A comparison of two methods in acquiring stimulus-response curves with transcranial magnetic stimulation

Background: The stimulus-response (S-R) curve is a well accepted constituent in transcranial magnetic stimulation (TMS) studies. However, it has been suggested that parameters of the S-R curve differ when stimuli are provided in a "ramped" (measured steps from low to high intensity), or "random" fashion. Hypothesis: We hypothesized that there would be no difference in the parameters of the S-R curve between either methodologies. Methods: Using a randomised cross-over design, 10 healthy participants (29.6 ± 6.4 yrs, 3 f) completed "ramped" or "random" curves in biceps brachii (BB) and first dorsal interosseous (FDI) muscles of both limbs. Curves were compared using mixed-factor ANOVA and correlated between limbs and methodologies. Results: No differences (P > 0.05) and high correlations (range 0.71-0.97; P < 0.001) were observed in BB and FDI data between curves. Conclusions: This study demonstrated that either methodology provides similar parameters of the S-R curve in healthy participants.