Postnatal Development of Projections of the Postrhinal Cortex to the Entorhinal Cortex in the Rat

The ability to encode and retrieve contextual information is an inherent feature of episodic memory that starts to develop during childhood. The postrhinal cortex (POR), an area of the parahippocampal region (PHR), has a crucial role in encoding object-space information and translating egocentric to allocentric representation of local space. The strong connectivity of POR with the adjacent entorhinal cortex (EC), and consequently the hippocampus, suggests that the development of these connections could support the postnatal development of contextual memory. Here, we report that POR projections of the rat develop progressively from the first to the third postnatal week starting in the medial EC (MEC) before spreading to the lateral EC (LEC). The increased spread and complexity of postrhinal axonal distributions is accompanied by an increased complexity of entorhinal dendritic trees and an increase of postrhinal-entorhinal synapses, which supports a gradual maturation in functional activity.