"This proposal will elucidate the circuit mechanism that underlies the spatial memory-related information processing in the interconnected brain areas of the hippocampus and entorhinal cortex (EC). Both of these areas are implicated in spatial memory and encode spatial information in neuronal activity patterns. The mechanisms underlying the emergence and coordination of spatial memory-related activity in these regions are needed to understand how these circuits process mnemonic information. Accordingly, here we aim at elucidating the representation of spatial memory by investigating these mechanisms at the circuit and synaptic levels of organisation. The first objective of this proposal is to characterise oscillatory synchronisation in hippocampo-EC circuits at different stages of memory processing. We hypothesise that network oscillations facilitate circuit interactions during memory processing. Therefore, using optogenetic techniques to disrupt oscillations, we aim at identifying critical periods during mnemonic processing when synchronisation is needed. Secondly, we intend to reveal how mnemonic information is encoded and exchanged between different areas of the hippocampo-EC system. We will test whether spatial memory-associated firing of dorsal hippocampal cells could be triggered by EC and/or ventral hippocampal cells that encode similar mnemonic features. In addition, this project will explore the role of temporal coding in the representation and consolidation of spatial memory traces. The third objective will investigate synaptic changes between connected CA3-CA3 and CA3-CA1 cell pairs during spatial learning. We will use cross-correlation analysis and electrical microstimulation to examine the rules that govern changes in synaptic efficacy by observing the probability of spike transmission.Overall, the proposal provides a comprehensive approach to understanding how hippocampo-EC circuits organise and store information during mnemonic processes."