Timeline of human gestation from early cortical formation, including key developmental cellular processes and milestones, highlighting the development of abundant action potentials in the cerebral cortex . Bottom, ion channel genes (ATP1A3, SCN3A, GRIN1, and GRIN2B) implicated in cortical malformations (MCDs) all maintain high expression in the developing human cortex . The specified genes are representative and are not a comprehensive list.