Breaking Research News – The sensory cortex is not a brick

Stuck record time for me again.  A new paper in BMC Neuroscience has demonstrated that electroacupuncture or acupressure induces changes in activity in the sensory cortex. Using magnetoencephalography (MEG) researchers have demonstrated that these treatments are reflected in altered activity in the sensory cortex. They go on to conclude that alongside evidence from other studies of activation of various sub-cortical regions in response to acupuncture that ”these therapies show potential for affecting S1 processing and possible altering maladaptive neuroplasticity”. Or in other words the observation that acupuncture leads to brain activation might mean that it could be effective in treating chronic pain.

grey Breaking Research News   The sensory cortex is not a brick

To me this is a bold interpretation of their data. What they have demonstrated is that stimulating sensory afferents leads to activation in the sensory cortex. A quick reflection on why we call it the “sensory cortex” should illustrate why this in itself is unsurprising. If they had not found altered activity what would they have concluded? That the participants were dead, that the sensory cortex is an inert brick (definitely worth a Nobel prize if replicated) or that the moniker “sensory cortex” is woefully misguided?

They also found that differing types of stimuli are reflected by different activation patterns and that the responses were attenuated as the 15 minute treatment went on. This is also not surprising since sensory perception, in part the result of this cortical activity, is a diverse feast of differing perceptual qualities. A prod and a prick do not feel identical and we might expect this to be reflected in the brain.

I have blogged on this problem of interpretation before. Brain activation in response to needling neither validates acupuncture nor provides a cogent mechanism for therapeutic action. That it activates sub-cortical networks involved “endogenous pain modulation” also does not distinguish acupuncture as a possibly effective active treatment since these networks are also implicated in the placebo response. Also, as I have oft repeated, given that our best evidence clearly indicates that it really doesn’t matter what you do with those needles, the sensory qualities of, or cortical responses to acupuncture seem unlikely candidates for a mechanism of action. It is not that the data in this study tells us nothing important. It adds to an existing body of data regarding how sensory input is cortically processed. But as a study of therapeutic mechanisms it attributes possible mechanisms to an effect that the best evidence tells us does not exist. I am reminded of this great line from the very naughty Daily Mash “it’s the equivalent of mapping the DNA of pixies or conducting a geological study of Narnia.”!

In my list of fantasy pointless facetious experiments I would like to perform brain imaging whilst having a research assistant bellow “ACUPUNCTURE!” or “PLACEBO!” at the unsuspecting participants. I predict that we would observe significant differences in specific brain regions that might just represent a therapeutic mechanism for bellowing the names of different therapies at people in pain. But perhaps that would just be silly.

About Neil

grey Breaking Research News   The sensory cortex is not a brickAs well as writing for Body in Mind, Neil O’Connell is a researcher in the Centre for Research in Rehabilitation, Brunel University, West London, UK. He divides his time between research and training new physiotherapists and previously worked extensively as a musculoskeletal physiotherapist. He also tweets! @NeilOConnell

He is currently fighting his way through a PhD investigating chronic low back pain and cortically directed treatment approaches. He is particularly interested in low back pain, pain generally and the rigorous testing of treatments. Link to Neil’s published research here. Downloadable PDFs here.

Reference

grey Breaking Research News   The sensory cortex is not a brick
Witzel T, Napadow V, Kettner NW, Vangel MG, Hamalainen MS, & Dhond RP (2011). Differences in Cortical Response to Acupressure and Electroacupuncture Stimuli. BMC neuroscience, 12 (1) PMID: 21794103

Madsen MV, Gøtzsche PC, & Hróbjartsson A (2009). Acupuncture treatment for pain: systematic review of randomised clinical trials with acupuncture, placebo acupuncture, and no acupuncture groups. BMJ (Clinical research ed.), 338 PMID: 19174438

Comments

  1. Julia Hush says:

    Wow! Stimulating sensory nerves activates the sensory cortex – I am flabbergasted. Nice one Neil.

  2. Hey Neil.. I’m not sure that I got out of this paper what you did, though I definitely wasn’t sure what the authors meant when they referred to ‘maladaptive neuroplasticity’. I’m not sure we know enough to assume we know what signals represent adaptation or maladaptation yet. Or even what maladaptation is.

    I agree with your point though that we need to be careful of the dangers of over-interpreting findings that regions of the brain light up in response to sensory input. Without more data we probably shouldn’t interpret these findings beyond that – touching my arm is processed in my brain.

  3. Neil O'Connell says:

    Thanks Julia and James.

    I am not sure what you can take from this paper. The flaw is in it’s conception – there is not a strong data-led case to suspect that any effect of acupuncture is secondary to sensory stimlation. There isn’t really a case to suggest that acupuncture has an effect beyond that of the theatrical placebo. So hunting for an mechanism from brain activation patterns in response to acupuncture treatments is an odd approach. Any interpretation of the data , which will inevitably show activation, or else the brain would be a really crappy organ, would have to be wildly speculative.

  4. Hi Neil thanks for a stimulating read..It seems you are convinced acupuncture is a placebo effect only.
    We seem to know too little to be making broad conclusions like this.

