Anatomic basis of cognitive-emotional interactions in the primate prefrontal cortex

Recognition that posterior basal and medial parts of the prefrontal cortex belong to the cortical component of the limbic system was important in understanding their anatomic and functional organization. In primates, the limbic system has evolved along with the neocortex and maintains strong connections with association areas. Consequently, damage to limbic structures in primates results in a series of deficits in cognitive, mnemonic and emotional processes. Limbic cortices differ in their structure and connections from the eulaminate areas. Limbic cortices issue widespread projections from their deep layers and reach eulaminate areas by terminating in layer I. By comparison, the eulaminate areas receive projections from a more restricted set of cortices and when they communicate with limbic cortices they issue projections from their upper layers and terminate in a columnar pattern. Several of the connectional and neurochemical characteristics of limbic cortices are observed as a transient feature in all areas during development. Anatomic evidence suggests that limbic areas retain some features observed in ontogeny, which may explain their great plasticity and involvement in learning and memory, but also their preferential vulnerability in several psychiatric and neurologic disorders.