Brain Uses Past to Peer Into Future

"We use what we have already experienced. That's what the brain does," said Paul Sanberg, director of the Center of Excellence for Aging and Brain Repair at the University of South Florida College of Medicine, in Tampa. "The brain takes what it has already experienced and uses it as a basis for future thought."

The finding may also explain a curious psychiatric phenomenon, according to Szpunar. "When you talk to amnesiacs, you see right away that they don't remember events from 10 minutes or 10 years ago," he noted.

"But another striking thing is that if you ask them, 'What are you going to do tomorrow?' they can't answer that, either," Szpunar said. "That's probably because imagining the future involves memories. So, if you don't have access to your memories, you won't be able to construct these novel images of the future."

Other types of people -- children under 5, or the clinically depressed, for example -- often have similar troubles projecting into the future, perhaps because of underdevelopment or impairment in certain brain regions, he said.

Surprisingly, the researchers found that brain areas associated with body movement also became activated as people imagined the future.

Again, the exact reason for that activity remains mysterious. But Szpunar theorized that the brain's motor centers physically "act out" these mental depictions of the future, to help make them more real.

Of course, none of this explains how people can imagine themselves in places they've never been -- a first-time trip to an exotic locale, for instance.

"We've actually done a follow-up study on that question," Szpunar said. "What we are finding is that the brain regions people use when they imagine themselves in familiar settings are not used when they imagine themselves in unfamiliar settings," he said. In the latter case, people tend to draw on general knowledge -- for example, images from magazines or television -- rather than from personal memories, he said.

According to Szpunar, the fMRI experiments are showing that the brain is an incredibly efficient machine, recycling memories to form mental storyboards of times yet to come.

"Highlighting this relationship between the past and the future is the most interesting thing about this research," Szpunar said.

More information

There's more on how the brain works at Harvard University.

SOURCES: Karl Szpunar, graduate student, department of psychology, Washington University, St. Louis; Paul Sanberg, Ph.D., director, Center of Excellence for Aging and Brain Repair, University of South Florida College of Medicine, Tampa; Jan. 2-5, 2007,Proceedings of the National Academy of Sciences