Discussion
In this study we sought to evaluate whether 10 Hz TMS trains to the dlPFC induce acute neural effects quantifiable in the early (20–80 ms) local TMS-evoked potential (TEP). Due to the well-described sensory responses to TMS, which we also observed after each pulse within a train, we applied the probe single pulses at latencies that should be clear of train-evoked sensory potentials (> 300 ms). We found that: (1) prefrontal TMS trains did not induce acute neural changes in the size of the sensor-space early TEP in regions local to the stimulation site but (2) suppressed the early TEP in a right frontal ROI when probed at 500 ms, and that (3) up to 12 sequential TMS trains did not elicit a cumulative effect on early local TEPs. In exploratory analyses, we found that TMS trains may induce (1) neural changes non-locally at later latencies (> 78 ms), (2) regularity in early local oscillatory phase dynamics, and (3) reduced source estimate amplitudes spanning 56–210 ms. In the context of previous work