Arguing pain-brain relationships in the fetus

How does the physical growth of the fetal brain relate to pain function? Addressing this question is not just of research interest, but has profound consequences in guiding clinical use of analgesic and anesthetic intervention for in utero surgery. Adult brains appear structurally and functionally specialized for types of pain; for example, acute pain preferentially engages medial prefrontal cortical and subcortical limbic regions [1,2]. However, the question of the relationship between such specializations and pain is still controversial in the debate concerning fetal pain [3, for review]. One ‘maturational’ perspective is that brain growth and pain function co-develop through innate genetic and molecular mechanisms, and that postnatal experience merely has a role in the final ‘fine tuning’ [4,5,6,7]. Evidence concerning the differential neuroanatomical development of brain regions is used to determine a lower gestational age when particular regions likely become functional for pain. Several authors claim that maturation within subcortical brain regions enables pain function as early as 20 weeks gestation [6,7], others claim expansion of thalamocortical regions at 24 weeks is necessary and sufficient. An alternative ‘expertise’ view is that brain development and pain function involve a prolonged process of co-specialization that is shaped by postnatal experience [3,8,9,10]. Based on this approach, some authors argue that the fetal brain is not functional for pain at any gestational stage because skills such as sense of self and mind-reading learnt in postnatal life are necessary for pain [3,8,9,10].

Maturational views of functional brain development assume that brain growth and the appearance of functions are equivalent or the same thing, in the way that water and H2O are equivalent or the same thing, which implies that concerning the question of fetal pain, the sequential coming ‘on-line’ of specific brain regions during fetal development is identical with the appearance of pain function. That is, pain function numerically shares all its properties or qualities with the brain. Things with qualitative identity share properties, so things can be more or less qualitatively identical. Apples and oranges are qualitatively identical because they share the quality of being a fruit, but two apples have greater qualitative identity. Maturational views of fetal pain demand more than this, however, since they imply numerical identity. Numerical identity implies total qualitative identity, and can only hold between a thing and itself. This means that a maturational view of fetal pain makes a very strong demand about pain capacity: specific brain regions and pain function co-develop in the fetus because they are numerically identical, one and the very same thing. Pain is in the brain.

Expertise views of fetal pain challenge the core maturational commitment of brain-pain numerical identity and present philosophical arguments and data which claim instead to show the non-identity of brain-pain relationships in the fetus and the necessity of postnatal experience and learning [3,8,9,10]. A representative philosophical argument driving expertise views of fetal pain is the following: All pains are personal experiences and therefore entirely subjective; All brains are physical objects and therefore entirely objective; There is a fundamental divergence between pain and the brain. Therefore, pain cannot be numerically identical to the brain. Thus, the argument:

1. Pains are subjective.

2. Brains are objective.

Therefore, since pains and brains fundamentally diverge,

3. Pain is not numerically identical to the brain.

I will now critically examine and discuss this argument. Take the first premise: ‘pains are subjective.’ On a reasonable interpretation of its meaning, to say that ‘pains are subjective’ is to say that pains are knowable by direct personal experience. However, since brain events such as brain growth are not knowable by direct personal experience, pains cannot be one and the same thing as brain events. Here is the argument:

1. Pains are knowable to me by direct personal experience.

2. Brain events are not knowable to me by direct personal experience.

Therefore, since pains and brains fundamentally diverge,

3. My pain is not numerically identical to my brain.

Once the argument is represented in this form, it is clear that it is fallacious. This can be observed if we compare the argument with the following example:

1. Ibuprofen is known by me to relieve pain.

2. Iso-butyl-propanoic-phenolic acid is not known by me to relieve pain.

Therefore, since ibuprofen and iso-butyl-propanoic-phenolic acid fundamentally diverge,

3. Ibuprofen cannot be identical to iso-butyl-propanoic-phenolic acid.

The premises in the example are true, but the conclusion is known to be false. The argument is fallacious because its core assumption – ‘fundamental divergence’ – is mistaken: it mistakenly assumes that a thing must be known by somebody somewhere. But the property ‘being known by somebody’ is not a necessary feature of anything, much less a property that might establish its identity or non-identity with something otherwise known. The truth of the premises may be due to nothing else but my ignorance of what turns out to be identical with what. This point entails that ‘being known by somebody’ is not a necessary feature of pain that might explain its identity or non-identity with the brain. The non-identity of fetal brain development and pain function cannot be established by this argument.

The argument needs to produce independent evidence for the idea of ‘fundamental divergence’, since it is not self-evident. To illustrate this point, consider the argument for pain-brain numerical identity that personal pain would have no influence on mammalian behaviour were it not numerically identical with brain events [11]. This apparently simple argument wasn’t established until fairly recently because a crucial premise was not available. This is the premise that physical effects like pain are determined by prior physical causes. This is an empirical premise, and one which scientific theories of pain didn’t take to be fully evidenced until the middle and late twentieth century [12, for review]. It is this evidential shift, and not the apparently obvious, which is responsible for the argument’s persuasive power. It remains to be seen if stronger evidence for pain-brain identity in the fetus is forthcoming.

