Is pain where you feel it in the body, or in the brain? Neurophenomenology and the spatial aspect of nociception

Pain is interesting, salient, mysterious. It may feel like it is in one specific place in or on the body. It may feel diffuse, with gradations, or it may seem referred from one area to another. What is happening in the brain and in the body as these spatial aspects of pain are experienced? How much of the causation of pain occurs where we feel it, and how much occurs in the brain? Below is a series of probes and thinking aloud about where pain is, with speculations to stimulate my thinking and yours.  I’m not a “pain expert”, nor a bodyworker that heals clients, nor a physiologist with a specialization in nociception, but a cognitive scientist, with clinical psychology training, interested in body phenomenology and the brain.  Please do post this essay to Facebook, share it, critique, respond, and comment (and it would be helpful to know if your background is in philosophy, neuroscience, bodywork, psychology, medicine, a student wanting to enter one of these or another field, etc). Pain should be looked at from multiple angles, with theoretical problems emphasized alongside clinical praxis, and with reductionistic accounts from neurophysiology juxtaposed against descriptions of the embodied phenomenology and existential structures.  As I have mentioned elsewhere, it is still early in the history of neurophenomenology…let a thousand flowers bloom when looking at pain. We need data, observations, insights and theories from both the experience side as well as the brain side. Francisco Varela aptly described how phenomenology and cognitive neuroscience should relate:

“The key point here is that by emphasizing a codetermination of both accounts one can explore the bridges, challenges, insights, and contradications between them. Both domains of phenomena have equal status in demanding full attention and respect for their specificity.”

We all know what pain is phenomenologically, what it feels like, but how to define it? The International Association for the Study of Pain offers this definition: “an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.” Of particular interest to neurophenomenology and embodied cognitive science is their claim that “activity induced in the nociceptors and nociceptive pathways by a noxious stimulus is not pain, which is always a psychological state.” Good that they do not try to reduce the experience of pain to the strictly physiological dimension, but I wonder how Merleau-Ponty, with his non-dualistic ontology of the flesh would have responded. Pain seems to transgress the border of mind and body categories, does it not? I am slowly biting off chucks of the work on pain at the Stanford Encyclopedia of Philosophy. Lots of provocative angles, including this one:

“there appear to be reasons both for thinking that pains (along with other similar bodily sensations) are physical objects or conditions that we perceive in body parts, and for thinking that they are not. This paradox is one of the main reasons why philosophers are especially interested in pain.”

Right now I am particularly interested in the spatial aspect of where pain seems to be, what I might label the spatial phenomenology of nociception. When I introspect on aching parts of my feet, it seems as if the pain occupies a volume of space. Using manual pressure I can find places on my feel that are not sore, right next to areas that are slightly sore, which are in turn near focal areas of highest pain. It seems as if the pain is locatable “down there” in my body, and yet what we know about the nociceptive neural networks suggests the phenomenology is produced by complex interactions between flesh, nearby peripheral nerves, the central nervous system, and neurodynamics in the latter especially. A way of probing this this would be to examine the idea that the pain experience is the experiential correlate of bodily harm, a sort of map relating sensations to a corresponding nerve activated by damage to tissue. So, is the place in my body where I feel pain just the same as where the damage or strain is? Or, Is pain caused by pain-receptive nerves registering what is happening around them, via hormonal and electrical signals? Or is pain actually the nerve itself being “trapped” or damaged, yet in a volume of undamaged tissue one can feel hurts? Could the seeming volume of experienced pain-space be a partial illusion, produced by cognizing the tissue damage as some place near or overlapping with yet not spatially identical to where the “actual” damage is, in other words a case of existential-physiological discrepancy? One scenario could be, roughly, that pain “is” or “is made of” nerves getting signals about damage to tissue; another would be that pain “is” the nerves themselves being damaged or sustaining stress or injury. Maybe pain involves both? Maybe some pain is one, or the other? In terms of remembering how my heel pain started, it’s not so easy, but I love to walk an hour or two a day, and have done so for many years. I recall more than ten years ago playing football in the park, wearing what must have been the wrong sort of shoes, and upon waking the next day, having pretty serious pain in my heel. Here are some graphics that, intuitively, seem to map on to the areas where I perceive the pain to be most focal:

