生物谷：你是左撇子嗎？你曾想過要改變嗎,？一份最新的研究指出,，糾正左撇子，讓他們強制使用右手會使大腦部分區(qū)域活性增強,。相關(guān)論文發(fā)表在《神經(jīng)學(xué)雜志》（Journal of Neuroscience）上,。
手的活動往往是由大腦的相反區(qū)域控制，如慣用右手者移動手指時,，其大腦左半部與動作有關(guān)區(qū)域的活性就會增強,。那么糾正左撇子又會怎樣呢,？
倫敦大學(xué)學(xué)院的Stefan Klöppel及同事就此做了實驗。他們讓慣用右手者,、左撇子以及左撇子糾正者完成一個簡單的任務(wù),，即根據(jù)看到的不同符號用不同的手按下按鈕。研究人員同時用核磁共振成像（MRI）掃描儀觀測他們大腦的活動,。
結(jié)果發(fā)現(xiàn),，正如所料，左撇子的大腦右半球與動作有關(guān)的區(qū)域活性強,，右手者（包括從左撇子糾正者）的大腦左半球這一區(qū)域的活性強,。令人感興趣的是，研究人員發(fā)現(xiàn)糾正者大腦左半球區(qū)域的活性更強,，并且糾正得越徹底活性越強,。
但是研究人員同時還發(fā)現(xiàn)，大腦另一些與動作規(guī)劃有關(guān)區(qū)域的活性并沒有這種轉(zhuǎn)變,，糾正者大腦這些區(qū)域的活性仍然與未糾正者大腦相應(yīng)區(qū)域的活性類似,，不過在強度上糾正者的增加了。Stefan Klöppel說：“他們看起來還是左撇子,，而且是強化了的左撇子,。”
美國賓州州立大學(xué)心理學(xué)家Clare Porac認為，許多糾正者很擅長雙手手工技巧,，這很好地支持了糾正者大腦兩個半?yún)^(qū)都具有活性的事實,。她認為此次研究說明了糾正者腦部活動會增強，但是他們的大腦工作強度并不會增加,。
Stefan Klöppel表示,，此次的研究有助于解釋大腦怎樣影響用手習慣。他說：“最重要的是我們知道了訓(xùn)練可以影響大腦的某些區(qū)域,，而對另一些區(qū)域則不起作用,。這不僅僅是關(guān)乎用手習慣，更重要的意義在于可塑性方面,。”（科學(xué)網(wǎng) ）
原始出處:
The Journal of Neuroscience, July 18, 2007, 27(29):7847-7853; doi:10.1523/JNEUROSCI.1299-07.2007
Can Left-Handedness be Switched? Insights from an Early Switch of Handwriting
Stefan Klöppel,1,2,4 Anna Vongerichten,1 Thilo van Eimeren,1,3 Richard S. J. Frackowiak,2,5,6 and Hartwig R. Siebner1,7
1NeuroImage-Nord, Hamburg-Lübeck-Kiel, Germany, 2Wellcome Trust Centre for Neuroimaging, University College London, London WC1N 3BG, United Kingdom, 3Department of Neurology, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany, 4Department of Neurology, Neurozentrum, University Clinic Freiburg, 79106 Freiburg, Germany, 5Laboratory of Neuroimaging, IRCCS Santa Lucia, 00179 Rome, Italy, 6Departement d'Etudes Cognitives, Ecole Normale Superieure, 75005 Paris, France, and 7Department of Neurology, Christian-Albrechts-University, 24105 Kiel, Germany
Correspondence should be addressed to Dr. Stefan Klöppel, Wellcome Trust Centre for Neuroimaging, 12 Queen Square, London WC1N 3BG, UK. Email: [email protected]
"Converted" left-handers are innately left-handed individuals forced as children to write with the right nondominant hand. We asked how a left-to-right handwriting switch shapes cortical sensorimotor representations of finger movements. In 16 adult converted left-handers and age-matched groups of 16 consistent right-handers and 16 left-handers, we studied movement-related neuronal activity with functional magnetic resonance imaging while participants performed simple unimanual and bimanual movements with right and left index fingers. In converted left-handers, movement-related activity in the primary sensorimotor hand area (SM1) and caudal dorsal premotor cortex (PMd) of the nondominant left hemisphere correlated with the left-to-right shift in handedness. The more right-handed converted left-handers had become, the greater the sensorimotor activation in these areas. Between-group comparisons showed that the switch from left to right hand also reinforced movement representations in the dominant right hemisphere. In converted left-handers, the right inferior parietal cortex and lateral PMd were more active relative to consistent right or left-handers in all motor tasks. These results suggest two distinct neuronal correlates of handedness in human sensorimotor cortex. Although those in executive sensorimotor cortex (i.e., SM1 and adjacent PMd) depend on the hand used throughout life, those in higher-order sensorimotor areas (i.e., inferior parietal cortex and rostrolateral PMd) are invariant and thus cannot be switched to the nondominant hemisphere by educational training.
Key words: handedness; converted left-handers; fMRI; motor control; parietal; plasticity
