Artefacts - TMSMultiLab/TMSMultiLab GitHub Wiki
TMS produces high-power electromagnetic pulses presented on or near the body. It will induce electrical artefacts in any other nearby or connected piece of equipment. This includes:
- electrophysiological recordings (EMG, EEG, ECG)
- electromagnetic equipment (tactile stimulators, loudspeakers)
- hardware devices like National Instruments data acquisition cards or connector boxes
- [insert more examples here]
Anecdotally, during one experiment using a vibrotactile device to present stimuli to participant's skin, we noted that all the stimuli felt the same, and that stimuli were being produced when they were not supposed to, at the same time as the TMS machine was triggered. Our setup included the TMS machine being placed around 25cm above a National Instruments connector box which we were using to create the stimuli to drive the vibrotactors. We plugged the output going to the vibrator into a data acquisition device and saw that every TMS pulse was accompanied by a very short electrical spike. We used the long NI cable to move the connector box away from the TMS machine and the artefact disappeared. Clearly, the TMS machine was not completely shielded, and either it or the cable to the coil was close enough to the NI connector to create a ~5uV spike which, when amplified, was clearly perceptible as a click. (A simpler solution was moving the connector box and cable so that it was >40cm below the TMS machine.)