from bestfootdoc.com

from setup.tristatehand.com

from plantar-fasciitis-elrofeet.com

If I palpate my heel, I become aware of a phenomenologically complex, rich blend of pleasure and pain. I crave the sensation of pressure there, but it can be an endurance test when it happens. Does the sensation of pressure that I want reflect some body knowledge, some intuitive sense of what intervention will help my body heal? How could this be verified or falsified? It is not easy to describe the raw qualia of pain, actually. I can describe it as achey and moderately distressing when I walk around, and sharp upon palpating. Direct and forceful pressure on the heel area will make me wince, catch my breath, want to gasp or make sounds of pain/pleasure, and in general puts me in a state of heightened activation. But I love it when I can get a therapist to squeeze on it, producing what I call “pain-pleasure”:

from indyheelpaincenter.com

This diagram below helps me map the sensations to the neuroanatomy. We need to do more of this sort of thing. This kind of representation seems to me a new area for clinical neurophenomenological research (indeed, clinical neurophenomenology in general needs much more work, searching for those terms just leads back to my site, but see the Case History section in Sean Gallagher’s How the Body Shapes the Mind).

from reconstructivefootcaredoc.com

What is producing the pain-qualia, the particular feeling? Without going too far into varying differential diagnosis, it is commonly attributed to plantar fasciitis.  There the pain would be due to nociceptive nerve fibers activated by damage to the tough, fibrous fascia that attach to the calcaneus (heel bone) being strained, or sustaining small ripped areas, and/or local nerves being compressed or trapped. A 2012 article in Lower Extremity Review states that “evidence suggests plantar fasciitis is a noninflammatory degenerative condition in the plantar fascia caused by repetitive microtears at the medial tubercle of the calcaneus.” There are quite a few opinions out there about the role of bony calcium buildups, strain from leg muscles, specific trapped nerves and so forth, and it would be interesting to find out how different aspects of reported pain qualia map on to these. Below you can see the sheetlike fascia fiber, the posterior tibial nerve, and it’s branches that enable local sensations:

from aafp.org

Next: fascia and the innervation of the heel, from below:

from mollyjudge.com

Another view of the heel and innervation:

from mollyjudge.com

Below is a representation of the fascia under the skin:

from drwolgin.com

There is a very graphic,under the skin, maybe not SFW surgeon’s-eye perspective on these structures available here. Heel pain turns out to be very common, and is evidently one of the most frequently reported medical issues. Searching online for heel pain mapping brings up a representation purportedly of 2666 patients describing where they feel heel pain: I can’t find where this comes from originally and can’t speak to the methodology, rigor, or quality of the study, but the supposed data are interesting, as is the implicit idea of spatial qualia mapping:  the correspondence of experienced pain to a volume of space in the body. It also quite well represents where the pain is that I feel. The focal area seems to be where the fascia fibers attach to the calcaneus, an area that bears alot of weight, does alot of work, and is prone to overuse. So, where is the pain? Is it in the heel or the brain? Is it in the tissue, the nerve, or both? Is there a volume of flesh that contains the pain? I am going to have to think about these more, and welcome your input. What about the central nervous system that processes nociceptive afferents coming from the body? A good model of pain neurophenomenology should involve a number of cortical and subcortical areas that comprise the nociceptive neural network: -primary somatosensory cortex (S1) and secondary somatosensory cortex (S2): -insula -anterior cingulate cortex (ACC) -prefrontal cortex (PFC) -thalamus Here are some representations of the pain pathways, or the nociceptive neural network:

from Moisset and Bouhassira (2007)

Moisett el (2009)

 

from Tracey and Mantyh (2012)

