Positive Health Online

Abstract

CROFT and co-workers, Department of Cognitive Neuroscience and Behaviour, Imperial College London, Medical Faculty, St Dunstan’s Road, London W6 8RF, UK, write about pain perception, hypnosis and 40 Hz oscillations.

Background

A number of regions of the brain are associated with the subjective experience of pain. This study considers the relations between cortical oscillations in response to pain, with and without hypnosis and hypnotic analgesia, and the experience of pain.

Methodology

33 subjects’ neural responses (EEG) were measured in the 40-540 msec period following electrical stimulation 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.

Results

Gamma activity (32-100 Hz) over prefrontal scalp sites predicted subject pain ratings in the control condition (p = 0.004), and no other frequency/topography combination did. This relation was present both in high and low hypnotizable subjects and was independent of performance and stimulus intensity. This relation was unchanged by hypnosis in low hypnotizable subjects but was not present in high hypnotizable subjects during hypnosis, suggesting that hypnosis interferes with this pain/gamma relation.

Conclusion

This study provides evidence for the role of gamma oscillations in the subjective experience of pain. Further it also supports the view that hypnosis involves the dissociation of the prefrontal cortex from other neural functions.

References

Croft RJ, Williams JD, Haenschel C, Gruzelier JH. Pain perception, hypnosis and 40 Hz oscillations. International Journal of Psychophysiology 46 (2): 101-108, Nov 2002.