Subjects: Behavioral health
Scientists at UC Berkeley have found that an afternoon nap improves cognition later in the day, and posit that the beneficial effects of a nap have to do with letting a particular area of the brain clear out short-term memory “storage space” so it can absorb new information.
To reach these conclusions, Matthew Walker and colleagues randomized 39 healthy adult volunteers into a nap group and a no-nap group.
The groups performed equally well on a midday test which involved absorbing a lot of facts. After that, the nappers retired for a 1.5 hour respite, while unfortunate souls in the no-nap group toiled away. Then, at 6 pm, both groups underwent further cognitive testing.
The scientists found that the nappers outperformed the non-nappers. In fact, the nappers performed better than they did on the first test, which occurred before their nap.
The results supported earlier research which showed that that the hippocampus temporarily stores fact-based memories before relaying them to the brain’s prefrontal cortex, and that the hippocampus has a relatively limited storage capacity.
They also supported earlier research showing that students who work through the night reduce their capacity to absorb new facts by 40% by the following morning.
According to Walker, “Sleep not only rights the wrong of prolonged wakefulness but, at a neurocognitive level, it moves you beyond where you were before you took a nap.”
Walker’s group also demonstrated using EEGs that the memory-refreshing process occurs during stage 2 non-REM sleep (non Rapid Eye Movement sleep). This is why, Walker suggests, humans spend nearly half their nap time in this stage of sleep.
Walker presented these preliminary findings at last month’s annual meeting of the American Association of the Advancement of Science (AAAS) in San Diego.