Quantifying brain activity while it is in a dream state has been accomplished for the first time, leading to a deeper understanding of the differences between the brain’s wakeful and sleeping states. The ability to dream is a fascinating aspect of the human mind. However, how the images and emotions that we experience when we dream form in our heads remains a mystery. Up to now, it has not been possible to measure the contents of one’s dreams, but scientists at Max Planck Institute of Psychiatry, at Charité hospital in Berlin and at Max Planck Institute for Human Cognitive and Brain Sciences in Leipzig have succeeded in analyzing the activities of the dreaming brain. Functional magnetic resonance imaging has helped researchers quantify, for the first time, the contents of dreams. (Photos: MPI of Psychiatry) Methods such as functional magnetic resonance imaging (fMRI) have helped visualize and identify the precise spatial location of brain activity during sleep. However, researchers have not been able to analyze specific brain activity associated with dream content because measured brain activity can be traced back only to a specific dream if the precise temporal coincidence of the dream content and measurement is known. Whether a person is dreaming is something that could be reported only by that individual. Therefore, the investigators enlisted the help of lucid dreamers — people who become aware of their dreaming state and can alter the content of their dreams. The scientists measured that the brain activity during the dreamed motion matched the one observed during a real executed movement in a state of wakefulness. Lucid dreamers were asked to become aware of their dream while sleeping in an MRI scanner and to report this “lucid” state to the 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 s. This enabled the scientists to measure the entry into REM (rapid eye movement) 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. Activity in the motor cortex during the movement of the hands while awake (left) and during a dreamed movement (right) are shown. Blue areas indicate the activity during a movement of the right hand, which is clearly demonstrated in the left brain hemisphere, while red regions indicate the corresponding left-hand movements in the opposite brain hemisphere. The brain activity measured from this time onward 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, actually was 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. The coincidence of the brain activity measured during dreaming 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 of Max Planck Institute for Psychiatry. The researchers confirmed the data obtained using MRI 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 [instead] involve activity in the regions of the brain that are relevant to the dream content,” said Michael Czisch, also of Max Planck Institute for Psychiatry. For more information, visit: www.mpg.de