functional organization of V2-to-V1 feedback (FB) circuits arising from, and terminating in specific cortical layers in macaque monkeys. At the time we submitted the parent R01 application, we could obtain non-naïve macaque monkeys at a cost of approximately $2,000 per animal. Due to a country-wide shortage of macaque monkeys, we can no longer obtain these non-naïve monkeys, and the current price for a cynomolgus macaque is $23,500 per animal (including shipping). This requires significant additional costs, which we cannot cover with the funds awarded. Therefore, with the present Supplement application we request additional funds to cover the increased costs of the animals, which are necessary to carry out the proposed studies.