Lucid dreaming can be induced by electric scalp stimulation, study finds | Life and style | The Guardian

By examining the sleepers' brainwaves over a range of frequencies, scientists have found that lucid dreamers demonstrate a shift towards a more "awake-like" state in the frontal and temporal parts of the brain, with the peak in increased activity occurring around 40Hz.

"Lucid dreaming is a very good tool to observe what happens in the brain and what is causally necessary for secondary consciousness," Voss said.

Now Voss and her team have reported that it is possible to induce lucid dreaming by delivering electrical stimulation, in the form of an alternating current to a sleeper's scalp at this frequency.
The study involved 27 volunteers, none of whom had experienced lucid dreaming before. The researchers waited until the volunteers were experiencing uninterrupted REM sleep before applying electrical stimulation to the frontal and temporal positions of the volunteers' scalps.

The applied stimulation had a variety of frequencies between two and 100Hz, but neither the experimenter nor the volunteer was informed which frequency was used, or whether a current was applied. Five to 10 seconds later the volunteers were roused from their sleep and asked to report on their dreams. Brain activity was monitored continuously throughout the experiment.

The results showed that stimulation at 40Hz resulted in an increase in brain activity of around the same frequency in the frontal and temporal areas. A similar, but smaller effect was observed at 25Hz. They also found that such stimulation often, but not always, induced an increased level of lucidity in the dreams of sleepers. At higher or lower frequencies, or when no current was applied, no change in brain activity was observed.