Neural correlates of conscious vs unconscious states can be studied by contrasting EEG markers of brain activity between those two states. Here, a task-free experimental setup was used to study the state dependent effects of occipital transcranial magnetic stimulation (TMS). EEG responses to single and paired pulse TMS with an inter-stimulus-interval (ISI) of 100 ms were investigated under Non-REM (NREM) sleep and wakefulness. In the paired pulse TMS condition adopting this long ISI, a robust positive deflection starting around 200 ms after the second pulse was found. This component was not obtained under wakefulness or when a single TMS pulse was applied in sleep. These findings are discussed in the context of NREM sleep slow waves. The present results indicate that the long interval paired-pulse paradigm could be used to manipulate plasticity processes in the visual cortex. The present setup might also become useful for evaluating states of consciousness.
Keywords: Consciousness; EEG; LICI; Paired-pulse TMS; Plasticity; Sleep; Slow waves; TMS.
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