The mammalian cerebral cortex was subject to a dramatic expansion in surface area during evolution. This process is recapitulated during development and is accompanied by folding of the cortical sheet, which allows fitting a large cortical surface within a limited cranial volume. A loss of cortical folds is linked to severe intellectual impairment in humans, so cortical folding is believed to be crucial for brain function. However, developmental mechanisms responsible for cortical folding, and the influence of this on cortical function, remain largely unknown. The goal of this proposal is to understand the genetic and cellular mechanisms that control the developmental expansion and folding of the cerebral cortex, and what is the impact of these processes on its functional organization. Human studies have identified genes essential for the proper folding of the human cerebral cortex. Genetic manipulations in mice have unraveled specific functions for some of those genes in the development of the cerebral cortex. But because the mouse cerebral cortex does not fold naturally, the mechanisms of cortical expansion and folding in larger brains remain unknown. We will study these mechanisms on ferret, an ideal model with a naturally folded cerebral cortex. We will combine the advantages of ferrets with cell biology, genetics and next-generation transcriptomics, together with state-of-the-art in vivo, in vitro and in silico approaches, including in vivo imaging of functional columnar maps. The successful execution of this project will provide insights into developmental and genetic risk factors for anomalies in human cortical topology, and into mechanisms responsible for the early formation of cortical functional maps.