(Thursday, July 5, 2pm)
Researchers often distinguish between nociception (damage detection) and pain, sometimes arguing that a response to noxious stimulation is either one or the other. The self-reports of people with cortical lesions, however, have shown that pain is a complex experience with multiple dimensions; different aspects of pain experience can be selectively impaired. In rare cases, some humans, after lesions in certain parts of their cortex, report that they still feel pain but no longer find it unpleasant. These lesions play a similar role in other mammals, but many non-mammalian species who probably do feel pain lack these cortical areas. Rather than telling us anything conclusive about the role of the cortex, these findings offer a unique opportunity to study the neural correlates of sentience and to better understand the capacity to feel pain in organisms who lack the cortical regions involved in human pain. Website
Berthier, M., Starkstein, S., & Leiguarda, R. (1988). Asymbolia for pain: A sensory-\limbic disconnection syndrome. Annals of Neurology, 24(1), 41-49.
Feinstein, Justin S., et al. (2016) Preserved emotional awareness of pain in a patient with extensive bilateral damage to the insula, anterior cingulate, and amygdala. Brain Structure and Function 221.3: 1499-1511.
Shriver, A. J. (2016). Cortex necessary for pain -- but not in sense that matters. Animal Sentience 1(3).
What is the ethical value off pain if we can distinguish pain and the unpleasantness off pain? If cingulate legion is related to unpleasantness of some memories or if insula lesions reduce unpleasantness of pain, pain doesn’t matter anymore but the ethical problem still remain about which organism can feel the unpleasantness of pain.
ReplyDeleteYou are right about the ethical aspect.
DeleteMoreover, the neurobiological distinction between "nociception" (damage-detection) and pain refers either to whether the damage-detection is felt (sentient) at all, or (if felt), whether it feels negative (i.e., whether it hurts).
Either way, whether (1) unfelt, or (2) felt but unhurtful, it would make no more sense to call it "pain" than it would to call an unheard vibration "sound." (Think about it: it's a valid version of the usually nonsensical quip about the sound of the tree falling in the woods out of earshot.)
The lobotomy patients who said "it still hurts but it no longer bothers me" obviously meant that "I still feel something that still resembles what it used to feel like so I can still recognize it, but it's no longer painful": i.e., it's no longer pain. We're not in the habit of calling things that don't hurt "painful" -- nor calling things that are not painful "pain." (If all they meant was that it still hurts, but a lot less, then that makes the distinction even more trivial.)
If you have a throbbing headache, and you take a pain-killer, the headache goes away, but the throbbing may still be there. Yet you wouldn't say "I still have the headache, but it doesn't hurt any more." If it doesn't hurt, it's still a head-sensation of some sort, but not a headache. (If it just hurts a lot less... then it still hurts, but a lot less, which is a banality, not a discovery of a fundamental dissociation between to aspects of pain.)
This is not playing with words: It's paying closer attention to what we really mean, rather than taking loose talk at face value. Especially when it is sentience itself (whether something is felt, and if so, what it feels like) that is at issue.
Totally agree with you. It seems to me that “pain” necessarily have a negative connotation. By definition of the English Oxford Dictionaries “pain” is: “Highly unpleasant physical sensation caused by illness or injury”. So, to me pain is unpleasant or it is not “pain” per se.
DeleteThank you for the presentation! My thoughts are more on humans for the moment. During the presentation, you mentioned that people who underwent a cingulotomies had chronic pains that eventually returned. That made me wondering if you think that there is any way possible to “stop” chronic pains. First, I was wondering what was your opinion on the fact that, at some point, we can recommend to a patient that is experiencing chronic pain to go see a psychologist? Since, it seems really difficult to get rid of chronic pain on a “biological” view, what do you think of a psychological view of chronic pain? Do you think that, at some point, the pain can be the “interpretation” of something psychological even if it is following a previous lesion/injury of the body (physical)?
ReplyDeleteSecond, more on a clinical view… I’m a physical therapist. I do have to deal with people who experience chronic pain. People that cannot manage the pain even with the medicine the doctor prescribes. Normally, my goal with them is to get them back at a more active life to get them out of a vicious circle, in which they often go once the pain is too intense. Therefore, while listening to you saying that chronic pain, even with surgery, can come back, it’s difficult for me to have a positive prognosis for the people experiencing chronic pain. Do you think there is anything to do with them to get them better and get them to don’t feel pain anymore, if we are ruling out the surgery?
