The posterior cingulate cortex (PCC) is the caudal part of the cingulate cortex, located posterior to the anterior cingulate cortex. This is the upper part of the "limbic lobe". The cingulate cortex is made up of an area around the midline of the brain. Surrounding areas include the retrosplenial cortex and the precuneus.
Cytoarchitectonically the posterior cingulate cortex is associated with Brodmann areas 23 and 31.
The PCC forms a central node in the default mode network of the brain. It has been shown to communicate with various brain networks simultaneously and is involved in diverse functions. Along with the precuneus, the PCC has been implicated as a neural substrate for human awareness in numerous studies of both the anesthetized and vegetative (coma) states. Imaging studies indicate a prominent role for the PCC in pain and episodic memory retrieval. Increased size of the ventral PCC is related to a decline in working memory performance. The PCC has also been strongly implicated as a key part of several intrinsic control networks.
Anatomy
Location and boundaries
The posterior cingulate cortex lies behind the anterior cingulate cortex, forming a part of the posteromedial cortex, along with the retrosplenial cortex (Brodmann areas 29 and 30) and precuneus (located posterior and superior to the PCC). The PCC, together with the retrosplenial cortex, forms the retrosplenial gyrus. The posterior cingulate cortex is bordered by the following brain regions: the marginal ramus of the cingulate sulcus (superiorly), the corpus callosum (inferiorly), the parieto-occipital sulcus (posteriorly), and Brodmann area 24 (anteriorly).
Cytoarchitectural organization
The posterior cingulate cortex is considered a paralimbic cortical structure, consisting of Brodmann areas 23 and 31. As part of the paralimbic cortex, it has fewer than six layers, placing its cell architecture in between the six-layered neocortex and the more primitive allocortex of core limbic structures. It has also been associated with the hippocampocentric subdivision of the paralimbic zone. The cytoarchitecture of the PCC is not entirely uniform, instead it contains distinct anterior and dorsal subregions, which are increasingly understood as distinct in function, as well as cytoarchitectural structure.
Structural connections
Nonhuman structure
In non-human primates the following structural connections of the posterior cingulate cortex are well documented: Reciprocal connection with other regions of the posteromedial cortex. High connectivity to other paralimbic and limbic structures. Reciprocal connections to the medial temporal lobe. Dense connections to the hippocampal formation, the parahippocampal cortex, the ventromedial prefrontal cortex, and subgenual parts of the anterior cingulate cortex. Prominent connections to the areas of heteromodal association in the front, temporal and parietal lobes. Strong reciprocal connections to the dorsolateral prefrontal cortex (roughly Brodmann area 46) and the frontal poles (Brodmann areas 10 and 11). Less prominent connections to Brodmann areas 9/46, 8 and 9. Connections to the dorsal parts of the anterior cingulate cortex. Dense connections to the thalamus in the form of a continuous strip that crosses numerous pulvinar nuclei and the striatum. As is true in other areas of the posteromedial cortex, the posterior cingulate cortex has no apparent connections to primary sensory or motor areas. Thus, it is unlikely to be involved in low-level sensory or motor processing.
Human structure
While many of the connections in non-human primates may be present in humans, they are less well documented. Studies have shown strong reciprocal connections to medial temporal lobe memory structures, such as the entorhinal cortex and the parahippocampal gyrus, the latter being involved in associative learning and episodic memory. In humans, the PCC is also connected to areas involved in emotion and social behavior, attention (the lateral intraparietal cortex and precuneus), learning and motivation (the anterior and lateral thalamic nucleus, caudate nucleus, orbitofrontal cortex and anterior cingulate cortex).
Function
The posterior cingulate cortex is highly connected and one of the most metabolically active regions in the brain, but there is no consensus as to its cognitive role. Cerebral blood flow and metabolic rate in the PCC are approximately 40% higher than average across the brain. The high functional connectivity of the PCC, signifies extensive intrinsic connectivity networks (networks of brain regions involved in a range of tasks that share common spatio-temporal patterns of activity).