Adult born granular neurons functionally integrate into the hippocampal network developing a specific response to spatial exploration when mature. This specific response to spatial exploration appears about 30 days after the neurons were born. This functional integration of adult born neurons into the behavioral relevant network resembles their functional and anatomical maturation process observed during the critical time for their survival, which occurs in the first 6 weeks after cell division. By comparing the recruitment probability of adult born neurons at some time points after their birth and including the different neurogenesis rates throughout the animal's life span, we developed a mathematical model suggesting that the contribution of adult born neurons to spatial information processing is highly relevant particularly at early adulthood. This model was partially confirmed by a study done in young and old rats, where we observed that even-though the rate of neurogenesis is significantly reduced in old rats, the likelihood of a mature (4 months old) new born neuron to be recruited by spatial exploration is the same between old and young animals. Finally, recent experimental evidence indicated that adult born neurons are preferentially recruited into circuits that process information about familiar objects presented shortly after learning, and that the recruitment probability of new neurons into familiar object representations is negatively correlated with the behavioral efficiency of the animal. Moreover, we had obtained evidence that spatial and object information processing recruits different new neuron populations, tagged at different periods of the animal's life. Altogether these results are contributing to develop our understanding of the role of adult born neurons in hippocampal information processing.