How schoolchildren fall asleep
Surveys show that many children already have a large sleep deficit at primary school age and a remarkable number of them suffer from sleep problems. An essential prerequisite for a child's individual learning efficiency is their state of mind during the day. And this in turn is closely linked to the restfulness of sleep. Sleep also fulfils two important functions for learning: the regeneration of brain functionality after the stresses of the day and the consolidation of newly learned memory content.
MEMORISING LEARNING CONTENT DURING SLEEP
Learning is a gradual process. First, new material is actively practised. Newly learnt content is then memorised, which happens during sleep, among other things. At a later stage, this new, successfully memorised information can then be recalled.
Research results show that procedural learning - i.e. the learning and memorisation of skills, movement patterns and physical sequences such as cycling - takes place primarily during rapid eye movement or REM sleep. Declarative memory, i.e. remembering facts and episodes, takes place in non-REM sleep, in which the contents of the declarative memory system are reactivated and transferred from the short-term memory (hippocampus) to the long-term memory (neocortex) of the brain.
During this process, special brainwave patterns, known as sleep spindles, occur. We now know that the number and strength of these sleep spindles influence memory performance. This connection has previously been proven in studies with adults. We have now been able to establish similar results in schoolchildren.
In a study of 54 fourth-graders aged eight to eleven in Salzburg, we investigated the correlation between sleep quality and cognitive performance. To do this, we first asked about the children's sleeping habits in order to rule out any environmental factors such as light, noise, heat or cold that might disrupt their sleep. The children then took part in a general test on intelligence and emotional abilities. Finally, we recorded their sleeping habits for a week.
The children kept a sleep diary and wore a so-called actigraph, a measuring device the size of a wristwatch that stores data on movement activities. For two nights, the children's sleep was recorded at home using a mobile electroencephalograph.
An afternoon nap for children helps them to memorise what they have just learned.
Dr Kerstin Hödlmoser
SENSIBLE POWER-NAPPING
The measurements from the first night served as baseline values. Before the second night, we presented the children with 50 pairs of words to memorise in order to determine their memory performance. In the morning, we repeated the task. On average, the children had completed 50.81 per cent of all word pairs correctly the night before, but only 48.65 per cent in the morning. On average, the reaction time for correct answers was better in the morning than the evening before.
Based on the aforementioned correlations between sleep spindle activity and memory performance in adults, we then divided the test subjects into two groups: Children with increased sleep spindle activity and children without increased sleep spindle activity. We found that although the memory performance of both groups was better in the evening than in the morning, children with more sleep spindles showed better memory performance. And it is not only memory performance that is related to the frequency of sleep spindles, but also the intelligence quotient. We can therefore conclude that intelligent children have better memory performance and more sleep spindles in the sleep EEG than less intelligent children.
Sleep also plays a role in motor learning. Previous research has shown that our memory processes motor tasks during sleep. Recently, Ines Wilhelm from the University Children's Hospital Zurich was able to prove for fine motor tasks that children consolidate unconsciously learnt memory content during sleep in such a way that it becomes conscious knowledge. In addition, unlike adults, children also seem to consolidate learning content more during the day, i.e. when they are awake.
This does not mean that sleep is less important for children's learning. On the contrary: Laura Kurdziel from the University of Massachusetts Amherst and her colleagues were able to show that a midday nap in kindergarten children massively supports the retention of newly learnt content. The improved memory performance persisted even after 24 hours. An afternoon nap is not only good for children. According to research, power napping - ideally 10 to 20 minutes - is also beneficial for adults.
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ABOUT THE AUTHOR:
Dr Kerstin Hödlmoser is an assistant professor, sleep researcher and co-director of the Laboratory for Sleep, Cognition and Consciousness Research at the University of Salzburg.
JACOBS FOUNDATION
As one of the world's leading charitable foundations, the Jacobs Foundation has been committed to promoting research in the field of child and youth development for 25 years. The Foundation aims to provide sustainable support for future generations by improving their development opportunities.