Computational and neural mechanisms of statistical pain learning, 2022, Mancini et al

Computational and neural mechanisms of statistical pain learning

Flavia Mancini, Suyi Zhang, Ben Seymour

Abstract

Pain invariably changes over time. These fluctuations contain statistical regularities which, in theory, could be learned by the brain to generate expectations and control responses.

We demonstrate that humans learn to extract these regularities and explicitly predict the likelihood of forthcoming pain intensities in a manner consistent with optimal Bayesian inference with dynamic update of beliefs.

Healthy participants received probabilistic, volatile sequences of low and high-intensity electrical stimuli to the hand during brain fMRI.

The inferred frequency of pain correlated with activity in sensorimotor cortical regions and dorsal striatum, whereas the uncertainty of these inferences was encoded in the right superior parietal cortex.

Unexpected changes in stimulus frequencies drove the update of internal models by engaging premotor, prefrontal and posterior parietal regions.

This study extends our understanding of sensory processing of pain to include the generation of Bayesian internal models of the temporal statistics of pain.

Full article: https://www.nature.com/articles/s41467-022-34283-9

 

Short Twitter thread by lead author

 

One obvious flaw when they notes 'The inferred frequency of pain correlated with activity in sensorimotor cortical regions and dorsal striatum':

Didn't she basically actually just map an experiment of how if you put an electrode on someone's hand and play around with different rhythms of 'strength of stimulus' and 'level of surprise/predictability', then at a certain threshold the brain goes from 'ooh ok what was that gentle tap' without yanking hand, to at a certain 'pain level' or 'surprise' an impulse being sent to move your hand?

A kid with a similar toy that would vibrate someone's wrist could tell them that, and given a similar amount of time come up with that real explanation. When did she convince herself he was watching anything different on an MRI? It's as deluded as thinking the placebo affect is all down to a patient's 'hope and expectation' and not the tendency of all involved including staff and those who wrote the questions to have erred on the side of a higher score when faced with a do I pick 5 or 6 on this arbitrary and tangential measure of what the tablet is supposed to do.

This would at best be something mapped to subtract from those experiencing pain just in case there is an element where they are planning movement at the same time?

If you are applying pain externally to someone's hand [as opposed to e.g. a nerve pain from inside the body] of course the sensorimotor cortex would be involved. Just like it would if you stroked someone with a feather or held their hand - with more action (as more calculations due to forward and backward processing being needed to make appropriate moves and placement ie planning) in brain if e.g. were catching a ball, or gauging where/how to place your foot on an icy path, or walking on hot sand.

It's called processing of information duh. Just like the processing involved that means you turn your body and eyes to the right place when someone taps you on the shoulder. And since when did pain operate in the way a pattern of hand taps would 'pattern-wise'? He's watching a bored person trying to play the game of guess whether the next tap will be 3 in a row or 4.

Even if brain was like a computer this simple idea - and how a game-coder would put such information into a game or a toy or a robot vacuum (for when it hits an object) not a neural network.

Your hand is technically something you can move away from that stimulus and it stops - bit different from a back spasm(?). That difference is quite fundamental in what you are watching re: the processing that is being observed.


Goodness knows what she actually was doing when she claimed "Unexpected changes in stimulus frequencies" - the person had an electrode on their hand so it wasn't that unexpected vs a sudden internal pain - and, if that means 'higher than before' ethics would have still prevented how high it could have gone so was it really pain at all?

So how does this person think their experiment of uncomfortable, but not painful, stimuli to a body part they could normally move from said type of stimulus and know is external (just say stop if it is too much) that someone would be expecting as they are in an experiment, bored, can then take its results and phrase it as if it is providing insight into chronic pain - which often originate from an injury or condition, and the source can't be seen, moved away from or simply resolved and doesn't self-limit?

This is just actually bigotry for someone to assume these are the same, minimising and misunderstanding being spread by it. Studying the 'non-pain' bit of pain and claiming pain is both like that and addressed by similar things to keeping your hand still whilst it is expectedly tapped. It misses by a mile the magnitude involved 'Chronic pain is like walking in the snow or being annoyed by a fly in the room' stuff.

It isn't 'OK' and shouldn't be socially acceptable for anyone to think it isn't their responsibility to understand what pain is to others in a realistic and interested sense (that's empathy of the kind that means you don't have a personality disorder because you notice others in pain and don't like that). Whether the 'intention' is claimed to be good of the lofty kind of 'I want to cure it', if you can't manage the first step of studying the right thing in the first place that isn't what you are doing at all. Has she met people and heard their experiences of pain to check what she was studying?

And shows that even their pet subject of stress is something they can't learn/understand as one key element involved in creating that is the ability to control, predict, or see an end to - and they recruited people to sit in a tube for an hour with something strapped to their hand and a big sheet telling them when it will end and what the ethical limit of any pain level will be, probably with a 'just say stop at any time' option. EXACTLY like what happens when someone gets a cluster headache or muscle spasm - not.

Give the expensive MRI time to someone who will use it productively not watching what undergrads (at least) already know as basics and pretending they've discovered something just because they haven't done their homework to realise none of this is what they think it is, and they are looking at nothing novel at all.

Edited a bit for sense etc