PAIN

Pain affects our perception

Pain affects our perception

Introduction

Pain is a complex perceptual phenomenon. The International Association for the Study of Pain's (IASP) definition of pain reflects the complexity of pain as a phenomenological experience unique to each person. According to the IASP (1986) definition, pain is “an unpleasant sensory and emotional experience normally associated with tissue damage or described in terms of such damage.” An important first step to understand pain is to clarify its difference from nociception. Nociception is a sensory process involving receptor activation (transduction), relay of information from the periphery to the central nervous system (transmission), and neural activity leading to control of the pain transmission pathway (modulation).

Pain, on the other hand, is an integrated perceptual process. Nociception may lead to pain perception, but it is not sufficient to account for pain as a clinical presentation. Thus, nociception is not synonymous with pain. The former is a physiological phenomenon, whereas the latter is a perceptual one, involving higher central nervous system mechanisms.

Discussion

In general, pain is considered as a warning sign implicating a disease or injury, and thus, many people consider it a “physical phenomenon.” Scholars and clinicians have conventionally accepted this assumption for centuries. On the other hand, when pain could not be accounted for by physical findings only, as in many cases of clinical pain syndromes, pain was considered as “mental.” Cartesian mind-body dualism dominated for centuries as a way of understanding pain, in which pain was somatic if there is an organic cause accounting for the experience or pain is “psychological” otherwise. It is only in the past quarter century that there has been a significant paradigm shift in thinking about pain as an integrated perceptual experience.

Sensory Model

Traditionally, there has been an implicit assumption that an isomorphic relationship exists between pain and nociception; pain was viewed as a sensory experience that should directly and linearly correspond to the degrees of noxious sensory stimuli impinging on the individual. Based on this model, the extent of organic pathology must account for the presence and extent of pain.

However, recent advancement in neural imaging helps us understand that the linear relationship between pathology and pain rarely exists. There are a large number of patients with severe pain syndrome whose exact pathology cannot be objectively identified, despite undergoing thorough diagnostic testing. It is also common to see patients who undergo an identical operation vary widely not only in their reports of postoperative pain severity but also in their responses to treatment. Conversely, imaging studies using computed tomography (CT) scans and magnetic resonance imaging (MRI) often reveal the presence of significant pathology in about a third of asymptomatic individuals.

Psychogenic Perspectives

When the presence of pain cannot be explained by physical pathology, conventional medical thinking was to consider those symptoms as psychological in origin. Similarly, if the pain is disproportionate to objectively determined physical pathology or if a patient does not respond to medical treatment targeted to modify nociceptive input, then pain is assumed to be also ...