Nociception, Pain and Mechanisms of Modulation

Lenoir, Cédric [UCL]

Pain is a complex experience resulting from the integration of several dimensions such as sensory, emotional, affective and contextual. Regarding the sensory aspect, pain may result from the activation of peripheral receptors called nociceptors, which are activated by different types of potentially harmful stimuli. The nociceptive information is then interpreted at the central level and may lead – but not necessarily – to a conscious percept of pain. The term nociception refers to the neuronal encoding and processing of the activity resulting from the activation of these nociceptors while pain results from the integration and interpretation of many dimensions beyond nociception. Therefore, there is a dissociation between nociceptive activity and pain perception. In other words, the central processing and interpretation of a nociceptive stimulus highly depends on cognitive factors such as expectation, attention and past experiences and does not unequivocally lead to the perception of pain. During this presentation, I will first start with a brief recap of the neurophysiological basis of nociception and acute pain and discuss the mechanisms of pain modulation that take place at different level of the nociceptive system. I will describe several recent experiments that have shed light on the complexity of these mechanisms. Then, I will address some aspects of the cerebral modifications thought to be related to chronic pain. To conclude, research perspectives will be discussed.