Physiopathology of pain

The different brain imaging techniques that have emerged in the last decades have raised major advancement in our understanding of the neurophysiological mechanisms implicated in pain in both healthy subjects and in patients suffering from different pain conditions. The new brain imaging protocols are developed based on the background of previous surgical, behavioral, psychophysical, and electrophysiological researches on nociception and pain in animal, healthy subject, and patients. Having a good background of normal and pathophysiological pain neurophysiology is essential for the design of research protocols that will take advantage of new brain imaging technologies to better investigate the complex phenomenon of pain. Pain is a dynamic phenomenon that is the end result of several factors. The association between nociceptive activity and pain perception depends on several intrinsic and extrinsic influences. For the same nociceptive stimulus, pain perception and related brain activity will greatly differ between subjects. Studies support that environment and genetic factors are both playing important roles and seem to be modality specific. The effect of environment on genetics, epigenetics (lasting changes in gene expression without alteration of DNA sequence), is essential to be taken into account in pain. Nerve injuries or even psychological factors could change the central nervous system by affecting DNA methylation and produce a "genomic" memory of pain in the adult cortex. Pain perception is then the result of inherited physiological and psychological factors that are influenced by and hopefully guide the development of new therapeutic approaches for the patients that are suffering.