TMS – EEG
The integrated system combining Transcranial Magnetic Stimulation (TMS) and electroencephalography (EEG) is a novel multi-modal approach which offers new prospects in cognitive neuroscience. TMS-EEG allows to measure cortical excitability and effective connectivity with a good spatial and temporal resolution.
Combining TMS with electroencephalography enhances the properties of the two techniques.
TMS-EEG allows indeed a direct measurement of the excitability of any cortical area (beyond primary motor or visual area) by directly perturbing the cortical activity, by means of TMS, and recording with the EEG the cortical response to this perturbation with a high temporal resolution (Taylor et al., 2008), computed as TMS-Evoked Potentials (TEPs). Continuous high definition EEG recording permits to probe the state of broader cortical networks, unveiling how activation spreads from the stimulated area to interconnected ones, thus allowing a direct measure of effective connectivity. TEPs are considered a reliable measure of brain activation state (Miniussi and Thut, 2010); beside, as long as the same parameters across sessions are maintained, the reliability of the technique has been probed (Casarotto et al., 2011), allowing to link any observed changes in TEPs to the experimental condition (i.e. brain state, task execution, neuromodulation, etc) rather than to others confounding variables.