Hypnotic analgesia reduces brain responses to pain seen in others

Claire Braboszcz, Edith Brandao-Farinelli, Patrik Vuilleumier
2017 Scientific Reports  
Brain responses to pain experienced by oneself or seen in other people show consistent overlap in the pain processing network, particularly anterior insula, supporting the view that pain empathy partly relies on neural processes engaged by self-nociception. However, it remains unresolved whether changes in one's own pain sensation may affect empathic responding to others' pain. Here we show that inducing analgesia through hypnosis leads to decreased responses to both self and vicarious
more » ... e of pain. Activations in the right anterior insula and amygdala were markedly reduced when participants received painful thermal stimuli following hypnotic analgesia on their own hand, but also when they viewed pictures of others' hand in pain. Functional connectivity analysis indicated that this hypnotic modulation of pain responses was associated with differential recruitment of right prefrontal regions implicated in selective attention and inhibitory control. Our results provide novel support to the view that self-nociception is involved during empathy for pain, and demonstrate the possibility to use hypnotic procedures to modulate higher-level emotional and social processes. Published: xx xx xxxx OPEN www.nature.com/scientificreports/ 2 SCientifiC RePORtS | 7: 9778 | presented. Oddball pictures of various other body parts (without any emotional content) were also inserted in the task allowing us to test for non-specific effects of hypnosis on alertness and processing of salient stimuli. We predicted that viewing painful hand pictures should activate the brain pain matrix 2, 3 but less so during hypnosis than normal state. Results Effect of hypnotic analgesia on brain responses during self-perception of pain. Painful thermal stimuli were adjusted to individual tolerance thresholds, using a staircase procedure similar to previous pain studies 5, 12, 13 . On each trial, participants reported whether heat was felt as painful or not, and their ratings were compared between the normal and hypnotic condition. Behavioral data from this task were not available for complete analysis in 6 participants due to technical recording problems. Fig. 1C and D show the distribution of temperatures for noxious stimuli during normal state and during hypnosis. The noxious stimuli temperature was higher during hypnosis than normal state (Fig. 1C) . The individual threshold results for noxious temperatures revealed that during hypnotic analgesia the participants reported pain for temperatures that were on average 1.3 degrees higher than threshold temperatures defined during the normal state (wilcoxon signed rank test p = 0.03). This increase in pain tolerance was observed in all but one participants (see Fig. 1D ) and cannot be attributed to habituation since the hypnotic and normal conditions were given in counterbalanced order across participants. Moreover, repeated short heat stimulation usually leads to pain sensitization rather than habituation 14 . This significant increase in temperature of the noxious thermal stimuli confirms the effectiveness of the hypnotic analgesia procedure. At the brain level, as expected fMRI results showed significant activations in bilateral anterior insula (left Z score = 6.65; right Z score = 6.03) and cingulate cortex (Z score = 6.29) to noxious compared to non-noxious heat stimuli, as well as somatosensory cortex (Z score = 5.46), thalamus (Z score = 5.77), and PAG (Z score = 5.76) (Fig. 1A . and Supp. Table 1) , during both the normal condition and hypnotic analgesia. However, contrasting painful heat stimulation in the normal versus analgesia condition revealed significant decreases in the left posterior insula under hypnosis together with the right amygdala (Fig. 1B) . A formal interaction contrast (i.e. [nox
doi:10.1038/s41598-017-10310-4 pmid:28852151 pmcid:PMC5575101 fatcat:auil6b2o55aixpqc54ueko3pei