Aside from the question of whether surgery (or medication) can remove the pain, do you believe that a pain can be anything other than brain- (and chemistry-) based?
DeleteIt may very well be that a behavioral or cognitive strategy could remove a pain that surgery or medication could not, but that is not the same thing as saying that the pain is not physical but "psychological." Apart from the question of the effective therapeutic strategy, "psychological" just means the pain is felt, i.e., sentient!
This is not to say that we understand how or why the brain causes sentience. But surely we have no doubt that it does indeed do so (just as it also causes behavior, as well as cognitive capacity and its execution.
I wanted to know about how we should define pain and nociception and I gave the example of listening to music and how the unpleasantness of listening to music that is too loud is something that is subjective to the individual. Two individuals exposed to the same stimulus have different reactions to it, including in terms of what we call pain. So should we define pain as a “subjective reaction of unleasantness to a given stimulus, percevied as harmful” and nociception as “detection of a harmful sensation”, the latter being much broader?
ReplyDeleteMany forms of sensory stimulation become painful (as well as damaging) if they become too intense. People differ (a little) in their thresholds for this. (We all know that listening to a lot of loud music raises our thresholds for auditory pain (but not just because of habituation but because of damage!).
DeleteThresholds, whether for ordinary sensation, nociception or pain do not shed light on the question of whether nociception is felt, nor whether, if felt, what it feels like.
But one thing is for sure: for nociception to be pain, it has (1) to be felt, not unfelt; and (2) if felt, it has to hurt (or at least feel unpleasant); otherwise it is not pain (even if it is a sensory detection of damage).
And obviously if it is a sensory detection of damage, but not felt, then it is neither sentient nor is it pain.
(Do you see how, at this point, the obtrusion of the knowing query "Aha, but if it hurts, are you 'aware' ('conscious,' bla bla) of it?" just reduces all of this to polysemous gibberish? If this is not evident by now then I was too sparing in my own obtrusions in the discussion during the Summer School!)
Pain is something you feel. If it does not hurt, it's not pain. And if it's not felt, it's not an "unfelt feeling": it's not a feeling at all. Most of what's going on in the brain is not felt. Sub-threshold sensory stimulation is unfelt (even if it is detected and processed by the brain). If a stimulus is felt, it can be constant or intermittent; it can be weak or intense; it can be remembered or forgotten. But "feeling something" versus "being aware of feeling something" is redundant. (That's why I recommend renouncing weasel-words in the discussion of sentience.)
Thank you for the presentation. If I well understand the conclusion, on an ethical point of view, we should focus researchs on how organisms can feel the value of a stimuli. Do you think that there's a difference between «to be able to feel something» and «to be able to attribute a value to a feeling»? I mean, do you think that this two capacities come together?
ReplyDeletePeople who talk about "valence" mean that most sensations are neutral (red, round, C#, Bb, smooth, sticky), some (warm/cool) can become more intense, and, depending on how hot or cold, can also become unpleasant or pleasant, as we saw in the last few days. That's "valence." In reinforcement terms it can also be reward or punishment. That's all there is to it.
DeleteThose who over-interpret valence think that all positive and negative feedback needs to be felt to be effective for, say, learning -- but learning robots are a counter-example to that.
At the end of the presentation i asked you a question about behaviour, and if you thought it was the most important metric for thinking about consciousness. In connection to this I was super curious about your metaphysical orientation to tackling the other minds problem. What is your metaphysical orientation to asking this question, and what role does empirical research into both neurology and behaviour play within that framework when it comes to the other minds problem?
ReplyDeleteI'll leave that to Adam to reply.
