生物谷綜合：據(jù)美國生活科學(xué)網(wǎng)報(bào)道,，一項(xiàng)針對一名中風(fēng)患者的個案研究顯示,，和兒童一樣，成年大腦可能也有“可塑性”,，具有創(chuàng)造新神經(jīng)通路的能力,。
過去的研究認(rèn)定：兒童的大腦具有創(chuàng)造新信號通道，改變或適應(yīng)缺陷的非凡能力，這種現(xiàn)象被科學(xué)家稱為大腦的可塑性,。但成年大腦是否同樣具有這種能力一直備受爭議,。在線版《神經(jīng)科學(xué)雜志》（The Journal of Neuroscience）9月5日發(fā)表了這項(xiàng)最新研究成果。它顯示,，至少有一名中風(fēng)患者的大腦視覺中樞的神經(jīng)系統(tǒng)能自行重組,，以修復(fù)遭損壞的神經(jīng)通路，最后的結(jié)果是視覺感知能力發(fā)生變化(可能有所改善),。
美國麻省理工學(xué)院麥戈文大腦研究所博士后丹尼爾·迪爾克斯和同事們研究了一名中風(fēng)患者的大腦,，他們把患者簡稱為“B.L.”。丹尼爾·迪爾克斯是約翰·霍普金斯大學(xué)攻讀研究生時完成這項(xiàng)研究的,。B.L.中風(fēng)損害了把信息從眼睛傳送到初級視覺皮層的神經(jīng)纖維,。初級視覺皮層是大腦后面灰質(zhì)中的一個區(qū)域，依然完好無損,。這種損害中斷了左上視區(qū)和初級視覺皮層通訊區(qū)之間的信息交流,，在左上視覺區(qū)中造成一個盲區(qū)。這項(xiàng)針對BL的研究顯示,，在盲區(qū)下面的東西看起來有些變形,。
研究人員猜測，這種變形是由初級視覺皮層的改組造成的,。這些神經(jīng)科學(xué)家對他們的想法進(jìn)行了研究,。當(dāng)正方形等物體的圖像出現(xiàn)在視區(qū)中的不同區(qū)域時，他們讓BL把注意力放在一個中心盲區(qū)上,。正方形突然出現(xiàn)在這個盲區(qū)時,，迪萊科斯什么也沒看到。當(dāng)正方形出現(xiàn)在這個盲區(qū)下面時,，他看到它變成長方形向上伸進(jìn)這個盲區(qū),。與此同時，這名患者還看到“像鉛筆一樣”的三角形和“像雪茄一樣”的圓形等,。
磁共振成像對大腦掃描顯示,，初級視覺皮層(左上視區(qū))對來自較低左視區(qū)的信息做出反應(yīng)，這種情況在“正常”成人大腦中不會出現(xiàn),。研究負(fù)責(zé)人說,，改變視覺信號的能力是可塑性特點(diǎn)之一，可以合理解釋視覺變形的原因,。丹尼爾表示：“我們發(fā)現(xiàn)了新的功能特性,。當(dāng)初級視覺皮層重新改組時，BL看到了不同圖像,。”
這一新發(fā)現(xiàn)為其他針對成人大腦可塑性能力的研究提供了有力證據(jù),。（援引新浪科技）
原始出處:
The Journal of Neuroscience, September 5, 2007, 27(36):9585-9594; doi:10.1523/JNEUROSCI.2650-07.2007
Behavioral/Systems/Cognitive
Human Adult Cortical Reorganization and Consequent Visual Distortion
Daniel D. Dilks,1,3 John T. Serences,2,4 Benjamin J. Rosenau,2 Steven Yantis,2 and Michael McCloskey1
Departments of 1Cognitive Science and 2Psychological and Brain Sciences, Johns Hopkins University, Baltimore, Maryland 21218, 3McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, and 4Department of Cognitive Sciences, University of California, Irvine, California 92697
Correspondence should be addressed to Daniel D. Dilks, McGovern Institute for Brain Research, Massachusetts Institute of Technology, 46-4141G, Cambridge, MA 02144. Email: [email protected]
Neural and behavioral evidence for cortical reorganization in the adult somatosensory system after loss of sensory input (e.g., amputation) has been well documented. In contrast, evidence for reorganization in the adult visual system is far less clear: neural evidence is the subject of controversy, behavioral evidence is sparse, and studies combining neural and behavioral evidence have not previously been reported. Here, we report converging behavioral and neuroimaging evidence from a stroke patient (B.L.) in support of cortical reorganization in the adult human visual system. B.L.'s stroke spared the primary visual cortex (V1), but destroyed fibers that normally provide input to V1 from the upper left visual field (LVF). As a consequence, B.L. is blind in the upper LVF, and exhibits distorted perception in the lower LVF: stimuli appear vertically elongated, toward and into the blind upper LVF. For example, a square presented in the lower LVF is perceived as a rectangle extending upward. We hypothesized that the perceptual distortion was a consequence of cortical reorganization in V1. Extensive behavioral testing supported our hypothesis, and functional magnetic resonance imaging (fMRI) confirmed V1 reorganization. Together, the behavioral and fMRI data show that loss of input to V1 after a stroke leads to cortical reorganization in the adult human visual system, and provide the first evidence that reorganization of the adult visual system affects visual perception. These findings contribute to our understanding of the human adult brain's capacity to change and has implications for topics ranging from learning to recovery from brain damage.
Key words: cortical reorganization; cortical plasticity; primary visual cortex; perceptual distortion; adult human visual system; visual perception
Received Jan. 13, 2006; revised July 17, 2007; accepted July 19, 2007.
Correspondence should be addressed to Daniel D. Dilks, McGovern Institute for Brain Research, Massachusetts Institute of Technology, 46-4141G, Cambridge, MA 02144. Email: [email protected]
