Reproducibility of TMS-Evoked EEG responses

Navigated transcranial magnetic stimulation combined with electroencephalography (nTMS-EEG), allows noninvasive studies of cortical excitability and connectivity in humans. We investigated the reproducibility of nTMS-EEG in seven healthy subjects by repeating left motor and prefrontal cortical stimulation with a 1-week interval. TMS was applied at three intensities: 90, 100, and 110% of subjects' motor threshold (MT). The TMS-compatible neuronavigation system guaranteed precise repositioning of the stimulation coil. The responses were recorded by a 60-channel whole head TMS-compatible EEG amplifier. A high overall reproducibility (r > 0.80) was evident in nTMS-EEG responses over both hemispheres for both motor and prefrontal cortical stimulation. The results suggest that nTMS-EEG is a reliable tool for studies investigating cortical excitability changes in the test-retest designs.