The Hippocampal-Cortical Networks Subserving Episodic Memory and Its Component Memory Systems for Object, Place and Temporal Order

We here review the status of research on the neurobiological mechanism of episodic memory as defined by an integrated memory of the experience of an object or event, in a particular place and time. A particular focus is the development of an animal model of episodic-like memory which combines the novel object preference test (what), the novel location preference test (where) and test for temporal order (when) (Kart-Teke et al., 2006). Behavioural, electrophysiological, imaging and lesion studies have shown that the prefrontal cortex (PFC), hippocampus and interconnected neural areas, such as the lateral entorhinal cortex, are implicated in the processing of memories for what, where or when. We ask whether the integration of memories for “what” “where” and “when” into episodic-like memory and its component memory systems for event, place and time of occurrence are dependent on these circuits. The prefrontal cortex processes what and where information and assists for the associated memories. The lateral entorhinal cortex is critical for the processing of object-related associative information but not object identity itself. The hippocampus is essentially involved in what, where and when memories. Thus, we focus on the roles of the PFC, hippocampus and lateral entorhinal cortex in the processing of episodic-like memory. Disconnection studies show that interactions between the PFC and hippocampus (CA1/CA3) and the interplay of the PFC and lateral entorhinal cortex are critical substrates for the establishment of an integrated episodic-like memory. We delineate a detailed neuronal network of episodic-like memory which includes these structures in the integration of memories for “what” “where” and “when” as prototype of episodic memory.