With the help of lucid dreamers — people who become aware of their dreaming state and are able to alter their dreams — scientists at the Max Planck Institute for Psychiatry in Munich, Germany were able to measure dream content for the first time.
Functional magnetic resonance imaging (fMRI) has enabled scientists to visualize and identify the precise spatial location of brain activity during sleep. But researchers have not been able to analyze specific brain activity associated with dream content, as measured brain activity can only be traced back to a specific dream if the precise temporal coincidence of the dream content and measurement is known.
In the new study, lucid dreamers were asked to become aware of their dream while sleeping in an fMRI scanner and to report this “lucid” state aware of their dream to researchers by means of eye movements.
They were then asked to voluntarily “dream” that they were repeatedly clenching first their right fist and then their left one for 10 seconds.
This enabled the scientists to measure the entry into REM sleep — a phase in which dreams are perceived particularly intensively — with the help of the subject’s electroencephalogram (EEG) and to detect the beginning of a lucid phase.
The brain activity measured from this time onwards corresponded with the arranged “dream” involving the fist-clenching.
A region in the sensorimotor cortex of the brain, which is responsible for the execution of movements, was actually activated during the dream. This is directly comparable with the brain activity that arises when the hand is moved while the person is awake.
Even if the lucid dreamer just imagines the hand movement while awake, the sensorimotor cortex reacts in a similar way.
Researchers say the correlation between brain activity and the conscious action shows that dream content can be measured.
“With this combination of sleep EEGs, imaging methods and lucid dreamers, we can measure not only simple movements during sleep but also the activity patterns in the brain during visual dream perceptions,” said Martin Dresler, Ph.D., a researcher at the .
The researchers were able to confirm the data obtained using magnetic imaging in another subject using a different technology.
With the help of near-infrared spectroscopy, they also observed increased activity in a region of the brain that plays an important role in the planning of movements.
“Our dreams are therefore not a ‘sleep cinema’ in which we merely observe an event passively, but involve activity in the regions of the brain that are relevant to the dream content,” explains Michael Czisch, research group leader at the Institute.