Dissociation of sensory and affective dimensions of pain using hypnotic modulation

Understanding the complex nature of pain perception requires the ability to separately analyze its psychological dimensions and their interaction, and relate them to specific variables and responses. The present study, theref ore, attempted to selectively modulate the sensory and affective dimensions of pain, using a cognitive intervention, and to assess the possible relati onship between these psychological dimensions of pain and changes in physio logical responses to the noxious stimuli. In three experiments, normal subj ects trained in hypnosis rated pain intensity and pain unpleasantness produ ced by a tonic heat-pain stimulus (1-min immersion of the hand in 45.0-47.5 degrees C water). Two experiments were designed to test hypnotic suggestio ns to decrease (Experiment one (Section 2.5.1)), or increase and decrease ( Experiment two (Section 2.5.2)) pain affect. Suggestions in Experiment thre e (Section 2.5.3) were directed towards an increase or decrease in pain sen sation. In Experiments one and two (Sections 2.5.1 and 2.5.2), the signific ant modulation in pain unpleasantness ratings was largely independent of va riations in perceived pain intensity. Moreover, in Experiment two (Section 2.5.2), there was a significant correlation between the stimulus-evoked hea rt-rate increase and ratings of pain unpleasantness, but not of pain intens ity, suggesting a direct functional interaction between pain affect and aut onomic activation. In Experiment three (Section 2.5.3), suggestions to modu late the sensory aspect of pain produced significant modulation of pain int ensity ratings, with secondary changes in pain unpleasantness ratings. Hypn otic susceptibility (Stanford Hypnotic Susceptibility Scale form A) was spe cifically correlated to pain unpleasantness modulation in Experiment two (S ection 2.5.2) and to pain intensity modulation in Experiment three (Section 2.5.3), suggesting that this factor relates to the primary process toward which hypnotic suggestions are directed. The specific pain dimension on whi ch hypnotic suggestions act depends on the content of the instructions and is not a characteristic of hypnosis itself. Results are consistent with a s uccessive-stage model of pain perception (e.g. Wade JB, Dougherty LM, Arche r CR, Price DD. Assessing the stages of pain processing: a multivariate ana lytical approach. Pain 1996;68:157-167) which provides a conceptual framewo rk necessary to study the cerebral representation of pain perception. (C) 1 999 International Association for the Study of Pain. Published by Elsevier Science B.V.