A new study reported in the journal Science on June 6, 2014 is groundbreaking in filling in some missing information about how sleep affects learning, memory, and performance. Over the last few decades, evidence has been accumulating that sleep is beneficial, and recently slow wave sleep has been found to be the sleep stage during which much memory consolidation takes place. It had been hypothesized that during sleep, some strengthening of connections between neurons occurs, along with some pruning of synapses that help establish memories. The new discovery is that the process of synaptic strengthening and weakening has been observed, providing support for the hypothesis.
A team of researchers at New York University and Peking University Shenzhen, China (Wang et al. 2014) used mice that were genetically engineered to express a florescent protein. After training them on a running/balancing task, they observed changes in synapses. One finding was that changes appeared on specific dendritic branches – that is they were not spread across an entire brain region. Periods of sleep or sleep deprivation followed training, and remarkably, only after sleep did some of the new branches appear. Moreover, the newly formed spines were still present a day later.
This new study builds importantly on a large body of literature that shows the importance of sleep for children. From birth, children spend much of their waking hours learning new information and skills. Infants sleep long hours and now it is clear that sleep is more than just “rest”. Active reprocessing of neuronal connections takes place during sleep. As children get older, their learning continues, as does their need for sleep. We have known for some time that sufficient sleep is vital for optimal learning, and we continue to attain better understanding of the underlying mechanisms of how sleep facilitates learning.
The implication is that if we want children to maximize their ability to learn and retain new information and skills, sufficient sleep is required. Parents have not made sleep a high enough priority for a majority of children. But neither the blame nor the solution for the problems lies with parents. Many of the practices governed by adults in contemporary society have diminished the time available for sleep. Adults have set early school start times, often for our own convenience in getting to work or to accommodate after school athletics. Adults have created, sold, and bought media devices that keep children from sleeping. Adults have sold and bought caffeinated drinks for children. Adults have scheduled activities that involve a great many children on school nights. All of these actions have developed slowly and have become customary, so that they are very resistant to change. Making sleep a bigger priority, fostering conditions that are conducive to sleep, and making more time available for sleep will take all concerted, continued effort at the individual and community level.
Wang, G., Wan Lai, C., Cichon, J., Ma, L., Li, W., & Gan, W-B. (2014). Sleep promotes branch-specific formation of dendritic spines after learning. Science, 344, 1173-1177.