Two new studies, one published last month and another slated for publication in early 2018, confirm through brain imaging and other techniques, that pain that persists long after the physical injury that originally caused the pain has healed, is a type of learned behavior that can be “unlearned” through a variety of non-medical interventions.
For a September 2017 electronic pre-print of an article to appear later this year in the journal Psychological Medicine, Yoshino and colleagues of Hiroshima University Medical School examined the resting state functional magnetic resonance (rFMRI) of both chronic pain patients and healthy controls. rFMRI, shows which parts of the brain are intrinsically connected to each other by demonstrating correlated simultaneous activity among multiple brain regions. Brain regions that are wired together typically “fire” at the same time “rest” at the same time, because one of the brain regions presumably stimulates another through synaptic connections. Thus separated regions of the brain that exhibit correlated activity are said to belong to the same “Intrinsic Connectivity Network (ICN).
Yoshino’s research in 29 chronic pain sufferers and 30 healthy control subjects revealed abnormally high ICN connectivity within the “Dorsal Attention Network” (where consciously directed focal attention is thought to originate)—including structures such as the orbitofronal cortex and inferior parietal lobule— in chronic pain sufferers vs. healthy controls. This finding lead the authors to suggest that the brains of chronic pain suffers might rewire themselves when patients’ repeatedly focus attention on pain and/or anticipation of pain. Furthermore this rewiring could play a key role, according to Yoshino, in the continuance of pain after physical damage that caused the pain has healed.
Neuroscientists such as Dr. Waschulewski-Floruss of Eberhard-Karls University of Tuebingen in Germany have found that “learning” of chronic pain, and re-wiring of the brain, arises through the process of classical conditioning.
In his original experiments on classical conditioning in dogs, Pavlov noticed that dogs naturally salivated when they saw food. The food, in Pavlov’s example was an Unconditioned Stimulus (UCS) and the salivation an Unconditioned Response (UCR) to seeing the food. After Pavlov repeatedly paired the ringing of a bell with the presentation of food, the bell, even in the absence of food, became a Conditioned Stimulus (CS) that produced salivation. Salivation produced by a bell—not food–was called the Conditioned Response (CR).
This type of learning in dogs is associated with the formation of novel neural connections, where sensory inputs from the dog’s acoustic system, which did not originally stimulate parts of the dog’s brain that triggered salivation, grew new connections (or greatly strengthened existing connections) that enable the acoustic system to stimulate salivation.
The figure below represents how an injury could lead to “learned” chronic pain, and the formation of new neural pathways (“natural” pathways are shown in blue, learned pathways are depicted in red ), even after an injury is healed.