Figure 1: Distinct stages for chronic pain.

Predispositions are pre-existing factors that place some individuals at risk for developing chronic pain following an injury. Duration of the transition state may be dependent on type of injury as well as also based on predisposing factors. The interaction between injury and predispositions generate the transition state which may, or not, lead to a new brain state of maintenance of chronic pain. The “peripheralist” viewpoint posits that all four stages are determined by nociceptive properties, controlled primarily by peripheral afferents and their interaction with spinal cord circuitry. The “centralists” advance the notion that predispositions are mainly determined by limbic brain properties, and that the interaction between nociceptive circuitry and predispositions creates the transition state, where brain learning and memory circuitry interact with the cortex to give rise to the neocortical state of chronic pain.