Sleepwalking: Sufferers have enhanced 'autopilot' that lets them move without thinking

Researchers made the discovery after testing the ability of sleepwalkers - somnambulists - to ignore distractions while performing a walking task.

A virtual reality technique was used to study sleepwalkers and non-sleepwalkers while they were awake.

Sleepwalkers' walking speed and accuracy was less affected by having to count backwards during the test, the scientists found.

Somnambulism affects 2-4 per cent of adults and has effects that range from small gestures to complex actions such as dressing, driving a car or playing a musical instrument while asleep.

Study leader Dr Oliver Kannape, a lecturer in cognitive neuroscience at the University of Central Lancashire, said: "Traditionally, little has been known about daytime markers of sleepwalking, mostly because of the difficulty in investigating this condition experimentally.

"Our research offers novel insight into this common sleep disorder and provides a clear scientific link between action monitoring, consciousness, and sleepwalking."

Participants wearing virtual reality headsets were asked to walk with an "avatar" towards a visual target, and then repeat the task while counting backwards in steps of seven.

At the same time, their walking speed and accuracy of movement were recorded.

Non-sleepwalkers slowed down significantly when having to count backwards, but sleepwalkers were not affected by the distraction, the study reported in the journal Current Biology showed.

Co-author Professor Olaf Blanke, head of the Laboratory of Cognitive Neuroscience at the Ecole Polytechnique Federale de Lausanne (EPFL) in Switzerland, said: "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.

"The research is also a first in the field of action-monitoring, providing important biomarkers for sleepwalkers while they are awake."