Characterization of cortical source generators based on electroencephalography during tonic pain

Abstract

Objective

The aim of the present study was to characterize the cortical source generators evoked by experimental tonic pain.

Methods

Electroencephalography (EEG) was recorded on two separate days during rest and with immersion of the hand in ice water for 2 minutes (cold pressor test). Exact low-resolution brain electromagnetic tomography source localization was performed in 31 healthy volunteers to characterize the cortical source generators.

Results

Reliability was high in all eight frequency bands during rest and cold pressor conditions (intraclass coefficients =0.47–0.83 in the cingulate and insula). Tonic pain increased cortical activities in the delta (1–4 Hz), theta (4–8 Hz), beta1 (12–18 Hz), beta2 (18–24 Hz), beta3 (24–32 Hz), and gamma (32–60 Hz) bands (all P<0.011) in widespread areas mainly in the limbic system, whereas decreased cortical activities were found in cingulate and pre- and postcentral gyri in the alpha2 (10–12 Hz) band (P=0.007). The pain intensity was correlated with cingulate activity in the beta2, beta3, and gamma bands (all P<0.04).

Conclusion

Source localization of EEG is a reliable method to estimate cortical source generators. Activities in different brain regions, mainly in the limbic system, showed fluctuations in various frequency bands. Cingulate changes were correlated with pain intensity.

Significance

This method might add information to the objective assessment of the cortical pain response in future experimental pain studies.

Keywords:

• EEG
• tonic pain
• source localization
• cingulate cortex
• eLORETA

Acknowledgments

This work was supported by the Innovation Fund Denmark – Individuals, Disease and Society (#10-092786/DSF) and the Obel Family Foundation.

Authors’ contribution

TMH was involved in conception and design of the study; acquisition of data; analysis and interpretation of data; drafting the article; and revising it critically for important intellectual content and final approval of the version to be published. EBM, SSO, and MG were involved in the analysis and interpretation of data and revised them critically for important intellectual content and final approval of the version to be published. JBF and AMD were involved in conception and design of the study; analysis and interpretation of data; and revising them critically for important intellectual content and final approval of the version to be published. All the authors discussed the results and commented on the manuscript.

Disclosure

The authors report no conflicts of interest in this work.