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TP Ruscheweyh/Flanagin: Supraspinal correlates of learned activation of descending pain inhibition in humans

PhD Student Philipp Graeff:

"Humans have powerful endogenous systems for inhibiting pain. One of them is the descending pain inhibitory pathway, originating in the brainstem and descending towards the spinal cord, where it inhibits pain transmission, thereby reducing the amount of nociceptive input that reaches the brain [2]. This system can be modulated by cognitive and emotional processes. E.g. distraction activates the descending pain inhibition while negative emotions deactivate the system [1,11,12] (Fig. 1). A remapping of the relationship between cortical pathways and descending pain inhibition likely is an important factor in chronic pain [5,6].
In our previous work, we developed a paradigm in which persons are trained to deliberately activate their descending pain inhibitory system [4,7,8]. Subjects learn to use cognitive-emotional strategies to activate their descending pain inhibition via online feedback on the state of their descending pain inhibition pathway. The nociceptive flexor (RIII) reflex, a measure of spinal nociception in humans, is used as feedback parameter, and a reduction in RIII reflex size indicates successful activation of the descending inhibition. Three RIII feedback training sessions are sufficient for subjects to learn to activate their descending pain inhibition system and to reduce clinical pain in chronic back pain patients [4,7,8].
In the present study, we plan to use functional magnetic resonance imaging (fMRI) to investigate which brain regions are used by RIII-feedback trained subjects to activate their descending pain inhibition and reduce their spinal nociception (Fig. 2,3). In short, the study will serve to identify which brain regions functionally activate the descending pain inhibitory pathways. This may also provide target regions for future real-time fMRI neurofeedback studies aiming at pain modulation."