International Journal of Psychophysiology 46 (2002) 101–108 0167-8760/02/$ - see front matter  2002 Elsevier Science B.V. All rights reserved. PII: S0167-8760 Ž 02 . 00118-6 Fasttrack article Pain perception, hypnosis and 40 Hz oscillations Rodney J. Croft , John D. Williams , Corinna Haenschel , John H. Gruzelier * a,b a,c a a, Department of Cognitive Neuroscience and Behaviour, Imperial College London, Medical Faculty, St. Dunstan’s Road, a London W68 RF, UK Centre for Neuropsychopharmacology, Swinburne University of Technology, Hawthorn 3122, Australia b School of Health and Social Sciences, Coventry University, Coventry, UK c Received 5 August 2002; received in revised form 1 September 2002; accepted 5 September 2002 Abstract A number of brain regions are associated with the subjective experience of pain. This study adds to our understanding of the neural mechanisms involved in pain by considering the relation between cortical oscillations in response to pain, with and without hypnosis and hypnotic analgesia, and the subjective experience of pain. Thirty- three subjects’ neural responses (EEG) were measured during the 40–540 ms period following phasic electrical stimulations to the right hand, under control and hypnosis conditions. Resultant FFT amplitudes for frequencies ranging from 8 to 100 Hz were computed. These were grouped into 7 scalp topographies, and for each frequency, relations between these topographies and pain ratings, performance and stimulus intensity measures were assessed. Gamma activity (32–100 Hz) over prefrontal scalp sites predicted subject pain ratings in the control condition (rs 0.50, Ps0.004), and no other frequencyytopography combination did. This relation was present in both high and low hypnotisable subjects and was independent of performance and stimulus intensity measures. This relation was unchanged by hypnosis in the low hypnotisable subjects but was not present in the highs during hypnosis, suggesting that hypnosis interferes with this painygamma relation. This study provides evidence for the role of gamma oscillations in the subjective experience of pain. Further, it is in keeping with the view that hypnosis involves the dissociation of prefrontal cortex from other neural functions.  2002 Elsevier Science B.V. All rights reserved. Keywords: EEG; Gamma oscillations; 40 Hz; Pain; Subjective experience; Hypnosis 1. Introduction Although the electroencephalograph (EEG) has proven a powerful tool in the study of pain due to its good temporal resolution, its success in eluci- dating pain has been largely restricted to evoked *Corresponding author. Tel.: q44-20-8846-7246; fax.: q 44-20-8846-1670. E-mail address: j.gruzelier@ic.ac.uk (J.H. Gruzelier). potential designs (e.g. Bromm and Lorenz, 1998). With regard to resting EEG the most consistent findings relating to changes in power spectra have been pain-related increases in beta activity (Bac- konja et al., 1991; Veerasarn and Stohler, 1992; Chen and Rappelsberger, 1994) and pain-related decreases in alpha activity (Backonja et al., 1991; Chen and Rappelsberger, 1994). However, due to the non-specificity of these measures as reported,