Our bodies may be at rest while we sleep, but new research finds more evidence that our brains are hard at work as we get our zzz's.

Sleep seems to help the brain consolidate memories so that they are readily available during waking hours, scientists reported at a recent meeting of the Organization for Human Brain Mapping in Toronto.

Dr. Pierre Orban and colleagues at the University of Liege in Belgium compared the brain functioning of well-rested and sleep-deprived people.

In the experiment, 22 volunteers explored a complex computerized town for about half an hour. After familiarizing themselves with the town, the participants had to find particular locations within about 30 seconds. During the fast-paced searches, researchers measured participants' brain activity using a type of brain imaging called functional magnetic resonance imaging (fMRI).

That night, 12 participants went home to sleep as usual, but 10 stayed in the lab and were not allowed to sleep. Then, a few days later, after everyone had several nights of normal sleep, researcher measured brain activity when the volunteers were put to the test again.

The well rested and those who had stayed up all night after the first day did equally well on finding their way around the virtual town. However, brain imaging showed that the two groups navigated using different parts of their brains.

Compared to people who had been sleep deprived, those who had not missed a night of sleep showed more activity in a section of the brain called the caudate nucleus. This suggests that navigating the town had become more of an automatic process in the well rested, according to the researchers, because the caudate nucleus is linked to automatic activities, such as body movement and coordination.

The current study adds another piece of evidence that sleep helps the brain reorganize the information it takes in during the day, according to the researchers.