DeleteThis presentation was both scientifically and philosophically educative. We learned that non-mammalian species who lack the same cortical set up as humans could still feel pain or unpleasantness through their own specific neurological systems. The fact that the neurobiology of non-human living beings differs from humans does not necessarily mean that they can never feel pain. Mr. Shriver also presented examples showing that among humans, the way pain is experienced and perceived is very diverse and that multiple levels of pain intensity exist. There is no scientific reason to believe that this diversity in pain sensitivity can't be felt by other mammalian and non-mammalian species. This brings us to consider other species as sentient on the basis that they can experience pain in their own way and react to it. I really appreciated the emphasis that was put all throughout the presentation on going beyond an anthropocentric representation of pain & sentience. I also very much enjoyed all the ethical questions that were raised such as how should we humans adapt our behavior towards other sentient beings considering that we can cause them harm/pain? If given the opportunity to not cause pain to another sentient being, do we have a moral obligation to do so? As a philosophy student and vegan myself, these are the questions I was looking forward to be discussed during this summer school and this presentation was particularly enlightening. Thank you!
ReplyDeleteHi Mathilde!
ReplyDeleteI share your feeling toward this presentation, I found that prof Shriver brought interesting nuances to the phenomenon of pain. What surprised me the most is the apparent plasticity of the brain, which can adapt and compensate his damaged regions by activating (rewiring) other regions for a same stimulus (regions that can eventually play the same functional role if we think about the cingulotomy that doesn’t clear pain for ever, and/or of the greater and additional dorsolateral prefrontal cortex and somatosensory cortex activity of the brain of patients with insula lesions during sensory processing (from the study of Starr et al (2009) showed in the presentation)).
From these observations, I find important, as prof Shiver did, to distinguish types of necessities ; the weak version that says : « A brain region X is necessary for pain if normal activity in that brain region is required for an organism O to experience pain at time T » from the strong version that says : « A brain region X is necessary for pain if normal activity is required for any organism to experience pain ». The latter, relatively to lesions studies, doesn’t seem to apply to specific regions of the Cortex. Only the weak type of necessity would do.
I find this distinction suitable to the precautionary principle that Jonathan Birch introduced last week : rather than concluding that pain is impossible when we don’t find in other species the particular cortical regions that seem implied in the normal perception of pain by human, let’s lean on the precautionary side, assuming that pain can still possibly be perceived through the activity of other brain regions, that it can even be redirected to the functions of other brain regions. In that sense, that fishes don’t feel pain because they don’t have a cortex doesn’t matter as prof Shriver concludes, the solicited regions in human perception of pain being relative to a weak and not a strong necessity.
Plusieurs personnes ont soutenu (et soutiennent encore) que le cortex est nécessaire à la sensation de douleur. Pour Shriver, il y a deux manières de concevoir la notion de nécessité ici. La première est celle suivant laquelle lorsque l’on dit “la région X est nécessaire à la douleur”, on dit qu’à un moment particulier dans le temps, si la région X ne peut pas exécuter son activité habituelle, alors la douleur ne sera pas possible. La deuxième est plus forte et stipule que “nécessité” dans “la région X est nécessaire à la douleur” signifie qu’à n’importe quel moment dans le temps, si la région X ne peut exécuter son activité habituelle, alors la douleur ne sera pas possible. Dans le sens faible de nécessité, Shriver semble d’accord, mais refuse d’endosser la version plus forte qui, admettons-le, est lourde de conséquences. En effet, ce n’est pas parce que la région “X” est nécessaire chez l’être humain à un moment particulier pour ressentir de la douleur que cette même région est nécessaire chez les poissons par exemple. Comme le remarque Shriver, les études démontrent que, même chez les humains, il n’y a pas de parties précises qui soient toujours nécessaires à la sensation de douleur. On peut bien concevoir qu’étant donné qu’il n’y a pas a priori d’endroit fixe et précis de la douleur dans le cerveau, elle puisse être implémentée différemment par d’autres endroits du cerveau chez d’autres animaux.
ReplyDeleteIl ne faut pas non plus commette l'erreur d'oublier que toutes ces soit-disant "régions" du cerveau sont par définition purement arbitraires, une peu comme les délimitations géographiques n'existent que dans notre imagination.
DeleteQuand on marche dans la vallée en direction de la montagne, à quel instant précis peut-on dire qu'on n'est officiellement plus dans la vallée, mais bien rendu sur la montagne? Il n'y a que nous qui puisse en décider, mais il n'y a rien d'objectif là-dedans!
Donc, sur papier, ça a l'air bien beau de dire "Ça, c'est l'aire X et ça, juste à côté, c'est l'aire Y. L'une est impliquée dans la douleur et l'autre non." mais à quel moment est-ce qu'on va déterminer qu'un neurone n'appartient pas à la même aire que l'autre collé à côté qui a l'air exactement pareil?