Broadly speaking, pain seems to be generated by tissue damage, inflammation, compromising the integrity of tissue, stress on localized regions, and so forth being processed by peripheral afferent pain pathways in the body, then phylogenetically ancient subcortical structures, and then the aforementioned cortical regions or nociceptive neural network.  As I have mentioned many times, making a robust account of how various regions of the brain communicate such that a person experiences qualia or sensory phenomenology will need to reference neurodynamics, which integrates ideas from the physics of self-organization, complexity, chaos and non-linear dynamics into biology.  It is gradually becoming apparent to many if not most workers in the cognitive neurosciences that there are a host of mechanisms regions of the brain use to send signals, and many of these are as time dependent as space dependent. Michael Cohen puts it thusly: “The way we as cognitive neuroscientists typically link dynamics of the brain to dynamics of behavior is by correlating increases or decreases of some measure of brain activity with the cognitive or emotional state we hope the subject is experiencing at the time. The primary dependent measure in the majority of these studies is whether the average amount of activity – measured through spiking, event-related-potential or -field component amplitude, blood flow response, light scatter, etc. – in a region of the brain goes up or down. In this approach, the aim is to reduce this complex and enigmatic neural information processing system to two dimensions: Space and activation (up/down). The implicit assumption is that cognitive processes can be localized to specific regions of the brain, can be measured by an increase in average activity levels, and in different experimental conditions, either operate or do not. It is naïve to think that these two dimensions are sufficient for characterizing neurocognitive function. The range and flexibility of cognitive, emotional, perceptual, and other mental processes is huge, and the scale of typical functional localization claims – on the order of several cubic centimeters – is large compared to the number of cells with unique physiological, neurochemical, morphological, and connectional properties contained in each MRI voxel. Further, there are no one-to-one mappings between cognitive processes and brain regions: Different cognitive processes can activate the same brain region, and activation of several brain regions can be associated with single cognitive processes. In the analogy of Plato’s cave, our current approach to understanding the biological foundations of cognition is like looking at shadows cast on a region of the wall of the cave without observing how they change dynamically over time.” But what of the original question? Is pain where you feel it in the body, or in the brain? It seems to me the answer must be both.  The experience of pain being localized there or a little on the left is a product of local tissue signals and receptor activation, which produces peripheral afferent nerve firing, which gets processed by spinal afferent neurodynamics, brainstem activation, thalamic gating, and then somatosensory, insular, anterior cingulated, and prefrontal cortical regions. Yet the real model of pain, one that invokes mechanisms and causes, remains elusive. And a good model of pain must account for the possibility of pain without suffering as well! For now, what I can offer are probes to get us speculating, thinking critically, and eventually building a clinical neurophenomenology of pain. If that interests you, by all means get involved.

History of the development of neurophenomenology-pt.1

(Part II is here, and Part III is here)

I will attempt in three essays to outline the sweep of ideas, researchers, and works that lead a few of us to speak of “neurophenomenology” as a more or less distinct field.  Part I traces 19th century psychology, neurology, and phenomenology roughly up to World War II. Part II examines the impact of cognitivism, the continued development of clinical neurology and basic neuroscience, the progression of phenomenological thought in psychology and medicine, and criticisms of cognitive science. Part III explores the early 1990’s origins of the emerging field of neurophenomenlogy within the broader context of interest in embodied cognition and consciousness studies. Any corrections, suggestions, or criticisms are welcome.

It may be too early to attempt a definitive characterization of the constitutive elements, at the least it is a combination of clinical studies by neurologists, psychiatrists, and psychologists, experimental work on the brain and mind, and philosophical analysis of consciousness and cognition. While the term “neurophenomenology” has a recent (early 1990’s) origin, the project of understanding the mysterious and profound relationship between brain events and awareness goes back at least as far as classical Greek philosophy. Physicians and philosophers have grappled with the enigma of existence and of consciousness for millenia. Psychology has roots in medicine, ethics, and the philosophy of mind and epistemology, but by the late 19th century,  the overlapping fields of biological psychology, psychiatry, behaviorism, and the psychophysiology and psychophysics of perception emerged. We can trace the series of research traditions that eventually developed  into “neurophenomenology” in the 1990’s through ideas and practices of  19th century researchers.  Understanding how these traditions drew from various sources, and subsequently interacted, requires we situate each field in then-current European disciplines. Elites were schooled in the Gymnasia, and acquired a broad and deep education before later specialization.  Physicians and/or laboratory experimentalists were expected to be familiar with classical and to an extent modern philosophy, and gentleman scholars would dabble in but also contribute to numerous fields: highly unlike the current hyper-specialization of academia. Psychology was very pluralistic at this stage: not yet fully divorced from philosophy, still possessing a sense that a field focusing on the richness and complexity of the human psyche must involve a study of consciousness.

