We may not be able to keep records of our night time imaginings, but we might be able to influence their contentby Philip Ball / October 23, 2014 / Leave a comment
In the movies—in films like Inception and Brazil—dreams look like, well, movies. But how much “visual” information do your dreams really contain? When you think about it, even familiar faces aren’t exactly “seen” so much as “sketched”— you know who they are because it’s your dream after all, not because you necessarily picture them in every detail. Do you actually “hear” what they say, or just somehow “know” it? Besides, dreams aren’t only or even primarily visual and aural. Often what strikes us most about a dream is the emotional aura, whether that’s fear, excitement or whatever. How could that ever be recorded in a “dream” home movie?
All the same, dreams can have extraordinarily precise content. Even if it’s a romanticized trope to be taken with a pinch of salt, people have found inspiration for songs, books and scientific theories in dreams. Perhaps you, like me, will have woken from dreams purely because you have become bored with their pedantic detail.
No one knows why we dream. One idea is that replaying events in the brain helps us to consolidate them in the memory—but of course many dreams are about things that never happened to us, or weird versions of things that did. Or maybe dreams serve no purpose, but are just the residual product of neurons firing at random while we sleep.
Whatever the case, the challenge of decoding dreams from our neural activity is in many ways no different to that of understanding anything the brain does. This activity can be measured in terms of the flows of blood (which are sensed by functional magnetic resonance imaging, fMRI), the patterns of electrical activity (detected by scalp sensors in electroencephalography, EEG) and the pulses of electrical current fired off by neurons, which can be detected directly with tiny invasive probes in the brain. Thanks to the new technique called optogenetics, it’s also possible now to make selected neurons emit light when they are active. All these methods are rather like watching the activity in a city from an aerial view of the traffic or from the patterns of lights in streets and buildings, and trying to deduce from those observations what the roles, intentions and motives of the inhabitants are.