Of course, the failure of this particular argument to establish its conclusion does not thereby abolish the expertise perspective and self-guarantee its opposite, the maturational perspective, or even prove that the two perspectives are mutually exclusive. Rather, what the failure of the argument shows is that apparently obvious logic is sometimes a poor guide to reality. Whether pain-brain identity is true or false is impossible to tell simply by arguing personal appearances.

References

[1] Apkarian AV, Hashmi JA, Baliki MN. Pain and the brain: specificity and plasticity of the brain in clinical chronic pain. Pain 2011; 152(3 Suppl): S49–S64.

[2] Wager TD, Atlas LY, Lindquist MA, Roy M, Woo CW, Kross E. An fMRI-based neurologic signature of physical pain. New England Journal of Medicine 2013; 368(15): 1388–1397.

[3] Derbyshire SWG, Raja A. On the development of painful experience. Journal of Consciousness Studies 2011; 18: 9–10.

[4] Anand KJ, Hickey PR. Pain and its effects in the human neonate and fetus. New England Journal of Medicine 1987; 317(21): 1321–1329.

[5] Anand KJ. Consciousness, cortical function, and pain perception in nonverbal humans. Behavioral and Brain Sciences 2007; 30(1): 82–83.

[6] Lowery CL, Hardman MP, Manning N, Clancy B, Whit Hall R, Anand KJS. Neurodevelopmental changes of fetal pain. Seminars in Perinatology 2007; 31(5): 275–282.

[7] Brusseau RR, Mashour GA. Subcortical consciousness: Implications for fetal anesthesia and analgesia. Behavioral and Brain Sciences 2007; 30(01): 86–87.

[8] Derbyshire SWG. Controversy: Can fetuses feel pain? BMJ: British Medical Journal 2006; 332(7546): 909–912.

[9] Derbyshire SWG. Fetal analgesia: where are we now? Future Neurology 2012; 7(4): 367–369.

[10] Szawarski Z. Do fetuses feel pain? Probably no pain in the absence of “self”. BMJ: British Medical Journal 1996; 313(7060): 796–797.

[11] Papineau D. Thinking about consciousness. Oxford: Oxford University Press; 2002.

[12] Perl ER. Pain mechanisms: a commentary on concepts and issues. Progress in Neurobiology 2011; 94(1): 20–38.

‘Robot Pain’

Abstract. Functionalism of robot pain claims that what is definitive of robot pain is functional role, defined as the causal relations pain has to noxious stimuli, behavior and other subjective states. Here, I propose that the only way to theorize role-functionalism of robot pain is in terms of type-identity theory. I argue that what makes a state pain for a neuro-robot at a time is the functional role it has in the robot at the time, and this state is type identical to a specific circuit state. Support from an experimental study shows that if the neural network that controls a robot includes a specific ’emotion circuit’, physical damage to the robot will cause the disposition to avoid movement, thereby enhancing fitness, compared to robots without the circuit. Thus, pain for a robot at a time is type identical to a specific circuit state.

Here.

Tania Lombrozo, ‘The Mind is Just the Brain’

UC Berkeley psychologist Tania Lombrozo has responded to the Annual Edge Question for 2014, ‘What scientific idea is ready for retirement?’, with a piece entitled ‘The Mind is Just the Brain’, in which she argues for the rejection (‘retirement’) of mind-brain identity theory.

Using a baking analogy to illustrate her case against reductionism, she writes:

But a theory of baking wouldn’t be very useful if it were formulated in terms of molecules and atoms. As bakers, we want to understand the relationship between—for example—mixing and texture, not between kinetic energy and protein hydration. The relationships between the variables we can tweak and the outcomes that we care about happen to be mediated by chemistry and physics, but it would be a mistake to adopt “cake reductionism” and replace the study of baking with the study of physical and chemical interactions among cake components.

But if you are interested in the project of explaining, predicting, and controlling the quality of your baked goods, then you’ll need something like a baking theory to work with.

Rejecting the mind in an effort to achieve scientific legitimacy—a trend we’ve seen with both behaviorism and some popular manifestations of neuroscience—is unnecessary and unresponsive to the aims of scientific psychology. 

In these passages, Lombrozo makes a common anti-reductionistic mistake of thinking that mind-brain identity makes mental experiences somehow unreal or even disappear. Her reasoning implies that a correct explanation of mental phenomena cannot involve scientific reduction of mental phenomenon to neurobiological mechanism. This misunderstanding trades on a peculiar view of reduction, where it is expected that in neuroscience, mind-brain identities eliminate mental experiences. I think this expectation is incorrect.

Temperature was ontologically reduced to mean molecular kinetic energy, but no person expects that temperature therefore ceased to be real or became scientifically disrespectable or redundant. Visible light was ontologically reduced to electromagnetic radiation, but light did not disappear. Instead, scientists understand more about the real nature of light than they did before 1873. Light is real, no doubt; and so is temperature. Some expectations about the nature of temperature and light did change, and scientific progress does occasionally require rethinking what was believed about phenomenon. In certain instances, previously respectable states and substances sometimes did prove to be unreal. The caloric theory of heat did not survive rigorous experimental testing; caloric fluid thus proved to be unreal. A successful mind-brain identity of mental phenomenon such as pain means only that there is an explanation of pain. It is a reduction. Scientific explanations of phenomenon do not typically make them disappear [1,2,3].

