Chiropractic And Consciousness: Part 2 – What The Research Says About Chiropractic And The Brain

It seems that the musculoskeletal/pain association is a hard one to shift when it comes to chiropractic, yet research is painting an interesting picture when it comes to how chiropractic can influence neurology. This month’s topic on the blog delves into something that has its roots in both research and philosophy, yet is in some ways an undiscovered frontier – can chiropractic influence consciousness? The unlikely starting point: chronic lower back pain, and subclinical neck pain.

For the Foundation, the topic first arose when Nimrod Weiner presented on it at “The Gathering” in September. It was a highlight in a jam-packed agenda, and it left attendees with a sense that there is more we must do, but that we can indeed do our bit to impact the way our patients experience and express life. It was a question rooted in both research and philosophy, but it’s a hard one to ponder unless you first ask, “What is consciousness?”

On one level, consciousness is defined as “the state of being conscious; awareness of one’s own existence, sensations, thoughts, surroundings, etc. [1].” But there is more to the story than that. Even the dictionary definition goes on to say it can also be “full activity of the mind and senses, as in waking life.”

Nimrod Weiner (chiropractor, blogger, previous Board Member and long-time friend of the Foundation) poignantly points out, “It depends on how you define consciousness.” To Nimrod, and for the sake of this article series, consciousness is our whole waking experience: from the first sensations we feel when we open our eyes in the morning, to our imaginings of what the day might hold, to our sense of pain or our mental clarity and ability to interact with our day.

He cites an example that many a chiropractor would have experienced – the patient who gets up off the table post adjustment and says, “Ah, I feel better. I’m ready to face my day now.” Even in that anecdotal, subjective way, the chiropractic adjustment has impacted the patient’s experience of their emotional and mental clarity, their consciousness of pain, and perhaps even their sense of wellness. But far beyond this, the research does point to very real impacts on the brain and body. By virtue of this, we can have a conversation about how chiropractic and consciousness may indeed link.

We may have little to claim as yet, as those “Ah, I feel better” moments have not yet made their way into research. Nor do we have research that spells out a “dimmed or altered state of consciousness in the absence of chiropractic care” using those explicit terms. What we do have is basic science showing the impact of lower back pain and subclinical neck pain, and numerous other studies that can link together and create a picture of chiropractic’s impact on consciousness.

Low Back Pain
The body of evidence surrounding the effect of lowback pain on brain activity is slowly but surely growing. It is this effect on the brain, as well as the experience of pain, that creates the link between low back pain and consciousness.

In 2004, the Journal of Neuroscience ran a paper (authored by Apkarian et al) that found chronic back pain to be associated with decreased prefrontal and thalamic grey matter density [2]. At the time that study was published, knowledge about the brain’s role in chronic pain conditions was “largely speculative [2],” but the association between chronic low back pain, diminished quality of life, and increased depression and anxiety was already apparent.

There were studies that revealed “reorganization of nociceptive coding by peripheral afferents and spinal cord neurons and provide evidence for apoptosis of spinal cord cells [2]” but these were in animal studies. This was extrapolated to a greater degree in 2015, when Vrana et al found that chronic low back pain caused significantly reduced activity in motor imaging-related brain regions [3]. These differences in motor imaging-driven cortical processing in chronic low back pain sufferers again pointed towards reorganisation processes in the sensorimotor network.

The Apkarian study, which used a control group, a pain group, and Magnetic Resonance Imaging, yielded enlightening results.

“Patients with CBP [chronic back pain] showed 5-11% less neocortical gray matter volume than control subjects. The magnitude of this decrease is equivalent to the gray matter volume lost in 10-20 years of normal aging. The decreased volume was related to pain duration, indicating a 1.3 cm³ loss of gray matter for every year of chronic pain. Regional gray matter density in 17 CBP patients was compared with matched controls using voxel-based morphometry and nonparametric statistics. Gray matter density was reduced in bilateral dorsolateral prefrontal cortex and right thalamus and was strongly related to pain characteristics in a pattern distinct for neuropathic and non-neuropathic CBP. Our results imply that CBP is accompanied by brain atrophy and suggest that the pathophysiology of chronic pain includes thalamocortical processes.”

This finding was and still is significant. Given the reach of the thalamocortical processes in the brain, it becomes clear that chronic back pain is not just a matter pertaining to the back alone. Given that thalamocortical processes reach from prefrontal cortex to thalamus and touch on somatosensory functions, potentially implicating issues like the sleep cycle, cortical drive to the muscles, and other functions of the brain, the flow-on effects could be quite profound.

