Living With Chronic Pain

The Amygdala May be Where Pain Starts

The astounding news that chronic pain is diagnosed more often than diabetes, hypertension and depression reinforces why finding better ways to combat pain is so important. The toll it takes on not just the individual, but the country in terms of health care costs and loss of productivity in the work force is overwhelming. Early diagnosis and intervention for any chronic medical issue is vital and can make all the difference in the trajectory that illness follows. Learning where the pain signals originate and how to alter them at the source could be the best answer for how to better treat this widespread issue. Exciting new research is looking in that direction.

Pain is both a sensory and affective experience. The perception of pain as being uncomfortable or unpleasant is what drives us to engage in behaviors that limit exposure to whatever stimuli is causing the sensation. We’ve discussed how the brain translates and encodes harmful stimuli as it ascends the spinal cord into nociceptive information- the ability to recognize and characterize noxious stimuli into a molecular signal that triggers an appropriate defensive responseButhow it transforms emotionally inert data ascending from the spinal cord into the perception of pain still remains foggy. 

We do know the amygdala is critical to the emotional and autonomic responses generated during fear and pain responses, often considered the home for the fight or flight response and general anxiety.

The amygdala is an almond shaped region located in the temporal lobe of our brain. 

  • It means “almond” in Greek
  • It exists on both sides of the brain as part of the limbic system- a neural network that mediates both emotion and memory
  • Initially thought to be predominantly unpleasant emotions like anxiety and fear, it is now known to be involved in our rewarding stimuli as well as sexual and eating behaviors.
  • Our emotions possess a valence, positive or negative and an intensity, high to low. These are cataloged within the amygdala for future reference and responses. 

On functional MRIs, the basolateral amygdala (BLA) displays heightened activity and altered functional connectivity in those of us who suffer from chronic pain. This suggests the BLA might be a critical player in shaping our pain perceptions. Recent studies show this may be due to the coordinated efforts of large neuronal ensembles, and that noxious stimuli seem to be encoded in a core set. Greater activation of this particular ensemble was predictive of increased pain behaviors suggesting that how the BLA processed the data actually influenced the magnitude of pain felt. It appears this is where emotionally inert data is transformed into a signal that promotes the motivation and perpetuation of pain behaviors we establish in order to protect ourselves.

Researchers found amazing results when it was damaged or impaired. Damage to this area of the amygdala created a rare phenomenon- noxious stimuli was still detected but without the sensations of pain or the desire to avoid it. Whereas impairment of the somatosensory cortex in this area reduced the ability to localize and describe the adverse sensations without altering aversion or avoidance. It appears that this BLA affective neural circuitry is the possible link between nociceptive inputs that encode our negative perceptions and then generates a behavioral response! The goal: to allow the signals through we need in order to survive e.g. a hand on the hot stove must be immediately removed, while distinguishing those that aren’t related to a life-threatening situation and can be diminished or stopped. This may be the place for just that option.

Reasoning takes place in the frontal lobes. It’s where we take in all the data and then make informed, reasoned decisions. The amygdala works automatically. When it perceives a threat, the fight or flight mode is triggered. But we then have the ability to process that information and decide if the threat is real and choose a logical response. When we are ruled by the amygdala alone reason is bypassed. Pain perceptions, accurate or not, are perpetuated unchecked. Studies have shown the amygdala can generate or facilitate pain-like behaviors even in the absence of tissue pathology. Deactivation of this area actually inhibited certain behaviors in both acute and chronic pain models. We may have found an off switch for pain.

Researchers believe the BLA is where computing and assigning a “pain tag” to emotional information occurs and those negative feelings associated with painful stimuli is then related to certain reactions. For example, I’m sure I’ll hurt when I exercise because any movement hurts, so exercise isn’t an option. This perception gets transformed and inputted into a hierarchy that stores data within this critical node of neurons that then shapes our pain experiences and motivates our ultimate behavior. Redefining these thoughts as discussed in the last few posts is exhausting and time consuming. How incredible would it be to have a treatment that starts here and helps us to understand the truth- yes, exercise may be uncomfortable but it brings necessary nutrients to painful areas, removes built up inflammation, releases spasms and stimulates pain inhibiting hormones like endorphins. Hearing it this way encourages working through the discomfort and promotes a more positive coding of the experience within the BLA node.

Learning more about this area of the amygdala could help delineate ways to selectively diminish the discomfort associated with pain, regardless of its source, while still preserving other needed reflexes and discriminatory processes required to detect and respond to life threatening issues, providing promising new treatments in the future.

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