EFFECTS OF A NEGATIVE VISUAL HYPNOTIC HALLUCINATION ON ERPS AND REACTION-TIMES

The study of changes in ERPs provoked by negative hypnotic hallucinati ons has thus far yielded contradictory results. Most previous studies have failed to separate specific changes in the processing of the hall ucinated stimuli from non-specific changes in arousal due to hypnosis. The present study addresses this issue with the combination of two ex perimental effects in the task designed to test the hallucination the noise-compatibility effect and the Simon effect. A choice reaction tas k was used in which targets appearing at either side of a screen were defined by color and were accompanied by irrelevant noise, and a negat ive hallucination suggestion was given for noise stimuli. Four highly hypnotizable subjects performed the task on two separate occasions, wi th and without the suggestion. Increases in reaction times and P300 la tencies were found as a function of noise and spatial stimulus-respons e (SR) incompatibility (Simon effect). Suggestion decreased the respon se times for all types of trials non-significantly, and it decreased s ignificantly those of left-hand responses. On the other hand, suggesti on reduced the increase in P300 latencies in noise-incompatible trials , but did not influence the Simon effect. This result indicates a spec ific effect of suggestion in the processing of hallucinated stimuli, w hich is consistent with the hallucinatory experience reported by the s ubjects. (C) 1998 Elsevier Science B.V.