There were numerous German psychophysics and psychological researchers looking for how consciousness and the brain were related, such as Herman von Helmholtz (1821-1894), Gustav Fechner (1801-1887), and Wilhelm Wundt (1832-1920).  Much effort was expended on rigorously correlating physiological and psychological measurements, resulting in establishing thresholds of perception and the limits of just noticeable differences. A number of laboratories used experimental methods where subjects told researchers what they were perceiving through verbal reports based on introspection.

Bold innovators like the justly renowned philosopher, psychologist and physician William James (1842-1910) also looked for the physical basis of experience. He pioneered research into neurology, performed psychological experiments, and made creative, yet disciplined, investigations into experiential aspects of mind. James’ use of crisp, lucid language describing consciousness and awareness pushed the threshold of what science, psychology, and philosophy could say about consciousness. James helped establish American experimental psychology, but really hit his stride with his still-fresh writings.  He described how memory and the enigmatic quality of the moment-by-moment flow of experience, and even wrote about altered states of consciousness. His central concept of consciousness being like a stream is still influential, and there is now a renewed appreciation for his work on how emotions are coupled to the physiological state of the body.  All in all, he is probably the most important figure in the history of American psychology. Yet his interdisciplinary boldness, penetrating curiosity and at times virtuostic powers of description of complex mental phenomena were not easily replicated by those researchers and younger colleagues he influenced.

William James, master theorist of consciousness

In the Principles of Psychology, James provided an admirably straightforward account of what introspection is:

“Introspective observation is what we have to rely on first and foremost and always. The word introspection need hardly be defined – it means, of course, looking into our own minds”

 

Fin-de-siecle psychophysics was in its golden years during his time, and while James’ wrote admiringly of the “philosophers of the chronometer” and other technically adroit experimental psychologists in his lab that measured perception and other phenomena, James himself continued his project of probing and describing the phenomenology of consciousness itself. While considered a father of introspectionist psychology and a forefather of both behaviorism and cognitive neuroscience, perhaps because of his hard-to-imitate brilliance, James did not leave a school of younger researchers to follow through on his research into consciousness.

In America, Europe, and Russia, generations of research into the organic basis of pathologies was reaching new heights of explanatory power. The German psychiatrist Emil Kraepelin (1856-1926) was formulating sophisticated theories of the physiological basis of mental illness in the early 20th century, in retrospect a crucial step in the early development of the now accomplished field we know as clinical neuropsychology. After each war, neurologists noted the correlations between location of trauma to the brains of the injured with deficits in speech, memory, movement, perception, affect,  emotion,and “body knowledge”. The Russian tradition culminated later in the influential work of Alexander Luria (1902-1977).

The force of new findings in clinical studies, physiology,  and experimental laboratory research eventually produced a scientific psychology that established itself as independent from moral philosophy, epistemology, metaphysics, and the philosophy of language. The success of  19th century psychophysics and neurophysiology, with breakthroughs such as Hermann von  Helmholtz‘s (1821-1894) measurement of the speed of the nerve impulse, provided ample justification for the fissure. Psychophysics experiments painstakingly produced data on the “just-noticeable difference” in light or stimulus intensity, etc. but there were real difficulties in establishing a consensus between the different laboratories on methodologies for dealing with subject’s reports on their perceptions.

While towering figures like Ernst Weber (1795-1878), Wilhelm Wundt (1832-1920), and Edward Titchener (1867-1927) were establishing a canon of principles and techniques for psychology, it proved extremely difficult to come up with one standard way to operationalize measurements that involved verbal reports about  subjective judgments and conscious experience. For all the brainpower deployed in various laboratories, by the 1930’s the tide was turning against scientific research into consciousness due to the influence of behaviorism, which reacted against the lack of an agreed-upon methodology in the German psychophysics-based psychology, especially involving introspection. The behaviorists marshaled an impressive array of experimental measurements techniques to establish causal relationships between stimulus and response, and then to infer lawlike generalizations. They stringently opposed the use of any mental concepts as inherently subjective and thus unscientific, and eschewed using first-person reports as much as possible. Within fields like the psychology of visual perception it was necessary to get verbal reports from subjects, but the behaviorists strove mightily to build a scientific psychology on purely physical principles. But if the behaviorists’ reacted against psychophysics for being insufficiently liberated from concerns with cognitive processes, others argued precisely the opposite. The philosopher Franz Brentano (1838-1917) wrote Psychology From An Empirical Standpoint in 1874, where he popularized the notion that the contents of experience constituted an important field of inquiry in their own right. Brentano’s influential theories of intentionality stressed the need to investigate the contents of awareness and their constitutive operations. Researchers working on cognition who were dissatisfied with the limitations of psychophysics ,and unpersuaded by the soon-to-be dominant anti-mentalist strictures of the behaviorists (such as physiologist Ivan Pavlov (1849-1936) and psychologist/advertising specialist John Watson (1878-1958))  rallied around this line of inquiry. Brentano made an impact among philosophers and psychologists and certain influential clinicians, and in some sense there is a diverse “School of Brentano“.

