Somatic disinhibition of granule cells improves information transmission and pattern separation in the dentate gyrus

Abstract

Cortical circuits operate in a tight excitation/inhibition balance. This balance is relaxed during learning processes, but neither the mechanism nor its impact on network operations are well understood. In the present study, we combined in-vivo and in-vitro neuronal recordings with computational modelling and demonstrated that synaptic plasticity in the afferents from the entorhinal cortex (EC) to the dentate gyrus (DG), in addition to strengthening the glutamatergic inputs into granule cells (GCs), depressed perisomatic inhibition. Computational modelling revealed a functional reorganization in the inhibitory network that explained several experimental findings, including depression of the feed-forward inhibition. In vitro results confirmed a perisomatic dominance of the inhibitory regulation with important functional consequences. It favoured GCs burst firing, improved reliability of input/output transformations and enhanced separation and transmission of temporal and spatial patterns in the EC-DG-CA3 network.