A combined team of researchers from the University of Cambridge and Ecole Normale Supérieure, a research institution in Paris, have found that even during sleep, our brain can still classify words.
According to the researchers, when people practice simple word classification tasks before nodding off—knowing that a “cat” is an animal or that “flipu” isn’t found in the dictionary, their brains still continue to make those classifications even in the unconscious state of mind.
“We show that the sleeping brain can be far more ‘active’ in sleep than one would think,” said Sid Kouider of Ecole Normale Supérieure in Paris.
“Far from falling [into] a limbo when we fall asleep, parts of our brain can routinely process what is going on in our surroundings and apply a relevant scheme of response. This explains some everyday life experiences such as our sensitivity to our name in our sleep, or to the specific sound of our alarm clock, compared to equally loud but less relevant sounds.”
The unconscious brain processes the speech and other complex tasks not only without being aware of what is perceived, but also without being aware at all. The researchers doubt that such subliminal processing of complex task can only be performed only if the task is automated.
Using an electroencephalogram (EEG), the researchers recorded the brain activity of the participants while they are asked to classify spoken words as either animals or objects by pressing a button, using the right hand for animals and the left hand for objects. This procedure allowed researchers to compute their response by mapping each word category to a specific plan for movement in the brain; and once this becomes automatic, the researchers placed participants in a darkened room with their eyes closed and continued the word classification task as they nodded off.
When the researchers continued the test – during the period of slumber – with an entirely new list of words to make sure the brain can extract the meaning of the words rather than a simpler pairing between stimulus and response, the participants continued to respond accurately, but rather more slowly. At that time, the participants were completely motionless and unaware.
Kouider said one could imagine people performing calculations on simple equations while falling asleep and then continuing to identify those calculations as correct or not during a snooze.
According to Kouider, any tasks that could become automated might be maintained during sleep and the ones that cannot be automated would not be maintained as sleep will take them over.
The researchers are now investigating the consequences of their findings, the activeness of brain, as we slumber.
“It will be worth thinking carefully about why animals, from fruit flies to humans, all show sleep or sleep-like states in the first place,” Kouider said.
“Research focusing on how to take advantage of our sleeping time must consider what is the associated cost, if any, and whether it is worth it.”
Further research on this will help us come upon more about the processing capacity of brain during sleep.
- Reference: Inducing Task-Relevant Responses to Speech in the Sleeping Brain
- Source: Cell Press
- Image: Echoisthename