Monosynaptic Inputs from Pre- and Parasubiculum Converge on Medial Entorhinal Cortex Principal Neurons

Interactions between the medial entorhinal cortex (MEC), presubiculum (PrS), and parasubiculum (PaS), all essential components of the hippocampalparahippocampal navigational system, are still poorly understood. The PrS and PaS are credited to provide directional information to MEC. Efferents from PrS and PaS show a laminar specific terminal distribution in MEC superficial layers, where they also contact apical dendrites of layer V neurons. Since spatially modulated neurons are present in all layers we tested whether principal neurons in all layers of MEC receive both inputs monosynaptically. Using a newly developed anatomical-electrophysiological slice approach, we show that principal neurons in all layers of MEC receive convergent monosynaptic inputs from PrS and PaS. Responses are layer specific and input frequency dependent. These results suggest that neurons in different layers of MEC uniquely process the same inputs, likely contributing to reported differences in their in vivo properties. Inputs converge in medial entorhinal cortex  141