Intensity of pain relates directly (and negatively) to level of concentration. When the pain is just moderate (5/10, most days for me), the visualisation itself is easier to focus on and I’m less likely to get pulled into distraction. The imagery is more vivid and less broken up. I’m working on a theory that this equates to the early stages of vipassana insight.
But when the pain is more severe — 7 or 8/10, like the day before yesterday — then I’ve noticed that the visualisation suffers. Despite repeatedly trying, the visualisation regions just won’t engage for any length of time. My stream of consciousness goes something like: images of red blobs … pain … distraction into some other conundrum. Wait while spinning in distraction for a few breaths, then repeat. Additionally there is a sense of desperation that goes along with that — as though the visualisation will spare me pain if only I can get it “perfect”. This feeling doesn’t occur on days when the pain is only 4-5/10. On those days, I’m far more laissez-faire about how the visualisation unfolds — almost preferring it to be asymmetrical, random. Messy, chaotic, wild and arty. Intuitive, like life. The desperation, perfectionism, rigidity around the visualisation being “good enough” the intensity to “get it right” are strictly phenomena from the realms of 7/10 and above.
Those thoughts do crop up even on days of moderate pain, but they’re easily laughed off, soothed with feelings of balance, and intuition that (in the words of the Desiderata) “no doubt the Universe is unfolding as it should”. Executive function and intuition, from the prefrontal area, the final brain region to mature in our early twenties. The adult shrug at misfortune that is frequently the only thing we have left to teach our teenage offspring.
Being swamped by that striving for perfection, that rigid feeling of the visualisation not being good enough, seems distinctly an artifact of strong pain.
“Damn it, I wasn’t seeing a whole half of that pain map, I forgot to transition through blue and violet, FML!” That kind of desperation arises because of seeking relief from the pain. This is ironic because, as Moskowitz writes “If focus is merely on immediate pain control, positive results will be fleeting and frustrating. Immediate pain control is definitely part of the program, but the real reward is to disconnect excessively wired pain networks and restore more balanced brain function in these pain processing regions of the brain.” 
Desperation to perfect the visualisation, out of fear of pain continuing, then turns that very fear into reality, creating what’s often termed a “self-fulfilling prophecy”. The act of predicting a result creates the result. I wonder how many irrational thought patterns, these kind of self-fulfilling prophecies, are frequently side effects of chronic pain flare ups in many people, both diagnosed and otherwise?
How does neural sensitivity (in physically compressed brain stem, hypersensitised pain circuits) relate to mental health and anxiety? And what other brain regions aside from pain processing may be involved in similar fashion with the manifestation of anxiety, obsessive-compulsive disorder, learning disabilities… ?
Further research required on my part, as I’m sure there are much more learned minds than my own who have thought of this already and pursued it beyond a mere thought experiment.
 Michael Moskowitz, Neuroplastic Transformation Workbook, https://www.amazon.com/Neuroplastic-Transformation-Workbook-Michael-Moskowitz/dp/0615814654