It is critical to clear-up a further common misconception about mind-brain identity theory. This is the misconception that mind-brain identity theory is equivalent to reductionism. The truth is that whereas identity theory is compatible with a wide range of reductionistic philosophies, it is not equivalent to all of them. Here are some illustrative examples [4]:

1) Identity theory is reductionistic in the sense that it denies minds are ontologically independent of brains and uniquely self-guaranteeing, in line with functionalist and realization (physicalist) philosophies of mind. But functionalism and realization physicalism are not equivalent to the identity theory, so identity theory is not uniquely reductionist in the sense of (1).

2) Identity theory is reductionistic in the minimal sense that it claims, in line with functionalist and realization (physicalist) philosophies, that mind is ‘nothing over and above’ the brain, but since identity theory and functionalist and realization philosophies are not equivalent, identity theory is not equivalent to reductionism. A philosopher could be a reductionist without being an identity theorist.

3) Identity theory is not reductionistic in the sense that it asserts ‘micro-reductionism’. Mental phenomena might be identified with innate genetic or molecular mechanisms (John Bickle), but this is optional, not required. The core metaphysical commitment of identity theory is that mental states are numerically identical to brain states. Nothing is expected in this core claim about the precise mechanistic nature of brain states, which is a scientific question, anyway.

4) Identity theory is not reductionistic in the sense that it asserts that (e.g.) psychology reduces to neuroscience, cognitive neuroscience reduces to molecular neuroscience, or philosophy of mind reduces to quantum mechanics. One can assert identity theory without asserting epistemic reductionism.

Positively, I entirely agree with Lombrozo when she says:

But if we want to know—for instance—how to influence minds to achieve particular behaviors, it would be a mistake to look for explanations solely at the level of the brain.

Understanding the mind isn’t the same as understanding the brain.

Understanding the mind requires first-person descriptions of mental states and experiences, and third-person scientific descriptions of associated brain states, and a method to integrate them, such as the experiential-phenomenological method [5]. So, Lombrozo is right: ‘Understanding the mind isn’t the same as understanding the brain.’ More precisely, I argue that her correct thesis implies that the subject matter of psychology is brain mechanism as related to mental phenomena. For example, the subject of pain science is brain mechanism as related to pain phenomena (e.g., acute pain, chronic pain, fetal pain, empathy for pain, dreamed pain, near-death pain, and so on). Pain research aims to discover the brain mechanisms subserving conscious pain experiences accessible only through introspection, which means that pain research is entirely reliant on the first-person point of view and on using first-person investigative methods. This necessarily includes introspection together with third-person methods (e.g., neuroimaging). Since pain research aims to know which experience types are generated by which brain mechanism, researchers must naturally know when specific pain experiences occur and what their personal qualities are.

The history of scientific pain research shows that introspection has been extensively used. For example, pain psychophysics typically uses subject pain verbal-report or non-verbal behavior (e.g., facial expressions) to infer the presence of pain. That is, pain psychophysics is committed to subject introspection. It is also important to remember that the validity of pain-related neuroimaging was established by the correlation of brain images with self-report of pain [6]. Pain psychophysics, like psychology, preserves an epistemological dualism in its subject matter while rejecting metaphysical dualism.

How then is mind-brain identity theory positioned relative to the indispensability of introspection in mind science? Personal introspection is a direct way of coming to know about personal experiences and their qualities. It is epistemological. Still, despite appearances to the contrary, what introspection reveals to us may be utterly mechanistic. It may be that what scientists study through third-person methods is numerically identical with what is personally experienced through introspection, that is, brain mechanisms of the appropriate type. There is only one type of activity in question: the brain mechanism with all and only physical properties. Thus, mind-brain identity theory is preserved in the study of the mind.

References

[1] Churchland PM (2007). Neurophilosophy at work. Cambridge, UK: Cambridge University Press.

[2] Churchland PS (1989). Neurophilosophy: Toward a unified science of the mind-brain. Cambridge, Mass.: The MIT Press.

[3] van Rysewyk S (2013). Pain is Mechanism. PhD Dissertation, University of Tasmania.

[4] Polger TW (2009). Identity Theories. Philosophy Compass4(5), 822-834.

[5] Price DD, Aydede M (2006). The Experimental Use of Introspection in the Scientific Study of Pain and its Integration with Third-Person Methodologies: The Experiential-Phenomenological Approach. In M Aydede (ed.), Pain: New Essays on Its Nature and the Methodology of Its Study, pp. 243-275. Cambridge, Mass.: MIT Press.

[6] Coghill RC, McHaffie JG, Yen YF (2003). Neural correlates of interindividual differences in the subjective experience of pain. Proceedings of the National Academy of Science USA, 100, 8538-8542.

An approach to understanding fetal pain and consciousness

The trend in the literature on fetal pain is to approach the question of consciousness in the fetus in terms of conscious states of pain. That is, first define what makes a pain a conscious mental state, and then determine being a conscious fetus in terms of having such a state. Thus, the possibility of a conscious fetus is thought to rely on theories of conscious pain states. Call this the state approach to fetal pain. 

