Being in the business of sleep, we were fascinated by a new research study out of France that demonstrates a sleeping brain continues to both hear and process speech.
Although the study name, Inducing task-relevant responses to speech in the sleeping brain, may be sleep-inducing, the findings are much more captivating.
In the study, volunteers did simple word association tasks. In one experiment, subjects were verbally given a word and pushed a button with their right or left hand depending on if the word was categorized as either an animal or an object. A second experiment used the same button pushing, but subjects selected left or right based on if the words were actual words or pseudowords.
Working in Your Sleep
Easy stuff, particularly when awake. Test subjects were wired to an electroencephalography (EEG) device, which allowed researchers to monitor brain activity. The EEG could clearly differentiate between the brain’s signals for a right or left hand button push.
The amazing part, however, happened after subjects fell asleep. What the researchers found was that most of the subjects continued to respond appropriately to the verbal words, if only in their brains. The subjects didn’t physically push the buttons while asleep, of course, but their brains did. Even while asleep, a left side word caused the appropriate brain activity: activity on the right side of the brain (left hand activities activate the right side of the brain and vice versa).
In other words, not only were the subjects hearing the words in their sleep, but they were also processing them, correctly determining if they were animal or object and activating signals for an appropriate left or right hand response! Previous studies had shown that external tones and odors can influence sleep, but this was the first formal study looking at external stimuli that was associated with a task. Beyond sleep walking, could this be an example of sleep working?
While the study does not allow sweeping conclusions to be drawn, it shows we might be processing more stimuli in our sleep from the external world than realized.
Next time you say something is so easy you can even do it in your sleep, you might just be right.
The study was published in the Sept. 24, 2014 issue of the journal Current Biology. The lead researcher was S. Kouider.