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 tha t reflect alterations in consciousness that correspond to subjects' subject ive experiences of perceptual alteration. To further test the Barabasz et a l. (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 CI obliterating instructions were tested during w aking and alert hypnotic conditions. High-hypnotizables showed greater ERP amplitudes in response to the negative hallucination condition and lower ER P amplitudes in response to the positive obstructive hallucination when com pared to the low-hypnotizables. Contrary to socio-psychological or role pla y conceptualizations, the hypnotic induction resulted in specific psychophy siological responses which could not be produced by waking imagination or b y the lows who were trying to mimic hypnotic responding.