In mammals, new neurons are recruited into restricted brain areas throughout life. Adult-born neurons produced in the subventricular zone of the lateral ventricle migrate rostrally towards the olfactory bulb. Although thousands of neurons reach this central structure every day, the functional impact of their integration into mature circuits remains a matter of debate. Recent investigations have revealed no striking sensory deficits per se when adult bulbar neurogenesis is challenged. However, some cognitive functions, such as perceptual learning and olfactory memory, are clearly impaired. In this review we highlight the role of network activity in shaping ongoing neurogenesis and, in turn, how the integration of adult-born neurons refines pre-existing network function, and consequently olfactory behavior.