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The role of the coil click in TMS assessed with simultaneous EEG
V Nikouline1, J Ruohonen, R J Ilmoniemi
1BioMag Laboratory, Medical Engineering Centre, Helsinki University Central Hospital, Finland. vadim@biomag.helsinki.fi
Objective:
We have used EEG to measure effects of air- and bone-conducted sound from the coil in transcranial magnetic stimulation (TMS).
Methods:
Auditory-evoked potentials to TMS were recorded in three different experimental conditions: (1) the coil 2 cm above the head, (2) the coil 2 cm above the head but rigidly connected by a plastic piece to the scalp, (3) the coil pressed against the scalp over the motor cortex.
Results:
The acoustical click from the TMS coil evoked large auditory potentials, whose amplitude depended critically on the mechanical contact of the coil with the head.
Conclusion:
Both air- and bone-conducted sounds have to be taken into account in the design and interpretation of TMS experiments.
