Supraspinal modulation of trigeminal nociception and pain: Emotional controls (ECON) and diffuse noxious inhibitory controls (DNIC)

The purpose of this study was to examine the modulation of trigeminal pain and nociception by two forms of supraspinal influences: emotional controls of nociception (ECON) and diffuse noxious inhibitory controls (DNIC). Trigeminal nociception and pain was assessed from the nociceptive blink reflex and pain ratings, respectively, following noxious stimulations delivered by a custom concentric electrode designed to selectively activate nociceptive fibers. ECON were engaged by the presentation of standardized picture stimuli (pleasant, neutral, and unpleasant) that have been shown to reliably evoke pleasure-induced inhibition and displeasure-induced facilitation of pain and spinal nociception. DNIC were engaged by the application of a forearm ischemia pain task. Results suggested ECON and DNIC modulated trigeminal nociception and pain. Emotional valence/pleasure (as assessed from trend analysis) explained 51% of the variance in pain ratings and 20% of the variance in blinks. Pain and nociceptive blinks were facilitated by unpleasant pictures and inhibited by pleasant pictures. Additionally, the DNIC task (forearm ischemia) inhibited pain and the blink reflex. The baseline vs. ischemia comparison for DNIC explained 17% of the variance in pain report and 7% of the variance in blinks. Exploratory analyses suggested ECON and DNIC modulation were uncorrelated, providing preliminary evidence that they are independent processes. This paradigm has important implications for future research on the pathophysiology of head and face pain. All procedures used in this study were approved by The University of Tulsa IRB. This work was partially supported by a University of Tulsa Faculty Summer Development Fellowship awarded to Jamie L. Rhudy, Ph.D. and a University of Tulsa Student Research Grant from The University of Tulsa Office of Research awarded to Amy Williams, M.A.