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.