The idea is fascinating and threatening at the same time: machines that are able to read human thoughts. That is already possible to some extent. With the help of brain waves, researchers were able to at least rudimentarily record what test subjects were thinking about - for example words such as "yes", "no", "thirst" or "hunger".
Scientists have now achieved an even more spectacular coup: They have reconstructed which images people have seen on the basis of brain activity alone. "This is a big leap towards a reconstruction of the inner world of images," says Jack Gallant of the University of California at Berkeley, in whose laboratory the experiment took place. "We are opening a window into the films of our mind."
The researchers first recorded the activity in the test subjects' visual center while they watched films for several hours. To do this, they used functional magnetic resonance imaging (fMRI). This procedure shows where a particularly large amount of blood is flowing in the brain. However, the blood flow always lags a few seconds behind the actual processing of the visual stimuli in the brain. Therefore, it was previously considered impossible to read dynamic brain activity from fMRI data.
Fortunatly, dreaming is a very private matter. You can tell your fellow human beings what goes on behind closed eyes at night - or keep them to yourself. Even during examinations in the sleep laboratory, in which the electrical brain activity is also recorded, the dreams have so far remained hidden. Now it is over. For the first time, researchers have succeeded in making the content of dreams visible and legible.
However, research is still at the very beginning of the art of dream reading. So far, only very simple dream actions can be recognized. "Nevertheless, it is an important step for dream research," says Michael Czisch from the Max Planck Institute for Psychiatry in Munich. Together with his colleague Martin Dresler and other researchers, the physicist reports in the journal Current Biology about the first successful attempt at dream reading.
More than a movie
As the team found out, the brain works fully in the dream. With hand movements that only occur in the head during sleep, the cerebral cortex shows the same activity patterns as with movements that are actually carried out while awake.
So far it was not clear what happens in the brain when you dream. “Now we know that it is by no means as if only a movie is shown in your sleep. The brain follows the movements from the dream, ”says the neuroscientist Dresler.
German researchers have for the first time read from a person's brain activity what he is dreaming. With the help of an imaging procedure, they were able to distinguish whether the subject was dreaming of clenching his left or right fist. This became possible because the brain showed a similar signal pattern during this dream act as with the ball of a fist in the waking state. “Although this was only a preliminary test, we are providing the first evidence that specific contents of dreams can be made visible during the REM phase,” the scientists report in the specialist magazine “Current Biology”.
So far it has been considered almost impossible to make dreams visible. "The main obstacle to the direct reading of dream content is the fact that the test subjects cannot control their dreams while sleeping and therefore cannot perform any predetermined actions," say the researchers led by Michael Czisch from the Max Planck Institute for Psychiatry in Munich . As a result, it was not possible to compare whether a dream experience evoked the same brain activity as the experience in the waking state. But you need this comparison in order to be able to recognize from the activity pattern what someone is dreaming at the moment.
A team of researchers led by Yukiyasu Kamitani of the ATR Computational Neuroscience Laboratories in Kyoto, Japan, used functional neuroimaging to scan the brains of three people as they slept, simultaneously recording their brain waves using electroencephalography (EEG).
Researchers in Japan can predict certain features of dreams by looking at the brain activity of sleeping volunteers. Credit: Glowimages
The researchers woke the participants whenever they detected the pattern of brain waves associated with sleep onset, asked them what they had just dreamed about, and then asked them to go back to sleep.
This was done in three-hour blocks, and repeated between seven and ten times, on different days, for each participant. During each block, participants were woken up ten times per hour. Each volunteer reported having visual dreams six or seven times every hour, giving the researchers a total of around 200 dream reports.
The remarkable breakthrough makes use of a fairly straightforward idea: that when we visualize certain types of objects in our minds, our brains generate consistent neural patterns that can then be correlated with what is being visualized. For instance, when you imagine a chair, your brain fires in a pattern that occurs whenever a chair is visualized. An algorithm can then be used to tie the data from a brain scan to the appropriate correlated images. And voilà! Your dream can be reconstructed.
So far the research is still fairly rudimentary — researchers only claim to get the dream right about 60 percent of the time — but it's still an extraordinary turn for the science of the mind.