Chapter 4 - Rhinal and medial prefrontal cortices

Summary

This chapter describes the structure and connections of the rhinal cortices and medial prefrontal cortex. We focus on this particular subset of cortical areas because they play a key role in the formation of declarative memories. Indeed, the rhinal cortices are the gateway to and from the hippocampal formation. However, the available evidence suggests that they are not simple relays but instead filter or select inputs. Although the computational rules underlying this function still elude us, it is clear that this process is altered in emotionally arousing conditions. Indeed, memory formation for emotional charged material is generally improved and much evidence suggest that inputs from the amygdala and medial prefrontal cortex mediate this facilitation of memory by emotions. This chapter summarizes data about the structure, connectivity, and physiological properties of these cortical regions. How they interact in memory formation will be considered in Chapter 9.

Cytoarchitectural organization and cell types

Rhinal cortices

The rhinal cortices occupy a strategic location in the temporal lobe because they relay most sensory inputs from the neocortex to the hippocampus. Moreover, the rhinal cortices represent the main return path for hippocampal efferents to the neocortex (reviewed in Witter et al., 2000). Although their precise contribution, compared with that of the hippocampus, remains debated (Brown & Aggleton, 2001), it is clear that the rhinal cortices are not simple relay stations. Indeed, rhinal neurons exhibit patterns of memory-related activity distinct from those seen in the hippocampus (reviewed in Suzuki, 1996; Eichenbaum, 2002).