The general objective of this plan is to study the differences of the DGCs along their own neuronal age on the neuronal synchrony of hippocampal circuit during exploratory behavior of novel and familiar spatial contexts of adult mice. We will combine optogenetics and electrophysiology in vivo techniques to study the electrical field activity of the neuronal hippocampal population together with the fire of the single units during behavior. We will perform longitudinal studies opto-stimulating or opto-silencing a specific cohort of DGCs to address the differential role of the same adult born DGCs at different neuronal developmental stages in the same adult mice.