1. Processing of Hippocampal Network Activity in the Receiver Network of the Medial Entorhinal Cortex Layer V
- Author
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Andrei Rozov, Franziska Lorenz, Märt Rannap, Alexei V. Egorov, Azat Nasretdinov, and Andreas Draguhn
- Subjects
0301 basic medicine ,Male ,Hippocampus ,Action Potentials ,Glutamic Acid ,Hippocampal formation ,Biology ,In Vitro Techniques ,Inhibitory postsynaptic potential ,03 medical and health sciences ,Glutamatergic ,Mice ,0302 clinical medicine ,Interneurons ,Cortex (anatomy) ,medicine ,Animals ,Entorhinal Cortex ,Research Articles ,Feedback, Physiological ,Neurons ,Neocortex ,General Neuroscience ,Excitatory Postsynaptic Potentials ,Electric Stimulation ,Electrophysiological Phenomena ,Mice, Inbred C57BL ,030104 developmental biology ,medicine.anatomical_structure ,nervous system ,Excitatory postsynaptic potential ,Memory consolidation ,Nerve Net ,Neuroscience ,030217 neurology & neurosurgery - Abstract
The interplay between hippocampus and medial entorhinal cortex (mEC) is of key importance for forming spatial representations. Within the hippocampal–entorhinal loop, the hippocampus receives context-specific signals from layers II/III of the mEC and feeds memory-associated activity back into layer V (LV). The processing of this output signal within the mEC, however, is largely unknown. We characterized the activation of the receiving mEC network by evoked and naturally occurring output patterns in mouse hippocampal-entorhinal cortex slices. Both types of glutamatergic neurons (mEC LVa and LVb) as well as fast-spiking inhibitory interneurons receive direct excitatory input from the intermediate/ventral hippocampus. Connections between the two types of excitatory neurons are sparse, and local processing of hippocampal output signals within mEC LV is asymmetric, favoring excitation of far projecting LVa neurons over locally projecting LVb neurons. These findings suggest a new role for mEC LV as a bifurcation gate for feedforward (telencephalic) and feedback (entorhinal–hippocampal) signal propagation.SIGNIFICANCE STATEMENTPatterned network activity in hippocampal networks plays a key role in the formation and consolidation of spatial memories. It is, however, largely unclear how information is transferred to the neocortex for long-term engrams. Here, we elucidate the propagation of network activity from the hippocampus to the medial entorhinal cortex. We show that patterned output from the hippocampus reaches both major cell types of deep entorhinal layers. These cells are, however, only weakly connected, giving rise to two parallel streams of activity for local and remote signal propagation, respectively. The relative weight of both pathways is regulated by local inhibitory interneurons. Our data reveal important insights into the hippocampal–neocortical dialogue, which is of key importance for memory consolidation in the mammalian brain.
- Published
- 2020