Functional structure of the intermediate and ventral hippocampo–prefrontal pathway in the prefrontal convergent system

• We focus on the regional differentiation of the hippocampo–prefrontal pathway.
• The pathway consists of the intermediate/ventral routes in short-term plasticity.
• Each route is involved in a different behavioural role in working memory.
• The two routes interact at the prefrontal cortex in short/long-term plasticity.
• Hippocampal regional information is processed into the prefrontal convergent system.

The hippocampo–prefrontal pathway is a unique projection that connects distant ends of the cerebral cortex. The direct hippocampo–prefrontal projection arises from the ventral to intermediate third of the hippocampus, but not from the dorsal third. It forms a funnel-shaped structure that collects information from the large hippocampal area and projects it to the prefrontal cortex. The anatomical regional differentiation of the projection has not been described. The hippocampal region is differentiated into structural and behavioural roles. For example, it has been shown that the ventral, but not the dorsal, hippocampus reciprocally connects with the amygdala and influences emotional behaviours. These data imply that hippocampal variation along the dorso–ventral axis is contained within the hippocampo–prefrontal pathway. Here, we present electrophysiological studies that demonstrate regional differences in short- but not long-term plasticity in the intermediate/posterior-dorsal and ventral routes of the hippocampo–prefrontal pathway. Furthermore, behavioural studies revealed that each route appears to play a different role in working memory. These results suggest that hippocampal regional information is processed through different routes, with the integration of individual regulatory functions in the prefrontal convergent system.