Two state approaches to fetal pain are present in the literature. One approach looks at the brain structure(s), pathways and circuits necessary for conscious pain states and then seeks to establish whether this substrate is present and functional in the fetus. There is broad agreement among researchers that the minimal necessary neural pathways for pain are in the human fetus by 24 weeks gestation [1, for review]. Some researchers argue that the fetus can feel pain earlier than 24 weeks because pain is enabled by subcortical brain structures [4,5,6].

Another phenomenal approach is to consider the subjective content of a conscious experience of pain, and to ask whether that content might be available to the fetus [1,2,3]. Based on this approach, some researchers argue that the fetus cannot feel pain at any stage because it lacks developmental abilities and concepts such as sense of self necessary for pain [1,2,3].

Although both state approaches are presented as opposites in the literature, they share the determination of fetal pain based on specific levels or degrees of complexity, whether of the brain structures and the relationship they have to the conscious state of pain, or of the subjective contents that constitute that state.

An alternate approach to understanding fetal consciousness that has not been explored in the literature on fetal pain is the extent to which pain is based on the arrangement of certain brain structures (or experiential contents), rather than a result of maturation or increase in complexity achieved by growth of the brain substrate which below a certain size does not enable consciousness [7,8]. Thus, whether the fetus is excluded in this regard is not due to its simplicity, but because its lack of certain brain arrangements necessary to enable consciousness.

According to this alternate view of fetal pain, a living creature’s subjective contents may differ greatly in complexity. To convey the range of conscious possibilities, consider the Indian ‘scale of sentience’ (cited in [8]):

‘This.’
‘This is so.’
‘I am affected by this which is so.’
‘So this is I who am affected by this which is so.’

The possibilities in this consciousness scale range from simply experienced sensation (‘This’; ‘This is so’) to self-consciousness (‘I am affected by this which is so’; ‘So this is I who am affected by this which is so’). Each stage in this scale presupposes consciousness. Any experience, whatever its degree of complexity, is conscious. It follows that to see, to hear, and to feel is to be conscious, irrespective of whether in addition a creature is self-conscious that it is seeing, hearing, and feeling [7]. To feel pain is to be conscious of that experience regardless of whether in addition one is self-conscious of being in pain. Self-consciousness is just one of many contents of consciousness available to big-brained living creatures with complex capacities: it is not definitive of consciousness [7,8]. The point of saying this is that it circumvents the logical mistake of misidentifying attributes unique to a specialized form of consciousness (e.g., self-consciousness) as general features of consciousness itself.

With this alternate view of consciousness now sketched in, we should determine where the fetus and where pain fall in the Indian scale of sentience. The possibilities in the scale extend from mere sensation to self-consciousness–where does the fetus fall in?

References

[1] Derbyshire S, Raja A. (2011). On the development of painful experience.Journal of Consciousness Studies18, 9–10.

[2] Derbyshire SW. (2006). Controversy: Can fetuses feel pain?. BMJ: British Medical Journal332(7546), 909.

[3] Szawarski Z. (1996). Do fetuses feel pain? Probably no pain in the absence of “self”. BMJ: British Medical Journal313(7060), 796–797.

[4] Anand KJ, Hickey PR. (1987). Pain and its effects in the human neonate and fetus. New England Journal of Medicine317(21), 1321–1329.

[5] Anand KJ. (2007). Consciousness, cortical function, and pain perception in nonverbal humans. Behavioral and Brain Sciences30(01), 82–83.

[6] Lowery CL, Hardman MP, Manning N, Clancy B, Whit Hall R, Anand KJS. (2007). Neurodevelopmental changes of fetal pain. In Seminars in perinatology (Vol. 31, No. 5, pp. 275–282).

[7] Merker B. (1997). The common denominator of conscious states: Implications for the biology of consciousness. Available at: http://cogprints.soton.ac.uk.

[8] Merker B. (2007). Consciousness without a cerebral cortex, a challenge
for neuroscience and medicine. Target article with peer commentary and author’s response. Behavioral and Brain Sciences, 30, 63–134.

The University of Tokyo Center for Philosophy, 3rd International Conference ‘Phenomenology of Pain’, Jan 4, 2014

The University of Tokyo Center for Philosophy, Uehiro Research Division,
Philosophy of Disability & Co-existence Project (UTCP/PhDC):

3rd International Conference ‘Phenomenology of Pain’

20140104_poster_ver4

Pain in the brain? The question of fetal pain

There is broad agreement among researchers that the minimal necessary neural pathways for pain are in the human fetus by 24 weeks gestation [1, for review]. However, some argue that the fetus can feel pain earlier than 24 weeks because pain can be enabled by subcortical brain structures [2,3,4,5]. Other researchers argue that the fetus cannot feel pain at any stage of gestation because the fetus is sustained in a state of unconsciousness [6]. Finally, others argue that the fetus cannot feel pain at any stage because the fetus lacks the conceptual postnatal development necessary for pain [7,8,9]. If a behavioral and neural reaction to a noxious stimulus is considered sufficient for pain then pain is possible from 24 weeks and probably much earlier. If a conceptual subjectivity is considered necessary for pain, however, then pain is not possible at any gestational age. According to [1], much of the disagreement concerning fetal pain rests on the understanding of key terms such as ‘wakefulness’, ‘conscious’ and ‘pain’.

