From learning in infancy to planning ahead in adulthood: Sleep's vital role for memory

April 8, 2014, Cognitive Neuroscience Society

Babies and young children make giant developmental leaps all of the time. Sometimes, it seems, even overnight they figure out how to recognize certain shapes or what the word "no" means no matter who says it. It turns out that making those leaps could be a nap away: New research finds that infants who nap are better able to apply lessons learned to new skills, while preschoolers are better able to retain learned knowledge after napping.

"Sleep plays a crucial role in learning from early in development," says Rebecca Gómez of the University of Arizona. She will be presenting her new work, which looks specifically at how enables babies and young children to learn over time, at the Cognitive Neuroscience Society (CNS) annual meeting in Boston today, as part of a symposium on sleep and .

"We want to show that sleep is not just a necessary evil for the organism to stay functional," says Susanne Diekelmann of the University of Tübingen in Germany who is chairing the symposium. "Sleep is an active state that is essential for the formation of lasting memories."

A growing body of research shows how memories become reactivated during sleep, and new work is shedding light on exactly when and how memories get stored and reactivated. "Sleep is a highly selective state that preferentially strengthens memories that are relevant for our future behavior," Diekelmann says. "Sleep can also abstract general rules from single experiences, which helps us to deal more efficiently with similar situations in the future."

Making the leap from the abstract

In Gómez's new work, she and colleagues are examining how can recognize instances similar, but not identical, to something they have learned and apply it to a new situation – so-called generalization. Examples in language include the ability to recognize the letter "A" in different types of font, understanding a word regardless of who is speaking it, or recognizing a grammatical pattern in a sentence never before heard.

"Sleep is essential for extending learning to new examples," she says. "Naps soon after learning appear to be particularly important for generalization of knowledge in and preschoolers."

In one of her new studies, Gómez played an artificial "training language" over loudspeakers to infants 12 months old who were playing. They then tested whether the infants recognized novel vocabulary after either taking a nap or being awake.

Babies who napped after learning the artificial language were able to take the language rules learned before the nap and apply them to recognizing entirely new sentences in the language. The researchers measured recognition of the linguistic rules by the length of time infants spent with their heads turned to listen to correctly versus incorrectly structured sentences in the language.

To create the artificial languages in her studies, Gómez mimics structure in natural language that may be useful in language learning. For instance, nouns and verbs have subtly different sound patterns in many languages. "If I want to study whether these patterns help infants learn language at a particular age, I build stimuli with similar characteristics into an artificial language," she says. "I can then test children of different ages to see when they are able to use this information."

Gómez's team is also investigating the role of naps for preschoolers who are learning words. "Infants who nap soon after learning are able to generalize after sleep but not after a similar interval of normal waking time," she says. "Preschoolers with more mature memory structures do not appear to form generalizations during sleep; however, naps appear to be necessary for retaining a generalization they form before a nap."

The difference between learning and memory in infants versus preschool children could be the result of different neural mechanisms, Gómez says. Research on nonhuman primates suggests that while most of the substructures of the hippocampus are in place in infancy, the substructures that may support replay of memories during sleep do not begin wiring up until 16-20 months of age and then take several more years to reach maturity.

"Therefore, we hypothesize that the benefits of sleep in infancy stem from different processes than those benefiting preschoolers," she says. While in infants, sleep may contribute to forgetting of less redundant information in the stimulus – e.g. talker voice, the actual words infants hear over and above the rhythmic pattern occurring for all stimuli – Gómez says that hippocampally-based replay may begin to contribute to more active integration and retention of sleep-dependent memories in preschool-aged children.

Next, Gómez and her colleagues plan to study when in development children no longer need to nap to retain learned information. Prior work shows that children who nap less than 4 times a week are able to retain new memories during nighttime sleep. However Gómez's team's work shows that these children still need to nap within 4 hours after learning to generalize their knowledge to new instances in the future. More research is needed to pinpoint when the transition occurs to more adult-like memory retention after .

Remembering what we want to do

Sleep not only helps us remember things that happened in the past but also helps us remember what we want to do in the future.

"Whether we make plans for the next holiday or whether we just think about what to have for dinner tonight, all of these plans heavily depend on our ability to remember what we wanted to do at the appropriate time in the future," says Diekelmann of the University of Tübingen. "The likelihood that we remember to execute our intentions at the appropriate time in the future is substantially higher if we have had a good night's sleep after having formed the intention."

There are two ways in which we can keep our intentions in mind, Diekelmann explains: One way is to think about the intentions all the time and constantly look for opportunities to execute them. "For example, if I want to drop a letter at the post office on my way to work, I can look for a post office all the way to my work place and think all the time 'I have to drop the letter.'" But this method, she says , is inefficient, as cognitive resources are necessary for other tasks like watching out for the traffic and maneuvering around people.

"The second way to remember intentions is to store them in the memory network," she says. "If the memory of the intention is stored well enough, it will come to mind automatically in the appropriate situation." For example, if the memory of the intention to drop the letter is stored strongly, then the intention will come to mind when passing the post office.

It is this second method that Diekelmann's team's recent studies sought to explore. In one new study, the researchers asked participants to remember word pairs, and after learning, told them they would have to detect these words in a different task two days later. They then let half of the participants sleep, while the other half stayed awake for one night. During the second night, all participants slept so that they would not be tired at testing.

