Social Pain, Physical Pain: Different After All?

By Neuroskeptic | December 7, 2014 5:48 am

In a paper just published, a group of neuroscientists report that they’ve changed their minds about how the brain processes social pain. Here’s the paper: Separate neural representations for physical pain and social rejection

The authors are Choong-Wan Woo and colleagues of the University of Colorado, Boulder. Woo et al. say that, based on a new analysis of fMRI brain scanning data, they’ve found evidence inconsistent with the popular theory that the brain responds to the ‘pain’ of social rejection using the same circuitry that encodes physical pain. Rather, it seems that although the two kinds of pain do engage broadly the same areas, they do so in very different ways.

Interestingly, three years ago this same group of researchers argued that social pain and physical pain are processed in the same way by the brain. That was back in 2011 with their highly-cited paper in PNAS: Social rejection shares somatosensory representations with physical pain. Woo didn’t contribute to that paper, but both the old first author, Kross, and the old senior author, Wager, are authors on the new paper.

In fact, the new paper is more or less just a reanalysis of the same fMRI data from the 2011 article, but using different statistical techniques. Here’s how Woo et al. describe their new approach:

Claims about shared representation in the previous studies have been based on findings of overlapping univariate fMRI activity between pain and rejection, which is not anatomically specific enough to bear on the question of whether the underlying neural representations are similar.

Here we used a more fine-grained analysis technique (MVPA) to demonstrate that the overlapping activity arises from distinct neural representations. MVPA is more likely to reflect population codes across neurons…

We demonstrate that multivariate patterns encoding the intensity of pain and rejection are separately modifiable by showing that pain and rejection each influenced distinct, uncorrelated fMRI patterns at the whole-brain level and within ‘pain-processing’ regions… [this] strongly implies the existence of distinct, non-shared neural representations for pain and rejection.

The image below shows the key finding: while both physical pain and rejection activated the same brain areas (S2, dACC etc.), Woo et al. report that the two kinds of stimuli evoke different patterns of activity within those areas.

pain_rejection

The authors further show that these different patterns of activity are each associated with an entirely different pattern of connectivity across other brain areas, which I think helps to counter a potential concern about the interpretation of MVPA.

As we’ve seen, this is all a bit of a volte face. The authors discuss their previous claims as follows:

We reported overlapping fMRI activity across pain and rejection within many pain-processing regions, based on univariate analyses. We interpreted these findings in terms of shared representations between pain and rejection. The co-localized representations may still point to important interactions between pain and rejection. However, the current findings at the multivariate pattern level suggest that the representations of pain and rejection are in fact distinct within and across regions.

Woo et al. have shown commendable scientific integrity in being willing to change their minds and update their theory based on new evidence. That sets an excellent example for researchers. But perhaps we should now also credit those who anticipated this: such as the Neurocritic blog in 2012:

Social Pain and Physical Pain Are Not Interchangeable

… Your anterior insula and anterior cingulate cortex might be very busy in both cases, but they’re also activated in many different situations (Yarkoni et al., 2011) … Sure, the affective components of pain might show some overlap with physical pain (Kross et al., 2011), but distinct networks are likely responsible for the unique aspects of these different qualia.

ResearchBlogging.orgWoo CW, Koban L, Kross E, Lindquist MA, Banich MT, Ruzic L, Andrews-Hanna JR, & Wager TD (2014). Separate neural representations for physical pain and social rejection. Nature Communications, 5 PMID: 25400102

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  • http://uneulv.wordpress.com/ Une Ulv

    Has the earlier paper been retracted as it is invalid?
    And how is doing what can be expected “sets an excellent example for researchers”? Is current science just another religion?

    • http://blogs.discovermagazine.com/neuroskeptic/ Neuroskeptic

      It’s still commendable to do what is expected when many people don’t do it.

      • D Samuel Schwarzkopf

        I think it should be more common. As the quote from that Platt’s Strong Inference paper I tweeted about the other day suggests, you should try to compare different hypotheses rather than test if one is true. If you only have one hypothesis, “you become attached to it”.

    • Wouter

      “Has the earlier paper been retracted as it is invalid?”
      No, and it probably won’t be. The only apparantly invalid part of the paper would be the interpretation of the data. But any interpretation of data is always a subjective matter, regardless of how straightforward or unambiguous results may appear. Hence, it should come as no surprise that interpretations are put forward in a paper’s subsection called ‘discussion’ and, just in case you’re not in the vicinity of a dictionary, discussion does not mean presentation of facts. The only thing (slightly) out of the ordinary here is that the original authors themselves abandon their previous interpretations in light of new data. So, what were you saying about religion exactly?

  • quadrill

    Well put Wouter! Couldn’t have said it better; let the ‘discussion’ commence …

  • D Samuel Schwarzkopf

    To be honest, I wouldn’t make such a big deal about them changing their
    mind on this though. It’s a well-known fact that the univariate
    “blobbology” of the past decades results in lots of reverse inference
    (“area A is active in process X, it is also active in process Y, hence X
    and Y are processed the same”). This is obviously an incorrect
    conclusion and this has been pointed out many times by many people.

