Electroacupuncture modulates cortical excitability in a manner dependent on the parameters used

Abstract

Introduction: There is evidence that electroacupuncture (EA) acts through the modulation of brain activity, but little is known about its influence on corticospinal excitability of the primary motor cortex (M1). Objective: To investigate the influence of EA parameters on the excitability of M1 in healthy individuals. Methods: A parallel, double blind, randomized controlled trial in healthy subjects, evaluating the influence of an EA intervention on M1 excitability. Participants had a needle inserted at LI4 in the dominant hand and received electrical stimulation of different frequencies (10 or 100 Hz) and amplitude (sensory or motor threshold) for 20 min. In the control group, only a brief (30 s) electrical stimulation was applied. Single and paired pulse transcranial magnetic stimulation coupled with electromyography was applied before and immediately after the EA intervention. Resting motor threshold, motor evoked potential, short intracortical inhibition and intracortical facilitation were measured. Results: EA increased corticospinal excitability of M1 compared to the control group only when administered with a frequency of 100 Hz at the sensory threshold ( p < 0.05). There were no significant changes in the other measures. Conclusion: The results suggest that EA with an intensity level at the sensorial threshold and 100 Hz frequency increases the corticospinal excitability of M1. This effect may be associated with a decrease in the activity of inhibitory intracortical mechanisms. Trial registration number: U1111-1173-1946 (Registro Brasileiro de Ensaios Clínicos; http://www.ensaiosclinicos.gov.br/ )

The Underlying Mechanism of Acupuncture on Enhancing Muscle Strength: A Review of Literature

“…They reported that the simple insertion of the needle is an adequate somatosensory stimulus to induce a significant modulation of MEP amplitude, the sign of which is specific to the investigated muscle and to the point of needle insertion. It has been demonstrated that when applying electroacupuncture or electrical stimulation to induce a motor response, it is vital that parameters creating a motor response that mimics a voluntary muscle contraction are used [81,82]. De Brito, et al [81] demonstrate that peripheral electroacupuncture or electrical stimulation that is sufficient to induce a motor contraction (30 Hz and 100 Hz) increased corticomotor responsiveness (P = 0.002), whereas stimulation at 10 Hz did not.…”

“…It has been demonstrated that when applying electroacupuncture or electrical stimulation to induce a motor response, it is vital that parameters creating a motor response that mimics a voluntary muscle contraction are used [81,82]. De Brito, et al [81] demonstrate that peripheral electroacupuncture or electrical stimulation that is sufficient to induce a motor contraction (30 Hz and 100 Hz) increased corticomotor responsiveness (P = 0.002), whereas stimulation at 10 Hz did not.…”