The study could also lead to identifying those at risk for developmental disorders such as autism and dyslexia.
"We found a basic form of learning in sleeping newborns, a type of learning that may not be seen in sleeping adults," said Dana Byrd, a research affiliate in psychology at the University of Florida.
Researchers tested the learning abilities of sleeping newborns by repeating tones that were followed by a gentle puff of air to the eyelids. After about 20 minutes, 24 of the 26 babies squeezed their eyelids together when the tone was sounded without the puff of air. The team studied 1- or 2-day-old infants, comparing them with a control group using EEG and video recordings. The brain waves of the 24 infants were found to change, providing a neural measurement of memory updating.
"This methodology opens up research areas into potentially detecting high risk populations, those who show abnormalities in the neural systems underlying this form of learning," she said. "These would include siblings of individuals with autism and siblings of those with dyslexia."
"While past studies find this type of learning can occur in infants who are awake, this is the first study to document it in their most frequent state, while they are asleep," Byrd said. "Since newborns sleep so much of the time, it is important that they not only take in information but use the information in such a way to respond appropriately."
Not only did the newborns show they can learn to give this reflex in response to the simple tone, but they gave the response at the right time, she said.
Learned eyelid movement reflects the normal functioning of the circuitry in the cerebellum, a neural structure at the base of the brain. This study's method potentially offers a unique non-invasive tool for early identification of infants with atypical cerebellar structure, who are potentially at risk for a range of developmental disorders, including autism and dyslexia, she said.
The capacity of infants to learn during sleep contrasts with some researchers' stance that learning new material does not take place in sleeping adults, Byrd said. The immature nature of sleep patterns in infants could help explain why.
"Newborn infants' sleep patterns are quite different than those of older children or adults in that they show more active sleep where heart and breathing rates are very changeable," she said. "It may be this sleep state is more amenable to experiencing the world in a way that facilitates learning."
Another factor is that infants' brains have greater neural plasticity, which is the ability for the neural connections to be changed, Byrd said. "Newborns may be very adaptive to learning in general simply because their brains have increased plasticity, increased propensity to be changed by experience," she said.