Pain-Associated Neural Plasticity in the Parabrachial to Central Amygdala Circuit : Pain Changes the Brain, and the Brain Changes the Pain

In addition to the canonical spino-thalamo-cortical pathway, lines of recently accumulated anatomical and physiological evidence suggest that projections originating in nociception-specific neurons in lamina I of the dorsal horn or the spinal nucleus of the trigeminal nerve to the lateral parabrachial nucleus (LPB) and then to the central amygdala (CeA) play essential roles in the nociception-emotion link and its tightening in chronic pain. With recent advances in the artificial manipulation of central neuronal activity, such as those with optogenetics, it is now possible to address many unanswered questions regarding the molecular and cellular mechanisms underlying the plastic changes in this pathway and their role in the pain chronification process.