    Neil O'Connell Reply:

    Hi Andrew,

    I would contest that we do know enough to reasonable draw this conclusion.

    Rather than repeat myself these previous posts set out my position quite clearly.
    http://bodyinmind.org/acupuncture-%e2%80%93-the-mysterious-case-of-the-missing-razor/
    http://bodyinmind.org/acupuncture-for-pain-placebo-review-paper/
    http://neiloconnell.posterous.com/65184912
    http://bodyinmind.org/acupuncture-adenosine-and-cycling-fish/

    What we have is a messy mountain of data, but a mountain for sure. What we observe is what one might predict from an inert but complex intervention with subjective outcomes. We see small effects gradually disappearing as the size and quality of the trials increases which leaves us with no effect of real acupuncture over sham, whatever type of sham you use. This should not be surprising since the treatment in its traditional guise possesses no scientific biological plausibility whatsoever. At some point a rationalist has to take stock of the data and say – “ah, thats what we might have expected”.

    Of course the industry is now vast and huge swathes of the public and professional folk who arguably should be more critical have been sucked in so no doubt the research effort will continue to mine little pockets of uncertainty. But in my view the question has indeed been answered and money and efforts would be better placed elsewhere.

    Andrew Reply:

    Thanks Neil. Fascinating stuff. What about dry needling myofascial trigger points ( and the pain associated with them) ?

    neil o'connell Reply:

    Hi Andrew,

    Trigger points are an odd case. I am probably in a minority in that I am unconvinced that they represent a clinically important, or indeed even a clinically reliable phenomenon.

    As for the evidence for dry needling a 2008 systematic review (http://www.ncbi.nlm.nih.gov/pubmed/18395479) produced unconvincing and limited evidence with an optimistic interpretation.

    Andrew Reply:

    Hi Neil do you have any science to show that myofascial trigger points have/have no significance or are unreliable as a phenomenon?

    Neil O'Connell Reply:

    Hi Andrew,

    I think that the burden of proof for a concept lies with its supporters.It is very difficult in science to prove a negative (hence failed therapies are never universally dropped – e.g. acupuncture) but I am not aware of strong confirmatory evidence.

    To date I have not encountered a genuinely joined up account of the pathophysiology of trigger points, nor seen convincing evidence that they are a reliable or clinically valid phenomena. But if such evidence was presented, and convincing I would alter my view.

    Andrew Reply:

    Well our understanding of the human body is not complete and there are limitations to the ability of science to observe, measure and analyze so that evidence may one day be revealed as our theories evolve. Thanks for keeping us clinicians questioning the what why and how’s of treating people in pain !

  5. Hi Neil,

    as always your posts are very informative and interesting. I would really appreciate it if you could tackle and share your thoughts on something similar regarding Reflexology.

    http://www.ncbi.nlm.nih.gov/pubmed/18938220

    Neil O'Connell Reply:

    Hi Spiros,

    Thanks. I guess my question should be “what do you think?” – does it seem plausible? The basic principles of reflexology are clearly bunk – there isn’t a map of the body and its vital systems in the foot (nor is there one on your ear, for any auricular acupuncturists who may happen to be passing). So first you have to ask why do that fMRI study in the first place? It’s as if anyones most wacky ideas are worthy of close scientific scrutiny, and I would argue that they are not.

    As for the study itself its method for matching cortical activity in response to foot stimulation with brain areas is very loose. Basically a case of seeing what lights up in the brain and then hunting for existing data that might link it to a body system. This is very susceptible to cofirmation bias and the texas sharpshooter fallacy I reckon (http://en.wikipedia.org/wiki/Texas_sharpshooter_fallacy): look at enough papers and you’ll find something that fits.

    The problem is that studies like this create a sciencey sounding noise that adds legitimacy to a cranky concept where none is really earned.

    Thats not to say that a foot massage is not a pleasant and relaxing thing to have done. But for my money reflexology is just a foot massage attached to a piece of creative stroytelling.

    Spiros Reply:

    Hi Neil,

    thanks for tyaking the time to answer my request. I am a reflexologist meaning that I am very capable of giving a good foot massage plus good at story telling. Hanging out with BiM has made me even better.
    Reading your posts on placebo, belief systems etc. is what I think actually got me and another 3 colleagues accepted in a public hospitals pain clinic here in Athens.

    Thanks again
    Spiros

    Neil O'Connell Reply:

    Hi Spiros,

    I’m glad BiM is helpful and congrats on the job. Out of curiosity would you ever drop the “reflexology” title and adopt the title “foot masseur”?

    spiros Reply:

    Hi Neil,

    yes,

    – if this would support the belief system of the recipient
    -if this would support my belief system
    -if this would bring more money in (we have a crisis in Greece you know)
    -if Doctors or Physio’s recognize that it “works”, and by law, only they can do Reflexology.

    Question (I read it somewhere): What do you call alternative medicine that works? Medicine.

    A Reflexologist can offer (the best ever!) foot massage, a massage therapist, cannot offer Reflexology, unless trained.

    I find it interesting that people, some physios, doctors are who want to believe.

    Thanks for your time Neil.
    Spiros – Athina