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Psychopaths’ brains wired to seek rewards no matter what, researchers say

March 15, 2010
Courtesy Vanderbilt University
and World Science staff

“Psycho.” The very word con­jures im­ages of cold, re­morse­less cri­min­ality. But sci­ent­ists don’t ful­ly un­der­stand how the brains of psy­cho­paths—peo­ple with anti­social, em­pathy-short and some­times cri­min­al per­son­a­lities—work.

A study has now found that the brains of psy­chopaths seem to be wired to keep seek­ing a re­ward at any cost. Sci­en­tists say the re­search clar­i­fies the role of the brain’s re­ward sys­tem in psy­chop­a­thy and opens a new ar­ea of study for un­der­stand­ing what drives these twisted minds.

The study from from Van­der­bilt Uni­vers­ity in Nash­ville, Tenn. is pub­lished in the March 14 is­sue of the re­search jour­nal Na­ture Neu­ro­sci­ence.

Ab­nor­mal­i­ties in how a brain struc­ture called the nu­cle­us ac­cum­bens, high­light­ed he­re, pro­cesses dopamine have been found in peo­ple with psy­cho­pathic traits, sci­en­tists say. (Cred­it: Greg­o­ry R.Samanez-Larkin and Josh­ua W. Buck­holtz )


“Psy­chopaths are of­ten thought of as cold-blood­ed crim­i­nals who take what they want with­out think­ing about con­se­quences,” Josh­ua Buck­holtz, a grad­u­ate stu­dent in psy­chol­o­gy and lead au­thor of the new stu­dy, said. “We found that a hyper-reac­tive dopamine re­ward sys­tem may be the founda­t­ion for some of the most prob­lem­at­ic be­hav­iors as­so­ci­at­ed with psy­chop­a­thy, such as vi­o­lent crime, re­cid­i­vism and sub­stance abuse.”

Dopamine is the brain chem­i­cal most closely as­so­ci­at­ed with pleas­ure and ex­cite­ment.

Pre­vi­ous re­search on psy­chop­a­thy has fo­cused on what these peo­ple lack­—fear, em­pa­thy and in­ter­per­son­al skills. The new re­search, how­ev­er, ex­am­ines what they have in abun­dance—im­pul­siv­ity, height­ened at­trac­tion to re­wards and risk tak­ing, said Buck­holtz and his co-auth­ors. Im­por­tant­ly, the lat­ter traits are those most closely linked with the vi­o­lent and crim­i­nal as­pects of psy­chop­a­thy, re­search­ers said.

“There has been a long tra­di­tion of re­search on psy­chop­a­thy that has fo­cused on the lack of sen­si­ti­vity to pun­ish­ment and a lack of fear, but those traits are not par­tic­u­larly good pre­dic­tors of vi­o­lence or crim­i­nal be­hav­ior,” said Van­der­bilt psy­chol­o­gist Da­vid Zald, co-au­thor of the stu­dy. 

“Our da­ta is sug­gest­ing that some­thing might be hap­pen­ing on the oth­er side of things. These in­di­vid­u­als ap­pear to have such a strong draw to re­ward—to the car­rot—that it over­whelms the sense of risk or con­cern about the stick.”

The re­search­ers used a brain im­ag­ing tech­nique called pos­i­tron emis­sion to­mog­ra­phy, or PET, to meas­ure dopamine re­lease, in con­cert with a probe of the brain’s re­ward sys­tem us­ing func­tion­al mag­net­ic im­ag­ing, or fMRI. “The really strik­ing thing is with these two very dif­fer­ent tech­niques we saw a very si­m­i­lar pat­tern—both were height­ened in in­di­vid­u­als with psy­cho­pathic traits,” Zald said.

Vol­un­teers for the study took a per­son­al­ity test to gauge their lev­el of psy­cho­pathic traits. These traits lie on a spec­trum: vi­o­lent crim­i­nals fall at its ex­treme end, but a nor­mally func­tion­ing per­son can al­so have psy­cho­pathic traits to some de­gree. These traits in­clude ma­ni­pu­la­tive­ness, ego­cen­tricity, ag­gres­sion and risk tak­ing.

The re­search­ers gave the vol­un­teers a dose of am­phet­a­mine, or speed, and then scanned their brains us­ing PET to view dopamine re­lease in re­sponse to the stim­u­lant. Sub­stance abuse has been shown in the past to be as­so­ci­at­ed with al­tera­t­ions in dopamine re­sponses. Psy­chop­a­thy is strongly as­so­ci­at­ed with sub­stance abuse.

