The influence of changes in the intensity of magnetic stimulation on coil output

摘要

AbstractWe measured the peak voltage induced in a sensing loop by a Magstim 200 magnetic stimulator. Coil output varied little for repeated stimulation at the same intensity over a wide range of coil output. In contrast, the first stimulus immediately after a change in intensity was of larger amplitude and showed greater variability than subsequent stimuli. The effect was seen for changes in intensity of 5 and 60 and was greater for reductions than for increases in stimulation intensity. Stimulation immediately after a reduction in intensity from 100 to 40 resulted in peak induced voltages as high as those recorded for repeated stimulation at 43 of maximum coil output. Increased coil output following changes in stimulation intensity may affect measurement of the threshold for motor cortical stimulation. The effect of a change in intensity could be minimized by delaying stimulation for at least 30 s or discarding the first stimulus after the change. © 1993 John WileySons, Inc