Revisiting the role of the insula in addiction

Brain lesions that damage the insular cortex (IC) interrupt addictive behaviors, suggesting that drug addiction sensitizes the insula. However, neuroimaging studies seem to lead to an opposite picture: structural neuroimaging studies show reduced gray matter volume of the IC of drug users, and functional neuroimaging studies show reduced IC activity when drug users perform decision-making tasks. These results have been interpreted as indicating that addictive behaviors are associated with reduced interoceptive signaling within the IC. Here, we use this apparent contradiction to examine the possible roles of the insula in addiction, identify open questions, and explore ways to address them.