“Our hy­poth­e­sis was that psy­cho­pathic traits are al­so linked to dys­func­tion in dopamine re­ward cir­cuit­ry,” Buck­holtz said. “Con­sis­tent with what we thought, we found peo­ple with high lev­els of psy­cho­pathic traits had al­most four times the amount of dopamine re­leased in re­sponse to am­phet­a­mine.”

The re­search sub­jects were lat­er told they would re­ceive some mon­ey for com­plet­ing a sim­ple task. Their brains were scanned with fMRI while they were per­form­ing the task. The re­search­ers found in those par­ti­ci­pants with more psy­cho­pathic traits the dopamine re­ward ar­ea of the brain, the nu­cle­us ac­cum­bens, was much more ac­tive while they were an­ti­cipat­ing the re­ward.

“It may be that be­cause of these ex­ag­ger­at­ed dopamine re­sponses, once they fo­cus on the chance to get a re­ward, psy­chopaths are un­able to al­ter their at­ten­tion un­til they get what they’re af­ter,” Buck­holtz said. Added Zald, “It’s not just that they don’t ap­pre­ci­ate the po­ten­tial threat, but that the an­ti­cipa­t­ion or mo­tiva­t­ion for re­ward over­whelms those con­cerns.”


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The brains of psychopaths seem to be wired to keep seeking a reward at any cost, a study has found. Scientists say the research clarifies the role of the brain’s reward system in psychopathy and opens a new area of study for understanding what drives these twisted minds. The study from from Vanderbilt University in Nashville, Tenn. is published in the March 14 issue of the research journal Nature Neuroscience. “Psychopaths are often thought of as cold-blooded criminals who take what they want without thinking about consequences,” Joshua Buckholtz, a graduate student in psychology and lead author of the new study, said. “We found that a hyper-reactive dopamine reward system may be the foundation for some of the most problematic behaviors associated with psychopathy, such as violent crime, recidivism and substance abuse.” Dopamine is the brain chemical most closely associated with pleasure and excitement. Previous research on psychopathy has focused on what these people lack—fear, empathy and interpersonal skills. The new research, however, examines what they have in abundance—impulsivity, heightened attraction to rewards and risk taking. Importantly, the latter traits are those most closely linked with the violent and criminal aspects of psychopathy, researchers said. “There has been a long tradition of research on psychopathy that has focused on the lack of sensitivity to punishment and a lack of fear, but those traits are not particularly good predictors of violence or criminal behavior,” said Vanderbilt psychologist David Zald, co-author of the study. “Our data is suggesting that something might be happening on the other side of things. These individuals appear to have such a strong draw to reward—to the carrot—that it overwhelms the sense of risk or concern about the stick.” The researchers used a brain imaging technique called positron emission tomography, or PET, to measure dopamine release, in concert with a probe of the brain’s reward system.using functional magnetic imaging, or fMRI. “The really striking thing is with these two very different techniques we saw a very similar pattern—both were heightened in individuals with psychopathic traits,” Zald said. Study volunteers took a personality test to gauge their level of psychopathic traits. These traits lie on a spectrum: violent criminals fall at its extreme end, but a normally functioning person can also have psychopathic traits to some degree. These traits include manipulativeness, egocentricity, aggression and risk taking. The researchers gave the volunteers a dose of amphetamine, or speed, and then scanned their brains using PET to view dopamine release in response to the stimulant. Substance abuse has been shown in the past to be associated with alterations in dopamine responses. Psychopathy is strongly associated with substance abuse. “Our hypothesis was that psychopathic traits are also linked to dysfunction in dopamine reward circuitry,” Buckholtz said. “Consistent with what we thought, we found people with high levels of psychopathic traits had almost four times the amount of dopamine released in response to amphetamine.” The research subjects were later told they would receive some money for completing a simple task. Their brains were scanned with fMRI while they were performing the task. The researchers found in those participants with more psychopathic traits the dopamine reward area of the brain, the nucleus accumbens, was much more active while they were anticipating the reward. “It may be that because of these exaggerated dopamine responses, once they focus on the chance to get a reward, psychopaths are unable to alter their attention until they get what they’re after,” Buckholtz said. Added Zald, “It’s not just that they don’t appreciate the potential threat, but that the anticipation or motivation for reward overwhelms those concerns.”