EEG P300 Event-Related Markers of Hypnosis

Abstract

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.

Negative and Positive Visual Hypnotic Hallucinations: Attending Inside and Out

“…The observed difference in ERP amplitude response between obstructive (reduced amplitude) and negative (enhanced amplitude) hallucinations (Barabasz et al, 1999;Jensen et al, 2001) is quite consistent with a searchlight or focusing model involving the anterior attention system and the anterior cingulate gyrus in particular. Breaching of a negative hallucination instruction would tend to trigger vigilance-something unexpected is happening that tends to break with the paradigm-and would likely activate the posterior attentional NEGATIVE AND POSITIVE VISUAL HYPNOTIC HALLUCINATIONS 135 system.…”

“…Subjects who may have reduced their perception but not eliminated it completely might well have been surprised by the odor, and surprise increases P300 amplitude (Baribeau-Braun, Picton, & Gosselin, 1983). Barabasz accepted this interpretation (Spiegel & Barabasz, 1988) and went on to demonstrate in an elegantly designed experiment that an obstructive hallucination results in reduced ERP amplitude, whereas a negative hallucination results in increased amplitude (Barabasz et al, 1999;Jensen, Barabasz, Barabasz, & Warner, 2001). A crucial difference in the two instructions is the hardiness of the paradigm in the case of obstructive hallucination and the need to break with the paradigm if it does not work completely in the case of negative hallucination.…”

The Power of mind: Blocking visual perception by hypnosis

“…Earlier results already indicated that amplitudes of later ERP components are reduced after the suggestion of a visual blockade 8, 17, 18 . Our study shows that this reduction is significant for a big sample consisting of low, middle and highly suggestible participants and thus conceptually replicates these observations.…”

Hypnotic phenomena and altered states of consciousness: a multilevel framework of description and explanation

“…For example, brain imaging and sensing methods suggest that some phenomena occur only after a hypnotic induction but not when the same subjects are using mental imagery (e.g. Kosslyn et al, 2000;Jensen et al, 2001). Thus there seems to be a puzzling little gap which needs to be explained unless we argue that the subjects did not actually try their best during the imagery condition because of either a 'hold-back' effect 14 (Zamansky, Scharf and Brightbill, 1964) or compliance (Wagstaff, 1981;.…”

“…Recent studies (e.g. Barabasz, Barabasz, Jensen et al, 1999;Jensen, Barabasz, Barabasz and Warner, 2001) have found changes, however, in P300 ERPs in association with a hypnotic induction, but not in a nonhypnotic imagination condition nor in low susceptible subjects. Barabasz, Barabasz, Jensen et al (1999) have further pointed out how different kinds of suggestions may lead to different results when measuring ERPs in association with hallucinations.…”