The entorhinal cortex (EC) is the major interface between the hippocampus and the neocortex. It channels multi-modal information into the hippocampus and relays most of its output to telencephalic structures. This unique position, together with its genuine function in sensory input integration and spatial orientation, makes the EC a key region for spatial cognition and context-dependent memory formation.

Understanding the function of the EC requires precise knowledge of its cellular constituents, local and long-range connectivity and state-dependent activity patterns. Knowledge of all these critical issues is far from complete, not at least due to the marked heterogeneity of entorhinal networks between dorsal/ventral and medial/lateral entorhinal regions. The symposium will elucidate recent progress in understanding the structure and function of entorhinal micro-networks, including.

• cell type-specific connectivity in defined layers of the EC;
• dorsal-ventral and medial-lateral differences of structure and function;
• connections between EC and subcortical or cortical networks;
• processing of patterned network activity within the EC.

Understanding the functional anatomy of the EC has been boosted by modern methods like cell-type specific connectivity studies using viral vectors, single and paired recordings from defined neuronal subtypes, and cell-specific optogeneticstimulation methods. Recent evidence suggests that neuronal activity is fed into specific, separate pathways within and between different entorhinal layers. The presence, relative weight, and overlap of these pathways vary along the dorsal-ventral and the medial-lateral axes of the hippocampal-entorhinal system. At the cellular level, it appears that different subtypes of principal cells and interneurons are differentially recruited by hippocampal, neo- and subcortical inputs which, in turn, affects activity patterns and signal propagation within the EC. The symposium will summarize the present state of knowledge on structure and function of entorhinal networks, focusing on (but not restricting itself to) the deep input-processing layers.

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