A motivation for thinking conceptual subjectivity is necessary for pain is the idea that subjective experiences such as pain cannot be reduced to or identified with the objective features of the brain [7,8,9]. All pains are personal experiences and therefore entirely subjective; all brain states are physical events and therefore entirely objective. There is a fundamental divergence between pain and the brain. Thus, pain cannot be in the brain. The basic argument:

1. Pain experiences are subjective.

2. Brain events are objective.

Therefore, since pain experiences and brain events fundamentally diverge,

3. Pain experiences are not identical to brain events.

Is this a good argument? Let’s examine its first premise – ‘pain experiences are subjective.’ On a reasonable interpretation of its meaning, to state that ‘pain experiences are subjective’ is to state that pain experiences are knowable by introspection. However, since brain events are not knowable by introspection, pain experiences cannot be identical to brain events. Here is the argument:

1. Pain experiences are knowable to me by introspection.

2. Brain events are not knowable to me by introspection.

Therefore, since pain experiences and brain events fundamentally diverge,

3. My pain experiences are not identical to any of my brain events.

Once the argument is represented in this form, it is clear that it is fallacious. This can be clearly observed if we compare the argument with the following example:

1. Ibuprofen is known to me to relieve pain.

2. Iso-butyl-propanoic-phenolic acid is not known by me to relieve pain.

Therefore, since ibuprofen and iso-butyl-propanoic-phenolic acid fundamentally diverge,

3. Ibuprofen cannot be identical to iso-butyl-propanoic-phenolic acid.

The premises in the example are true, but the conclusion is known to be false. The argument is fallacious because the core idea of the argument – ‘fundamental divergence’ – makes an erroneous assumption; namely, it assumes that a thing must be known by somebody. But the property ‘being known by somebody’ is not a necessary feature of any thing, much less a property that might establish its identity or non-identity with some thing otherwise known. The truth of the premises may be due to nothing else but my ignorance of what turns out to be identical with what. These considerations challenge the assumed epistemology in the conceptual subjectivity view of pain.

They also challenge the related claim made by proponents of conceptual subjectivity that any description of a pain given in objective scientific terms will necessarily always exclude the personal experience of that pain [7,8,9]. The argument made here is by now familiar: since descriptions of pain in personal subjective terms are different from scientific descriptions of pain, it follows that a pain and its private subjectivity cannot be identical with a brain event and its public objectivity. Only persons can feel pain – brain cells and protein channels can’t. Clearly, the argument begs the issue in question: whether or not the subjective features of a pain I personally experience are identical with some objective features of my brain that might be discovered by neuroscience is precisely the question at issue [10,11].

Besides, in order to understand a scientific explanation of pain, neuroscience does not require of a person that he both understands the explanation and feels pain as a condition of understanding. Neuroscience aims to explain pain, that is its main purpose. Too much is demanded of neuroscience if, in addition to formulating an explanation of pain, it is meant to re-create pain in somebody as a requirement of understanding [10,11]. This expectation is therefore much too strong.

References

[1] Derbyshire SWG, Raja A. (2011). On the development of painful experience.Journal of Consciousness Studies18, 9–10.

[2] Anand KJ, Hickey PR. (1987). Pain and its effects in the human neonate and fetus. New England Journal of Medicine, 317(21), 1321–1329.

[3] Anand KJ. (2007). Consciousness, cortical function, and pain perception in nonverbal humans. Behavioral and Brain Sciences30(1), 82–83.

[4] Lowery CL, Hardman MP, Manning N, Clancy B, Whit Hall R, Anand KJS. (2007). Neurodevelopmental changes of fetal pain. In Seminars in perinatology, 31(5), 275–282.

[5] Merker B. (2007). Consciousness without a cerebral cortex, a challenge
for neuroscience and medicine. Target article with peer commentary and author’s response. Behavioral and Brain Sciences, 30, 63–134.

[6] Mellor DJ, Diesch TJ, Gunn AJ, Bennet L. (2005). The importance of ‘awareness’ for understanding fetal pain. Brain research reviews49(3), 455-471.

[7] Derbyshire SWG. (2012). Fetal analgesia: where are we now? Future Neurology7(4), 367-369.

[8] Derbyshire SWG. (2006). Controversy: Can fetuses feel pain? BMJ: British Medical Journal332(7546), 909.

[9] Szawarski Z. (1996). Do fetuses feel pain? Probably no pain in the absence of “self”. BMJ: British Medical Journal313(7060), 796–797. 

[10] Churchland PS. (2002). Brain-wise: V: Studies in Neurophilosophy. MIT press.

[11] van Rysewyk S. (2013). Pain is Mechanism. PhD Dissertation, University of Tasmania.

Pain experience and the self

Conscious pain is always personal. It is experienced from the view of oneself, and is not real or meaningful apart from this perspective.

