Different Eeg Effects of Long-interval Paired Pulse Tms in Awake and Nrem State

Different EEG effects of long-interval paired pulse TMS in AWAKE and NREM state. Occipital transcranial magnetic stimulation (TMS) applied in a task-free experimental setup during wakefulness leads to relative more positive slow-wave brain potentials in frontal and central areas the of brain (Stamm, Aru, & Bachmann, 2011). Current study tested whether paired pulse TMS during wakefulness is associated with increase of slow negative processes compared to the deep sleep (NREM state). Interestingly, qualitatively and quantitatively different processes take place when second TMS impulse is added. Here it is shown that longinterval paired pulse TMS (with inter-pulse-interval 100 ms) targeted at V1 (calcarine area) will trigger slow wave potential during sleep while single pulse TMS fails to do so. It is proposed that globally expressed differences in the TMS-induced potentials may be due to inhibitory and excitatory effects of the thalamocortical system. The ability to evoke slow waves noninvasively at much lower intensities of the TMS than it was previously thought is important for several reasons (as discussed in this work) and could be used to develop clinical tools.