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Hallucinations, consciousness and pain

By Noigroup HQ Science and the world 28 Sep 2018

Our thanks to Cody Weisbach for once again contributing to noijam. Cody has written previously about The Notorious TMJ and the comedic process, failing to get good, and physical therapy .

Controlled Hallucination


Pain is a conscious experience, so in order to understand pain, we have to dive into how consciousness works. That is one of the reasons consciousness has been given some time in past posts on noijam (here, here and here for example).

One way to think about consciousness is as a controlled hallucination.

Not in a pathological way. Just in a way that is so fundamental to our experience and how we perceive our environment that it feels all too normal. At least that is Anil Seth’s argument in his (incredibly popular) TED talk called Your Brain Hallucinates Your Conscious Reality.

Here’s three things that I took from the talk and how they relate to pain.

1) Perception is Based on a Best Guess

Lorimer Moseley has touched on the topic of perception being a best guess in his book Painful Yarns. One of the ways he did so was by using vision as a base for understanding perception, then applying the same concepts to pain. Seth takes this concept to an even more fundamental level and argues that not only is perception based on a best guess, but that it is our brains’ only option.

Here’s how Seth Explains it.

“Imagine being a brain. You’re locked inside a bony skull, trying to figure what’s out there in the world. There’s no lights inside the skull. There’s no sound either. All you’ve got to go on is streams of electrical impulses which are only indirectly related to things in the world, whatever they may be. So perception — figuring out what’s there — has to be a process of informed guesswork in which the brain combines these sensory signals with its prior expectations or beliefs about the way the world is to form its best guess of what caused those signals. The brain doesn’t hear sound or see light. What we perceive is its best guess of what’s out there in the world.”

Day to day living doesn’t make it seem as if we are a brain locked in a bony skull, but it’s hard to argue that that is not what’s happening. I also like the acknowledgement that the information from the outside world comes in streams of electrical impulses that are only indirectly related to the outside world.

2) Perception is Based on Many Inputs, Some from the Outside World, Many if Not More are Internal

In order to figure out what is going on outside the locked bony skull, it turns out that our brain relies on more than just the electrical impulses that are indirectly related to the outside world. Our brains also rely on electrical signals generated internally, like thoughts, past experiences, etc.

For our patients, this can be a very challenging, and sometimes a threatening concept. Moseley also addressed this challenge by using visual illusion as a demonstration.

Seth did this as well and even used the exact same visual illusion, but he took it one step further with what I found to be a brilliant and compelling audio example. Listen to the clip below, which I pulled from the presentation.

Click on the image above for a link to the audio recording

Here’s Seth’s interpretation.

“OK, so what’s going on here? The remarkable thing is the sensory information coming into the brain hasn’t changed at all. All that’s changed is your brain’s best guess of the causes of that sensory information.”

Instead of perception depending largely on signals coming into the brain from the outside world, it depends as much, if not more, on perceptual predictions flowing in the opposite direction.”

Once you hear the meaning of the audio change without any change in the signal it gets very hard to deny that perception is significantly moulded by internal factors.

The funny thing to me is that once I got the extra cue, it was impossible for me to perceive that same sensory information the way that I did the first time around. It’s not dissimilar from trying to unsee a visual illusion. Perhaps this is one of the reasons why improving persistent pain is so challenging. Once you hear the cue, it is very difficult to “un-hear” it. Some more examples of this kind of ‘auditory illusion’ (formally known as sine wave speech) were used in this post.

3) Perception isn’t Passively Experienced, but Actively Created

If you accept that perception is based on a best guess and that it is based on many inputs, then it is hard to disagree with this last point, which is essentially Seth’s thesis of the whole talk. In his words…

“We don’t just passively perceive the world, we actively generate it. The world we experience comes as much, if not more, from the inside out as from the outside in.”

To me, this statement is very closely related to the fundamental goal of Explaining Pain, which is to “…shift one’s conceptualization of pain from that of a marker of tissue damage or disease to that of a marker of the perceived need to protect the body tissue.

To that end, I have been including the video as supporting material in my Explain Pain curriculum and have found it useful as a way to reinforce or even lay the foundation for concepts like neurotags, the orchestra in the brain, how heavily pain relies on context, and linear versus emergent thinking.

Summing Up

Pain is a conscious experience and therefore if you want to understand pain, you need to know a thing or two (or three!) about consciousness and perception. Anil Seth’s TED talk covers a lot of ground for being only 17 minutes long. Do yourself a favor and go watch the whole thing. I’ve only scratched the surface of it here, and there is a lot more including the rubber hand illusion, interoception and using virtual reality to simulate hallucinatory experiences.


-Cody Weisbach

Cody is a Physical Therapist in Boulder Colorado, with a special interest in pain. Cody can be found on Twitter @CodyWeisbach.


  1. MAT

    Love this TED Talk, is the theory of predictive processing an evolution of the neuromatrix theory?

