the legacy of Cartesian “objectivity” makes it hard to understand patient verbal reports

clinical neurophenomenology, embodiment, introspection, medicine, symptom reports

Psychiatrist Allan Beveridge (2002) hones in on a facet of the patient-physician relationship relevant to neurophenomenology: the over-adoption in medicine of the scientific attitude of objectivity towards phenomena. While entirely appropriate in the many research contexts, this may make understanding the personal body-knowledge of the patient more difficult (pg. 101):

In the mental state examination, a standard method of describing the clinical encounter is to contrast the patient’s supposedly ‘subjective’ account with the doctor’s ‘objective’ description. In this model, the doctor is granted a privileged position: the clinician’s perspective is taken to be superior to that of the patient. The doctor’s objective approach is considered neutral, scientific and representing the truth of the matter. In contrast, the patient’s subjective report is regarded as unreliable, distorted and potentially false. The lowly status of the subjective perspective is further emphasized by the frequent use of the accompanying prefix, merely. On reflection, this dichotomy is an extraordinary one. It is held that the doctor is an authority on the patient’s inner experiences. The doctor knows more about how the patient is thinking and feeling than the patient him-/herself

This “scientific” medical stance towards patient subjective reporting is consistent with the Cartesian heritage of the sciences of the mind. The implications, hidden or unexamined commitments should be critically examined if the verbal reports about patient body-states are to be better grasped by science and medicine. To the extent cognitive science, psychology, neuroscience, and medical fields uncritically base their methodologies on unexamined premises, certain problems may appear just due to the very choices of what is considered “data”. The relegation of patient verbal reports to the category of “merely subjective” allows for Cartesian assumptions about cognition to create difficulties at the outset of any research project attempting to model personal knowledge of the body. It may be that the very categories of subject and object, or scientific knowledge vs. subjective or “folk psychological” naïve theories of the body, present foundational problems for understanding how neurophysiological processes relate to verbally reportable knowledge of the body. But as a practical matter, health care professionals must simply cope with patient statements as one more data source (Ersser and Atkins, 2000, pg. 68):

Clinical decisions involve information of a necessary type and quality. Professionals take account of both objective and subjective data during the clinical assessment process to decide on a patient’s health care need and care plan. The difficulty lies in professionals understanding how best to reconcile their objective perspective with that of the patient, when formulating clinical judgments

Before a doctor revives technical training, he or she is a person with experiences of health and sickness. The verbal reports of patients are interpreted by professionals with their own history of embodiment. To what extent does their personal body knowledge consciously or unconsciously affect their clinical intuition about the accuracy of patient verbal reports? Does expert knowledge of the body gained from studying anatomy and physiology allow for better knowledge of one’s own body? Such questions point to our current rather murky understanding of embodied cognition, underscoring the need for models capturing richer, more subtle aspects of experience, cognition, and brain.

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The brain and the internal state of the body

embodiment, interoception, visceral perception

Hugo Critchley et al. (2004) state that (pg.189) “the internal state of the body is conveyed through a dedicated lamina-1 spinothalamocortical pathway that converges with vagal afferents”. These afferent nerves are noteworthy for the smallness of their diameter in comparison with the larger afferents that apparently deal with proprioception, the perception of the body in space. Physiologist Bud Craig has written that the difference in size of these nerves signify “a simple physiological distinction between the inside and the outside of the body.’’ (Craig, 2002, p. 657)

The heart connects to the brain through the autonomic or visceral nervous system, traditionally thought to operate mostly without conscious control (breathing being a notable exception).  The sympathetic projections of the autonomic system can increase heart rate in stressful situations, while the parasympathetic fibers slow the heart down when appropriate. There are also two sets of nerves connecting heart and brain:  spinal nerves,with the dorsal root containing afferent sensory projections, and the ventral root for efferent motor fibers. In addition to spinal nerves, the vagus nerve supplies parasympathetic fibers including mostly (85%) afferent fibers, while the rest are brain-to-viscera efferent (brain to motor) fibers that project from the medulla oblongata in the brainstem, and which, if working properly, can rapidly increase or decrease heart rate as needed via innervation of the cardiac muscle. The afferent fibers projecting from viscera to brainstem do so viscerotopically, preserving information about spatial extension or location of the viscera in the body that is subsequently processed (many researchers would say “represented”) in the brain.

Evolutionarily/phylogenetically ancient structures such as the nucleus of the solitary tract and the pons transform the incoming afferent “signal” from viscera such as the heart, and eventually pass it along to the “gateway to the cortex” or thalamus. From there thalamo-cortical fibers project to regions such as insula, cingulate gyrus, and somatosensory and orbitofrontal cortices, regions implicated in interoceptive activity and cognitive processes handling internal body information.   These regions have been investigated for processes corresponding to cardiac activity:

insula

Insula, or the Island of Reil
somatosensory cortex with S1 and S2 colored

somatosensory cortex with S1 and S2 colored

fMRI of orbitofrontal cortex

fMRI of orbitofrontal cortex

Some researchers (notably (Olga Pollatos and Rainer Schandry, 2004), (Gray et al., 2007) have identified a heartbeat evoked potential that can be detected with EEG measurements: an increase in amplitude of neuroactivity or neuronal firing, detectable after averaging many instances together and subtracting “background” activity as noise,  that seems to occur after a heartbeat. It is intriguing, and possibly of great significance for models of body-knowledge and interoceptive information access, that higher amplitude in the heartbeat evoked potential correlates well with better heartbeat perception in the Pollatos and Schandry research.

Data coming from fMRI and other imaging studies (magnetic electroencephalography, or MEG, and cerebral blood flow, or CBF) should shed additional light on the relative activity levels of cortical and subcortical structures that enable conscious perception of heartbeats, as well as unconscious central nervous system response to cardiac processes.

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

Uncategorized

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

clinical neurophenomenology, embodiment, medicine

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

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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 20th 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

clinical neurophenomenology, interoception, introspection, medicine, symptom reports, visceral perception

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.