21st Congress of the European Sleep Research Society
Paris, France

04.09.2012 - 08.09.2012
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Home - 05.09.2012 - New approaches to the study of sleep and dreams: tACS and tDCS


New approaches to the study of sleep and dreams: tACS and tDCS

Wednesday, September 05, 2012, 14:00 - 16:00

Effects of Transcranial alternating current stimulation (tACS) on sleep and dreaming

U. Voss, R. Holzmann, M. Nitsche, W. Paulus (Frankfurt, Darmstadt, Goettingen, DE)

Objectives: The current experiment was carried out to test a possible causal relationship between activity in the 40 Hz frequency band and secondary, i.e. higher order consciousness in dreams. Specifically, we investigated whether it is possible to change the brainís state of consciousness from normal REM-sleep dreaming to lucid dreaming through low voltage 40 Hz stimulation at fronto-temporal sites of the scalp. This incorporates two important steps: a demonstration that an externally applied low voltage electrical current is effective in changing the ongoing EEG and evidence that the dream content is altered as a function of the applied current.
Methods: We tested 13 subjects during 3 consecutive nights in the Goettingen sleep laboratory. Transcranial alternating current stimulation (tACS) was performed only after 3 am and only during REM phases. In nights 1 and 3, subjects were stimulated with 40 Hz or 2 Hz currents, counterbalanced for time of night. In night 2, participants received sham stimulations. Stimulations were carried out in double-blind
fashion.
Results: Our analyses show that the external application of a weak electrical current changes the ongoing cortical activity as evidenced by EEG recordings. This effect was traceable for the 40 Hz but not for the 2 Hz condition which is most likely due to the high delta power that is naturally present during REM sleep. Regarding subjective correlates of induced EEG changes during REM sleep, we observed increased dissociative thought specific to 40 Hz stimulation. Dissociative thought has been shown to be typical for lucid dreaming, especially in young children.
Conclusion: We interpret this finding as strong support for the 40 Hz band hypothesis stating that frequencies around 40 Hz are somehow involved in higher order or secondary consciousness. Moreover, results suggest a causal relationship between lucid dreaming and 40 Hz activity in fronto-temporal areas of the brain.
Although the method itself has been shown to influence cognitive performance by other laboratories, this is the first demonstration of an effect on the ongoing EEG. We consider our results a proof-of-principle, and trust that it will encourage further research into the possibilities and boundaries of low current electrical stimulation of the brain during sleep.