All pains cluster around one’s personal aperture as around a single point or origin from which they are all perceived, irrespective of where in the body pain is felt. The sensation of a pain in a hand is sensed as located in the hand, but that pain sensation in the hand is not felt from the hand, but from about the same spatial location from which that hand is personally seen, even if pain is felt in complete darkness or in a dream. It is the ‘here’ with regard to which any pain is ‘there.’

It may intuitively feel that this single experiential point is located at the mid-point between the centers of rotation of the two eyes. Mach’s drawing above shows a monocular view of this point given in peripheral vision. In fact, the empirically determined location of the point is deeper inside the head, in the midsagittal plane, roughly 4–5 cm behind the bridge of the nose. Initially developed by Herring (1879/1942), this determination identifies the intersection of a few lines of sight obtained by fixating certain locations in the environment and aligning pins with them along each of the lines of sight or attention.

The self thus located is the origin of all lines of sight/attention and so cannot be any kind of self-representation (Merker, 2007, 2013). It defines the view point from which any and all representations of sensory experience are perceived, including personal pain. It is the point from which attention is directed and relative to which percepts are located in the space whose origin it defines (Merker, 2007, 2013).

To think that self must involve a kind of self-representation is to transfer sensory experience from the sensory state to one of its sub-domains (the self), which I think motivates viewing the self as a kind of cartesian homunculus. On this cartesian view, pain is interpreted in presence of the self. To my mind, it seems the other way round: the self in pain finds itself in the presence of pain (the ‘content’ of pain). The self of any conscious pain is not inherently conscious. Pain is intruder, not self. That is why pain is an aversion.

From this single experiential point we look out upon the world along straight and uninterrupted lines of sight. This orientation is dramatically reversed in the experience of pain. During pain, attentional focus is rapidly and involuntarily moved backwards along these same lines toward their most proximal origin. I believe this reverse direction helps to characterize the meaning of conscious pain as intrusion or threat to oneself.

References

Hering, E. (1879/1942). Spatial Sense and Movements of the Eye. Trans. C. A. Radde. Baltimore, MD: American Academy of Optometry (Original work published in 1879).

Mach, E. (1897). Contributions to the Analysis of the Sensations. La Salle, IL: Open Court.

Merker, B. (2007). Consciousness without a cerebral cortex, a challenge
for neuroscience and medicine. Target article with peer commentary and author’s response. Behavioral and Brain Sciences, 30, 63–134.

Merker, B. (2013). The efference cascade, consciousness, and its self: naturalizing the first person pivot of action control. Frontiers in Psychology, doi:10.3389/fpsyg.2013.00501.

Pain in the brain is like a melody in music

A flash of lightning produces a single sound. Pain in the brain is not like that. Neurons in the brain can excite or inhibit many other neurons, to which they are connected. Pain is not controlled by a single neuron.

A flash of lightning has no intended direction. But pain in the brain is not like that. The synaptic connections between neurons enable coordinated patterns of activation between millions of interconnected neurons. A type of pain is just a type of activation pattern.

Pain in the brain is not conducted like a symphony orchestra by a single individual. It is more like a free-jazz ensemble whose music is produced by loose and coordinated effort among the ensemble members.

‘Do you try to find the real artichoke by stripping it of its leaves?’ Wittgenstein once said. The same can be said of pain in the brain.

The brain is a causal mechanism to convey pain as a sensation. Pain also conveys to us itself. Pain in the brain is like a melody in music. When we feel a pain, the pain doesn’t convey something else that compounds with the activation patterns in the brain. We get the feeling of a pain because pain just is an activation pattern.

In the absence of a general theory of pain or brain function, metaphor and philosophy serve useful placeholder roles.

It is not obvious that experiences of pain are identical to brain activation patterns. In reply, it is not obvious that an ensemble of human beings could produce exciting jazz music, either.

Explaining pain: Comment on Robinson, Staud and Price (2013)

Here, I briefly respond to Robinson, Staud and Price6 concerning what constitutes the ‘neural signature’ of pain (p. 325), note a logical mistake in their article, and highlight a reason why explaining pain is difficult. It is probable that conscious pain may be subserved by an unconscious physical base with a specific neurophysiological signature. Explaining pain in this direct way aims first to describe the base as a correlate of pain, then ultimately to achieve a reductive neurophysiological explanation of pain. Multiple evidential lines demonstrate that the neurophysiological base of pain need not be limited to one physical location, as Robinson, Staud and Price rightly note (p. 325). Since the hypothetical pain base is probably distributed, and therefore is more akin to the immune system than the liver, it is mistaken to expect that if it is not confined to a single neural region, or a single pattern of functional interaction, then there cannot be a physical signature of pain, as Robinson, Staud and Price appear to think (p. 325). Instead of a region-based view of the hypothetical pain base, it may be more accurate to think of it as a distributed mechanism.5, 8

The mechanism of pain could involve any number of neurophysiological systems (nervous, endocrine, immune), or reciprocal interactions between them, or any number of neurophysiological levels (pathway, network, single cell, molecular), or reciprocal interactions between them.1, 7, 8 The probability of a distributed mechanism, combined with the open-ended probability concerning the systems and level at which the mechanism exists, explains why current hypotheses and theories of pain in the literature, including those made in the article by Robinson, Staud and Price, are relatively unconstrained. However, the absence of constraints is not indicative of the likely truth of Cartesian dualism, the futility of searching for neurophysiological pain correlates, or the unreliability of verbal pain self-report. Rather, it indicates that pain science has much to do.

