“Pain is both an aspect of interoception (the sense of the physiological condition of the body) and a specific behavioral motivation. This striking conceptual shift incorporates the multiple facets of pain into one concrete framework, and it provides sound explanations for pain as both a specific sensation and a variable emotional state”.
“Changes in the mechanical, thermal and chemical status of the tissues of the body – stimuli that can cause pain – are important first of all for the homeostatic maintenance of the body.”
“Pain normally originates from a physiological condition in the body that automatic (subconscious) homeostatic systems alone cannot rectify, and it comprises a sensation and a behavioral drive with reflexive autonomic adjustments.”
“The behavioral drive that we call pain usually matches the intensity of the sensory input but it can vary under different conditions, and can become intolerable or, alternatively, disappear, just as hunger or thirst.”
“The new view of pain as a homeostatic emotion arises directly from functional anatomical findings in cat and monkey, rather than from philosophical considerations.”
“These results have identified specialized central substrates that represent pain, temperature, itch, muscle ache, sensual touch and other bodily feelings as discrete sensations within a common pathway.”
“These data indicate that in humans pain is an emotion that reflects specific primary homeostatic afferent activity.”
“Activity that produces pain in humans ascends in this pathway because its primary role has been homeostasis for millions of years.”
“Humans experience increasing discomfort at temperatures below 24C, but cold does not normally produce pain until 15C, where HPC activity accelerates and, significantly, cooling-specific lamina I cell activity plateaus.”
“This physiological evidence confirms the anatomical finding that homeostasis, rather than the heuristic simplification ‘nociception’, is the fundamental role of the small-diameter afferent fiber and lamina I system and is the essential nature of pain.”
“These findings indicate that pain in humans is a homeostatic emotion reflecting an adverse condition in the body that requires a behavioral response.”
“The new findings provide specific substrates for each of these aspects within a common framework of homeostasis.”
“This new view differs fundamentally from the prior conventional view in several ways. It incorporates specific sensory channels for different kinds of pain and for pain of different tissue origins. It provides a fast (sharp) pain channel that can elicit fight-or-flight behavior and a slow (burning) pain channel that can engage long-term responses, sickness behavior and immune function”.
“This perspective suggests new directions for research that could have strong impact on clinical therapy. For example, other homeostatic variables, such as salt and water balance, could have direct impact on the integrated activity that underlies the motivation called ‘pain’, as in the mysterious fibromyalgia syndrome.”
“Understanding the mechanisms underlying the augmentation of activity in the polymodal nociceptive channel could be particularly fruitful for identifying new therapies for chronic pain.”
