美國科學(xué)家在12月20日的《The Journal of Neuroscience》上發(fā)表文章,，聲稱根據(jù)他們的大腦成像研究發(fā)現(xiàn),，人類大腦的獎賞機(jī)制具有變化的靈敏度,，那些易受刺激影響的人們的大腦獎賞中心表現(xiàn)得最活躍。
??美國匹茲堡大學(xué)的Ahmad Hariri博士和同事們與他們在Mount Sinai醫(yī)學(xué)院和芝加哥大學(xué)的合作者們,，通過對45個研究對象的研究發(fā)現(xiàn),，大腦的重要獎賞回路部分——腹側(cè)組織層（ventral striatum）的活動，與人的沖動有直接的關(guān)系,。
??密歇根大學(xué)生物心理學(xué)計劃的Terry E. Robinson博士說：“這些數(shù)據(jù)是令人激動的,，因為這能夠由個人復(fù)雜的心理結(jié)構(gòu)，如‘沖動’,，來區(qū)分個人大腦組織的不同,。這也許會有助于研究上癮的機(jī)理,。”
??Hariri的小組通過兩個計算機(jī)任務(wù)來對研究對象進(jìn)行測試。首先,，參與者們對一系列短期和長期的薪酬進(jìn)行選擇,。他們或者選擇當(dāng)天得到10美分到105美元或者選擇五年后得到100美元乘以七個點數(shù)之一。然后根據(jù)他們的選擇計算出所謂的“轉(zhuǎn)換點數(shù)”——使他們對當(dāng)天拿到錢和在未來拿到錢同樣滿意的點數(shù),。
??七個月后,，研究對象被告知如果他們能夠正確地猜出一系列卡片上的數(shù)字就能夠得到報酬，同時科學(xué)家們使用依賴血氧濃度變化(BOLD)的功能核磁共振（fMRI）來測量研究對象在回答正確和錯誤時的大腦活動,。這些圖像反映了參與者對正面和負(fù)面“獎賞”反饋的反應(yīng),。然后通過把圖像和研究對象的轉(zhuǎn)換點數(shù)對應(yīng)的沖動值相匹配，就得到了研究結(jié)果,。
??結(jié)果表明,，那些表現(xiàn)出強(qiáng)烈地直接酬金獎勵偏愛的人的腹側(cè)組織層對金錢獎勵的正負(fù)反饋表現(xiàn)得最活躍。
??Hariri說：“我們的發(fā)現(xiàn)表明腹側(cè)組織層在滿意和延遲,、沖動和謹(jǐn)慎之前的選擇起了關(guān)鍵的作用,。而這些選擇對于我們現(xiàn)在和未來的安康具有深遠(yuǎn)的意義。”
英文原文：
Impulsiveness linked to activity in brain's reward center
A new imaging study shows that our brains react with varying sensitivity to reward and suggests that people most susceptible to impulse -- those who need to buy it, eat it, or have it, now -- show the greatest activity in a reward center of the brain. The study appears in the December 20 issue of The Journal of Neuroscience.
In their study of 45 subjects, Ahmad Hariri, PhD, and colleagues at the University of Pittsburgh and collaborators at Mount Sinai School of Medicine and the University of Chicago showed that activity in the ventral striatum, a core component of the brain's reward circuitry, correlated with individuals' impulsiveness.
"These data are exciting because they begin to unravel individual differences in brain organization underlying differences in complex psychological constructs, such as 'impulsivity,' which may contribute to the propensity to addiction," says Terry E. Robinson, PhD, of the University of Michigan biopsychology program.
The Hariri team tested the subjects on two computer-based tasks. First, participants indicated their preferences in a series of immediate-versus-delayed, hypothetical monetary rewards. They chose between receiving an amount from 10 cents to $105 that day and receiving $100 at one of seven points up to five years in the future. "Switch points"—the value at which they were equally likely to choose getting money today as getting $100 at a future point in time—were calculated for each person.
Seven months later, subjects were told they could win money if they correctly guessed numbers on a series of cards while scientists used blood oxygenation-level dependent (BOLD) functional magnetic resonance imaging (fMRI) to measure brain activity in response to correct and incorrect guesses. These images reflected participants' reactions to positive and negative "reward" feedback. After matching images to the subjects' switch points on the index of impulsiveness, the researchers looked for patterns.
Individuals indicating the strongest preference for immediate over delayed rewards showed the most ventral striatum activity associated with positive and negative feedback for a monetary reward.
"Our findings suggest that the ventral striatum plays a key role in striking a balance between gratification and delay, impulsive action and prudent choice, that can have far-reaching implications for our current and future well-being," says Hariri.
The team aims to examine the role of specific factors that drive the sensitivity of the ventral striatum next. One target of future research will be genes that regulate levels of the neurotransmitter dopamine and how they vary among individuals, Hariri says.
