Sonic hedgehog expression in corticofugal projection neurons directs cortical microcircuit formation. Harwell CC, Parker PRL, Gee SM, et al. Sonic hedgehog expression in corticofugal projection neurons directs cortical microcircuit formation. Neuron. 2012;73(6):1116-26. doi:10.1016/j.neuron.2012.02.009 Read more