Neurophysiological mechanism and pain experiences can be correlated for a variety of reasons: the mechanism is part of the cause of pain; the mechanism is part of the effect of pain; the mechanism indirectly parallels pain; the mechanism is what pain can be identified with.2, 8 Discovering the neurophysiological signature of pain requires the identification of some neurophysiological mechanism with pain. The correlation of mechanism x with pain is informative because x may be the one for identifying pain. Correspondingly, mechanism y that does not correlate with pain indicates that y may not be the one. If there is a pain mechanism with a neurophysiological signature identifiable with pain experiences, the scientific and clinical benefits could be huge. Thus, investigating pain directly is worth a try.

Now, it is quite possible that a scientist may be looking at an instance of the pain signature without comprehending that it is an instance. This will occur if the physical base of pain does not possess an identifying property that is obvious to naïve researchers, but is comprehensible only through the availability of a more complete general theory of brain function.2, 3, 4, 8 The limitations in explaining pain are not simply technological. After all, how would a person know, independently of Antoine Lavoisier’s studies on oxygen, that metabolizing, burning and rusting are identical with the same mechanism, but that lightning and sunlight are not? Thus, Robinson, Staud and Price are right in asserting that it is misconceived to replace pain ratings with neuroimaging data, especially at this early stage of pain investigations.

References

Chapman CR, Tuckett RP, & Song CW: Pain and stress in a systems perspective: reciprocal neural, endocrine, and immune interactions. J Pain 9: 122-145, 2008.

Churchland PS: A neurophilosophical slant on consciousness research. Progress in brain research 149: 285-293, 2005.

Frith CD, Perry R, Lumer E: The neural correlates of conscious experience: an experimental framework. Trends in Cognitive Science 3: 105-114, 1999.

Northoff, G: Philosophy of the brain: The brain problem (Vol. 52). Amsterdam, John Benjamins Publishing Company, 2004.

Northoff, G: Region-Based Approach versus Mechanism-Based Approach to the Brain. Neuropsychoanalysis: An Interdisciplinary Journal for Psychoanalysis and the Neurosciences 12: 167-170, 2010.

Robinson ME, Staud R, & Price DD: Pain Measurement and Brain Activity: Will Neuroimages Replace Pain Ratings? J Pain 14: 323-327, 2013.

Tracey I, Mantyh PW: The Cerebral Signature for Pain Perception and Its Modulation. Neuron 55: 377-391, 2007.

van Rysewyk S: Pain is Mechanism. PhD Thesis, University of Tasmania, 2013.

Why are pain patients all unique? A type-token identity theory answer

Variations in response to pain have been reported in clinical settings (e.g., Bates et al. 1996; Cherkin et al. 1994; Jensen et al. 1986; Unruh, 1996; Wormslev et al. 1994). Patients with similar types and degrees of wounds vary from showing no pain to showing severe and disabling pain. Many chronic pain patients show disabling chronic pain despite showing no observable wound. Other patients show severe wounds but do not show pain. Why is it that two persons with identical lesions do not show the same pain or no pain at all? Why are all pain patients unique?

I propose that mind-brain identity theory may offer an answer to this difficult question. There are two main versions of identity theory: type and token identity. A sample type identical property is to identify “Being in pain” (X) with “Being the operation of the nervous-endocrine-immune mechanism” (Y) (i.e., X iff Y) (Chapman et al. 2008; van Rysewyk, 2013). For any person in pain the nervous-endocrine-immune mechanism (NEIM) must be active, and when NEIM is active in a person, he or she is in pain. Thus, type identity theory strongly limits the pattern of covariation across persons. According to token identity theory, for a person in mental state X at time t, X is identical to some neurophysiological state Y. However, in the same person at time t1, the same mental state X may be identical to a different neurophysiological state Y2. Token identity theory doesn’t limit the pattern of covariation across persons; it only claims that, at any given time, some mind-brain identity must be true.

In response to the topic question, I propose a hybrid version of identity theory – ‘type-token mind-brain identity theory’. Accordingly, for every person, there is a type identity between a mental state X and some neurophysiological state Y. So, when I am in pain, I am in NEIM state Y (and vice versa), but this NEIM state Y may be quite different across persons. Type-token identity theory therefore proposes a type identity model at the level of every person (i.e., it may vary across persons). A type-token identity theory implies that group-level type identities (i.e., type-type) cannot fully explain the pattern of covariation in pain responses across persons. Measuring changes of a pattern of psychological and neurophysiological indicators over time may then support a unidimensional model of chronic pain for each pain patient. Thus, being in chronic pain for me is identical with a specific pattern of NEIM activity (Chapman et al. 2008; van Rysewyk, 2013), but for a different patient, the same state of pain may be identical to a different pattern of NEIM activity. In preventing and alleviating chronic pain, it is therefore essential to best fit the intervention to the type-token pain identity profile of the patient.

