Monday, August 23, 2010

Entorhinal Cortex

The entorhinal cortex is situated in the medial temporal lobe. It functions as a hub in a widespread network for memory and navigation. The entorhinal cortex is the main interface between the hippocampus and neocortex. The EC-hippocampus system plays an important role in autobiographical/declarative/episodic memories and in particular spatial memories including memory formation, memory consolidation, and memory optimization in sleep. The EC is also responsible for the pre-processing (familiarity) of the input signals in the reflex nictitating membrane response of classical trace conditioning, the association of impulses from the eye and the ear occurs in the entorhinal cortex.

The entorhinal cortex functions as a relay station, linking the hippocampus with the cerebral cortex. It is through the entorhinal cortex that the hippocampus maintains interconnections with the neocortical multi-modal associations areas of the temporal, frontal, and parietal lobes. The superficial layers - layers II and III - of EC project to the dentate gyrus and hippocampus: Layer II projects primarily to dentate gyrus and hippocampal region CA3; layer III projects primarily to hippocampal region CA1 and the subiculum. These layers receive input from other cortical areas, especially associational, perirhinal, and parahippocampal cortices, as well as prefrontal cortex. EC as a whole, therefore, receives highly-processed input from every sensory modality, as well as input relating to ongoing cognitive processes.