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Brain region linked to introspective thinking

Sept. 16, 2010
Courtesy of the American Association 
for the Advancement of Science 
and World Science staff

A spe­cif­ic brain re­gion is larg­er in peo­ple who are good at turn­ing their thoughts in­ward and re­flect­ing on their de­ci­sions, a new study sug­gests.

This pro­cess of “think­ing about your think­ing,” called in­tro­spec­tion, is a key part of hu­man con­scious­ness. But sci­en­tists have not­ed plen­ty of varia­t­ion in peo­ples’ abil­i­ties to in­tro­spect.

The study is to be pub­lished in the Sept. 17 is­sue of the re­search jour­nal Sci­ence.

A cross-section of the brain show­ing activity in the an­te­ri­or pre­fron­tal cor­tex, high­light­ed in yel­low and red. This re­gion was cor­re­lated with in­tro­spect­ive ac­cu­racy in a new study. (Im­age © Sci­ence/AAAS)
“We want to know why we are aware of some men­tal pro­cesses,” while oth­ers pro­ceed with­out awareness, said Ste­phen Flem­ing of Uni­vers­ity Col­lege Lon­don, one of the au­thors. 

“There may be dif­fer­ent lev­els of con­scious­ness, rang­ing from simply hav­ing an ex­pe­ri­ence, to re­flect­ing up­on that ex­pe­ri­ence. In­tro­spec­tion is on the high­er end of this spec­trum. By meas­ur­ing this pro­cess and re­lat­ing it to the brain we hope to gain in­sight in­to the bi­ol­o­gy of con­scious thought.”

The brain re­gion found to be ap­par­ently linked to in­tro­spec­tion is the called the an­te­ri­or pre­fron­tal cor­tex, right be­hind our eyes, said the sci­en­tists, who were led by re­searcher Ge­raint Rees of the uni­vers­ity. The “gray mat­ter” in this re­gion tends to be larg­er in people with great­er in­tro­spective abil­ity, they ex­plained. Gray mat­ter con­sists of the types of brain cells chiefly known for pro­cessing in­forma­t­ion, called neu­rons.

Al­so linked to in­tro­spec­tion is the “white mat­ter” con­nect­ed to this brain re­gion, the in­ves­ti­ga­tors said. White mat­ter con­sists of nerve fibers, thread-like ex­ten­sions of neu­rons which link the cells to each oth­er so that sig­nals can pass be­tween them.

It re­mains un­clear how the rela­t­ion­ship be­tween in­tro­spec­tion and the two types of brain mat­ter really works, Rees and col­leagues said. The find­ings don’t nec­es­sarily mean that all peo­ple with more gray mat­ter in the an­te­ri­or pre­fron­tal cor­tex have more in­tro­spective thoughts, but they do es­tab­lish a cor­rela­t­ion, they stressed.

Rees and col­leagues de­signed a test of in­tro­spective abil­i­ties in which 32 par­ti­ci­pants were shown two screens, each con­tain­ing six pat­terned patches. One screen, though, con­tained a patch that was slightly brighter than the oth­ers. The re­search­ers asked the par­ti­ci­pants to iden­ti­fy which screen con­tained the brighter patch, and then to rate how con­fi­dent they felt about their fi­nal an­swer.

By work­ing with the par­ti­ci­pants, the in­ves­ti­ga­tors ad­justed the task to each per­son’s skill lev­el, un­til they all per­formed equally well. But their per­for­mance still var­ied in the ac­cu­racy with which they judged their own de­ci­sion­mak­ing. This was tak­en as a meas­ure of in­tro­spective abil­ity.

It’s un­known wheth­er these dif­fer­ences are in­nate or a re­sult of learn­ing, the in­ves­ti­ga­tors not­ed. Al­so un­clear is the na­ture of the men­tal com­puta­t­ions and bi­o­log­i­cal pro­cesses be­hind in­tro­spec­tion.

Still, the find­ing may help sci­en­tists un­der­stand how cer­tain brain in­ju­ries af­fect the abil­ity to re­flect on one’s own thoughts and ac­tions, Flem­ing said. With such an un­der­standing, it may even­tu­ally be pos­si­ble to tai­lor ap­pro­pri­ate treat­ments to pa­tients, such as stroke vic­tims or those with se­ri­ous brain trau­ma, who may not even un­der­stand their own con­di­tions.

“Take the ex­am­ple of two pa­tients with men­tal ill­ness—one who is aware of their ill­ness and one who is not,” said Flem­ing. “The first per­son is likely to take their med­ica­t­ion, but the sec­ond is less like­ly. If we un­der­stand self-a­wareness at the neu­ro­lo­g­i­cal lev­el, then per­haps we can al­so adapt treat­ments and de­vel­op train­ing strate­gies for these pa­tients.”

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A specific brain region is larger in people who are good at turning their thoughts inward and reflecting on their decisions, a new study suggests. This process of “thinking about your thinking,” called introspection, is a key part of human consciousness. But scientists have noted plenty of variation in peoples’ abilities to introspect. The study is to be published in the Sept. 17 issue of the research journal Science. “We want to know why we are aware of some mental processes,” while others proceed without awareness, said Stephen Fleming of University College London, one of the authors. “There may be different levels of consciousness, ranging from simply having an experience, to reflecting upon that experience. Introspection is on the higher end of this spectrum. By measuring this process and relating it to the brain we hope to gain insight into the biology of conscious thought.” The brain region found to be apparently linked to introspection is the called the anterior prefrontal cortex, right behind our eyes, said the scientists, who were led by researcher Geraint Rees of the university. The “gray matter” in this region is larger in more introspective types, they explained. Gray matter consists of the types of brain cells chiefly known for processing information, called neurons. Also linked to introspection is the “white matter” connected to this brain region, the investigators said. White matter consists of nerve fibers, thread-like extensions of neurons which link the cells to each other so that signals can pass between them. It remains unclear how the relationship between introspection and the two types of brain matter really works, Rees and colleagues said. The findings don’t necessarily mean that all people with more gray matter in in the anterior prefrontal cortex have more introspective thoughts, but they do establish a correlation, they stressed. Rees and colleagues designed a test of introspective abilities in which 32 participants were shown two screens, each containing six patterned patches. One screen, though, contained a patch that was slightly brighter than the others. The researchers asked the participants to identify which screen contained the brighter patch, and then to rate how confident they felt about their final answer. By working with the participants, the investigators adjusted the task to each person’s skill level, until they all performed equally well. But their performance still varied in their ability to look inward and judge their own decisionmaking. This was taken as a measure of introspective capacity. It’s unknown whether these differences are innate or a result of learning, the investigators noted. Also unclear is the nature of the mental computations and biological processes behind introspection. Still, the finding may help scientists understand how certain brain injuries affect the ability to reflect on one’s own thoughts and actions, Fleming said. With such an understanding, it may eventually be possible to tailor appropriate treatments to patients, such as stroke victims or those with serious brain trauma, who may not even understand their own conditions. “Take the example of two patients with mental illness—one who is aware of their illness and one who is not,” said one of the study’s authors, Stephen Fleming from University College London. “The first person is likely to take their medication, but the second is less likely. If we understand self-awareness at the neurological level, then perhaps we can also adapt treatments and develop training strategies for these patients.”