What are the systems-level mechanisms allowing for formation of memories? The conceptual picture that emerges is that the representation of a novel object or event is incorporated into representation of the spatio-temporal context in the hippocampus, a structure critical for memory. The accepted broad mechanistic framework for this process is that perceived information about the world is transferred from multimodal neocortical areas to the hippocampal region where it is actively encoded for future use or long-term storage. Both transfer of information to and encoding in the hippocampus relies on the external sensory inputs and internal network dynamics, which both change with animal behaviour. However the quantitative link between diverse exploratory behaviour that rodents use to actively sample external sensory inputs during learning, oscillatory network dynamics that controls information flow and hippocampal encoding and population activity of hippocampal neurons is not established. We use marker-based high-resolution tracking of the rat biological motion to quantitatively and objectively segment and classify its exploratory behaviour. We combine behaviour analysis with state-of-the-art multichannel extracellular recording of populations of hippocampal neurons and oscillatory dynamics in entorhino-hippocampal circuits. In the talk I will present our recent advances along two directions. First, we show that population activity of hippocampal neurons is changing dynamically with changes of exploration modes. Second, we identify and characterize diverse local and global synchronization dynamics across entorhinal-hippocampal circuits.
Taken together the constraints imposed by spontaneous exploratory behaviour and network dynamics on activity of hippocampal neurons give rise to an important temporal framework for the analysis of the mechanisms of memory encoding.