Transcranial Magnetic Stimulation (TMS) and Electroencephalography (EEG) are two of the most commonly used modalities to investigate signal propagation in the cortex and cognitive processes. As TMS provides a non-invasive and low-risk method to elicit/inhibit certain cognitive processes in the brain, it is a versatile tool, but as such, it depends on the output generated by the TMS pulse into an observable behavioral/physiological response to investigate its effect. EEG on the other hand provides an easy and affordable way to measure the electrical brain activity. Several studies in the last 10 years have investigated the synergistic properties of a combined TMS-EEG measurement. From Veniero et al. [3Veniero D., Bortoletto M., Miniussi C. TMS-EEG co-registration: on TMS-induced artifact Clin Neurophysiol 2009 ;  120 : 1392-1399 [cross-ref]

Cliquez ici pour aller à la section Références] we know that care has to be taken for certain artifacts and that some are system dependent. Some TMS machines generate more (polluted) power line noise in the EEG than others, which make filtering a non-trivial task. Both the exponential artifact and the increased power line noise levels that are shown in the EEG can be filtered out with readily available methods [1Neuro A.N.T. b.v. ASA User Manual  :  (2015). 342-343

Cliquez ici pour aller à la section Références]. Other artifacts like a long amplifier recovery time and ringing are EEG amplifier specific while a charge delay is TMS machine specific and can be very hard to correct as the effects can be different from trial to trial and from channel to channel. Other pitfalls lie in the practical setup: power line noise, leakage, holding the coil steadily over a fixed position to generate an accurate MEP/TEP. When combined, TMS-EEG recordings can unravel fundamental details about human cognitive processing that would otherwise be impossible to investigate, like in the study conducted by Romei et al. [2Romei V., Bauer M., Brooks J.L., Economides M., Penny W., Thut G., et al. Causal evidence that intrinsic beta-frequency is relevant for enhanced signal propagation in the motor system as shown through rhythmic TMS Neuroimage 2016 ;  126 : 120-130 [cross-ref]

Cliquez ici pour aller à la section Références] in which the influence of intrinsic brain rhythms for (sub)cortical signal propagation is assessed.