Arguably the most  influential among the students and followers of Brentano was the mathematician and philosopher Edmund Husserl (1859-1938). Husserl was fascinated (obsessed?) with the foundations of logic, mathematics, epistemology, and cognition.  Convinced by direct criticism from the celebrated logician Gottlob Frege (1848-1925) that psychological principles were epistemologically inadequate to foundationalize mathematical and logical truths, Husserl would eventually synthesize Brentano’s research into the primacy of intentional awareness within cognition with a quest for the undoubtable (or “apodictic”) core principles of mathematics, logic, and philosophy.  After producing light-reading classics such as Philosophie der Arithmetik, he developed a research program  into the first principles of cognition, logic, and epistemology called phenomenology.  While Husserl attracted many philosophers and certain psychologists to his cause with the 1900-1901 publication of the highly influential Logical Investigations, his continual probing of the constituent ideas underlying mathematical and logical truth was to an extent a solitary quest.

His acolytes and disciples found the Logical Investigations of great importance, yet they did not take up Husserl’s overarching project of a securing a logical foundation for all science, math, and philosophy. In the case of Martin Heidegger, phenomenology was redefined as the means for a still more fundamental investigation into ontology.

Edmund Husserl: logician, philosopher, and phenomenologist

Before WWII Husserlian phenomenology was perhaps the most important development in European philosophy, and influenced a number of other fields, such as psychology and medicine.Because his phenomenology took conscious experience as a source of data (following Brentano) many researchers interested in consciousness and cognition were excited by Husserl’s radically rigorous approach and penetrating exploration of how mental processes constitute, shape,  and structure the phenomena of which we are aware. His notion that cognition actively constructs the contents of awareness (compare to Jacob von Uexkull‘s (1864-1944) notion of the umwelt) would be familiar to modern cognitive neuroscientists but to early 20th century psychologists and philosophers was revolutionary. Husserl  influenced the philosophers Martin Heidegger (1889-1976), Jean-Paul Sartre (1905-1980), and Maurice Merleau-Ponty (1908-1961), the logician/mathematician Kurt Godel (1906-1978), the philosopher-theologian Karol Wojtyla (1920-2005), as well as (in more recent years) the prescient critic of Artificial Intelligence philosopher Hubert Dreyfus, and the cognitive neuroscientist Francisco Varela (1946-2001).

In America and Britain, these developments in Continental thought were generally of no interests to the behaviorists, who aside from biologically/medically-based critiques of the sort offered by neurologist Karl Lashley (1890-1958), enjoyed near-hegemony in scientific psychology. But eventually, the rise of computers led to the “cognitive revolution” : the  development of symbolic or information-processing theories of the mind that did not respect orthodox behaviorist’s strictures against the use of mental concepts.  In time, this  willingness to use mental concepts again would open the door to the study of consciousness in psychology and neuroscience . After WWII, the introduction  of computers led to cybernetic,  information-processing, symbolic-logical, and representational models of language, memory, behavior, reasoning, and even awareness.

(Part II is here, and part III is here)

Modularism vs. globalism in cognitive neuroscience: implications for a science of body-knowledge

Models of how people are able to access physiological state information should take into account a long-running divide in cognitive neuroscience about to what extent explanations, models, and purported mechanisms privilege local, reductionistic, and/or modular theories, as opposed to global and holistic theories that emphasize connectedness with and interdependence of particular systems to the entire brain. The debate is described by the dynamicist Walter Freeman (Freeman and Holmes, 2005) :

