Does the cortical response to electroacupuncture depend on stimulation frequency? Results of a pilot EEG study first proposed at the AACP Conference in 2001
© Tony Steffert (Open University) and
David Mayor (University of Hertfordshire)
EEG (electroencephalography) is a low-cost, accessible method of investigating electrical brain activity that is sensitive to rapid changes (unlike fMRI). Electroacupuncture (EA) and Transcutaneous Electrical Acupoint Stimulation (TEAS) are methods of acupuncture-like stimulation. This pilot crossover study, first proposed at the 2001 AACP Conference,1,2 explores the relationship between frequency of TEAS applied peripherally and frequencies of cortical electrical activity detected centrally.
To determine whether there is a central ‘frequency following response’ (FFR) to peripheral stimulation (i.e. if TEAS is applied at 2.5 Hz, is that frequency more likely to appear in the EEG).
In each 2-hour session, TEAS (Equinox, Liverpool) was applied at ‘strong but comfortable’ intensity for five minutes at six different combinations of LI4 and ST36 (in balanced order). Five participants attended for two sessions (2.5 Hz or 10 Hz TEAS), two for one session each. EEG was monitored for five minutes before and after each 5-minute stimulation following standard EEG procedures (frequency bands and filtering, average reference montage), using the 10/20 system of electrode location (19 electrodes with linked ears as reference).3-5 The Mitsar EEG-202 amplifier and WinEEG software (v2.91.54) were used (Mitsar Ltd, St Petersburg). Following artefact processing, various standard EEG data were exported, including spectral power, asymmetry, average band frequency and standard deviation, autocorrelation and coherence. Statistical computation was carried out in SPSS (v 20) and Microsoft Excel (v 14).
Of the various standard and nonstandard EEG measures investigated for the group, few showed convincing evidence of a FFR. Individual responses were very variable.
A central frequency following response to peripheral stimulation remains possible. However, data has yet to be analysed from further pilot studies using longer stimulation periods, concurrent rather than subsequent monitoring, and comparing EA and TEAS. Further research is required using different acupoints and more participants.
1. Mayor D.F. (2001) CNS resonances to peripheral stimulation: is frequency important? Journal of the AACP Nov, 29-63.
2. Mayor D.F. (ed) (2007) Electroacupuncture: A practical manual and resource. Churchill Livingstone (Elsevier), Edinburgh.
3. Kropotov J.D. (2009) Quantitative EEG, Event-related Potentials and Neurotherapy. Academic Press (Elsevier), London.
4. Thompson T., Steffert T., Ros T., Leach J., Gruzelier J. (2008) EEG applications for sport and performance. Methods 45 (4), 279-88.
5. Chen M., Gruzelier J., Steffert T., Thompson T., Leach J. (2008) Combining transcutaneous electrical acupuncture with neurofeedback training: effects on cognitive performance and EEG spectrum. Society of Applied Neuroscience, second biennial meeting, Seville, 7-11 May. Revista Española de Neuropsicología 10, 140. URL http://www.manu.edu.mk/costb27/Abstracts/Seville.pdf.
QUESTIONS FOR YOU:
On the basis of our findings so far (Background information), do you think that a ‘frequency following response’ (FFR) is likely?
What do you think we should explore next, given limited time and resources:
o The effects of stimulation using other stimulation frequencies (e.g. 5 Hz or 80 Hz)
o The effects of other acupuncture-related modalities, such as tuina or laser acupuncture
o The effects of treatment for a particular condition (if so, which)
Questions such as:
o Whether baseline differences or other confounding factors are responsible for our findings
o Whether FFR is more likely at some scalp electrodes than others
o Whether some measures used should be given more weight than others
o Whether we should just go back and repeat our Pilot with larger samples
We would also like to ask whether you would be interested in taking part in any of our future research, either as a participant (‘subject’), practitioner, in recruiting participants, or to help with data analysis.
You can let us know by emailing David Mayor (details below). You can find out more about our project so far by going to www.qeeg.co.uk/electroacupuncture/eaffr.htm (also accessible through the QR code above). There you will find the poster, together with details of our Methodology, References, and so on. The poster may also be reproduced on the AACP post-conference website.
To Elizabeth McLean of the AACP, for her assistance in preparing this poster, to Professor Tim Watson, our ever-supportive project supervisor, and to Robert Kozarski and Jade Collard for their statistical assistance. External funding has not been sought or obtained for this project so far.
David Mayor acupuncture practitioner