Effects of Hypnotic Instructions on P300Event-Related-Potential Amplitudes: Research and Clinical Implications

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Abstract
Apparently conflicting findings in two recent studies of the effects of hypnotic hallucination on the P300 component of cortical event-related potentials are examined. In one study, Barabasz and Lonsdale (1983) found an increase in P300 amplitude in response to hypnotic anosmia instructions. However, Spiegel, Cutcomb, Ren, and Pribram (1985) obtained a decrease in P300 amplitude after instructing high hypnotizables that an imaginary cardboard box blocked their view of the stimulus generator. These differences are reconciled on the basis of differences in the hypnotic instructions given. The former study employed language which emphasized negation (“You will not smell anything at all”), while the latter had subjects focus on a competing obstructive hallucination. The anosmia subjects were surprised when they smelled anything at all, leading to an enhanced P300 response, while the subjects in the visual study were so absorbed in the hallucinated obstruction that perception of the stimulus was reduced. Clinical implications of these two studies are examined.