“In one view, cortex is a collection of modules like a piano keyboard, each with its structure, signal, and contribution to behavior. In the other view, the neocortex is a continuous sheet of neuropil in each cerebral hemisphere, which embeds specialized architectures that were induced by axon tips arriving from extracortical sources during embryological development. Localizationists analogize the neocortex to a cocktail party with standing speakers; each module gives a signal that, when activated like a voice in a room, by volume conduction occupies the whole head and overlaps other signals… Globalists analogize neocortex to a planetary surface, the storms of which are generated by intrinsic dynamics and modified by the structural features of the surface”

The issue of “module activation” vs. “global pattern dynamics” should be kept in mind while reviewing the evidence for specific regions as crucial to biological models of sensation or perception. Nonetheless, for researchers investigating the neurophysiological basis of access to interoceptive information or body-knowledge focus on a number of cortical areas of interest, particularly somatosensory cortex, orbitofrontal cortex, insular cortex, and cingular cortex/cingulate gyrus. The somatosensory cortex or (S1) is conceived as containing “maps” of body surface areas. A standard interpretation would explain the perception of touch, temperature, and pain as occurring through sensory nerves, which are joined into the spinal cord, and which eventually route through the thalamus, and then the cortical region known as the postcentral gyrus.

One standard refinement to the traditional model gives the label “primary somatosensory cortex” only to the area shown in red, Brodmann area 3 (Kaas, 1983). In any event, primary somatosensory cortex/S1 is conventionally modeled as having four complete maps of the body surface. Arguably, the biological/anatomical grounding of this concept allows one to state that the somatosensory cortex/SI contains “multiple representations of the sensory surface of the body,” without running the risk of invoking representationalist epistemologies, with their polymorphous and “mentalistic” significations. Over time, a picture has emerged of sensation occurring on the outer surface of the body, and then activating S1: neurons in these regions are firing (generating electrical discharges and secreting “signaling” molecules across synapses) at a higher amplitude. Any model that accounts for how perception and awareness of the body is possible will likely need to reference the role of somatosensory cortex.

Another cortical region implicated in interoception or internal perception is that part of the frontal lobes known as the orbitofrontal cortex, which can be defined as that part of the prefrontal cortex that receives certain key afferent projections from the thalamus (the so-called “gateway to the cortex), which receives afferent projections from the body, including the visceral organs. In theory, enhanced activation of physiological state (such as heart rate increase) should be reflected in increased activation of orbitofrontal cortices.

Studies of the role of cortex in processing internal body state often emphasize the role of the (formerly) obscure structure known as the insula, a cortical structure which is nonetheless tucked away underneath the visible cortical layers. The anterior portion of the insula is especially implicated in interoception and internal body-state “information gain”.

Yet another specialized brain area becomes more active in those psychophysiological processes involving internal body state dynamics: a collection of white-matter fibers known as the cingulate gyrus of the cortex.

Again, it should be stressed that neuroscientists may debate the extent to which any one region’s activity should be privileged against global overall processes. Certainly, S1, orbitofrontal cortices, anterior insula and anterior cingulate gyrus are only one of a series of regions that play a part in allowing visceral perception, interoception, or a gain in information about the inside of the body. Emphasizing the contribution of such discreet areas carries forward the “modularist” tradition, while other models will stress more of a global or holistic system of interactions, which is a classic debate in psychology and neurology (Gardner, 1985). Arguably, the pre-understanding of how much processing is done by local “modules” as opposed to collective and global activities influences the very means of data collection (Freeman and Holmes, 2005).

Gallagher and Coles on body schema vs. body image and the body percept

The philosopher Shaun Gallagher has collaborated with neurologist Jonathan Coles on the significance of patients with enigmatic body-knowledge problems (Gallagher and Coles, 1998).  Gallagher has analyzed this clinical data in the light of phenomenology and neuroscience, and has  an essential book  for anyone interested in neurophenomenology: How the Body Shapes the Mind

Gallagher is formulating a sophisticated take on embodied cognition that redresses the relative lack of attention by Varela and others to clinical studies of body knowledge disorders .  I have believed for some years that the wealth of neurological case studies  presenting puzzling data needs more focus in neurophenomenology. Since the early 20^th century, numerous patients with body knowledge based disorders and pathologies have come to light, leading to the notion of a body schema (Head and Holmes, 1911), which Gallagher and Coles (p.372) say involves:

