EEG P300 event-related markers of hypnosis.

Barabasz, Barabasz, Jensen, Calvin, Trevisan, and Warner (1999) showed that, when subjects are stringently selected for hypnotizability and responses are time locked to events, robust markers of hypnotic responding emerge that reflect alterations in consciousness that correspond to subjects' subjective experiences of perceptual alteration. To further test the Barabasz et al. (1999) hypothesis, we obtained EEG visual P300 event-related potentials (ERPs) from 20 high- and low-hypnotizable subjects. The effects of positive obstructive and negative obliterating instructions were tested during waking and alert hypnotic conditions. High-hypnotizables showed greater ERP amplitudes in response to the negative hallucination condition and lower ERP amplitudes in response to the positive obstructive hallucination when compared to the low-hypnotizables. Contrary to socio-psychological or role play conceptualizations, the hypnotic induction resulted in specific psychophysiological responses which could not be produced by waking imagination or by the lows who were trying to mimic hypnotic responding.