If you start a task before nodding off, your brain can
continue to conduct it once you fall asleep, scientists have found.
During sleep people are far from being totally shut down from the
environment. They can continue performing what they were doing before falling
asleep and this can involve understanding the meaning of what is being said
around them, said Dr Sid Kouider of the Ecole Normale Supérieure in Paris.
The study builds on previous work on subliminal processing by showing that
speech processing and other complex tasks 'can be done not only without being
aware of what you perceive, but also without being aware at all.'
Researchers suspect that such unconscious processing isn't limited by the
complexity of the task, but by whether it can be made automatic or not. Scientists
recorded brain activity of volunteers while they were awake and 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.
Once that process had become automatic, the researchers placed participants
in a darkened room to recline comfortably with eyes closed and continue the
word classification task as they drifted off to sleep. Once the participants were asleep, the testing continued but with an
entirely new list of words to ensure that responses would require the
extraction of word meaning rather than a simpler pairing between stimulus and
Brain activity showed that the participants continued to respond accurately,
although more slowly, even as they lay completely motionless and unaware. The
results of the study suggested any task that could become automated might be
maintained during sleep but that tasks that can't be automated will stop as
sleep takes over.
Further tests are on going to investigate the consequences
of their findings for learning as we slumber. The study was published in the
journal Current Biology.