人的大脑分为左右两个半脑。按照目前公认的左右脑分工理论，人鼻尖右边视野的信息由左脑处理，鼻尖左边视野的信息则由右脑处理。但德国研究人员最近发现，一名右脑先天发育障碍的病人居然拥有近乎正常的视力，其左脑适应性地承担起了处理所有视觉信息的任务。
位于法兰克福的马克斯·普朗克认知与脑科学研究所日前发表公告说，他们通过对这名病人的研究发现，人脑在某一个脑半球遇到发育障碍时可作出自我调整。就视觉而言，眼部神经细胞的突起通常是按固定方向伸展，分别与左边或是右边的大脑皮层相连。而一种信使物质可以影响着神经突起的伸展方向。
研究发现，在右半脑遇到发育障碍的情况下，信使物质就会引导本来应通向右脑的神经突起向左半脑方向伸展。由于要处理全部视觉信息，这名患者左脑的大脑皮层还发生了结构性变化，这种变化使得这名患者最终拥有了较为正常的视觉。
研究人员估计，这名病人的右脑发育障碍大约是在胚胎发育一个月后出现的。这个例子说明了大脑在发育初期针对较严重的问题时，具有自我调整能力。虽然这种能力会随着年龄的增长而减弱，但即使在成年人身上也还是有所体现，比如一些中风病人的症状会出现自我缓解。
这项研究成果已发表在最新一期美国《国家科学院学报》上。（生物谷Bioon.com）
生物谷推荐原始出处：
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 ooth 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 chia 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, ooth and continuous maps from contra- and ipsilateral hemifield overlap each other, whereas in ventral V2 and V3 ipsilateral quarter field representations invaded all distinct cortical patches. This reveals a surprising flexibility of the self-organizing developmental mechanis responsible for map formation.
