Immediate transcranial evoked potential (i-TEP) of the primary motor hand area

COEX 

The transcranial evoked potentials (TEPs), which are the EEG recorded responses to a TMS pulse, have been mainly used to study the late (>30 ms) cortical responses, due to the artifacts induced by the TMS. Specifically, the first 5 ms are covered by the magnetically induced ringing artifact, and the first 10 to 20 ms are affected by the twitch of the scalp muscles. Here, I will show how to minimize these artifacts in order to unveil the immediate brain response of the primary motor hand area (M1-HAND) to TMS (ca. 2 milliseconds after the pulse), which we called immediate TEPs (i-TEPs). Thereafter, I will talk about the properties of i-TEPs and about how they are affected by stimulation intensities and current directions. Finally, I will discuss their properties in relation to previously observed physiological brain activity with the aim of understanding their origin.