Recent research suggests that chronic pain can result in brain inflammation which alters neurological activity in parts of the brain associated with motivation and mood regulation. Thus, rather than chronic pain resulting in psychiatric symptoms on purely psychological grounds by wearing down the sufferer, research suggests that there is a direct causal, biophysical link between the experience of pain and damage to the brain. Researchers believe that this inflammation may play a role in the depression, substance abuse and anxiety which sufferers of chronic pain struggle with.
Catherine Cahill, associate professor of anesthesiology & perioperative care at UCI, Christopher Evans of UCLA’s Brain Research Institute, along with her colleagues, found that pain-derived brain inflammation sped up the growth and initiated activation of immune cells known as microglia in the brains of rodents. Microglia produce chemical signals in neurons which impede dopamine release; a neurotransmitter important in the experience of reward and pleasure.
Morphine and related opioid substances typically produce dopamine response, but failed to do so in the mice. Thus, their reward-motivated behavior was impaired. However, when the animals were treated with a chemical that inhibits microglial activation, dopamine release and the reward-motivated behavior which accompanies it, was restored. The experiment provides an avenue of future research in the treatment of the devastating psychological effects of chronic pain.
Indeed, it is becoming increasingly clear that chronic pain may result in permanent brain damage. Those with chronic pain exhibit continual activation of a front region of the cortex associated with emotion. This causes neurons to become worn out, and neuronal connections, altered in harmful ways. The researchers conducted fMRI to scan the brains of individuals with chronic low back pain, along with a group of healthy controls. Both groups had to track a moving bar across a computer screen. While the pain sufferers were able to complete the task effectively, they had to use their brain differently than the control group.
Brain equilibrium was maintained in the control group, with certain parts shutting off while others remained on. The previously mentioned part of the cortex, however, remained on continually in the brains of chronic pain sufferers regardless of the activity of the rest of the brain. Constant firing wears out neurons, causing brain cell death. The continual perception of the subjective experience of pain, according to the researchers, may cause permanent brain damage and irreversible alterations in wiring. More specifically, the researchers believe that the chronic experience of pain may produce emotional problems in those who might not have otherwise suffered from it.
