Rab18, a Ras-like small GTPase, is recently identified to negatively regulate the secretory pathway and is essential for neural development. Surprisingly, postpartum Rab18^-/- mice display higher rates of neonaticide and infanticide, suggesting that these mice have defects in maternal behaviors and might suffer from postpartum psychosis. Since adult neurogenesis is required for maternal behaviors and has anxiolytic effect, we hypothesize that Rab18 may regulate innate behaviors by controlling adult neurogenesis. In addition, we aim to study downstream signaling pathways of Rab18 in postnatal neural stem cells with Rab18 null mice and neural stem cell culture.