Does High Frequency Transcutaneous Electrical Nerve Stimulation (TENS) Affect EEG Gamma Band Activity?

Background: Transcutaneous electrical nerve stimulation (TENS) is a noninvasive, inexpensive and safe analgesic technique used for relieving acute and chronic pain. However, despite all these advantages, there has been very little research into the therapeutic effects of TENS on brain activity. To the best of our knowledge, there is no evidence on the effect of high frequency TENS on the gamma band activity.  Objective: Investigation of the effect of high frequency TENS on the electroencephalographic (EEG) gamma band activity after inducing ischemic pain in healthy volunteers is considered.Methods: The modified version of Submaximal effort tourniquet test was carried out for inducing tonic pain in ۱۵ right-handed healthy volunteers. The high frequency TENS (۱۵۰µs in duration, frequency of ۱۰۰ Hz) was applied for ۲۰ minutes. Pain intensity was assessed using Visual Analog Scale (VAS) in two conditions (after-pain, after-TENS). EEG gamma band activity was recorded by a ۱۹-channel EEG in three conditions (baseline, after-pain and after- TENS). The repeated measure ANOVA and paired-sample T- tests were used for data analysis.Results: EEG analysis showed an increase in gamma total power after inducing pain as compared to baseline and a decrease after the application of TENS (mean±SD: .۰۴۳±.۰۲۹ to .۰۸۸±.۰۴۲ to .۰۳۸±.۰۲۲ μV۲ ).The analysis of VAS values demonstrated that the intensity of induced pain (mean±SD: ۵۱.۵۳±۹.۸۶) decreased after the application of TENS (mean±SD: ۱۸.۶۶±۱۰.۲۸). All these differences were statistically significant (p<.۰۰۱).Conclusion: The results of this study revealed that the high frequency TENS can reduced the enhanced gamma band activity after the induction of tonic pain in healthy volunteers. This finding might help as a functional brain biomarker which could be useful for pain treatment, specifically for EEG-based neurofeedback approaches.Â

Keywords:

Transcutaneous Electric Nerve Stimulation (TENS) , Gamma rhythm , Oscillations , Pain measurement , Tourniquet pain test , Electroencephalography (EEG)