The hippocampus is one of two regions in the adult mammalian brain that continues to generate new neurons in adulthood and throughout life. Despite the small number of new neurons generated, they contribute enhanced hippocampal long-term potentiation and are necessary for certain forms of animal behavior such as contextual fear learning and behavioral response to antidepressant treatments. This thesis discusses how antidepressant treatments and neurotrophic factors influence the functional integration of adult-born hippocampal neurons, and in turn impact behavior. Specifically, chronic antidepressant treatment accelerates the maturation of newborn neurons and stimulates a form of hippocampal long-term potentiation that is dependent upon neurogenesis. In addition, cell-autonomous TrkB signaling in adult progenitors and newborn neurons influences the long-term survival of new neurons, their ability to exhibit long-term plasticity, animal behavior in contextual fear conditioning and anxiety-like behavior in response to stress. Furthermore, cell-autonomous TrkB signaling in adult progenitors and newborn neurons mediates the antidepressant-induced acceleration of maturation and enhanced survival of new neurons. Overall, these findings offer insight into how functional integration of adult-born hippocampal neurons influences an animal's behavior, and may uncover ways to develop better and faster acting antidepressant treatments.