To understand the nature of consciousness is perhaps the holy grail of neuroscience, not to mention philosophy and psychology. Although we are a long way off from that goal, current studies can give us some insight into our own awareness by examining and manipulating the brain during lucid dreaming.
In lucid dreaming, the dreamer is aware that he or she is dreaming while the dream continues. Lucid dreaming is also associated with several other dream states, including being able to control the dream or taking on a third person perspective. The dreamer may experience dream events, but also have access to waking memories.
Scientists have reported that the brains of people who are in a state of lucid dreaming exhibit a phenomenon known as phase synchrony. This means that the neurons in the brain are synchronizing with each other and firing with a particular common frequency. Oscillations (or colloquially, waves) of certain frequencies are grouped together and named with greek letters, and different frequencies correspond with different states. For example, the characteristic frequency for a state of relaxed wakefulness is in the alpha band of about 8-13 Hz. During lucid dreaming, there is an increase in the gamma band of frequencies, corresponding to about 40 Hz. This increase happens especially in the frontal an temporal lobes of the brain.
For many years, scientists have wondered whether these synchronized brain waves are a cause of the self-awareness in lucid dreams, or a consequence. A new study out this week, spearheaded by neuroscientist Ursula Voss, sought to address this question by passing alternating current at a variety of frequencies between two electrodes placed on the surface of the scalp. Voss and her team waited until their human volunteers were dreaming in a state of REM sleep for at least two minutes before starting to apply the current, which they hoped would entrain the neurons in the brain to the same frequency as they used for stimulation. After stimulating for 30 seconds, they woke the dreamers up and asked them questions about their dreams.
When the scientists stimulated the brain with a 25 or a 40 Hz current, similar to what is observed in gamma waves, the subjects reported an increase in lucidity compared to other stimulation frequencies. Here is how one subject described it:
“I was dreaming about lemon cake. It looked translucent, but then again, it didn’t. It was a bit like in an animated movie, like the Simpsons. And then I started falling and the scenery changed and I was talking to Matthias Schweighöfer (a German actor) and 2 foreign exchange students. And I was wondering about the actor and they told me ‘yes, you met him before,’ so then I realized ‘oops, you are dreaming.’ I mean, while I was dreaming! So strange!”
This study represents a huge moment for neuroscience, because it is the first report that transcranial stimulation is capable of causing an alteration in conscious awareness. Moreover, this study suggest that brainwaves of the 40Hz band are not simply a feature of higher cognitive functions, but can actually cause them. Strange indeed.
Reference: Induction of self awareness in dreams through frontal low current stimulation of gamma activity. (2014) Ursula Voss, Romain Holzmann, Allan Hobson, Walter Paulus, Judith Koppehele-Gossel, Ansgar Klimke & Michael A Nitsche. Nature Neuroscience.