Biomedicine and pain

The focus of my research is on contemporary biomedical construction of pain as an object, i.e. the different ways in which pain has been conceptualized and approached as a specific site of investigation in biomedicine. A significant shift in the scientific conception of pain occured in the second half of XXth century. In 1965, Ronald Melzack and Patrick D. Wall propose the Gate Control theory of pain mechanism. This theory denies a fixed and direct relationship between stimulus and pain perception, and emphazises the role played by psychological factors in pain. The IASP utilizes this perspective on the phenomenon, describing pain as “an unpleasant sensory and emotional experience associated to an actual or potential tissue damage or described in the terms of such a damage.” The relationship between pain and damage is pivotal in the definition of pain as a pathological entity. In particular, the biomedical approach to pain appears to be strongly characterized by a dualistic view of its aetiology. Disease conceptions such as “psychogenic pain” and chronic pain are deeply influenced by the ways in which psychological factors have been interpreted as components, or as causes of pain. In the second part of my dissertation, I focus on fibromyalgia, which is emblematic of the problematic acknowledgment of chronic pain as a disease. Even if fibromyalgia is actually treated in Rheumatology, its status as a disease is blurred, mainly because of its complex symptomatology including both physiological manifestations and psychological ones. In the conclusion, I present a scenario of the different ways in which this disease is dealt with in biomedical knowledge, through medical literature, clinical practice, and patients’ accounts. The findings of an ethnographic enquiry in the Rheumatology Division of a local clinic and a visual research on patients’ experiences are analyzed and discussed.

Visual-somatosensory interactions in mental representations of the body and the face

The body is represented in the brain at levels that incorporate multisensory information. This thesis focused on interactions between vision and cutaneous sensations (i.e., touch and pain). Experiment 1 revealed that there are partially dissociable pathways for visual enhancement of touch (VET) depending upon whether one sees one’s own body or the body of another person. This indicates that VET, a seeming low-level effect on spatial tactile acuity, is actually sensitive to body identity. Experiments 2-4 explored the effect of viewing one’s own body on pain perception. They demonstrated that viewing the body biases pain intensity judgments irrespective of actual stimulus intensity, and, more importantly, reduces the discriminative capacities of the nociceptive pathway encoding noxious stimulus intensity. The latter effect only occurs if the pain-inducing event itself is not visible, suggesting that viewing the body alone and viewing a stimulus event on the body have distinct effects on cutaneous sensations. Experiment 5 replicated an enhancement of visual remapping of touch (VRT) when viewing fearful human faces being touched, and further demonstrated that VRT does not occur for observed touch on non-human faces, even fearful ones. This suggests that the facial expressions of non-human animals may not be simulated within the somatosensory system of the human observer in the same way that the facial expressions of other humans are. Finally, Experiment 6 examined the enfacement illusion, in which synchronous visuo-tactile inputs cause another’s face to be assimilated into the mental self-face representation. The strength of enfacement was not affected by the other’s facial expression, supporting an asymmetric relationship between processing of facial identity and facial expressions. Together, these studies indicate that multisensory representations of the body in the brain link low-level perceptual processes with the perception of emotional cues and body/face identity, and interact in complex ways depending upon contextual factors.