To sleep, perchance to dream

WEDNESDAY, 21 MAY 2014

“You’re just a dream monster and you can’t hurt me.”

Imagine being asleep – and trapped in a nightmare. Now imagine, within the dream, suddenly realising that you are dreaming: you promptly chase away the monster menacing you, then go off to eat cucumber sandwiches in a gazebo on a lake of gin and tonic. This phenomenon of dream awareness is known as ‘lucid dreaming’. Now, a 2014 study in Nature Neuroscience has linked lucid dreaming with specific patterns of brain activity – as well as finding a way to trigger it experimentally.

Lucid dreaming has fascinated meditation practitioners, psychologists and neuroscientists alike for decades, mainly because it bridges two broad states of consciousness. The first, primary consciousness, tends to be concerned with the immediate present, with limited self-awareness. In an ordinary dream, for example, we do not understand that we are dreaming and cannot usually predict what will happen next. Secondary consciousness is associated with self-reflective awareness and other higher cognitive functions, normally when we are awake. Since lucid dreams contain elements of both primary and secondary states, studying lucid dreaming could allow us to understand how people transition between states of consciousness.

We already know that different states of consciousness – and stages of sleep – are marked by different patterns of electrical activity in the brain. These are caused by rhythmic firing of nerve cells in various brain regions, and are often known as ‘waves’ because they form regular wave-like patterns on EEG (a detector commonly used to measure electrical activity), and have a specific frequency. For example, alpha waves have frequency 7.5-12.5 Hz and occur during ‘rapid eye movement’ sleep, or REM, which is when we are most likely to dream. Gamma waves have the highest frequency (25-100 Hz); these have been linked with long-term meditation practice, and, more recently, lucid dreaming. However, no-one has been able to establish a causative relationship between lucid dreams and gamma activity – until this year’s Nature Neuroscience paper.

Gamma waves

So what did the Nature researchers do? They asked participants to spend 4 nights in a sleep laboratory, with electrodes placed on their heads to monitor their stage of sleep. At roughly the same time each night, when REM sleep started, the researchers applied a mild electrical stimulus to each sleeper’s brain. (This was done via the electrodes, and even when awake the participants could not hear or feel the stimulus.) After sleeping a little longer, the subjects were then woken up to give detailed reports about their dreams, including an experimentally verified rating of ‘lucidity’.

Surprisingly, the researchers found that a stimulus of 25-40 Hz not only caused a spike in gamma activity, but also reliably increased the frequency of lucid dreams. This is even more convincing when we consider that none of the participants had previously experienced lucid dreaming! If lucid dreaming could also be induced in people with sleep disturbances (who were excluded from the test subjects here) it could be used therapeutically as well. People with post-traumatic stress disorder are often terrorised by nightmares; by giving them control over their dreams, ‘induced’ lucid dreaming could increase their quality of sleep – and life.

More broadly, though, this research shows that we can now reliably trace the development of a form of self-awareness: from ‘primary conscious’ dreaming, to lucid dreaming, to fully waking. This is potentially another step on the path to understanding how ‘higher’ states of consciousness work, and definitely something to meditate on.

Full paper here:

Voss et al. (2014) Nature Neuroscience (Epub ahead of print) <http://www.nature.com/neuro/journal/vaop/ncurrent/full/nn.3719.html>

Gamma waves and meditation:

Lutz et al. (2004) PNAS <http://www.pnas.org/content/101/46/16369.full>