Diversity of mnemonic function within the entorhinal cortex: a meta-analysis of rodent behavioral studies

The entorhinal cortex (EC) has been shown to be an integral piece of the hippocampal memory system. It sits in a unique position within the brain with strong, intricate, reciprocal connectivity with the hippocampus as well as a vast array of neocortical regions. Topographical patterns of afferent and efferent projections suggest that the EC can be divided into the medial and lateral regions, each of which can be further divided into dorsal, intermediate, and lateral bands. These EC sub-regions, with variable anatomical features, indicate a multifaceted role of the EC in memory processing. The present article reviews rodent behavioral studies which tested the effect of manipulation to EC sub-regions in several different memory paradigms. An analysis of the specific targets of EC manipulations reveals an important role of the caudomedial EC for spatial memory. In recognition memory paradigms, damage to the lateral EC impairs recognition of the combined information of objects, locations, and environmental contexts relevant to the content of an experience; whereas damage to medial EC preferentially impairs the recognition of the spatial arrangement of objects relevant to the spatial location of an experience. Fewer studies have examined the impact of EC manipulations on contextual memory and temporal associative memory, the results of which are fairly conflicting and possible confounds are explored. Our summary provides further support for the functional dissociation within the EC for learning and memory and generates several ideas for future investigations.