But it would take a good many years to follow that conclusion to its possible endpoint. The basic science is there though. We just need to make the links.

There are solid indications that somatosensory function, cortical drive and the prefrontal cortex can be positively impacted by chiropractic care. The New Zealand College of Chiropractic, and its champion Dr Heidi Haavik, have spent a good many research hours investigating the various ways chiropractic care can influence such things. The results are quite profound.  While we will save the details for a following blog post, the scoop is this – we now have evidence that:

• Chiropractic care shortens the cortical silent period (hinting at improved functions of consciousness via improvements in the way the prefrontal cortex processes information. Read more on that )
• Chiropractic care improves proprioception, which is essentially a physical function of consciousness – knowing where we are in space. (Read more on that )
• In older people, chiropractic care may decrease falls risk by increasing their choice stepping reaction time, multisensory processing and health-related quality of life. While the first one is related to both processing speed and proprioception, multisensory process and health-related quality of life touch on other aspects of how the individual may experience and interact with life in a physical and mental/emotional way. I.e. It affects multiple aspects of consciousness. (Read more on that )
• We have evidence that chiropractic care may increase bite force, and cortical drive to upper and lower limb muscles, thus providing more evidence on how the brain drives the muscles pre and post adjustment [3, 4]. This links to a physical aspect of consciousness driven from the brain.
• We can see that chiropractic care may affect sensorimotor integration in the prefrontal cortex [5, 6]. This, again is a physical manifestation of consciousness as it affects the speed and confidence with which we can respond to things we experience in our waking hours.

Here we see a number of functions of consciousness, all impacted by the chiropractic adjustment (and the various different names it was given to get these studies into journals).

Neck Pain

One area that deserves top billing all on its own is that of neck pain – be it clinical or subclinical.  In fact, recent research has begun to reveal the cascade of issues that can have neck pain (subclinical or clinical) at its heart. They include:

1. Proprioceptive differences in upper limbs [8]
2. Negative impacts on cortical and cerebellar motor processing [9]
3. Decreased mental response times for complex rotation tasks. [10]
4. Altered multisensory integration [11]

Although all four studies (referenced below) were chiropractic-based studies, the last one may be of particular interest because of one simple fact: it shows the difference in multisensory integration at baseline and at 4-week follow up in comparison to an asymptomatic control group.

Researchers were working with the hypothesis that “individuals with SCNP [subclinical neck pain] would possess slower response times for both unisensory and multisensory conditions because of the ongoing effects of unreliable proprioceptive feedback from the neck [4].”

While the auditory stimulus data didn’t reveal a notable difference, there was a statistically significant difference in response times for visual and multisensory stimuli. Researchers said:

“These differences are not simply because of slower movement times in general, because previous studies of people with SCNP reported no difference in simple response times in this population but found that the SCNP group had slower response times in more complex tasks (mental rotation) [4].”

Response times for the visual stimulus in this study were slower by 48ms baseline and 37ms at week 4, when compared with the control group. This was found to be statistically significant, as was the multisensory stimulus response time that was slower for the SCNP group by an average of 52ms at baseline and 47ms at week 4.

For the purpose of this study, participants were required to not seek treatment until after the 4-week check in. This allowed researchers to see if the symptoms improved on their own. They did not.

Additionally, a recent study indicated an increased reliance on visual input in people with chronic neck pain [5]. This, combined with findings of impaired mental rotation abilities in SCNP patients [3], lead researchers to state:

“If patients with neck pain have an increased reliance on vision and their visual and multisensory processing response times are impaired, as indicated in the present study, it is problematic. Our study identified worse visual and multisensory reaction times in SCNP vs. asymptomatic young adults, which was not compensated for by increased multisensory gain between the 2 groups, for both the standard t test and CDF analysis. The lack of change over 4 weeks suggests that left untreated, even subclinical neck pain can affect multisensory processing [4].”

The link back to consciousness

While each study could take us down a veritable rabbit hole of consciousness-related possibilities, one theme that is emerging is this: proprioception matters. Optimal communication from brain to body (and vice versa) via a spinal cord that is free from subluxations (or dysfunctional spinal segments, or whatever you want to call them), matters. Because unless these two things are working properly, you will move slower, you will think slower when it comes to complex rotation tasks, and then of course there is the issue of pain.

Put simply, and perhaps more philosophically – your ability to perceive the world around you, to process it well, and to respond appropriately to it – that is, your consciousness, will be dimmed in terms of pain, proprioception and processing speed.

