Reproducibility of TMS—Evoked EEG responses

Abstract

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.

Transcranial Magnetic Stimulation-Electroencephalography Responses in Recovered and Symptomatic Mild Traumatic Brain Injury

“…In TMS of DLPFC, the same major ERPs can be identified. Based on ERP amplitudes, however, DLPFC has lower excitability than M1 19,31 and a distinct global mean field amplitude waveform. 20 It is also plausible that clinical conditions such as mTBI may differentially affect responses to nTMS of motor and prefrontal areas.…”

“…In nTMS-EEG, certain individually highly reproducible deflections are found, including P30, N45, P60, N100, and P200. 19,20 Besides activation of the tissue immediately under the stimulation coil, TMS-evoked deflections also reflect the spread of activation to more distant brain areas. This, in turn, is affected by corticocortical, thalamocortical, and interhemispheric connections.…”

“…Converging evidence from several studies, however, shows that direct effects of TMS to the N100-P200 are substantial, probably more important than sensory stimulation. 19,25,26,33,34 The N100 is sensitive to certain clinical conditions, including ADHD 35 and mild cognitive impairment, 27 where reduced N100 amplitudes have been found. The balance of cortical inhibitory and facilitatory circuits in paired-pulse TMS-EEG is also reflected in latencies.…”

Characterization of GABAB-receptor mediated neurotransmission in the human cortex by paired-pulse TMS–EEG

“…In order to smooth the TEP, we filtered the data between 1 and 45 Hz. In accordance with the literature (Lioumis et al, 2009;Premoli et al, 2014), five TEP components were considered (non-overlapping time windows of interest [TOI] given in brackets; P, positive deflection; N, negative deflection): P25 (17 -37 ms), N45 (38 -57 ms), P70 (58 -84 ms), N100 (85 -150 ms) and P180 (160 -230 ms) (Figure 2A). TOIs were chosen on the basis of the grand average of single-and paired-pulse TEPs, and were equal in both TMS (i.e., single-and paired-pulse) and across drug conditions.…”

“…the negative potentials at around 45 (N45) and 100 (N100) milliseconds post stimulus (Lioumis et al, 2009;Rogasch et al, 2013), can be linked to GABAAR-and GABABR-mediated neurotransmission, respectively. In the current study, we extend these studies by applying paired-pulse TMS-EEG and pharmacology to characterize and study the spatiotemporal dynamics of LICI directly at the level of the cortex.…”