Increases in arousal are associated with reductions in the human nocioceptive flexion threshold and pain ratings: Evidence for dissociation between nocioception and pain

The nociceptive flexion has been regarded as an objective correlate of pain perception. This study examined whether the nociceptive flexion reflex is modulated by physiological arousal in the same manner as pain. Cardiovascular activity, nociceptive physiological arousal: Rest, number repetition, and mental arithmetic. Heart rates were faster and R-wave to pulse intervals longer during rest compared to number repetition. Both mental arithmetic and number repetition were associated with reduced nociceptive flexion reflex thresholds compared to rest. Although the nociceptive flexion reflex thresholds were the same during mental arithmetic and number repetition, pain ratings were lower during mental arithmetic than number repetition and rest. The results indicate that nociception was facilitated but pain was inhibited by increased physiological arousal. This dissociation suggests that the nociceptive flexion reflex threshold is not a suitable correlate of pain during states of increased arousal.