Identified neuronal ensembles subserving spatial coding in the medial entorhinal cortex

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Local and distant input control medial entorhinal cortex excitation.

The activity of spatially-tuned excitatory neurons in the hippocampal-entorhinal formation – i.e. place cells in the hippocampus and grid cells in the medial entorhinal cortex (mEC) – is a prerequisite for the generation of spatial maps. The mechanisms underlying the generation of spatial representations are not known, but are likely to depend on the interaction between excitatory and inhibitory neurons within local microcircuits in the hippocampus and mEC, as well as the interaction between these two brain regions.

Here we propose to employ tracing studies and in vitro electrophysiological investigations to characterize the connectivity between modularly structured neuronal ensembles in the mEC. Furthermore, we will perform photostimulation-assisted neuronal excitation and inhibition in freely moving mice to study the role of defined excitatory neurons in microcircuits of the mEC and their contribution to the generation of local grid cells and hippocampal place cells.

The scheme shows the hippocampus in grey with the firing field of a place cell, and the medial entorhinal cortex in green with modularly organized structures comprising grid cells and interneurons. Examples of firing fields and peristimulatiom histograms for the two cell types are shown in the magnified module on the right, and representative action potential firing for an interneuron and an excitatory cell to the right of the module below. Question marks denote putative connections that will be characterized in vitro and in vivo.
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*Principal investigators of other projects within the CRC