References

Bates, M. S., Edwards, W. T., & Anderson, K. O. (1993). Ethnocultural influences on variation in chronic pain perception. Pain, 52(1), 101-112.

Chapman, C. R., Tuckett, R. P., & Song, C. W. (2008). Pain and stress in a systems perspective: reciprocal neural, endocrine, and immune interactions. Journal of Pain 9: 122-145.

Cherkin, D. C., Deyo, R. A., Wheeler, K., & Ciol, M. A. (1994). Physician variation in diagnostic testing for low back pain. Who you see is what you get. Arthritis & Rheumatism, 37(1), 15-22.

Jensen, M. P., Karoly, P., & Braver, S. (1986). The measurement of clinical pain intensity: a comparison of six methods. Pain, 27(1), 117-126.

Unruh, A. M. (1996). Gender variations in clinical pain experience. Pain, 65(2), 123-167.

van Rysewyk, S. (2013). Pain is Mechanism. Unpublished PhD Thesis. University of Tasmania.

Wormslev, M., Juul, A. M., Marques, B., Minck, H., Bentzen, L., & Hansen, T. M. (1994). Clinical examination of pelvic insufficiency during pregnancy: an evaluation of the interobserver variation, the relation between clinical signs and pain and the relation between clinical signs and physical disability. Scandinavian journal of rheumatology, 23(2), 96-102.

Will science make painfulness disappear?

Some philosophers worry that neuroscience will make painfulness disappear. Broadly, the objection is that if a science reduces a macro phenomenon to a micro phenomenon, then the macro phenomenon is not real or disappears (e.g., Searle, 1992). Using this conception of ‘reduction’, it is then reasoned that because it is observably obvious that a pain is real, it cannot be reduced to neuroscience. This misunderstanding trades on an idiosyncratic understanding of reduction, where it is expected that in science, reductions make macro phenomenon disappear. This expectation is confused.

Temperature was reduced to mean molecular kinetic energy, as recounted above, but no person expects that temperature therefore ceased to be real or became scientifically disrespectable or redundant. Visible light was reduced to electromagnetic radiation, but light did not disappear. Instead, scientists understand more about the real nature of light than they did before 1873. Light is real, no doubt; and so is temperature. Some expectations about the nature of temperature and light did change, and scientific progress does occasionally require rethinking what was believed about phenomenon. In certain instances, previously respectable properties and substances sometimes did prove to be unreal. The caloric theory of heat did not survive rigorous experimental testing; caloric fluid thus proved to be unreal. While no one expects that painfulness will cease to be real or become scientifically disrespectable if it is successfully explained by neuroscience, everyone believes that debilitating chronic pain will be controlled and eventually disappear as a result of scientific reduction. But this belief may turn out to be quite wrong. Simple prudence suggests that we wait and see.

Thus, the reduction of a macro phenomenon means only that there is an explanation of the phenomenon. Scientific explanations of phenomenon do not typically make them disappear. As neuroscience matures, the future of current conceptions of painfulness and sensory experience generally will rely on the empirical facts, and the enduring accuracy of current macro level theories (Churchland, 1993).

Churchland, P.M. (1993). Evaluating our self-conception. Mind and Language, 8, 211-222.
Searle, J.R. (1992). The Rediscovery of Mind. Cambridge, Mass.: MIT Press.

‘The human fetus cannot feel pain’

Fetal pain perception is often modelled on the same neural structures as in the adult.

However –

(1 The neural structures involved in pain processing in early development are unique and different from adults.

(2 Some of these structures and mechanisms are not maintained beyond specific developmental periods.

The immature pain system plays a signalling role during each stage of development, and fulfils this role using different neural resources available at specific developmental times.

Thus, the error here is reading the adult into the fetus.

Does science make things disappear?

If a science reduces a macro phenomenon to a micro phenomenon, then the macro phenomenon either is not real or ‘goes away’. Is this true? Does science make things disappear?

Obstetrics is true, and babies are born every day. Or, are babies born in spite of obstetrics? Does understanding gynecology make women sterile?

At the same time, a science of pain will hopefully reduce – or eliminate – much pain (mammalian and non-mammalian). Science makes pain ‘go away’. Surely a good thing.

How would you explain to a person who cannot experience pain, what pain is?

How would you explain to a person who could never experience pain, what pain is?

Do the following:

1. Get a dairy food that is extremely spoiled.

2. Get the person to fill his or her mouth with this delightful food.

(ESSENTIAL: The food has to remain in the person’s mouth! Under no circumstances can the person spit out the food and clean his her mouth.)

3. Chew the food.

This test is a good model for the nature of pain.

Pain is aversive. We want to avoid pain. Eating spoiled food is the same: we want to avoid at all costs putting, much less chewing and swallowing, bad food.

Having a really bad taste in your mouth is like having a pain in your body.

#SciFund update: video complete!

My #SciFund video is finally complete!

Quite a mission to do (first time), but I am happy with the finished product.

Click on the image:

 

 

 

 

 

 

 

 

Here is a map showing the global distribution of participating scientists in Round 1 (2011) and Round 2 (May, 2012) of the #SciFund Challenge:

SciFunders Standing Tall and Talented