如果你是一個老年嬰兒潮，你或許已經(jīng)注意到自己在某些方面的困難,，比如開車到陌生的地點或在超市挑選新品牌的橄欖油,，你可以認為你大腦中的腦白質(zhì)負主要責任。
一項有關(guān)大腦圖譜的最新研究發(fā)表在4月11日的Journal of Neuroscience雜志上,，研究人員發(fā)現(xiàn)人在新的環(huán)境下做決定的能力,，隨著年齡的增長而減弱，并其這一減弱與連接大腦皮層中稱為內(nèi)側(cè)前額葉皮質(zhì)區(qū)域與大腦深處其他兩塊區(qū)域的兩條特定的白質(zhì)通路的完整性有關(guān),。
灰質(zhì)是大腦的一部分,，腦、脊髓內(nèi)神經(jīng)元集中的地方，色澤灰暗,，所以稱為灰質(zhì)?；屹|(zhì)內(nèi)功能相同的神經(jīng)細胞體集合一起稱為神經(jīng)核,。在過去，大多數(shù)腦成像的研究集中于灰質(zhì),。然而最近,，神經(jīng)學家已經(jīng)開始更多關(guān)注白質(zhì)研究。白質(zhì)鏈接與大腦的處理速度和注意力等有關(guān),，這項研究是首次探討了學習和決策與腦白質(zhì)之間的聯(lián)系,。
大腦掃描圖
影像科學范德比爾特的心理學系和研究所博士后研究員Gregory R. Samanez-Larkin說：決策能力的下降與白質(zhì)的完整性的證據(jù)表明，有可能將來會有有效的方式介入這一過程,。一些研究表明白質(zhì)的連接可以通過加強認知訓練等具體形式來提高,。
這項研究涉及了25名從21到85歲不等的成年人。他們被要求完成貨幣政策的學習任務(wù),，任務(wù)的目的是引發(fā)這些人心理學家所說的概率性獎勵學習,。Samanez-Larkin說：根據(jù)以往的經(jīng)驗和結(jié)果的不確定性，每當我們嘗試選擇最佳替代決定是,，我們都是靠概率性獎勵性學習來實現(xiàn)的,。
在同一天，研究人員利用磁共振成像技術(shù)對參與者的大腦進行掃描,。實驗發(fā)現(xiàn)丘腦中關(guān)鍵性白質(zhì)連接存在于與決策有關(guān)的大腦區(qū)域（內(nèi)側(cè)前額葉皮質(zhì)）,、與情緒和動機方面有關(guān)的內(nèi)側(cè)前額葉皮層腹側(cè)紋狀體。（生物谷：Bioon.com）
doi:10.1523/JNEUROSCI.5756-11.2012
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Frontostriatal White Matter Integrity Mediates Adult Age Differences in Probabilistic Reward Learning
Gregory R. Samanez-Larkin, Sara M. Levens, Lee M. Perry, Robert F. Dougherty, and Brian Knutson
Frontostriatal circuits have been implicated in reward learning, and emerging findings suggest that frontal white matter structural integrity and probabilistic reward learning are reduced in older age. This cross-sectional study examined whether age differences in frontostriatal white matter integrity could account for age differences in reward learning in a community life span sample of human adults. By combining diffusion tensor imaging with a probabilistic reward learning task, we found that older age was associated with decreased reward learning and decreased white matter integrity in specific pathways running from the thalamus to the medial prefrontal cortex and from the medial prefrontal cortex to the ventral striatum. Further, white matter integrity in these thalamocorticostriatal paths could statistically account for age differences in learning. These findings suggest that the integrity of frontostriatal white matter pathways critically supports reward learning. The findings also raise the possibility that interventions that bolster frontostriatal integrity might improve reward learning and decision making.
