Time past, time future intricately connected in the brain: study

January 2, 2007

Human memory, the ability to recall vivid mental images of past experiences, has been studied extensively for more than a hundred years. But until recently, there's been surprisingly little research into cognitive processes underlying another form of mental time travel -- the ability to clearly imagine or "see" oneself participating in a future event.

Now, researchers from Washington University in St. Louis have used advanced brain imaging techniques to show that remembering the past and envisioning the future may go hand-in-hand, with each process sparking strikingly similar patterns of activity within precisely the same broad network of brain regions.

"In our daily lives, we probably spend more time envisioning what we're going to do tomorrow or later on in the day than we do remembering, but not much is known about how we go about forming these mental images of the future," says Karl Szpunar, lead author of the study and a psychology doctoral student in Arts & Sciences at Washington University.

"Our findings provide compelling support for the idea that memory and future thought are highly interrelated and help explain why future thought may be impossible without memories."

Scheduled for advance online publication Jan. 1 in Proceedings of the National Academy of Sciences, the study sheds new light on how the human mind relies on the vivid recollection of past experiences to prepare itself for future challenges, suggesting that envisioning the future may be a critical prerequisite for many higher-level planning processes.

Other study co-authors are Jason M. Watson, a Washington University doctoral graduate now assistant professor of psychology at the University of Utah; and Kathleen McDermott, an associate professor of psychology in Arts & Sciences and of radiology in the School of Medicine at Washington University.

McDermott, principal investigator for the University's Memory and Cognition Lab, where the research is based, suggests that the findings are notable for two reasons.

First, the study clearly demonstrates that the neural network underlying future thought is not isolated in the brain's frontal cortex, as some have speculated. Although the frontal lobes play a well-documented role in carrying out future-oriented executive operations, such as anticipation, planning and monitoring, the spark for these activities may well be the very process of envisioning oneself in a specific future event, an activity based within and reliant upon the same neurally distributed network used to retrieve autobiographical memories.

Second, within this neural network, patterns of activity suggest that the visual and spatial context for our imagined future often is pieced together using our past experiences, including memories of specific body movements and visual perspective changes – data stored as we navigated through similar settings in the past.

These findings, McDermott suggests, offer strong support for a relatively recent theory of memory, which posits that remembering the past and envisioning the future draw upon many of the same neural mechanisms. Previous speculation has been based largely on the anecdotal observation of very young children, cases of severe depression and brain damaged persons with amnesia.

"There's a little known and not that well investigated finding that if you have an amnesic person who can't remember the past, they're also not at all good about thinking about what they might be doing tomorrow or envisioning any kind of personal future," McDermott explains. They comprehend time and can consider the future in the abstract sense (e.g., that global warming is a concern for the future), but they cannot vividly envision themselves in a specific future scenario.

"The same is true with very small children -- they don't remember particularly what happened last month and they can't really tell you much of anything about what they envision happening next week. This is also the case with suicidally depressed people. So, there's this theory that it all goes hand-in-hand, but nobody has looked closely enough to explain exactly how or why this occurs."

In this study, researchers relied on functional magnetic resonance imaging (fMRI) to capture patterns of brain activation as college students were given 10 seconds to develop a vivid mental image of themselves or a famous celebrity participating in a range of common life experiences.

Presented with a series of memory cues, such as getting lost, spending time with a friend or attending a birthday party, participants were asked to recall a related event from their own past; to envision themselves experiencing such an event in their future life; or, to picture a famous celebrity -- specifically former U.S. President Bill Clinton -- participating in such an event.

The "Clinton-Imagine" task was introduced to help researchers establish a baseline level of brain activity for a cognitive event that was in many ways similar to the other two tasks but did not involve the mental projection of oneself through time. Bill Clinton was chosen because pre-testing showed he was easy for participants to visualize in a variety of situations.

Comparing images of brain activity in response to the "self-remember" and "self-future" event cues, researchers found a surprisingly complete overlap among regions of the brain used for remembering the past and those used for envisioning the future – every region involved in recollecting the past was also used in envisioning the future.

