Development of an Electroencephalography Data Acquisition System for Clinical Research into Transcranial Magnetic Stimulation Evoked Potentials

We have developed a module to be inserted in-line between electroencephalography (EEG) electrodes and any standard EEG headbox that will prevent amplifier saturation during transcranial magnetic stimulation (TMS). By preventing amplifier saturation TMS evoked potentials (EPs) seen in the millisecond range immediately following TMS can be collected accurately. The new system uses a pre-proven EEG instrumentation concept, sample-and-hold circuitry (Ilmoniemi, 1997), to keep standard EEG front-end amplifiers stable during TMS pulses.