Critical periods for integration and functional activation of new neurons in the accessory olfactory bulb of adult female mice.

Stem cells of the subventricular zone (SVZ) produce neuronal precursors able to reach the main MOB) and the accessory olfactory bulb (AOB). In the AOB of adult female mice, the survival of these neurons increases after chronic exposures to male soiled bedding. After one month, new neurons are functionally integrated into the AOB circuitry, but it remains unclear when these cells are preferentially recruited into adult circuits and whether they support any specific sensory function. To investigate these questions, we analyzed the sensory-driven positive selection of newborn AOB granule cells in adult females after exposure to soiled bedding. We found that AOB newborn cells undergo positive selection by short-term exposure to male pheromones one week after their genesis. To determine whether and when newly generated AOB cells become involved in the processing of male individual stimuli, we quantified the percentage of newly-generated neurons activated by familiar or unfamiliar male bedding. We found that AOB newborn cells are specifically recruited shortly and transiently after their integration by experienced male individual pheromones; this functional recruitment is specific for newly born neurons, as older ones do not show a similar response. Moreover, we show that after this sensory driven neurogenic response the activity of the vomeronasal system induced by pheromones is attenuated. Taken together these results suggest that AOB new granule cells are likely to gate important individual odour information to brain centres related to the vomeronasal pathway.