    I don’t see this so much as the authors “changing their mind” but reanalysing their data with a more sensitive method that reveals additional information. It’s not like their original inferences are wrong. Under the level of detail permitted by the original analysis the results show that the two things look the same in the brain.

    I think the bigger issue here is the continued hype of MVPA. What they are really showing is that there are finer spatial patterns of activation than the broad cluster scale of the original findings that track physical pain and social rejection and that these patterns are distinct. So this still is mainly about “where in the brain lights up” only now looking at a better resolution than previously.

    The truth is that pain and rejection could very well show even the same multivoxel patterns and yet still not be processed the same. For one thing it could just be that the population of neurons are overlapping but distinct (mixed up perfectly). It could also be that the same neurons are involved in both but they are coding it differently.

    This new study can’t shed any light on this. What it shows is simply that a more sensitive method for doing the same thing as the original study shows that the spatial pattern of responses is not the same. But it can’t even rule out the possibility that neurons in the same voxels are nonetheless involved in both processes.

    • http://blogs.discovermagazine.com/neuroskeptic/ Neuroskeptic

      While it’s true that these general issues have been much discussed in the past few years, there remains a large “back catalogue” of “blobology” papers published before these issues were widely known (let’s say 2011 and before).

      A lot of neuroscientists are now using MVPA etc. and not just blobology but many of the same people used blobology a few years ago.

      Which raises the question of what should we do with all of those old papers if we no longer have confidence in the logic of the inference?

      These authors have shown one solution – reanalyse the data and publish a new interpretation, even if that runs counter to the original conclusions. Which to my mind is a very good idea. So I’ve highlighted it :)

      And as a bonus they got two publications for the price of one!

      • D Samuel Schwarzkopf

        Don’t get me wrong. There is nothing inherently wrong with “blobbology”. I’ve never really done such studies but there is a place for them. It just entails an exploration localising activity related to a task or mental state or (if we want to relate it to the discussion of brain-behaviour correlations) even some behavioural trait etc. This can generate useful knowledge because it helps develop new hypotheses about what particular brain areas are actually doing which can guide new experiments etc.

        The only thing that goes wrong is that people are prone to making these sweeping reverse inferences about such findings. My biggest pet peeve with all this is that the very same thing is true about MVPA. I think you’re right that there is still a backlog of blobbological experiments to be published (and in some cases yet to be conducted by late-comers to the scene).

        But the same applies to MVPA. You wouldn’t believe how often people have approached me asking about how to employ MVPA with their particular experiment etc. My question is usually “Why do you think MVPA will tell you anything interesting that other experiments don’t?” I think MVPA is the new blobbology. It’s basically the same as when people had to do fMRI rather than behavioural experiments just because “you need to do fMRI to publish these days”…

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  • http://blogs.discovermagazine.com Longmire

    I realize that in our current time and culture we aren’t expected to analyze our own experience or even trust it as such but who would claim that the feeling of say knocking your elbow into something or not being acknowledged in a group would give the same “feeling” but that’s irrelevant I suppose because the word we describe the two with are the same.

    • feloniousgrammar

      Terms can be confounding. I have to wonder how various kinds of stress works with the “pain” and how that could be sorted through imagery. The pain of giving birth to a healthy and wanted baby and the pain of the stillbirth of a wanted baby may be the same on a physical pain scale; but the emotions are profoundly different and the pain of the latter can be extreme and harder to bear than the physical pains of giving birth.

  • David Winter

    One of my problems with this research is that they appear to use very different methods to stimulate physical and social pain. The physical pain is generated in the here and now with direct stimulation. The social pain is generated by getting people to look at photos of ex-partners. One is directly experienced pain, the other is recollected pain. It’s hardly surprising that brain regions are activated in different ways and that social pain looks more like sadness.

    The technical analysis of data may be more sophisticated but the experimental set-up is still a bit dodgy looking

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  • Joe Masters

    Interesting. This reminds me of how the anterior cingulate cortex was once thought to (paradoxically) be activated both in patients with depression and in optimists. Closer inspection of the data revealed that subtly different regions of the anterior cingulate were in fact activated in these two groups.

    Brilliant commentry by the Neurocritic here: http://neurocritic.blogspot.co.uk/2007/10/but-my-subgenual-cingulate-is-sad.html

  • http://www.pheromones.com jvkohl

    “My
    feeling is that the social brain has many levels. If you don’t
    understand the foundational level, then you can do brain imaging until
    you’re blue in the face, but you still will not understand the process
    at a deep causal level.” — Jaak Panksepp

    See also:
    http://dx.doi.org/10.1007/s00429-014-0895-5 It links a single amino acid
    substitution to cell type differentiation and changes during the
    development of behavior.

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  • Lingfei Tang

    As soon as I saw the word “qualia”, all my respect is gone. Qualia is about the different feelings for the same process, whereas here we are talking about two different processes.
    The iterative process is really how it works in every kind of research. Of course, one may find that physical pain and social pain share some common neural circuits, but these are essentially two different kinds of pains. Just because they share SOME neural networks does not exclude the possibility that they are different in others.

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Neuroskeptic is a British neuroscientist who takes a skeptical look at his own field, and beyond. His blog offers a look at the latest developments in neuroscience, psychiatry and psychology through a critical lens.

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