Differentiating transcranial magnetic stimulation cortical and auditory responses via single pulse and paired pulse protocols: A TMS-EEG study

Objective: We measured the neurophysiological responses of both active and sham transcranial magnetic stimulation (TMS) for both single pulse (SP) and paired pulse (PP; long interval cortical inhibition (LICI)) paradigms using TMS-EEG (electroencephalography). Methods: Nineteen healthy subjects received active and sham (coil 90 degrees tilted and touching the scalp) SP and PP TMS over the left dorsolateral prefrontal cortex (DLPFC). We measured excitability through SP TMS and inhibition (i.e., cortical inhibition (CI)) through PP TMS. Results: Cortical excitability indexed by area under the curve (AUC((25-275ms))) was significantly higher in the active compared to sham stimulation (F(1,18) = 43.737, p < 0.001, eta(2) = 0.708). Moreover, the amplitude of N100-P200 complex was significantly larger (F(1,18) = 9.118, p < 0.01, eta(2) = 0.336) with active stimulation (10.38 +/- 9.576 mu V) compared to sham (4.295 +/- 2.323 mu V). Significant interaction effects were also observed between active and sham stimulation for both the SP and PP (i.e., LICI) cortical responses. Finally, only active stimulation (CI = 0.64 +/- 0.23, p < 0.001) resulted in significant cortical inhibition. Conclusion: The significant differences between active and sham stimulation in both excitatory and inhibitory neurophysiological responses showed that active stimulation elicits responses from the cortex that are different from the non-specific effects of sham stimulation. Significance: Our study reaffirms that TMS-EEG represents an effective tool to evaluate cortical neurophysiology with high fidelity. (C) 2021 Published by Elsevier B.V. on behalf of International Federation of Clinical Neurophysiology.

Automated summary

The study compared the neurophysiological responses of active and sham transcranial magnetic stimulation (TMS) in both single pulse (SP) and paired pulse (PP) paradigms using TMS-EEG, demonstrating significant differences in excitatory and inhibitory responses between active and sham stimulation. This reaffirms the effectiveness of TMS-EEG in evaluating cortical neurophysiology with high fidelity.