Brainstem in pain control.

One of the most powerful systems in the brain is that which alters the processing of noxious information. The processing of noxious stimuli into the experience of pain is important for survival, as it warns an individual of danger and motivates them to either escape the source of pain, or to confront and control it, that is, fight/flight. While pain is important for survival, it can be powerfully modulated in a range of situations, such as intense emotional state changes, stress, during shifts in attention and expectation, and after confrontational responses where it aids in rest and recuperation. Given its biologic importance, the circuits responsible for pain modulation are located in regions of the brainstem considered phylogenetically primitive. While in many situations, higher cortical regions can drive the modulation of pain, these higher regions are thought to contact the brainstem which in turn modulates incoming noxious information from the spinal cord and caudal brainstem. Understanding the brainstem circuits that control noxious information is vital for our understanding of how the brain modulates pain in various situations. The following is a review of the brainstem circuits that control noxious inputs and considers how higher brain regions can drive these brainstem sites to modulate overall intensity of pain.