An Electrophysiological and Psychophysical Analysis of Hypnotic Visual Hallucinations

Abstract

We examined the physiological and behavioral concomitants of high hypnotizable subjects reporting the capacity to hypnotically hallucinate. Subjects were required to perform a lexical decision task under baseline and four hypnotic hallucination conditions: obstructive, transparent, negative, and semantic. Analyses were conducted on various evoked potential components and psychophysical indices (RTs, sensitivity, response bias). Overall, hypnotic hallucinations did not alter VEPs over baseline; however, more liberal analyses indicated that the obstructive hallucination produced suppressions in the VEPs at P₁ (left occipital), P₂ (midline parietal) and P₃ (midline parietal) compared to baseline. P₁ latencies were also larger in the obstructive condition. Lexical decisions took longer in the hallucination conditions, and both sensitivity and response bias were reduced in these conditions. The relationship of these indices to attention are discussed.