The dynamics of hippocampal encoding: beyond the spatial metaphor

Every animal on our planet wanders around when looking for something. Whether it is in search of food, a mate, or home, navigation is one of the most performed cognitive behaviors in Nature. Nevertheless, our understanding of how the brain is capable of solving such a simple problem − to move from one point to another − is still incomplete. The decomposition of navigation into cognitive components reveals the complexity of such behavior. To reach a goal, one has to first understand its current position, then to estimate the target position, followed by identifying a route towards the goal-location and, finally, to physically orchestrate a set of motor-actions leading to the desired location. Extensive research on the mammalian hippocampus has revealed its critical role in spatial navigation, memory, and learning. However, the mechanisms for spatial memory encoding, episodic representation, and their behavioral counterparts are still not fully understood. Moreover, we do not know if the mechanisms involved in spatial representation also scale up to conceptual representation from a purely spatial domain, such as task cognitive demands. In this thesis, we present a set of studies focused on spatial and cognitive representation in the insect and mammalian organisms. We show that the problem of spatial representation requires multi-level solutions working simultaneously: from biophysical neuronal mechanisms to behavioral aspects of navigation. Furthermore, with physiological studies of the human medial temporal lobe, we propose that the mechanisms involved in spatial representation also extend to higher-order cognitive representations, therefore suggesting that the hippocampus handles information that is dimension independent.