美國麻省理工（MIT）的一項(xiàng)研究可能有助于治療感覺障礙（sensory disorders）,。通常情況下,，人用兩只眼睛看東西會(huì)比較清晰,，而出現(xiàn)感覺障礙的人則在蓋住一只眼看東西時(shí)會(huì)比較好,。MIT的研究人員確定出了讓人“雙眼看世界”的基因,。
與馬和老鷹不同（它們的眼睛長在頭的兩側(cè),，能夠看當(dāng)兩側(cè)不同的場景）,，人類的兩只眼睛只看到同一個(gè)場景。來自MIT的Picower學(xué)習(xí)和記憶研究所的研究人員鑒定出了負(fù)責(zé)將兩只眼看到的圖像混合起來形成在大腦中形成有用圖像的基因,。
這項(xiàng)研究的結(jié)果刊登在9月4日的Public Library of Science(PLoS) Biology上,。該研究揭示出一種新基因是雙眼看東西所必須的。
雙眼視物使我們能感知深度（即能感知立體的事物）并進(jìn)行詳細(xì)的視覺加工過程,。這些由每個(gè)眼睛投影的圖像被排列并在大腦的視丘腦和皮層中匹配,。
MIT的研究人員發(fā)現(xiàn)，基因Ten_m3和Bcl6在大腦視覺和觸覺通路的早期發(fā)育中起到關(guān)鍵作用,。Ten_m3似乎對(duì)大腦感知來自每只眼睛的兩個(gè)不同圖像至關(guān)重要,。
在敲除了Ten_m3基因的小鼠中，來自兩只眼的反射在大腦中被錯(cuò)配,。因?yàn)槊恐谎鄣姆瓷湟种苼碜粤硪恢谎鄣姆瓷?，因此即使是在眼睛能正常工作時(shí)，小鼠也是瞎的,。
引人注意的是,，研究人員發(fā)現(xiàn)當(dāng)一只眼睛的輸出信息在分子水平上被抑制時(shí)，敲除小鼠可能再獲光明,。當(dāng)一只眼的沖突輸入被關(guān)閉時(shí),，另外一只眼睛就能正常工作了，盡管只是單眼視覺。這個(gè)功能恢復(fù)的例子證實(shí)這種基因直接負(fù)責(zé)創(chuàng)造出來自兩眼的相配的反射,。
視覺的形成需要有完整的視覺分析器,，包括眼球和大腦皮層枕葉，以及兩者之間的視路系統(tǒng),。由于光線的特性,，人眼對(duì)光線的刺激可以產(chǎn)生相當(dāng)復(fù)雜的反應(yīng)，表現(xiàn)有多種功能,。當(dāng)人們看東西時(shí),，物體的影像經(jīng)過瞳孔和晶狀體，落在視網(wǎng)膜上,，視網(wǎng)膜上的視神經(jīng)細(xì)胞在受到光刺激后,，將光信號(hào)轉(zhuǎn)變成生物電信號(hào)，通過神經(jīng)系統(tǒng)傳至大腦,，再根據(jù)人的經(jīng)驗(yàn),、記憶、分析,、判斷,、識(shí)別等極為復(fù)雜的過程而構(gòu)成視覺，在大腦中形成物體的形狀,、顏色等概念,。
人的眼睛不僅可以區(qū)分物體的形狀、明暗及顏色,，而且在視覺分析器與運(yùn)動(dòng)分析器（眼肌活動(dòng)等）的協(xié)調(diào)作用下,，產(chǎn)生更多的視覺功能，同時(shí)各功能在時(shí)間上與空間上相互影響,，互為補(bǔ)充,，使視覺更精美、完善,。因此視覺為多功能名稱,，我們常說的視力僅為其內(nèi)容之一，廣義的視功能應(yīng)由視覺感覺,、量子吸收,、特定的空間時(shí)間構(gòu)圖及心理神經(jīng)一致性四個(gè)連續(xù)階段組成。
原始出處:
PLoS Biology
Ten_m3 Regulates Eye-Specific Patterning in the Mammalian Visual Pathway and Is Required for Binocular Vision
Catherine A. Leamey1,2*, Sam Merlin1, Paul Lattouf1, Atomu Sawatari1, Xiaohong Zhou3, Natasha Demel1, Kelly A. Glendining1, Toshitaka Oohashi3, Mriganka Sur2, Reinhard Fässler3
1 Department of Physiology, Bosch Institute and School of Medical Sciences, University of Sydney, Sydney, Australia, 2 Brain and Cognitive Sciences and Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America, 3 Department of Molecular Medicine, Max-Planck Institute for Biochemistry, Martinsried, Germany
Binocular vision requires an exquisite matching of projections from each eye to form a cohesive representation of the visual world. Eye-specific inputs are anatomically segregated, but in register in the visual thalamus, and overlap within the binocular region of primary visual cortex. Here, we show that the transmembrane protein Ten_m3 regulates the alignment of ipsilateral and contralateral projections. It is expressed in a gradient in the developing visual pathway, which is consistently highest in regions that represent dorsal visual field. Mice that lack Ten_m3 show profound abnormalities in mapping of ipsilateral, but not contralateral, projections, and exhibit pronounced deficits when performing visually mediated behavioural tasks. It is likely that the functional deficits arise from the interocular mismatch, because they are reversed by acute monocular inactivation. We conclude that Ten_m3 plays a key regulatory role in the development of aligned binocular maps, which are required for normal vision.
Received: February 2, 2007; Accepted: July 9, 2007; Published: September 4, 2007
* To whom correspondence should be addressed. E-mail: [email protected]
Figure 1.Expression of Ten_m3 in Developing Visual Pathway
The expression of Ten_m3 is shown using in situ hybridisation (A) and (B) or immunohistochemistry (C).
(A) Coronal section through the retina at E16. Ten_m3 is highly expressed in the retinal ganglion cell layer where it is highest in ventral retina (arrow).
(B) Coronal section through the dLGN at P0. Ten_m3 is expressed high dorsally (arrow) and low ventrally.
(C) Coronal section through the dLGN showing immunoreactivity for Ten_m3. Expression is highest in the dorsal region of the nucleus (arrow). High expression is also seen laterally in the optic tract (OT) and in the vLGN. Expression is also visible in fine fascicles traversing the nucleus (small arrowhead) and in larger bundles that appear to be heading to and/or from the internal capsule (large arrowhead). The dashed line delineates the boundaries of the dLGN in (B) and (C). Orientations are as indicated. D, dorsal; L, lateral; M, medial. Scale bars indicate 100 μm.
(D–F) Graphs plotting relative Ten_m3 expression at P0–2. Ten_m3 mRNA is graded across the dorsoventral axis of the retina (D) and the DM-VL axis of the dLGN ([E] DM-VL axis illustrated by the double-headed arrow in [B]). Expression levels of Ten_m3 protein (F) are also graded along the DM-VL axis of the dLGN.
