Dynamics of dentate gyrus-septal neuronal networks in the mouse

Marlene Bartos (PI), Federico Torelli

Our daily life depends on the processing and storing of the continuous stream of information which enables us to adapt our behavior to changes in our environment. It is therefore believed that during exploration of new environments, groups of coactive principal cells, the granule cells in the DG emerge during the learning process representing new memories. Inhibitory GABAergic interneurons are of key importance in the process of memory formation. Perisomatic inhibitory PV interneurons control the action potential output of principal cells and thereby contribute to the synchronization of cell assemblies and the generation of local fast brain rhythms such as gamma oscillations. In contrast, dendritic inhibitory SOM interneurons have been proposed to control synaptic plasticity at dendrites and to filter synaptic inputs to principal cells. Moreover, our preliminary data indicate that DG-SOM interneurons project over long distances to the medial septum and are targets of PV interneurons in the medial septum projecting back to the DG. Despite the broad knowledge of the interneuron types in the DG, little information is available on the functional contribution of perisomatic and dendritic inhibition to the control of granule cell activity patterns and to the formation of cell assemblies. Moreover, it is unclear how their activity is synchronized with theta oscillations driven by the medial septum. Here, we aim to address these fundamental questions by juxtacellular and whole-cell recording from identified DG-interneurons in head-fixed behaving mice. By recording optogenetically identified single GABAergic units as well as manipulating them by means of optogenetics, we will identify the role of interneurons in pattern separation.