Prefrontal cortex is not functionally uniform. Major subdivisions are the dorsolateral prefrontal region and the orbitofrontal cortical region (OFC). Dorsolateral prefrontal cortex has reciprocal projections to and from other neocortical association cortices, limbic structures such as the hippocampus (via the cingulate cortex and ventral prefrontal cortex), and diencephalic regions (eg, lateral regions of the dorsomedial thalamic nucleus, as well as to ventral and anterior thalamic areas) (Fuster 1997). Dorsolateral prefrontal cortex has non-reciprocal efferent connections with basal ganglia sites, sending fibers to the anterolateral portion of the head of the caudate nucleus. The dorsolateral prefrontal cortex is a primary neocortical target of ascending dopaminergic innervation; an ascending catecholaminergic pathway originating in the midbrain ventral tegmental area also projects onto dorsolateral prefrontal sites (for reviews, see Oscar-Berman et al 1991; Panksepp 1998). Neuroanatomical connections with OFC parallel those of dorsolateral cortex, but the two systems are distinctly different. Primary OFC connections are with the medial thalamus (the magnocellular region of the dorsomedial nucleus), the hypothalamus, the ventrolateral portion of the head of the caudate, and the amygdala (Fuster 1997). The OFC
