Space, time and memory in the medial temporal lobe

This thesis focuses on memory and the representation of space in the medial temporal lobe, their interaction and their temporal structure. Chapter 1 briefly introduces the topic, with emphasis on the open questions that the subsequent chapters aim to address. Chapter 2 is dedicated to the issue of spatial memory in the medial entorhinal cortex. It investigates the possibility to store multiple independent maps in a recurrent network of grid cells, from a theoretical perspective. This work was conducted in collaboration with Remi Monasson, Alexis Dubreuil and Sophie Rosay and is published in (Spalla et al. 2019). Chapter 3 focuses on the problem of the dynamical update of the representation of space during navigation. It presents the results of the analysis of electrophysiological data, previously collected by Charlotte Boccara (Boccara et al., 2010), investigating the encoding of self-movement signals (speed and angular velocity of the head) in the parahippocampal region of rats. Chapter 4 addresses the problem of the temporal dynamics of memory retrieval, again from a computational point of view. A continuous attractor network model is presented, endowed with a mechanism that makes it able to retrieve continuous temporal sequences. The dynamical behaviour of the system is investigated with analytical calculations and numerical simulations, and the storage capacity for dynamical memories is computed. Finally, chapter 4 discusses the meaning and the scope of the results presented, and highlights possible future directions.