人的大腦分為左右兩個半腦,。按照目前公認(rèn)的左右腦分工理論,，人鼻尖右邊視野的信息由左腦處理，鼻尖左邊視野的信息則由右腦處理,。但德國研究人員最近發(fā)現(xiàn),，一名右腦先天發(fā)育障礙的病人居然擁有近乎正常的視力，其左腦適應(yīng)性地承擔(dān)起了處理所有視覺信息的任務(wù),。
位于法蘭克福的馬克斯·普朗克認(rèn)知與腦科學(xué)研究所日前發(fā)表公告說,，他們通過對這名病人的研究發(fā)現(xiàn)，人腦在某一個腦半球遇到發(fā)育障礙時可作出自我調(diào)整,。就視覺而言,，眼部神經(jīng)細(xì)胞的突起通常是按固定方向伸展，分別與左邊或是右邊的大腦皮層相連,。而一種信使物質(zhì)可以影響著神經(jīng)突起的伸展方向,。
研究發(fā)現(xiàn)，在右半腦遇到發(fā)育障礙的情況下,，信使物質(zhì)就會引導(dǎo)本來應(yīng)通向右腦的神經(jīng)突起向左半腦方向伸展,。由于要處理全部視覺信息，這名患者左腦的大腦皮層還發(fā)生了結(jié)構(gòu)性變化,，這種變化使得這名患者最終擁有了較為正常的視覺,。
研究人員估計，這名病人的右腦發(fā)育障礙大約是在胚胎發(fā)育一個月后出現(xiàn)的,。這個例子說明了大腦在發(fā)育初期針對較嚴(yán)重的問題時,，具有自我調(diào)整能力。雖然這種能力會隨著年齡的增長而減弱,，但即使在成年人身上也還是有所體現(xiàn),，比如一些中風(fēng)病人的癥狀會出現(xiàn)自我緩解。
這項研究成果已發(fā)表在最新一期美國《國家科學(xué)院學(xué)報》上,。（生物谷Bioon.com）
生物谷推薦原始出處：
PNAS doi: 10.1073/pnas.0809688106
Bilateral visual field maps in a patient with only one hemisphere
Lars Mucklia,b,c,1, Marcus J. Naumerd and Wolf Singerb,c
aCentre for Cognitive Neuroimaging, Department of Psychology, University of Glasgow, 58 Hillhead Street, Glasgow G12 8QB, United Kingdom;
bBrain Imaging Center, Goethe University, 60528 Frankfurt am Main, Germany;
cDepartment of Neurophysiology, Max Planck Institute for Brain Research, Deutschordenstrasse 46, D-60528 Frankfurt am Main, Germany; and
dInstitute of Medical Psychology, Goethe University, 60528 Frankfurt am Main, Germany
In mammals smooth retinotopic maps of the visual field are formed along the visual processing pathway whereby the left visual field is represented in the right hemisphere and vice versa. The reorganization of retinotopic maps in the lateral geniculate nucleus (LGN) of the thalamus and early visual areas (V1–V3) is studied in a patient who was born with only one cerebral hemisphere. Before the seventh week of embryonic gestation, the development of the patient's right cerebral hemisphere terminated. Despite the complete loss of her right hemisphere (di- and telencephalon) at birth, the patient's remaining hemisphere has not only developed maps of the contralateral (right) visual hemifield but, surprisingly, also maps of the ipsilateral (left) visual hemifield. Retinal ganglion-cells changed their predetermined crossing pattern in the optic chiasm and grew to the ipsilateral LGN. In the visual cortex, islands of ipsilateral visual field representations were located along the representations of the vertical meridian. In V1, smooth and continuous maps from contra- and ipsilateral hemifield overlap each other, whereas in ventral V2 and V3 ipsilateral quarter field representations invaded small distinct cortical patches. This reveals a surprising flexibility of the self-organizing developmental mechanisms responsible for map formation.
