(HealthDay News) -- Your past may be key to your dreams for the future, new research suggests.
In experiments using high-tech brain imaging, scientists have found that neurological memory centers are highly active whenever people envision upcoming events.
"It shows us that memory is just as important to imagining the future as it is to remembering the past," said lead researcher Karl Szpunar, a graduate student in the department of psychology at Washington University, in St. Louis.
Besides furthering understanding of the brain, the findings might help research into amnesia and depression, Szpunar added.
His team published its findings in this week's issue of the Proceedings of the National Academy of Sciences.
According to Szpunar, there's been a century of intensive research on how the brain recalls the past but precious little on how it projects into the future -- something only humans are thought able to do. "No one had really looked at how it is that we form these vivid mental images of events that have not yet occurred," he said.
To find out more, Szpunar's team had 21 young adults undergo real-time functional MRI (fMRI), which tracks ongoing activity in the brain. Participants were asked to ponder a variety of personal scenarios, either from the past or the imagined future.
One surprise emerged early. "Until now, people had really thought that thinking about the future is a process that occurs solely in the brain's frontal lobe," Szpunar said. However, the fMRI data showed that a variety of brain areas were activated when subjects daydreamed about the future -- in the cortex's frontal and posterior lobes, in the cerebellum, and elsewhere.
Most important, neurological memory centers leapt into activity whether participants were recalling the past or envisaging their future, the researchers found.
The exact role of memory in the latter case isn't clear, but Szpunar has a theory.
"In order to form these vivid mental images of the future, what we are doing is relying on our memories," he said. "For example, if I am imagining myself at the grocery store, the mental images that I have stored in my head are of the local grocery store -- it's not just coming out of thin air. I'm retrieving it from my memory and using it in this novel way."
One expert said the theory makes sense based on what scientists know about the brain.
"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.
There's more on how the brain works at Harvard University.