Afferent determinants in temporal pain contrast enhancement

Pain perception is influenced by the processing of peripheral noxious afferents in the central nervous system. Such descending endogenous pain modulation has been described as an essential factor in the development and maintenance of chronic pain. A commonly used test to quantify the inhibitory aspects of pain modulation is the phenomenon of temporal contrast pain enhancement, also called offset analgesia (OA), which is characterized as a disproportionate reduction in pain following a small decrease in a stimulus. However, the underlying mechanisms are not yet well understood, since in addition to exclusively descending pain modulation, ascending influences are also discussed, which have not yet been systematically investigated. The aim of this project is to investigate the ascending influence of temporal contrast pain enhancement during the OA paradigm in order to present inferences on anatomical determinants in the peripheral nervous system. The methods used in the project will (6 experiments in total) involve psychophysical experiments, neurophysiological investigations, experimental human surrogate models, and clinical investigations in patients. A total of 270 healthy participants and 60 patients with polyneuropathy will be randomly assigned to experimental conditions.It is expected that pain modulating processes of temporal contrast pain enhancement will not only modulate descending but also ascending noxious stimuli. Specific afferent determinants (nerve fibers) might play a crucial role in this process. Thus, this project should contribute to a better understanding of the mechanisms of the ascending pain modulation system and may significantly contribute to the understanding of acute and chronic pain symptoms and their ascending mechanisms.