After decades of research we have a great deal of evidence affirming the importance of sleep on cognition and memory consolidation. It's becoming very clear that information acquired during waking states is imprinted on a deeper level when followed by a sleep period. One compelling study from 2016 revealed sleeping to be a vital part of a study strategy, and students should take sporadic power naps to help memorize information faster.
No one is doubting the value of a good, old-fashioned siesta, but new research led by the University of Bristol has found short naps can even help a person process information they were not even consciously aware of perceiving. The study adds weight to prior work finding sleep improves a person's problem solving abilities, suggesting a nap helps one process unconscious information.
The study recruited 16 healthy subjects and gave them to two different tasks – a control task, and a masked prime task. The control task is a conventional response challenge, where a subject responds after being shown a blue or red square on a screen, while the masked prime task is altogether more fascinating.
It involves subjects being shown a word on a screen for about one second, but immediately preceding that word they are shown another word, for maybe 30 or 40 milliseconds. This word is followed by a mask looking something like XXXXX for 500 milliseconds. So the three-part stimulus would play along the lines of: Peace - XXXXX - Joy.
The idea is that the first word is not consciously perceived, although it does activate a neural response. Interestingly, if the first "masked prime" in the pair is incongruent with the second target word, a person's neural response time is slower than if the pair of words are compatible.
Participants' neural responses to the tests were tracked using an EEG. After the first round of tests some participants were directed to have a 90-minute nap, while others stayed awake. The tests were then repeated and, intriguingly, the nap-cohort displayed improved neural response speed to the masked prime task. However, no difference was identified in performance on the control task between the two groups.
The researchers hypothesize that the 90-minute nap somehow improved the participants' ability to process subconscious information so when they re-performed the masked prime test they displayed faster responses.
"The findings are remarkable in that they can occur in the absence of initial intentional, conscious awareness, by processing of implicitly presented cues beneath participants' conscious awareness," says Liz Coulthard, one of the researchers on the project.
The research offers a fascinating insight into how the brain potentially processes information that we don't consciously perceive. The research team is commencing further study into this intriguing phenomenon, investigating possible underlying neural mechanisms that are hoped to lead to ways for us to optimize our learning and goal-orientated decision making in the future.
The research was published in The Journal of Sleep Research.
Source: University of Bristol
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