Cingulate cortex

The cingulate cortex is a part of the brain situated in the medial aspect of the cortex. It is extended from the corpus callosum below to the cingulate sulcus above, at least anteriorly.

History
Cingulum means belt in Latin. The name was likely chosen because this cortex, in great part, surrounds the corpus callosum. Cingulate is an adjective (cingularis or cingulatus). The cingulate cortex is a part of the "grand lobe limbique" of Broca (1898) that consisted (in addition to the olfactory part, which is no more considered there today) of a superior cingulate part, supracallosal; and an inferior hippocampic part, infracallosal. The limbic cortex was separated from the remainder of the cortex by Broca for two reasons: first that it is not convoluted, and second that the gyri are directed parasagitally (contrary to the transverse gyrification). Since the parasagittal gyrification is observed in non-primate species, the limbic lobe was thus declared to be "bestial". As with other parts of the cortex, there have been and continue to be discrepancies concerning boundaries and naming. Brodmann (1909), a student of C. and O.Vogt, who worked on cercopithecus (and not much in human (Bailey and von Bonin)), elaborated a system of numeration that had unfortunately no typological logics (1, 2 and 3 are sensory, 4 is motor, 5 is parietal, 6 is premotor and 7 is again parietal!). Area 25 was even not placed by him in the same place in the human brain. Area 24 (anterior) was distinguished from 23 (posterior) on the basis that it was agranular. More recently, the typographical von Economo's system was adopted by Bailey and von Bonin. Simple typographical naming should be preferred, for evident heuristic purposes.

Subdivisions
Based on cytoarchitectonics it has been divided into the Brodmann areas 23, 24, 26, 29, 30,  31 and 32. The areas 26, 29 and 30 are usually referred to as the retrosplenial areas.

Anterior cingulate cortex
This corresponds to the area 24 of Brodmann LA of von Economo and Bailey and von Bonin. It is continued anteriorly by the subgenual cortex (area 25). It is cytoarchitectonically agranular. It has a gyral part on the surface and a sulcal part. Anterior cingulate cortex can further be divided in the perigenual anterior cingulate cortex and midcingulate cortex. The anterior cingulate cortex receives primarily its afferent axons from the anterior nucleus (nucleus anterior of the thalamus, see thalamus). The nucleus anterior receives mamillo-thalamic afferences. The mamillary neurons receive axons from the subiculum. The whole forms a part of Papez' circuit.The anterior cingulate cortex sends axons to the anterior nucleus and through the cingulum to other Broca's limbic areas.

Posterior cingulate cortex
Corresponds to area 23 of Brodmann, LP of von Economo and Bailey and von Bonin. It is granular. It is followed posteriorly by the retrosplenial cortex (area 29). Dorsally is the granular area 31. The posterior cingulate cortex receives a great part of its afferent axons from the superficial nucleus (or nucleus superior- falsely LD-) of the thalamus (see thalamus), which itself receives axons from the subiculum. To some extent it thus duplicates Papez' circuit. It receives also direct afferents from the subiculum of the hippocampus.

Cingulum and interconnections
At the base of the cingulate cortex is a thick parasagittal bundle, strongly increasing in evolution, the cingulum. In humans, it can even be dissected. The cingulum is used for the connections of the 2 above described subdivisions and with the parahippocampic gyrus

Cingulate cortex can also be differentiated based on its thalamic connections1: midlline and intralaminar nuclei.