Previous research has suggested that older adults don’t remember newly acquired motor skills as well as young adults do, perhaps because the posttraining stages of the learning process appear diminished. Understanding the impact of sleep on memory could also help another at-risk group of learners at the other end of the age spectrum. When comparing Down syndrome children who are sleep deprived with those who sleep normally, she has observed a vocabulary difference of more than 190 words on language tests, even after controlling for behavioral differences. “Kids with Down syndrome that are sleep-impaired look like they have very large differences in language,” says Jamie Edgin of the University of Arizona who studies sleep and cognition in such children. The effects are particularly strong in children with developmental disorders, who often suffer from sleep disruptions. Toddlers who sleep less than 10 hours display lasting cognitive deficits, even if they catch up on sleep later in their development ( Sleep, 30:1213-19, 2007). How sleep and memory interact at different ages has been an open question.Īt that age, adequate nighttime sleep becomes critical for learning. By the time they are two years old, “we think that children have the brain development that supports an active process of consolidation,” she adds. “The net effect is that sleep permits infants to retain more of the redundant details of a learning experience,” says experimental psychologist Rebecca Gómez of the University of Arizona. Instead, sleep merely seems to prevent infants from forgetting as much as they would if they were awake. As a result, researchers hypothesize that infants don’t replay memories during sleep, the way adults do. In children younger than 18 months, learning is thought to occur in the cortex because the hippocampus isn’t yet fully developed.
These studies have suggested that dampened sensory inputs. Until recently, most of the research into the relationship between memory and sleep has been conducted using young adults or animal models. “By staying awake, they have more interference from daytime experiences,” Spencer explains. She found that habitual nappers benefitted the most from daytime rest, largely because their memories decayed the most without a nap. Spencer wondered if developmental stage altered the relationship between sleep and memory, and chose nearby preschool children as subjects. But the older adults that Rebecca Spencer was studying at the University of Massachusetts Amherst didn’t seem to experience the same benefit.
PAMELA SPEDERīy the early 2000s, scientists had found that sleep helps young adults consolidate memory by reinforcing and filing away daytime experiences. NIGHTY NIGHT: Goffredina Spanò from Jamie Edgin’s University of Arizona lab uses polysomnography to measure sleep in a toddler with Down syndrome.