En ayant construit ces catégories pour s'aider à faire une carte du cerveau, il est facile de se mettre à les réifier en disant "Cette zone sert à tel truc." mais dans le fond, ça ne nous dit pas grand chose à part de nous donner des repères pour savoir dans quel coin regarder. Ce genre d'approche cartographique, si c'est vraiment tout ce qu'on a de plus sophistiqué pour "comprendre" le cerveau à ce jour, ne fait-elle pas grand chose d'autre que trahir notre humiliante incompréhension des mécanismes de la cognition?
Thank you for the lovely presentation, however I wonder: considering the fact that the insula is the part of the brain that causes pain (moreover "feelings"), would people or animals be considered non sentient if they have a nonfunctionning insula?
ReplyDeleteThanks for the talk! Very interesting theory brought by A. Shriver. In fact, I was very surprised by the examples of nociception without pain; e.g. the soldiers who have severe injuries but can't feel it. And also the examples of pain without nociception. Althought, I think those examples are very specific and are not enough to prove this theory.
ReplyDeleteI do not study in this area so it was quite hard for me to understand everything that was said. I also found interesting the theory of pain without hurting (feel pain but not unpleasant anymore).
My question is for Fernanda. I find the portion of your talk where you discussed the case of a person who didn’t have a cerebellum fascinating. Are there studies that show how that person’s brain was rewired? Where the functions normally acted by the cerebellum in one specific place or was it distributed all over the brain?
ReplyDeleteBeyond the category "pain without nociception", there is also the particular case of the neuropathy,a pain based on erroneous nociception. Researchers of the Institute for neurosciences of Montpellier found a pain pathway involving a ligand receptor called Flt3. They believe the activation of the Flt3 signalling pathway in primary sensory neurons is an essential element for the persistence of peripheral neuropathic pain (https://presse.inserm.fr/une-piste-innovante-pour-combattre-la-douleur-chronique/30860/, https://www.nature.com/articles/s41467-018-03496-2). According to one of the researchers involved, Dr Jean Valmier, to develop a new medication based on the previous findings could be an alternative to the treatments involving electricity (ex. cortical stimulation, etc. https://www.ouest-france.fr/leditiondusoir/data/23726/reader/reader.html#!preferred/1/package/23726/pub/34160/page/9 (in french). As I do not have a medical, neurological or biological background, I wanted to know if the particular case of peripheric neuropathy in humans is also one of those pathways outside the influence of the cortex?
ReplyDeleteDr Shriver's and his colleagues' findings will certainly have a huge impact on bioethics, having impacts beyond the question of non humans animals (fetuses, pre-term infants, behaviorally unrespondent humans etc.). I also agree with previous comments, ie that an ethical debate will, or rather should persist: do we have to prevent nociception or pain even if this sensation is perceived as neutral?
Il faut distinguer la nocioception de la douleur. Le nociception est l’aspect neurologique/biologique de la douleur. Des nocicepteurs, des récepteurs de la douleur, envoient des signaux qui peuvent engendrer une réaction physique. La douleur est une perception, c’est-à-dire qu’elle est beaucoup plus subjective à la personne. Par exemple, pour une même blessure, une personne pourrait ne même pas réagir, mais avoir mal, alors qu’une autre pourrait se mettre à pleurer. Cependant, la nocioception et la douleur sont des processus inter-reliés. Il faut un stimulus physique pour engendrer de la douleur, sauf peut-être dans le cas de la douleur psychologique et des émotions.
ReplyDeleteLe cortex ne semble donc pas nécessaire pour la douleur, mais permet peut-être une perception plus complexe et plus subjective d’événements ou stimuli douloureux. Par exemple, les «cingulotomy», des lésions localisées pour traiter la douleur chronique chez des patients en phase terminales. Après un certains moments, des patients disent toujours ressentir de la douleur, mais qu’ils la trouvent moins dérangeantes. Est-ce que le changement de volume du cortex pourrait entraîner perception moins complexe et moins subjective de la douleur? Est-ce que la douleur chez des bébés de même âge, dont le cortex n’est pas encore développé, est moins subjective?