Newborn infants are in a dream state about 70 percent of their sleep time, according to Hugo Lagercrantz, a pediatrician.
The serene facade of a resting baby belies a brain churning with activity.
A new study, published online this week in the Proceedings of the National Academy of Sciences, reveals active brain regions in sleeping infants.
Other recent research has found evidence in adult brains of 10 so-called resting-state networks, which are clusters of neurons that stay "online" while a person is in a resting state.
Whether the same activity occurred in resting infants was not known.
"This study shows that there is an activity going on in the infant brain," said study team member Hugo Lagercrantz of the Astrid Lindgren Children's Hospital in Sweden.
Peter Fransson, a neuroscientist at the Karolinska Institute in Sweden, Lagercrantz and colleagues scanned the brains of 12 sleeping infants for 10 minutes using functional magnetic resonance imaging (fMRI), finding five resting-state networks engaged in spontaneous activity. As with findings in adult brains, the regions were associated with visual, motor and auditory processing.
What does this mean for a new mom? "This confirms the concept that talking, singing and rocking the baby is not meaningless as earlier believed, but very good for the baby," Lagercrantz told LiveScience.
For neuroscientists, the finding could shed light on how the human brain develops, since fewer networks were found in infant brains compared with those of adults.
"Now we have also shown there is a developmental aspect, that these networks perhaps gradually develop in the infant brain, or through adulthood and up," Fransson said.