What these neck-pain related studies also reveal is a simple but actionable truth: chiropractic care can help.

And here’s an interesting point: if people’s consciousness could become more fully expressed as a result of chiropractic, then does that mean that the subluxation dims people’s conscious experience? Does that mean that the subluxation actually dims people’s consciousness? How could that be?

We’ve often thought that by treating neck pain or back pain, we were staying in a mechanistic, orthopaedic model. When we bridge the worlds of science and philosophy this way we can see that, rather than being a pain and movement issue alone, neck pain and chronic back pain can create other impacts and these can influence both physical, mental and emotional aspects of consciousness. When chiropractic care becomes part of the solution, we can help lift that state of consciousness back to where it should be – fully experiencing and expressing life, able to respond to complexity, able to process multisensory stimuli, and able to live life free from the experience of pain that stems from nociception.

What a gift we have to offer the world.

Tune in next week when we talk about chiropractic, consciousness and brain plasticity.

References

1. Staff writer, (2018), “Consiousness,” Com,   https://www.dictionary.com/browse/consciousness
2. Apkarian A, Sosa Y, Sonty S, Levy R, Harden N, Parrish T, and Gitelman, Chronic Back Pain Is Associated with Decreased Prefrontal and Thalamic Gray Matter Density. Journal of Neuroscience 17 November 2004,  24 (46) 10410-10415; DOI: https://doi.org/10.15
3. Vrana A, Hotz-Boendermaker S, Stämpfli P, Hänggi J, Seifritz E, Humphreys BK, et al. (2015) Differential Neural Processing during Motor Imagery of Daily Activities in Chronic Low Back Pain Patients.PLoS ONE 10(11): e0142391. https://doi.org/10.1371/journal.pone.0142391
4. Haavik H, Ozyurt M, Niazi I, Holt K, Nedergaard R, Yilmaz G, Turker K (2018), “Chiropractic Manipulation Increases Maximal Bite Force in Healthy Individuals,” Brian Sciences, 2018, 8, 76; doi:10.3390/brainsci8050076
5. Haavik, H.; Niazi, I.K.; Jochumsen, M.; Sherwin, D.; Flavel, S.; Türker, K.S. Impact of spinal manipulation on cortical drive to upper and lower limb muscles. Brain Sci. 2017, 7, 2
6. Haavik H, Murphy B (2007), “Cervical spine manipulation alters sensorimotor integration: a somatosensory evoked potential study,” Clin Neurophysiol. 2007 Feb:118(2):391-402 https://www.ncbi.nlm.nih.gov/pubmed/17137836 Retrieved 8 May 2018
7. Lelic D, Niazi IK, Holt K, Jochumsen M, Dremstrup K, Yielder P, Murphy B, Drewes AM, Haavik H (2016), “Manipulation of Dysfunctional Spinal Joints Affects Sensorimotor Integration in the Prefrontal Cortex: A Brain Source Localization Study,” Neural Plast. 2016; 2016:3704964. doi: 10.1155/2016/3704964, https://www.ncbi.nlm.nih.gov/pubmed/27047694retrieved 8 May 2018
8. Haavik H, and Murphy B (2011), “Subclinical Neck Pain and the Effects of Cervical Manipulation on Elbow Joint Position Sense,” JMPT Vol 34, Iss 2, Feb 2011, pp. 88-97, https://doi.org/10.1016/j.jmpt.2010.12.009
9. Daligadu J, Haavik H, Yielder P, Baarbe J, and Murphy B (2013), “Alterations in Cortical and Cerebellar Motor Processing in Subclinical Neck Pain Patients Following Spinal Manipulation,” JMPT Vol 36, Iss 8, October 2013 pp. 527-537, https://doi.org/10.1016/j.jmpt.2013.08.003
10. Baarbe J, Holmes M, Murphy H, Haavik H, Murphy B (2016), “Influence of Subclinical Neck Pain on the Ability to Perform a Mental Rotation Task: A 4-week Longitudinal Study with a Healthy Control Group Comparison,” JMPT  39, Iss. 1, Jan 2016 pp. 23-30, https://doi.org/10.1016/j.jmpt.2015.12.002
11. Farid B, Yielder P, Holmes M, Haavik H, and Murphy B (2018), “Association of Subclinical Neck Pain With Altered Multisensory Integration at Baseline and 4-Week Follow-up Relative to Asymptomatic Controls,” JMPT  41 Number 2. Feb 2018, pp. 81-91