Electroencephalographic recording during transcranial magnetic stimulation in humans and animals.

OBJECTIVE We report on the development of an EEG recording system, comprised of electrodes and amplifiers that are compatible with TMS (single and rapid-rate) in both human and animal studies. METHODS We assembled a versatile multi-channel EEG recording system consisting of: (1) two types of electrodes that are safe during TMS or rTMS. (2) Low slew-rate EEG amplifiers that recover within a few milliseconds after the application of TMS pulses. RESULTS The two electrode types: (a) a conductive-plastic surface electrode with a conductive-silver epoxy coat and (b) a subdermal silver wire electrode (SWE) are compatible to TMS pulses. The amplifiers recover within 30 ms, so that the EEG can be viewed online, essentially without interruption and/or blocking or excessive artifact. CONCLUSIONS Our TMS compatible electrode and EEG recording system allows safe and online viewing/recording of the subject's (human or animal) EEG/EP during experiments or studies involving TMS or rTMS applications. The TMS compatible electrode/amplifier system can be used with any EEG recording instrument. SIGNIFICANCE A simple recording technique coupled with new electrodes permit safe and readable EEG records during TMS in humans and animals. Such online monitoring of the EEG would allow control of TMS/rTMS parameters based on EEG activity.