What we know and do not know about the functions of the orbitofrontal cortex after 20 years of cross-species studies.

When Pat Goldman-Rakic described the circuitry and function of primate prefrontal cortex in her influential 1987 monograph (Goldman-Rakic, 1987), she included only a few short paragraphs on the orbitofrontal cortex (OFC). That year, there were only nine papers published containing the term "orbitofrontal," an average of less than one paper per month. Twenty years later, this rate has increased to 32 papers per month. This explosive growth is partly attributable to the remarkable similarities that exist in structure and function across species. These similarities suggest that OFC function can be usefully modeled in nonhuman and even nonprimate species. Here, we review some of these similarities.