Selectivity of dendritic inhibition in the medial entorhinal cortex
The medial entorhinal cortex (MEC) comprises a large variety of functionally distinct neurons that are organized in a layer-specific manner. For example, grid cells are most abundant in LayerII, whereas cells responsible for working memory has been shown in LayerIII-V. Little is known, however, about how the GABAergic inhibitory circuits in the MEC support this allocation of tasks to different layers. Here, we reveal that the dendrite-targeting, somatostatin (SOM)-expressing GABAergic interneurons in the MEC are well suited to differentially modulate specific cell types, meanwhile parvalbumin expressing fast spiker interneurons inhibit all principal cells equally. Specifically, we show that SOM cells generate a strong, long-lasting inhibition on LayerIII-V pyramidal cells via combined GABAergic and somatostatinergic action, but only moderately control LayerII stellate and pyramidal cells. This specific inhibitory network motif is able to modulate working-memory formation processes without affecting grid-cell formation in superficial layers.