Hypnotic analgesia reduces R-III nociceptive reflex: further evidence concerning the multifactorial nature of hypnotic analgesia

Abstract

Mechanisms of hypnotic analgesia were investigated by examining changes in the R-III, a nociceptive spinal reflex, during hypnotic reduction of pain sensation and unpleasantness. The R-III was measured in 15 healthy volunteers who gave VAS-sensory and VAS-affective ratings of an electrical stimulus during conditions of resting wakefulness, suggestions for hypnotic analgesia, and attempted suppression of the reflex during non-hypnotic conditions. The H-reflex was also measured to monitor and control for general changes in alpha-motoneuron excitability. Hypnotic sensory analgesia was related to reduction in the R-III after controlling for changes in the H-reflex (R2 = 0.51, P < 0.003), suggesting that hypnotic sensory analgesia is at least in part mediated by descending antinociceptive mechanisms that exert control at spinal levels in response to hypnotic suggestion. The relationship between hypnotic affective analgesia and reduction in R-III approached significance (R2 = 0.26; P = 0.053). Reduction in R-III was 67% as great and accounted for 51% of the variance in reduction of pain sensation. In turn, reduction in pain sensation was 75% as great and accounted for 77% of the variance in reduction of unpleasantness. The results suggest that 3 general mechanisms may be involved in hypnotic analgesia. The first, implicated by reductions in R-III, is related to spinal cord antinociceptive mechanisms. The second, implicated by reductions in pain sensation over and beyond reductions in R-III, may be related to brain mechanisms that serve to prevent awareness of pain once nociception has reached higher centers, as suggested by Hilgard.(ABSTRACT TRUNCATED AT 250 WORDS)

Neural Mechanisms of Antinociceptive Effects of Hypnosis

“…Third, a statistically significant decrease in pain ratings was observed during the HS only, a finding that is in agreement with our clinical practice. 2,15 Furthermore, our subjects testified that they were in the HS before each scan and confirmed their hypnotic experience during debriefing. Each of these points, taken in isolation, does not prove the presence of the HS in our subjects, but together they form a body of arguments that, by their cooccurrence, strongly suggest that this was indeed the case.…”

Catastrophizing is related to pain ratings, but not nociceptive flexion reflex threshold

“…The NFR is a polysynaptic spinal reflex subserving withdrawal from potentially noxious stimuli. Individual differences in the intensity of electrocutaneous sural nerve stimulation required to elicit the NFR provide indirect evidence of supraspinal modulation, with higher thresholds suggesting enhanced descending inhibition and lower thresholds suggesting decreased inhibition of spinal nociceptive transmission (Willer et al, 1979;Kiernan et al, 1995;Danziger et al, 1998). For example, Willer et al (1979) reported that NFR was dampened during performance of a mental arithmetic task, and enhanced during anticipation of an intense noxious stimulus.…”

“…For example, Willer et al (1979) reported that NFR was dampened during performance of a mental arithmetic task, and enhanced during anticipation of an intense noxious stimulus. More recent studies have examined the effects of hypnosis on NFR (Kiernan et al, 1995;Danziger et al, 1998), and have demonstrated that hypnotic suggestion of analgesia results in strong NFR inhibition in some participants while others show reflex facilitation. Animal studies provide convincing evidence of supraspinal modulation of nociceptive flexion reflexes, with the periaqueductal gray playing a major role in the control of spinal nociceptive neurons through relays in the rostral ventromedial medulla (Willis, 1988;Fields and Basbaum, 1999).…”

Neurophysiology of pain and hypnosis for chronic pain

“…These studies have concluded that hypnosis can impact pain by affecting a number of different neurophysiological processes that make up the pain matrix, rather than by influencing a single mechanism or process. Specifically, research indicates that hypnosis can impact activity in: (1) the periphery and spinal cord [67][68][69], (2) the thalamus [65,70,71], (3) the sensory cortices [72,73], (4) the insula [70,71,73], (5) the ACC [35,70,71,[73][74][75], and (6) the prefrontal cortex [70,71,73,76]. Given the extensiveness of these previous reviews, this section will briefly review past research that has examined the neurophysiological effects of hypnotic analgesia, specifically focused on the role of suggestion type [35,72,77].…”