The team monitored the activity of the neurons while the rats were learning to find their way through a maze, and again while the rats were sleeping. The patterns of activity matched so closely that the team could tell were the rat would be in the maze if it were awake.

Although Wilson cautions there were no experiments to determine if the rats' performance improved after these "dreams," he says the results may mean the rats are "learning to be more efficient to perform a task they were familiar with."

But even if the rats are honing their maze-running skills by re-living earlier experiences in their hippocampi, it doesn't mean they are dreaming in the way humans understand it.

"We cannot look at any neuron's activity and say that the person or animal is conscious or aware of that activity," says Robert A. Stickgold, assistant professor of psychiatry at Harvard Medical School.

Stickgold said the observed activity in the rat hippocampus "probably have to do with consolidation of memories. Whether there is anyone home to perceive these memories is another question."

Although the technical functions of the hippocampus may be the same in both species, each animal probably perceives things very differently. It is unclear whether or not rats are self-aware at all.

"The structure of the regions such as the hippocampus is very similar [in rats and humans]" Wilson says. "We always like to believe we have special higher order faculties, and that's certainly true, but we need to identify the similarities before we can determine what the differences are."

According to Wilson, whose research has focused on the human brain, the similarities between the rat and human brain mean they probably work in the same way.