The orbitofrontal cortex (OFC) is a prefrontal cortex region in the frontal lobes of the brain which is involved in the cognitive process of decision-making. In non-human primates it consists of the association cortex areas Brodmann area 11, 12 and 13; in humans it consists of Brodmann area 10, 11 and 47. The OFC is functionally related to the ventromedial prefrontal cortex. Therefore, the region is distinguished due to the distinct neural connections and the distinct functions it performs. It is defined as the part of the prefrontal cortex that receives projections from the medial dorsal nucleus of the thalamus, and is thought to represent emotion, taste, smell and reward in decision-making. It gets its name from its position immediately above the orbits in which the eyes are located. Considerable individual variability has been found in the OFC of humans. A related area is found in rodents.
Structure The OFC is divided into multiple broad regions distinguished by cytoarchitecture, including Brodmann area 47/12, Brodmann area 11, Brodmann area 14, Brodmann area 13, and Brodmann area 10. Four gyri are split by a complex of sulci that most frequently resembles a "H" or a "K" pattern. Extending along the rostro-caudal axis, two sulci, the lateral and orbital sulci, are usually connected by the transverse orbital sulcus, which extends along a medial-lateral axis. Most medially, the medial orbital gyrus is separated from the gyrus rectus by the olfactory sulcus. Anteriorly, both the gyrus rectus and the medial part of the medial orbital gyrus consist of area 11(m), and posteriorly, area 14. The posterior orbital gyrus consists mostly of area 13, and is bordered medially and laterally by the anterior limbs of the medial and lateral orbital sulci. Area 11 makes up a large part of the OFC involving both the lateral parts of the medial orbital gyrus and the anterior orbital gyrus. The lateral orbital gyrus consists mostly of area 47/12. Most of the OFC is granular, although the caudal parts of area 13 and area 14 are agranular. These caudal regions, which sometimes include parts of the insular cortex, respond primarily to unprocessed sensory cues.
Connections The connectivity of the OFC varies somewhat along a rostral-caudal axis. The caudal OFC is more heavily interconnected with sensory regions, notably receiving direct input from the pyriform cortex. The caudal OFC is also the most heavily interconnected with the amygdala. Rostrally, the OFC receives fewer direct sensory projections, and is less connected with the amygdala, but it is interconnected with the lateral prefrontal cortex and parahippocampus. The connectivity of the OFC has also been conceptualized as being composed of two networks; an orbital network composed of most of the central parts of the OFC, including most of the areas 47/12, 13, and 11; a medial network composed of the medial most and caudolateral regions of the OFC, as well as areas 24, 25 and 32 of the medial prefrontal cortex. The medial and orbital networks are sometimes referred to as the "visceromotor network" and the "sensory network", respectively.
Afferents The OFC receives projections from multiple sensory modalities. The primary olfactory cortex, gustatory cortex, secondary somatosensory cortex, superior and inferior temporal gyrus (conveying visual information) all project to the OFC. Evidence for auditory inputs is weak, although some neurons respond to auditory stimuli, indicating an indirect projection may exist. The OFC also receives input from the medial dorsal nucleus, insular cortex, entorhinal cortex, perirhinal cortex, hypothalamus, and amygdala.
Efferents The orbitofrontal cortex is reciprocally connected with the perirhinal and entorhinal cortices, the amygdala, the hypothalamus, and parts of the medial temporal lobe. In addition to these outputs, the OFC also projects to the striatum, including the nucleus accumbens, caudate nucleus, and ventral putamen, as well as regions of the midbrain including the periaqueductal gray, and ventral tegmental area. OFC inputs to the amygdala synapse on multiple targets, including two robust pathways to the basolateral amygdala and intercalated cells of the amygdala, as well as a weaker direct projection to the central nucleus of the amygdala.
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