Figure 4.

Circuit model for context-guided memory retrieval and schema formation. Cortical inputs arrive to the hippocampus via the rhinal cortices in which there are partially segregated “what” and “where” processing streams, labeled ‘item dominated’ and ‘place dominated’, respectively. In general, there is a large degree of inhibition preventing the flow of information into the hippocampus. However, when the rhinal activity is coincident with inputs from the prefrontal cortex, the ‘prefrontal gate’, information can arrive into the hippocampus and therefore shape the hippocampal memory space. In the dorsal hippocampus, the sparse representations favor representations for more specific episodes, while the denser representations observed more ventrally are more suitable for generalization – this is the context code. The strong monosynaptic connections from the ventral hippocampus to the prefrontal cortex provide a contextual signal which can then trigger activation of the context-appropriate rules for memory retrieval stored in the prefrontal cortices.