The dentate gyrus (DG) plays a key role in the emergence of spatial and contextual map representation within the hippocampus during learning. Granule cells (GCs) of the DG receive their major spatial cortical input from the medial entorhinal cortex (MEC) via the perforant path. To determine whether inputs from the MEC (in particular layer II stellate cells) play a role in the capacity of the DG to differentiate between different environments, we aim to modulate their activity using DREADDs. Thanks to these pharmacogenetic tools, we can de- or hyper-polarize MEC-layer II stellate cells during exploration of familiar and novel environments and test the impact of this manipulation on GCs spatial representation. Using 2- Photon in vivo calcium imaging to capture GCs activity, we plan on casting light on the implication of MEC layer II cells in the emergence of the spatial representation of a novel environment in the hippocampus. Our preliminary results suggest that depolarization of MEC layer II cells results in a marked reduction (i.e. silencing) of the activity of the GCs that were showing place fields under baseline conditions, while a new, smaller sub-population of GCs would become active. On the other hand, hyperpolarization of MEC layer II cells would elicit milder effects on GCs, including a reduction in the activity rate, but no global remapping. These data confirm the importance of MEC layer II cells in the emergence of DG spatial maps and reveal their crucial role in ensuring the stability over time of these hippocampal representations.