Historical perspective and modern views on pain physiology: from psychogenic pain to hyperalgesic priming

Pain is the topic to which I mostly contributed during my scientific career, after my initial training in Moruzzi’s laboratory at the time when my research was focused on the physiology of specific “states”, i.e. sleep and animal hypnosis. In this review I will present, without claiming to be complete, the seminal discoveries and the consequent evolution of the concepts of pain providing the readers with sufficient details to understand the arguments and the conclusions. The three experimental theories already formulated at the end of the nineteenth centuries – the Specificity Theory, the Intensive-Summation Theory and the Aristotelian concept that pain is an affective quality – presented three conflicting concepts about the nature of pain. The Specificity Theory, definitively formulated by Schiff (1858) and von Frey (1894), stated that pain is a specific sensation with its own sensory apparatus independent of touch. The Intensive-Summation Theory, elaborated by Goldsheider (1998) propose that every stimulus can produce pain if it is strong enough and that stimulus intensity and central summation are the critical determinants of pain. The Affective Quality of Pain was supported by many philosophers and improved by Marshall (1895), who proposed the Pleasure-Pain Theory. In the attempt to reconcile the views of physiologists, philosophers and psychologists, Strong (1895) suggested that pain consisted of the original sensation and the psychic Historical perspective and modern views on pain physiology: from psychogenic pain to hyperalgesic priming