Final Report Summary - GABACELLSANDMEMORY (Linking GABAergic neurones to hippocampal-entorhinal system functions)
As often in science, during the course of the planned experiments we made unexpected findings that opened an entirely new avenue of research. Thus, based on virus-mediated tracing, we discovered a new type of GABAergic neurons, namely long-range GABAergic neurons that diverge from the classical “interneuron” phenotype, i.e. Their axon does not arborize locally but projects to remote brain areas. Using optogenetics in vitro and in vivo, we functionally characterized long-range GABAergic neurons and came to the conclusion that by virtue of their connectivity – they inhibit preferentially local interneurons in the target area - they are ideally suited to synchronize remotely located networks.
Also based on optogenetics, we characterized local and distant connectivity of defined neuronal cell types in the medial and lateral entorhinal cortex and revealed principles of connectivity that were known only in part or not at all. Of note, GABAergic interneurons mediate most of the local connectivity between excitatory cell types in the superficial layers of the medial entorhinal cortex. The data obtained in the course of this grant, with a special focus on GABAergic interneurons and projection neurons, is essential for understanding spatial coding and spatial memory.