Sleepwalking, or somnambulism, is an abnormal sleep condition in which a person performs complex movements in the absence of full consciousness, such as walking, eating, getting dressed, or even driving a car or playing a musical instrument.
Now new research reveals that sleepwalkers may have a multi-tasking advantage while they are awake. The study uncovers significant differences in how the brains of sleepwalkers and non-sleepwalkers control and perceive body movement.
For the study, both sleepwalkers and non-sleepwalkers, wearing full-body motion capture suits, were asked to walk towards a target object, in this case a virtual cylinder, in a room full of IR-tracking cameras at EPFL (Ecole polytechnique fédérale de Lausanne).
Each participant was shown a life-size avatar that could truthfully replicate or deviate from their actual trajectory in real-time. Participants could therefore be tricked into walking along a modified trajectory to compensate for the avatar deviation. Their walking speed and accuracy of movement along with their movement awareness were then recorded and analyzed.
As expected, there was no difference between sleepwalkers and non-sleepwalkers in this first part of the task. But when the researchers added a layer of complexity, however, a clear distinction emerged between the two groups.
Participants were asked to count backwards in steps of seven starting from 200. While non-sleepwalkers had to significantly slow down during this task, sleepwalkers maintained a similar walking velocity in both conditions, showing a strong link between sleepwalking and automatic control of locomotion during full wakefulness.
In addition, sleepwalkers were more accurate at detecting changes in the virtual reality feedback when faced with the mental arithmetic task.
“We found that sleepwalkers continued to walk at the same speed, with the same precision as before and were more aware of their movements than non-sleepwalkers,” said EPFL neuroscientist Dr. Olaf Blanke.
“The research is also a first in the field of action-monitoring, providing important biomarkers for sleepwalkers, while they are awake.”
Sleepwalking is caused by a partial arousal from slow-wave or deep sleep, however it was still unknown which functional brain mechanisms are affected by this pathophysiology. The new link between sleepwalking and conscious movement control sheds new light into the brain mechanisms of sleepwalking and may be used one day to aid diagnosis of sleepwalking while the person is awake, rather than requiring an overnight stay in a sleep laboratory.
“Traditionally, little has been known about daytime markers of sleepwalking, mostly because of the difficulty in investigating this condition experimentally,” said Dr. Oliver Kannape from the University of Central Lancashire (UCLan) and lead author of the study.
“Our research offers novel insight into this common sleep disorder and provides a clear scientific link between action monitoring, consciousness, and sleepwalking.”
Sleepwalking currently affects between two to four percent of adults and over 10 percent of children.
The new findings are published in the journal Current Biology.