Right-frontal slow negative potentials evoked by occipital TMS are reduced in NREM sleep.

Occipital transcranial magnetic stimulation applied in a task-free experimental setup leads to enhanced relative negativity of frontally recorded evoked slow potentials under the influence of caffeine (Murd et al., 2010 [26]). We tested whether this increased negativity could be reversed when a similar magnetic stimulation is applied during quiet sleep where consciousness is absent. Consistently with the hypothesis, non-REM sleep led to relative more positive slow brain potentials, compared to wakefulness. This effect was lateralized to the right hemisphere. We conclude that TMS indeed elicits slow negative potentials in higher arousal states, but the effect has hemispheric specificity depending on how arousal is manipulated.