doi:10.1016/j.neuroimage.2005.05.002 
Copyright © 2005 Elsevier Inc. All rights reserved.
Hypnosis decouples cognitive control from conflict monitoring processes of the frontal lobe
Tobias Egnera, 
, 
, Graham Jamiesonb and John Gruzelierc
aFunctional MRI Research Center, Columbia University, Neurological Institute Box 108, 710 West 168th Street, New York, NY 10032, USA
bDepartment of Psychology, University of New England, Armidale, NSW 2351, Australia
cDivision of Neuroscience and Psychological Medicine, Imperial College London, St. Dunstan's Road, London W6 8RF, UK
Received 13 January 2005;
revised 2 May 2005;
accepted 3 May 2005.
Available online 17 June 2005.
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Abstract
Hypnosis can profoundly alter sensory awareness and cognitive processing. While the cognitive and behavioral phenomena associated with hypnosis have long been thought to relate to attentional processes, the neural mechanisms underlying susceptibility to hypnotic induction and the hypnotic condition are poorly understood. Here, we tested the proposal that highly hypnotizable individuals are particularly adept at focusing attention at baseline, but that their attentional control is compromised following hypnosis due to a decoupling between conflict monitoring and cognitive control processes of the frontal lobe. Employing event-related fMRI and EEG coherence measures, we compared conflict-related neural activity in the anterior cingulate cortex (ACC) and control-related activity in the lateral frontal cortex (LFC) during Stroop task performance between participants of low and high hypnotic susceptibility, at baseline and after hypnotic induction. The fMRI data revealed that conflict-related ACC activity interacted with hypnosis and hypnotic susceptibility, in that highly susceptible participants displayed increased conflict-related neural activity in the hypnosis condition compared to baseline, as well as with respect to subjects with low susceptibility. Cognitive-control-related LFC activity, on the other hand, did not differ between groups and conditions. These data were complemented by a decrease in functional connectivity (EEG gamma band coherence) between frontal midline and left lateral scalp sites in highly susceptible subjects after hypnosis. These results suggest that individual differences in hypnotic susceptibility are linked with the efficiency of the frontal attention system, and that the hypnotized condition is characterized by a functional dissociation of conflict monitoring and cognitive control processes.
Keywords: Hypnosis; Cognitive control; Conflict monitoring; Attention; Frontal lobe
Fig. 1. Stroop performance and ACC BOLD responses at varying levels of response conflict. (A) Mean reaction times (±SEM) for the different Stroop trial types. (B) Mean accuracy rates (±SEM) for the different Stroop trial types. (C) Significant activations to moderate response conflict (top panel: incongruent word-naming/congruent color-naming > congruent word-naming) and the high conflict contrast (bottom panel: incongruent color-naming > congruent word-naming) in the (right) ACC. Activity is displayed at a false discovery rate (FDR) of P = 0.05 with an extent threshold of at least ten contiguous voxels. For display purposes, activations are superimposed on a partially inflated right hemisphere medial wall of a normalized single subject T1 scan (segmentation and inflation was carried out with Brain VISA software; http://brainvisa.info/index.html).
Fig. 2. Conflict-susceptible regions of the ACC and their response magnitudes in subjects of low and high hypnotic susceptibility, at baseline and following hypnosis. (A) ACC ROIs displaying significant activation (FDR < 0.05) to both moderate and high response conflict, superimposed on a partially inflated right hemisphere medial wall of a normalized single subject T1 scan (segmentation and inflation was carried out with Brain VISA software; http://brainvisa.info/index.html). (B) Mean conflict-related ACC activity (beta weights ± SEM) from the ROIs in panel A for baseline and hypnotic conditions, in participants with low and high hypnotic susceptibility.
Fig. 3. Cognitive-control-related area in left LFC and its response magnitudes in subjects of low and high hypnotic susceptibility, at baseline and following hypnosis. (A) LFC ROI displaying significantly higher activation (uncorrected P < 0.001) to color-naming than to word-naming trials, superimposed on a partially inflated left hemisphere of a normalized single subject T1 scan (segmentation and inflation was carried out with Brain VISA software; http://brainvisa.info/index.html). (B) Mean control-related LFC ROI activity (beta weights ± SEM) for baseline and hypnotic conditions, in participants with low and high hypnotic susceptibility.
Fig. 4. Stroop accuracy data and EEG gamma band coherences. (A) Performance accuracy (±SEM) on the Stroop task for low and high susceptible hypnotic subjects, at baseline and in hypnosis. (B) Mid- to left frontal EEG gamma band coherence values following high conflict trials, in low and high susceptible hypnotic participants, at baseline and in hypnosis.
Table 1.
Anterior cingulate foci activated by moderate response conflict, high response conflict, or both
Note. BA = Brodmann Area; Talairach labels: CG = cingulate Gyrus, AC = Anterior Cingulate.
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