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October 27, 2008

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Scans pinpoint brain regions that “see the future”

Jan. 2, 2007
Courtesy Washington University in St. Louis 
and World Science staff

Our abil­i­ty to viv­id­ly re­call past ex­pe­ri­ences has been an ob­ject of more than a cen­tu­ry’s worth of sci­ent­i­fic scru­tiny. But there has been sur­pris­ing­ly lit­tle re­search, sci­ent­ists say, in­to the men­tal pro­cesses be­hind an­oth­er form of men­tal “time trav­el”: the abil­i­ty to vis­u­al­ize one­self in the fu­ture. 

Now, psy­chol­o­gists re­port that they have found, us­ing brain scans, that re­mem­ber­ing the past and en­vi­sion­ing the fu­ture may go hand-in-hand. Each pro­cess sparks strik­ingly si­m­i­lar pat­terns of ac­tiv­i­ty in the same broad net­work of brain re­gions, the sci­en­tists say.

“Not much is known about how we go about form­ing these men­tal im­ages of the fu­ture,” said Karl Szpu­nar of Wash­ing­ton Uni­ver­si­ty in St. Lou­is, the stu­dy’s lead au­thor. The find­ings, he added, sug­gest “fu­ture thought may be im­pos­si­ble with­out mem­o­ries,” be­cause the two pro­cesses are so close­ly linked.

The find­ings are pub­lished in this week’s ear­ly on­line edi­tion of the re­search jour­nal Pro­ceed­ings of the Na­tion­al Acad­e­my of Sci­ences. But the main idea isn’t to­tal­ly new: it ech­oes and backs up what some oth­er re­search­ers have been re­cent­ly spec­u­lat­ing.

In the Dec. 21 ad­vance on­line is­sue of the jour­nal Trends in Cog­ni­tive Sci­ences, re­search­ers with Har­vard Uni­ver­si­ty in Cam­bridge, Mass., hy­poth­e­sized that the “same core brain net­work” un­der­lies at least three or four pro­cesses in­volv­ing “self-pro­jec­tion.” These are re­mem­ber­ing the past, en­vi­sion­ing the fu­ture, try­ing to see things from an­oth­er per­son’s view­point, and pos­si­bly some forms of nav­i­ga­tion.

Ac­cord­ing to the Wash­ing­ton Uni­ver­si­ty re­search­ers, the new study il­lum­i­nates how the hu­man mind re­lies on rec­ol­lec­tion of past ex­pe­ri­ences to pre­pare it­self for fu­ture chal­lenges.

The stu­dy, they added, al­so showed that the net­work for fu­ture thought is­n’t re­strict­ed to one higher-level brain re­gion called the front­al cor­tex, as some had spec­u­lat­ed. Al­though this brain re­gion car­ries out fu­ture-oriented op­er­a­tions such as an­tic­i­pa­tion, plan­ning and mon­i­tor­ing, the spark for these ac­tiv­i­ties may be en­vi­sion­ing one­self in a spe­cif­ic fu­ture event, they said. This ac­tiv­i­ty arises in a wid­er net­work, al­so used to re­trieve mem­o­ries of past events. 

The net­work, they added, seems to piece to­geth­er the vis­u­al and spa­tial con­text for an im­ag­ined fu­ture us­ing the past, in­clud­ing mem­o­ries of spe­cif­ic body move­ments and vis­u­al per­spec­tive changes. 

Pre­vi­ous spec­u­la­tion on the sub­ject had been based large­ly on an­ec­do­tal ob­ser­va­tions of very young chil­dren, cases of se­vere de­pres­sion and am­ne­sia, said study co-au­thor Kath­leen Mc­Der­mott.

“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,” she said. That is, they com­pre­hend time and can con­sid­er the fu­ture ab­stract­ly, such as think­ing that budg­et deficits are a con­cern for times ahead, but can’t viv­id­ly en­vi­sion them­selves in a fu­ture sce­nar­i­o. 

Small chil­dren, too, “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.”

The re­search­ers used a brain-scanning tech­nol­o­gy called func­tion­al mag­net­ic res­o­nance im­ag­ing to cap­ture pat­terns of brain ac­ti­va­tion as col­lege stu­dents de­vel­oped men­tal im­ages of them­selves or a ce­leb­ri­ty par­ti­ci­pat­ing in 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 form­er U.S. Pres­ident Bill Clin­ton par­ti­ci­pat­ing in such an event. 

The sci­en­tists said that al­most every brain re­gion in­volved in rec­ol­lect­ing the past was al­so used in en­vi­sion­ing the fu­ture. These re­gions in­clud­ed sev­er­al parts of the cor­tex, the out­er, wrin­kly ar­ea of the brain—spe­cif­ically, sub­re­gions known as the me­di­al prefront­al cor­tex, pos­te­ri­or cin­gu­late cor­tex, me­di­al tem­po­ral cor­tex and oc­cip­i­tal cor­tex.

The re­sults “of­fer a ten­ta­tive an­swer to a long­stand­ing ques­tion re­gard­ing the ev­o­lu­tion­ary use­ful­ness of mem­o­ry,” Mc­Der­mott said. “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.”

* * *

Scientists have closely studied memory, our ability to vividly recall past experiences, more than a century. But there has been surprisingly little research, researchers say, into the mental processes behind another form of mental “time travel”: the ability to visualize oneself in the future. Now, psychologists report that they have found, using brain imaging, that remembering the past and envisioning the future may go hand-in-hand. Each process sparks strikingly similar patterns of activity in the same broad network of brain regions, the scientists say. “Not much is known about how we go about forming these mental images of the future,” said Karl Szpunar of Washington University in St. Louis, lead author of the study. The findings, he added, suggest “future thought may be impossible without memories,” because the two processes are so closely linked. The findings are published in this week’s early online edition of the research journal Proceedings of the National Academy of Sciences. But the main idea isn’t totally new: it echoes what some other researchers have been recently speculating based on previous studies with more limited evidence. In the Dec. 21 advance online issue of the journal Trends in Cognitive Sciences, researchers with Harvard University in Cambridge, Mass., hypothesized that the “same core brain network” underlies three or four processes involving “self-projection.” These are remembering the past, envisioning the future, trying to see things from another person’s viewpoint, and possibly some forms of navigation. According to the Washington University researchers, the new study sheds new light on how the human mind relies on the vivid recollection of past experiences to prepare itself for future challenges. The study, they added, also showed that the network for future thought isn’t restricted to a higher-level region called the frontal cortex, as some had speculated. Although this brain region carries out future-oriented operations such as anticipation, planning and monitoring, the spark for these activities may be the very process of envisioning oneself in a specific future event, they explained. This activity arises in a wider network also used to retrieve memories of past events. The network, they added, seems to piece together the visual and spatial context for an imagined future using the past, including memories of specific body movements and visual perspective changes. Previous speculation on the subject had been based largely on anecdotal observations of very young children, cases of severe depression and amnesia, said study co-author Kathleen McDermott. “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,” she said. That is, they comprehend time and can consider the future abstractly, such as thinking that budget deficits are a concern for times ahead, but can’t vividly envision themselves in a future scenario. Small children, too, “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.” The researchers used a brain-scanning technology called functional magnetic resonance imaging 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 partici pating 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, partici pants 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 former U.S. President Bill Clinton partici pating in such an event. The scientists said that almost every brain region involved in recollecting the past was also used in envisioning the future. These regions included several parts of the cortex, the outer, wrinkly area of the brain—specifically areas known as the medial prefrontal cortex, posterior cingulate cortex, medial temporal cortex and occipital cortex. The results “offer a tentative answer to a longstanding question regarding the evolution ary 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.”