    1. Hi Mat
      I’ll go out on a limb and say no. The neuromatrix is more aligned with the classical ‘bottom up’ picture of; ‘ascending’ input -> crunched/processed in the brain -> output of percept, movement etc. Predictive Processing on the other hand is much more ‘top down’ with generated predictions about the causes of current sensory inputs flowing downwards (and sideways) and attempting to ‘explain away’ the upwards flow of prediction errors. Perception and action in Predictive Processing are in some ways more alike than different. It is a wondrous rabbit hole to get lost down! Happy to provide a curated list of resources if you ever want to take that trip!
      My best

      1. Hi Tim, thanks for the response. Yes I would love a list of resources of predicted processing. I love challenging what i think I know. Thanks for your great work
        Mat R

  2. Ralph Samwell

    One way to NOT think about consciousness is a ‘controlled hallucination.’
    All pain is real, and important that the patient is never given any reason to delegitimise their pain and experience by introducing a word that by definition means factious, figment of imagination, perception of something not present.
    A controlled hallucination means; one can make the spiders that are climbing the wall dance for you. The spiders still aren’t there but you can manipulate them through control. Controlled pain means the intensity of pain IS there but with control you aren’t climbing the wall in pain. Pain real; hallucination spiders not.
    As with most TED talks, entertainment and spin is the order of the day rather than accuracy.

    Perception maybe based upon a best guess, but that “guess’ is an Eon of trial and error/successful natural selection. Innate nature knowledge of fluid and causal mechanics of physics of the environment we are born into. That best guess is NOT us making stuff up as some pet theory but a long trait of fight/ flight survival programming. (all light and sound is in the skull, those two frequencies get transferred and interpreted by the brain as the best guess of reality not hallucination.) “informed guess” is an oxymoron, it’s not a guess if it’s informed; “empirical guess” would be a better term.
    We are either born with or/and learn thing in shade are darker than in light. The same colour shade will look darker because it has been placed in the shadow and lighter if placed out of the shadow. In other words, the illusion is already primed to before the you look at it, to change its perceived shade, and so yet aging NOT an hallucination but based upon the REALITY that things look darker in shade than in light. Without depth of field ability, distinguishing light and shade, you are far more likely to miss that branch you are reaching for and fall to your death. Not hallucination, reality. Perceptual prediction based upon reality, reality being the laws of physics. Hearing what you expect to hear, based upon past reality. Feeling what you expect to feel based upon past reality. How many times do you have to run into a wall before you accept, “yup, it’s bad idea”? If expectation and reality (cause-effect) coincide, this reinforces learning. Optical visual illusions exist because we have wiring in our brain for our best chance of surviving the REAL world of safety and harm. Just because an artist can come up with a clever magic trick doesn’t mean we need to believe the girl has been sawn in half.
    We don’t ‘actively generate’ the world, it was there before we existed and it will be there after we are gone. The tree, still makes a sound, when it falls, even if nobody is there to witness it. That is BS about anthropomorphic importance, is at best an assuming philosophical navel gazing at worst puts human back at the centre of the universe. Rubber-hands do not prove our reality is an illusion, it just shows our perception of what is real can be manipulated.
    …shift one’s conceptualization of pain from WHAT WAS a marker of tissue damage or disease to that of a UNEEDED marker of the perceived need to protect the body tissue THAT HAS NOW HEALED.”

    1. Hi Ralph
      Why so angry, ranty and YELLING? Why not disagree with some civility?

      Just because it is the most glaring; there is nothing in the post about “actively generating the world”, rather the idea put forth is that perception is an active process. Neither was there any talk about trees falling in the forest – where did that come from?

      Why not go and do the reading behind some of the ideas presented and then make reasoned, informed comments? Anil Seth has put together a useful list of resources for those interested in getting into consciousness science

      My best

  3. Ralph Samwell

    Thanks Tim, the weakness of typed media, just as I wasn’t shouting the T in the name Tim.
    Not sure where you’re seeing the lack of civility, another weakness in the typed interpretation. Language is more than words and open to interpretation.
    “actively generating the world” is a direct quote from the article.
    You’re not familiar with the philosophical tree metaphor, it’s well known?
    Thanks for the advice, i have, just finished James Gleick’s Chaos and Robert Sapolski’s Behaviour, i’m sure you must have read.
    In terms of the ideas behind Seth, it’s been done before, many times,
    Begley’s Plastic Mind 2009, Ramachandran’s Phantoms 1998, John Searle’s
    even on TED; Brian Little: Who are you, really? The puzzle of personality
    Dan Dennett, Steven Pinker etc etc. far more current than Seth.
    As with any specialist, they a lot about very little.
    Nothing new here with Seth and is fundamentally flawed to account for all pain,
    it tries to ignore Physics, we don’t base reality of fantasy, we base it on cause effect physics, tissue damage for example.
    I prefer Benedetti don’t you?

  4. Mick Thacker

    I really don’t think you can legitimately make that last point Ralph – fundamentally Anil’s commentary is based on the need to combat the effects of the second law of thermodynamics – you can’t get more physics than that! – that is to minimise entropy (better considered as surprised). Anil is pointing out that one has to use a combination of prediction, model construction and action to make sense of any situation the person finds themselves/ puts themselves in. Your suggestion there is nothing new may be accurate but not based on those sources quoted (perhaps true if you quoted Kant or Helmholtz or Gregory – who were suggesting something similar ideas to lthis but not Ramachandran, Searle etc nor even Dennett who has actually shifted his position towards these constructs recently. My comment is based actually based on a chat I had with him recently😊). We certainly do produce our perception of pain in response to the cause-effect criteria as you suggest there are numerous examples of pain perception without the causative factors you suggest(demand) – tissue damage.
    I think you dismiss Anil a little too lightly – look at his academic training/ record/ publications would yours hold up to compare?

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