[Neurobiology of the chronicisation of pain in children: the memory of pain and its painful memory].

Reviewing the development of nociceptive circuits provides the rationale behind the need to modify and reduce premature painful experiences, especially during the "plastic" neonatal phase. Indeed, if physiological mechanisms of the functional nociceptive system follow a harmonious and predetermined development, it is the individual personal experience, intrinsically random, which will shape the final reactivity of this system and the later painful experience. If pain would not have been the organism's alarm system, we could have simply compared it by analogy to other sensorial systems, which its development depends exclusively on the presence of environmental stimuli. The eyes wait for light, the ears for sound, the skin to be touched, the tongue to taste and the olfactory bulbs to smell. However with pain it is not the quantitative exposure that determines its development, but rather the context-laden aspects of its affliction which in turn create the complex experience and "memory" of pain. Prolonged, but also "unnecessary" exposure to pain transforms it into a futile sensation, which impacts the individual immediately but also resonates into its future. This article reviews recent neurobiological mechanisms (such as neural circuitry, neurotrophins, peripheral and central sensitization, inhibitory pathways) now known to develop during the chronicisation and apprenticing of pain in the growing individual. Its cognizance is vital for a better comprehension of adult pain.