Role of orbitofrontal cortex connections in emotion.

The orbitofrontal cortex is extensively connected with diverse neural areas that underlie its participation in emotional function. It receives extensive sensory input and sends output to areas important for emotional processing and expression, including medial temporal cortical areas, hypothalamic and brain stem autonomic areas, and the amygdala. In the rat, the functional relationship between the orbitofrontal cortex and amygdala has been investigated in numerous recent studies. Clearer understanding of the complex connections between the rat orbitofrontal cortex and the amygdala is fundamental to elucidating the functional contributions of these pathways. Recent work shows that, as in the primate, the subdivisions of the rat orbitofrontal cortex issue different patterns of projections to the amygdala, with intriguing variations in the relative distribution of projections to the sensory-related basal areas compared with output areas, such as the central nucleus. Notably, as has been observed in the monkey, the rat orbitofrontal cortex targets the intercalated nuclei, which contain GABAergic interneurons and provide local inhibitory influences within the amygdala. The complex connections between the orbitofrontal cortex and the amygdala, as well as other areas involved in emotion, suggest important implications for the role of the orbitofrontal cortex in anxiety disorders, in which emotional expression is not appropriate to the situation.