In the test session, participants performed a task that included some of the previously learned words from the pairs. The researchers did not remind the participants of their intention to detect the words but just recorded how many words they detected. They wanted to see whether participants still succeeded in detecting the words when they had to do an additional task at the same time that required their full attention. "We expected that, if participants had stored the intention sufficiently strong in their memory, then seeing the words should automatically bring to mind the intention to detect the words," Diekelmann says.

Indeed, the researchers found that participants who were allowed to sleep were able to automatically detect the words. "With sleep, the participants performed perfectly well and detected almost all of the words even when they had to perform two challenging tasks in parallel," Diekelmann says. Those participants who stayed awake during the first night after forming the intention, however, performed substantially worse in detecting at the same time as other tasks.

"Even when we have to do a lot of different things at the same time, sleep ensures that our intentions come to mind spontaneously once we encounter the appropriate situation to execute the intention," Diekelmann says.

An ongoing goal of sleep and memory researchers is to find out how sleep selects which memories are worthy to store for the long-term. "It is generally believed that there is some kind of tagging mechanism that marks which memories are relevant and should be stored for the long-term and which are not," Diekelmann says. "Yet, we are far from understanding what that tagging mechanism is and how it works."

Explore further: Reading to toddlers before naps significantly enhances learning

More information: Diekelmann and Gómez are presenting their work, along with Ken Paller and Jessica Payne, in the symposium "Mechanisms of Memory Consolidation During Sleep," Tuesday, April 8, 2014 at the CNS annual meeting in Boston. More than 1,500 scientists are attending the meeting in Boston, MA, from April 5-8, 2014.

Related Stories

Reading to toddlers before naps significantly enhances learning

February 17, 2014
(Medical Xpress)—A connection between sleep and learning has already been identified as beneficial for adults and older children. Now Sussex psychologists Dr Jessica Horst and PhD candidate Sophie Williams have shown that ...

Team finds daytime naps enhance learning in preschool children

September 23, 2013
Sleep researchers at the University of Massachusetts Amherst today offer the first research results showing that classroom naps support learning in preschool children by enhancing memory. Children who napped performed significantly ...

Sweet dreams can spell out improved language skills for youngsters

November 27, 2012
(Medical Xpress)—A good night's sleep can help children to acquire and retain vocabulary, according to new research by psychologists at the University of York and Sheffield Hallam University.

Learn that tune while fast asleep

June 24, 2012
Want to nail that tune that you've practiced and practiced? Maybe you should take a nap with the same melody playing during your sleep, new provocative Northwestern University research suggests.

Sleep consolidates memories for competing tasks, researchers show

March 20, 2013
Sleep plays an important role in the brain's ability to consolidate learning when two new potentially competing tasks are learned in the same day, research at the University of Chicago demonstrates.

Recommended for you

Research reveals atomic-level changes in ALS-linked protein

January 18, 2018
For the first time, researchers have described atom-by-atom changes in a family of proteins linked to amyotrophic lateral sclerosis (ALS), a group of brain disorders known as frontotemporal dementia and degenerative diseases ...

Fragile X finding shows normal neurons that interact poorly

January 18, 2018
Neurons in mice afflicted with the genetic defect that causes Fragile X syndrome (FXS) appear similar to those in healthy mice, but these neurons fail to interact normally, resulting in the long-known cognitive impairments, ...

How your brain remembers what you had for dinner last night

January 17, 2018
Confirming earlier computational models, researchers at University of California San Diego and UC San Diego School of Medicine, with colleagues in Arizona and Louisiana, report that episodic memories are encoded in the hippocampus ...

Recording a thought's fleeting trip through the brain

January 17, 2018
University of California, Berkeley neuroscientists have tracked the progress of a thought through the brain, showing clearly how the prefrontal cortex at the front of the brain coordinates activity to help us act in response ...

Midbrain 'start neurons' control whether we walk or run

January 17, 2018
Locomotion comprises the most fundamental movements we perform. It is a complex sequence from initiating the first step, to stopping when we reach our goal. At the same time, locomotion is executed at different speeds to ...

Neuroscientists suggest a model for how we gain volitional control of what we hold in our minds

January 16, 2018
Working memory is a sort of "mental sketchpad" that allows you to accomplish everyday tasks such as calling in your hungry family's takeout order and finding the bathroom you were just told "will be the third door on the ...

2 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

russell_russell
not rated yet Apr 08, 2014
An ongoing goal of sleep and memory researchers is to find out how sleep selects which memories are worthy to store for the long-term.

You are encouraged to and by all means test this - a "tag" mechanism.

An alternative hypothesis is the "repair" of DNA. The "damage" done to DNA from learning is the "tag" here. Which doves tails to any purpose you are assigning or contributing to sleep.
The purpose of sleep is where repair to damaged DNA is most efficient. The repaired is what-was-learned now stored permanently. You don't need to store an entire intention ever.
You need to simply stored a cue that "avalanches" random recall that include any of the intention parts. Recalling (reconstruction) any part of any storage leads (eventually) to total recall - all reconstruction is faulty. What is "repaired" is never the original beforehand - before the learn process (damage) and memory stored (repair). Totally irrevalent is the deformation intention undergoes - the whole process ...
russell_russell
not rated yet Apr 08, 2014
...to punctually remember...is the whole point, not how well the intention is replicated from the repair of neuronal DNA.

Repetition is the mother of learning. Why? Because that is where the greatest "damage" occurs, where more and more neuronal DNA for the same event takes place.

Your welcome. Test anyway. Any step of this can be tested. For example, without external stimuli, less neuronal DNA damage occurs - simply use noninvasive bio markers.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.