Pain and emotion interactions in subregions of the cingulate gyrus

Vogt, B.A. (July 2005). Pain and emotion interactions in subregions of the cingulate gyrus. Nature Neuroscience Reviews, Volume 6, 533-544.

Beyond Brodmann's simplistic account of the cingulate gyrus with two divisions, recent cytoarchitectural studies favor a four-region model based on connections and function. This includes the ACC, the MCC, the PCC, and the RSC. This new theoretical construct, in conjunction with new neuroimaging data, is shedding light on the cingulate's role in pain and emotion processing.

Regarding emotion, it seems that the cingulate cortex processes emotion differentially.

• ACC - Activity during sadness is greatest in the sACC, believed to be important for storage of negatively valenced memories, and which has projections to subcortical autonomic centers. Happiness tends to elicit activity in the pACC, but this is not an autonomic integration center.
  
• MCC - Fear is associated with activity in the aMCC, the only cingulate structure to receive input from amygdala.
  
• PCC - The vPCC also shows activity during happiness, but is believed to be characterized by the assessing the self-relevance of emotional events (an emotional pre-processor).
  
• RSC - The RSC is still poorly understood but is believed to play a role in memory access of valenced information.

Regarding pain processing, we also see evidence for differential processing, but we also see overlap in processing pain and emotion.

• MCC - It appears the aMCC could be related to fear-avoidance behaviors (as alluded to above). More posteriorly, activations in the pMCC evoke skeletomotor body orientations but without affective (autonomic) or emotional (valenced) content.
  
• PCC - The dPCC, likewise, seems to be involved in orienting the body in response to noxious sensory stimuli.
  

In quick summary, authors hypothesize that the midline and intralaminar thalamic nuclei (MITN) provide the primary source of nociceptive information to the cingulate; as such, the cingulate is likely to have access to nearly full body receptive fields for cutaneous, muscle, and visceral noxious stimuli. However, each subregion of the cingulate differs in the density of these inputs, how they use the information for pain processing, and how they projection to other structures. The cingulate gyrus is likely to mediate three main aspects of pain processing: unpleasantness or 'suffering' in the pACC, fear-avoidance in the aMCC, and body orientation in response to noxious stimuli in the pMCC and dPCC.