Anyone who has studied introductory psychology has heard about Pavlov's dogs and the concept of conditioning. Pavlov observed that dogs salivate when presented with food. This is an unconditioned (or innate, instinctual) response to the stimulus of food. He noted that over time his dogs would salivate when approached by his assistant (not that the assistant was a tasty morsel but that they associated the assistant with dinnertime). He then performed some experiments. He would ring a bell (a neutral stimulus) and the dogs would not salivate. Then he rang the bell while presenting the dogs with food and they would salivate. After some repetitions of this, the dogs would salivate when hearing the bell rung, even when no food was on offer, a conditioned response. This type of classical conditioning is one mechanism whereby physical pain can be produced in response to a stimulus which the unconscious mind associates with a painful experience.
If you read some of the stories in the books and websites listed under resources in Part 1 you might come across some anecdotes which illustrate this process. I paraphrase:
A Viet Nam veteran who was injured in the leg during an incident involving a helicopter recovered fully from the injury. However, periodically over the years he would suddenly experience intense pain in the previously-injured leg which would last for several days before dissipating. One day his wife commented on the helicopter flying overhead and it dawned on him that every time he heard a helicopter's engine his leg hurt.
One lady experienced intense pain whenever she drove through a particular town. She eventually realized that the town was en route to the in-laws' home where she often felt the same pain because of the stressful atmosphere. In time she experienced the pain when travelling that route even when not visiting the family.
Have you every taken an instant dislike to someone whom you have never met before and wondered why? Perhaps he or she reminds you of someone with whom you have previously had a bad experience. Have you ever had memories flood back instantly transporting you in your mind's eye to someplace else in response to a song, fragrance, or scenery? This is because the parts of the brain involved with memory, pleasure and emotion are very closely associated, and are also connected to the parts of the brain which process the flight and fight response. The limbic system is also closely connected to the thalamus which is the clearing house for the processing of painful stimuli.
One of the questions I have learned to ask patients with unexplained pain is: "What was going on in your life when it first happened?" This sometimes gives a clue as to the meaning of the pain and how to approach it.
David is a fan of books and no doubt will be sharing some good reads here.