Pain and the Spatial Boundaries of the Bodily Self

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Frédérique de Vignemont

Many discussions have been had about the relationship between pain and consciousness. Can humans be unaware of their pains? Can only animals that are fully conscious be said to be in pain? These questions, among others, are still a matter of controversies. Surprisingly, however, most of these discussions left untouched the issue of self-consciousness, although there is a sense in which it seems to be intimately connected with pain. One might report, for instance, how one feels extremely self-aware when one is in deep pain, as if the rest of the world ceased to exist. One of the main features of pain is indeed that it can grab our attention far more than any other bodily experiences. One may then say that by attracting attention to the body, pain enhances our sense of the bodily self, which otherwise remains recessive and elusive. However, one faces many difficulties if one wants to account for the relationship between pain and self-consciousness. For one thing, the notion of self-consciousness is a ragbag of various concepts of the self, from the embodied sensorimotor self to the disembodied mental and narrative self. Here, I shall exclusively focus on the former. In particular, I will investigate how the awareness of one’s body as one’s own (hereafter, sense of bodily ownership) is related to pain. An intuitive sense is that one feels pain only in parts of the body that one feels as one’s own. Pain can be experienced in phantom limbs, but they are experienced as parts of one’s own body. The challenge then is to understand the nature of the relationship between pain and the sense of bodily ownership. It can be conceived at least from the following two angles. To what extent does pain require self-consciousness, and more specifically the sense of bodily ownership? Conversely, to what extent does self-consciousness, and more specifically the sense of bodily ownership, require pain? Offering the beginning of an answer to this last question shall be my main objective in this chapter.

How am I aware that this specific body is my own? One strategy to answer this question consists in rephrasing it in spatial terms. The question then is how I am aware of the spatial boundaries of my body. Many factors can come into play. One may note, for instance, that tactile, thermal, proprioceptive, and interoceptive signals carry information exclusively about one’s own body. One may then conclude that through bodily sensations, where one can or cannot feel oneself, one can draw the boundaries of one’s body. On this view, the body that I feel as mine is the body that I feel from the inside. More recently, it has been suggested that vision, the sense of space par excellence, plays a crucial role and that multisensory correspondence allows distinguishing self from nonself. In this view, the body that I feel as mine is the body common to various sources of sensory information. Another proposal puts emphasis on efferent rather than afferent information. In this view, the body that I feel as mine is the body that I can directly control. In this manifold of factors, how does pain contribute to the sense of bodily ownership? Does it play any specific role or is it just one type of bodily sensation among others?

AN APPARENT PARADOX

When in pain, I experience disorder as located within a boundary of whose exterior I can have no similar awareness; I am aware that a part of my body—not just of that body—is disordered.

(Bain [2], p. 523)

Seeing injuries and feeling pain have a different phenomenology. It is not only that the latter is more unpleasant than the former. They seem to have a different relationship to the sense of bodily ownership. When I see a blow on a face, I can remain unaware that this is actually my face that I see injured in the mirror. By contrast, when I feel the blow, I cannot help but feel that this is my own face that hurts. Consequently, one cannot conceive feeling pain in a part of the body that feels as alien [2, 6, 16]. Or so it seems. The limits of the philosophers’ imagination do not always match what can actually be found in the neurologic literature. We know that some patients do not feel parts of their body as belonging to them and feel them as alien. This is the case in somatoparaphrenia after parietal lesions. Patients then deny ownership of parts of their body to such an extent that they can attribute their so-called alien limb to another individual or that they ask to be amputated of it. Yet some clinical reports indicate that some—but not all—patients with somatoparaphrenia are able to feel pain in their “alien” limb:

Patient: I still have the acute pain where the prosthesis is. Examiner: Which prosthesis? P: Don’t you see? This thing here (indicating his left arm). The doctors have attached this tool to my body in order to help me to move. But it’s completely useless and very painful (…) Once home could I ask my wife, from time to time, to remove this left arm and put it in the cupboard for a few hours in order to have some relief from pain? [14]

Another patient whose “alien” hand was pinched winced and cried out, but still denied that the hand was his own [17]. Hence, pain and the sense of bodily ownership can come apart. More precisely, one can be in pain in a body part that one does not feel as one’s own. It is not because I feel pain in a specific part of the body that I will experience this body part as mine. To feel pain is not sufficient for the sense of bodily ownership.

The question I asked in the introduction, however, was not whether pain could be sufficient, but whether it was necessary for the sense of bodily ownership. In order to answer this question, one needs to analyze the consequences of pain deprivation. What happens when one has never been in pain? This has been tested in animals. For instance, some terrier dogs were raised in isolation preserved from pain. They required more intense electric shocks to learn avoidance responses, and they spent more time near the experimenter after he burnt their noses with a flame [18]. Another pain deprivation study was done with infant monkeys that were raised preserved from all threats, in the absence of potentially damaging objects and of elders who could slap or bite them. Still they could hear, see, and touch themselves. When released, these monkeys viciously bit their own limbs and torn their flesh [13]. Thus, if one has not been hurt before, pain partly loses its unpleasantness, or at least its motivational force. Since these animals were also in social deprivation, one might say that they could not learn from others what were bad for them or how to react to it. However, the social explanation does not suffice to explain why they also engaged in acts of self-destruction. Interestingly, self-inflicted injuries can also be found in patients with congenital pain insensitivity [4, 9, 10, 23]. These patients are characterized by dramatic impairment of pain sensation since birth, caused by a hereditary neuropathy or channelopathy. They show a complete lack of discomfort, grimacing, or withdrawal reaction to prolonged pinpricks, strong pressure, soft tissue pinching, and noxious thermal stimuli. Like the animals raised in isolation, they can sometimes have endogenous pain (stomachache, for instance), but no exogenous pain. Like them also, they often engage in self-mutilation, including burns and self-amputations of fingertips and tongues.

Not to avoid pain is one thing, but to voluntarily injure oneself is another thing. The former can be explained by abnormality of nociceptive processing. But the latter requires further explanation. The hypothesis that I want to suggest is that self-injuries after pain deprivation are caused by the failure to recognize that this body that one injures is to be protected because it is one’s own body. In this view, past pain experiences contribute to the development of the representation of the boundaries of one’s own body and in their absence, one may lose track of what belongs to oneself and what does not. In other words, when patients bite their fingertips, they are not aware that they are biting their own

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