“…a system of motor capacities, abilities, and habits that enable movement and the maintenance of posture. The body schema is not a perception, a belief, or an attitude. Rather, it is a system of motor and postural functions that operate below the level of self-referential intentionality, although such functions can enter into and support intentional activity. The preconscious, subpersonal processes carried out by the body- schema system are tacitly keyed into the environment and play a dynamic role in governing posture and movement. Although the body-schema system can have specific effects on cognitive experience…it does not have the status of a conscious representation or belief”

Gallagher and Coles maintain that progress in understanding embodied cognition requires a distinction between this body schema and the notion of the body image (p.371):

“The body image consists of a complex set of intentional states-perceptions, mental representations, beliefs, and attitudes–in which the intentional object of such states is one’s own body. Thus the body image involves a reflective intentionality. Three modalities of this reflective intentionality are often distinguished in studies involving body image:

(a) the subject’s perceptual experience of his/her own body;

(b) the subject’s conceptual understanding (including mythical, cultural, and/or scientific knowledge) of the body in general; and

(c) the subject’s emotional attitude toward his/her own body”

Gallagher emphasizes the wide variety of ambiguous and contradictory ways these terms have been used, and while noting some critics have proposed that deploying new terms could eliminate such confusion, he labors to develop a dependable, standard use of the technical terminology that can serve to make sense of clinical neurophenomenology such as that of the patient I.W, who suffered damage to nerves below the neck. This man now has to consciously will in order to perform actions people normally take for granted (p. 374):

“Maintaining posture is, for him, an activity rather than an automatic process. His movement requires constant visual and mental concentration. In darkness he is unable to control movement; when he walks he cannot daydream, but must concentrate constantly on his movement. When he writes he has to concentrate on holding the pen and on his body posture. IW learned through trial and error the amount of force needed to pick up and hold an egg without breaking it. If his attention is directed toward a different task while holding an egg, his hand crushes the egg”

The usefulness of the crisp distinction between body schema and body image becomes apparent when trying to explain the patient’s body experience and body knowledge (though Gallagher states that there is not in fact such a simple distinction possible in many cases). Normal people can perform such acts without much explicit attention, which is to say such common actions are enabled by the subconscious processes characterizing the body schema. I.W, on the other hand, must carefully and consciously go through the necessary steps to perform everyday acts. Adopting Gallagher’s distinction, we could say in the absence of the unconscious body schema, the patient must now depend on his conscious body image. To the extent this distinction is true; it should help a great deal in unpacking the various meanings of body-knowledge.

symptom verbal reports and existential-physiological discrepancy

While the anatomical basis of how nerve projections enable perception of the body is rather well known, physicians confront situations where patient verbal reporting about symptoms does not match models based on neurophysiological mechanisms. For instance, the Merck Manual Medical Library (2009) states:

“Painful stimuli from thoracic organs can produce discomfort      described as pressure, gas, burning, aching, and sometimes sharp pain. Because the sensation is visceral in origin, many patients deny they are having pain and insist it is merely discomfort”

The Mayo Clinic Heart Book (Gersh, 2000) describes the concept of uncomfortable feeling of thumping inside the chest known as palpitations, but does so from the point of view of patients (pg. 38):

“Although the apparent cause of the thumping in the chest would seem to be the heartbeat, this is not always the case. Some people have a normal heart rate during their palpitations. Presumably, they are either anxious or experiencing chest wall twitching that is mistaken for heartbeats”

Situations where the “folk physiological” (see Churchland, 1989, for a description of expert knowledge vs. folk beliefs) understanding of the body is apparently falsified by science can be labeled examples of existential-physiological discrepancy (Laughlin, McManus, D’Aquili, 1990). Mismatches between body-as-experienced compared to the “objective body” of scientific medicine and physiology (including the feeling of “phantom limbs” by amputees) are based on the idea that people may often have very limited “true” access to physiological processes. A more commonly presented variant or subset of this principle is the idea of “referred pain”, where the region causing understood to be causing the pain is spatially removed from the area where the patient senses it.

The Merck Manual (2009) gives an example: sometimes pain felt in one area of the body does not accurately represent where the problem is, because the pain is referred there from another area. Pain can be referred because signals from several areas of the body often travel through the same nerve pathways in the spinal cord and brain. For example, pain from a heart attack may be felt in the neck, jaws, arms, or abdomen. Pain from a gallbladder attack may be felt in the back of the shoulder.