During the experiment, participants were not required to describe details or explain the origin of mental images elicited by the memory cues, but in post-testing questionnaires most indicated that they tended to place future-oriented images in the context of familiar places (e.g. home, school) and familiar people (e.g. family, friends), which would require the reactivation of those images from neural networks responsible for the storage and retrieval of autobiographical memories.

Conversely, the neural networks associated with personal mental time travel showed significantly less activity when participants imagined scenarios involving Bill Clinton. The reason, researchers suggest, is that participants had no personal memories of direct interaction with Clinton, and thus, any images of him had to be derived from neural networks responsible for semantic memory – our context-free general knowledge of the world. In fact, participants later reported that their mental images of Clinton tended to be less vivid (e.g. "I see Bill Clinton at a party in the White House, alongside several faceless senators").

"Results of this study offer a tentative answer to a longstanding question regarding the evolutionary usefulness of memory," McDermott concludes. "It may just be that the reason we can recollect our past in vivid detail is that this set of processes is important for being able to envision ourselves in future scenarios. This ability to envision the future has clear and compelling adaptive significance."

Source: Washington University in St. Louis

Explore further: How to support someone with dementia—and feel better yourself

Related Stories

How to support someone with dementia—and feel better yourself

February 13, 2018
Visiting a loved one with dementia can feel frustrating, even hopeless, but there are ways to turn that precious time into a better experience, says a University of Alberta researcher.

Study finds depression and fatigue increase women's risk of work-related injuries

February 13, 2018
Women who suffer from depression, anxiety, and fatigue are more likely to be injured at work, according to a new study published in the Journal of Occupational and Environmental Medicine led by researchers from the Colorado ...

Why so many doctors in the UK are at risk of burnout

February 12, 2018
More than a thousand GPs have sought professional help from the NHS GP Health Service since it was set up in 2017, with most cases involving stress, anxiety and depression and about 2% addiction.

Why ignoring mental health needs of young Syrian refugees could harm us all

January 30, 2018
When a seven-year-old student in eastern Aleppo was asked at the peak of the bombardment campaign by the Assad regime in 2015 to draw a picture, he did not draw children playing, nor did he draw a blue sky or a smiling sun.

Landmark firefighter health study leads to improved support

February 2, 2018
The South Australian Metropolitan Fire Service (MFS) and the University of Adelaide have conducted a landmark study into the mental and physical health of MFS firefighters.

Staying awake—the surprisingly effective way to treat depression

January 23, 2018
The first sign that something is happening is Angelina's hands. As she chats to the nurse in Italian, she begins to gesticulate, jabbing, moulding and circling the air with her fingers. As the minutes pass and Angelina becomes ...

Recommended for you

Study looks at how newly discovered gene helps grow blood vessels

February 19, 2018
A new study published today found that a newly discovered gene helps grow blood vessels when it senses inadequate blood flow to tissues.

Scientists produce human intestinal lining that re-creates living tissue inside organ-chip

February 16, 2018
Investigators have demonstrated how cells of a human intestinal lining created outside an individual's body mirror living tissue when placed inside microengineered Intestine-Chips, opening the door to personalized testing ...

Data wave hits health care

February 16, 2018
Technology used by Facebook, Google and Amazon to turn spoken language into text, recognize faces and target advertising could help doctors fight one of the deadliest infections in American hospitals.

Researcher explains how statistics, neuroscience improve anesthesiology

February 16, 2018
It's intuitive that anesthesia operates in the brain, but the standard protocol among anesthesiologists when monitoring and dosing patients during surgery is to rely on indirect signs of arousal like movement, and changes ...

Team reports progress in pursuit of sickle cell cure

February 16, 2018
Scientists have successfully used gene editing to repair 20 to 40 percent of stem and progenitor cells taken from the peripheral blood of patients with sickle cell disease, according to Rice University bioengineer Gang Bao.

Appetite-controlling molecule could prevent 'rebound' weight gain after dieting

February 15, 2018
Scientists have revealed how mice control their appetite when under stress such as cold temperatures and starvation, according to a new study by Monash University and St Vincent's Institute in Melbourne. The results shed ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.