日前,，美國(guó)加州大學(xué)洛杉磯分校的一組研究人員運(yùn)用一種新型的腦成像掃描儀發(fā)現(xiàn),，人類智商在很大程度上與大腦神經(jīng)的軸突及其走向和位置相關(guān),，而這些特征則主要由基因控制。相關(guān)研究刊登在最近一期《神經(jīng)學(xué)》雜志上,。
研究人員發(fā)現(xiàn),，基因似乎通過(guò)決定進(jìn)入髓磷脂中大腦神經(jīng)軸突的數(shù)量來(lái)影響智商。覆蓋在神經(jīng)軸突外的髓磷脂主要由脂肪構(gòu)成,，可使快速信號(hào)直接進(jìn)入大腦,。髓磷脂越厚，神經(jīng)沖動(dòng)越快,。
負(fù)責(zé)該項(xiàng)研究的加州大學(xué)洛杉磯分校副教授保羅•湯普森和他的同事使用了一種被稱為“哈爾迪”（HARDI：高分辨率漫射成像儀）的大腦掃描儀,，分別對(duì)23對(duì)同卵雙胞胎和異卵雙胞胎進(jìn)行了大腦掃描。該掃描儀類似于對(duì)類固醇進(jìn)行掃描的高分辨率核磁共振成像儀,，但速度更快,，分辨率更高。核磁共振掃描儀主要用來(lái)測(cè)量腦容量,，而“哈爾迪”則通過(guò)追蹤經(jīng)過(guò)腦白質(zhì)的信號(hào)來(lái)測(cè)量髓磷脂的數(shù)量,。如果信號(hào)在一個(gè)特定的方向快速擴(kuò)散，說(shuō)明大腦處理信息速度快,。如果信號(hào)擴(kuò)散沒(méi)有明確的方向性,，則說(shuō)明智力略低。
研究人員發(fā)現(xiàn),，大腦回路中髓磷脂形成的軌跡如同一個(gè)倒置的U形,，高峰在中年，而后就開(kāi)始慢慢下降,。湯普森認(rèn)為,，找出那些能夠促進(jìn)生成高含量髓磷脂的基因，將對(duì)預(yù)防一些腦部疾病的發(fā)生起重要作用,，如多發(fā)性硬化癥和孤獨(dú)癥,，這些疾病都與髓磷脂的受損相關(guān)。（生物谷Bioon.com）
生物谷推薦原始出處：
The Journal of Neuroscience, February 18, 2009, doi:10.1523/JNEUROSCI.4184-08.2009
Genetics of Brain Fiber Architecture and Intellectual Performance
Ming-Chang Chiang,1 Marina Barysheva,1 David W. Shattuck,1 Agatha D. Lee,1 Sarah K. Madsen,1 Christina Avedissian,1 Andrea D. Klunder,1 Arthur W. Toga,1 Katie L. McMahon,2 Greig I. de Zubicaray,2 Margaret J. Wright,3 Anuj Srivastava,4 Nikolay Balov,4 and Paul M. Thompson1
1Laboratory of Neuro Imaging, Department of Neurology, University of California, Los Angeles, School of Medicine, Los Angeles, California 90095-7334, 2University of Queensland, Functional Magnetic Resonance Imaging Laboratory, Centre for Magnetic Resonance, Brisbane, Queensland 4072, Australia, 3Queensland Institute of Medical Research, Brisbane, Queensland 4029, Australia, and 4Department of Statistics, Florida State University, Tallahassee, Florida 32306
Correspondence should be addressed to Dr. Paul M. Thompson, Laboratory of Neuro Imaging, Department of Neurology, University of California, Los Angeles, School of Medicine, 635 Charles E. Young Drive South, Suite 225E, Los Angeles, CA 90095-7334.
The study is the first to analyze genetic and environmental factors that affect brain fiber architecture and its genetic linkage with cognitive function. We assessed white matter integrity voxelwise using diffusion tensor imaging at high magnetic field (4 Tesla), in 92 identical and fraternal twins. White matter integrity, quantified using fractional anisotropy (FA), was used to fit structural equation models (SEM) at each point in the brain, generating three-dimensional maps of heritability. We visualized the anatomical profile of correlations between white matter integrity and full-scale, verbal, and performance intelligence quotients (FIQ, VIQ, and PIQ). White matter integrity (FA) was under strong genetic control and was highly heritable in bilateral frontal (a2 = 0.55, p = 0.04, left; a2 = 0.74, p = 0.006, right), bilateral parietal (a2 = 0.85, p < 0.001, left; a2 = 0.84, p < 0.001, right), and left occipital (a2 = 0.76, p = 0.003) lobes, and was correlated with FIQ and PIQ in the cingulum, optic radiations, superior fronto-occipital fasciculus, internal capsule, callosal isthmus, and the corona radiata (p = 0.04 for FIQ and p = 0.01 for PIQ, corrected for multiple comparisons). In a cross-trait mapping approach, common genetic factors mediated the correlation between IQ and white matter integrity, suggesting a common physiological mechanism for both, and common genetic determination. These genetic brain maps reveal heritable aspects of white matter integrity and should expedite the discovery of single-nucleotide polymorphisms affecting fiber connectivity and cognition.
