Functional interactions of prefrontal cortex and the hippocampus in learning and memory

The prefrontal cortex (PFC) is associated with executive function and the hippocampus with declarative and episodic memory. Yet both the PFC and the hippocampus are described as specialized for representing events that are extended in time (Wilson et al. Trends Neurosci 33:533-540, 2010) and encoding sequences of events that unfold over time (Eichenbaum, Neuron 44:109-120, 2004). Bidirectional interactions between the two structures in an intention-recollection cycle (cf. Fuster et al. Brain Res 330:299-307, 1995) may describe how their complementary and distinct functions contribute to goal-directed learning and memory. Beyond what, where, and when, the external facts that define episodes (Morris 2001), hippocampal representations include why and how. These internal features include outcome expectancies and abstract rules computed by the PFC, extracted from outcomes integrated across many behavioral episodes. PFC signals stored along with high-level percepts in hippocampal representations can therefore guide memory retrieval. Hippocampal signals relayed to the PFC let remembered events select associated goal, rule, and procedure representations. The bidirectional interactions associate individual items with multiple goals and individual goals with multiple items. By including outcome expectancies and abstract rules as episodic elements in a content-addressable memory system, an intention-recollection cycle reduces proactive interference and guides selective memory retrieval.