Networks within the orbital and medial prefrontal cortex

The orbital and medial regions of the prefrontal cortex (OMPFC) can be divided into at least 22 architectonic areas, based on differences in staining with a number of methods and on differences in connections. The connections of these areas indicate that they can be divided into two interconnected groups or networks. The orbital network includes most of the areas on the orbital surface, and receives inputs from several sensory modalities that appear to be related to food or feeding. The medial network includes areas on the medial surface, and a few orbital areas. It provides output to visceromotor control areas in the hypothalamus and periaqueductal gray. Both networks have substantial interconnections with limbic structures, including the amygdala and hippocampal formation, suggesting that the OMPFC is involved in affective as well as sensory and visceromotor functions. This is strengthened by imaging studies of mood disorders in humans, which indicate that areas within the OMPFC have abnormal activity (either increased or decreased) in patients with familial major depressive disorder and bipolar disorder.