光成像结合电生理方法研究猫视皮层及急性眼压升高对其功能的影响

【作者】 陈昕；

【导师】 寿天德；

【作者基本信息】 复旦大学 ， 生物物理， 2004， 博士

【摘要】 (一) 猫的初级视皮层神经元的组织存在着内在的、固有的特性。功能相似的神经元相互聚集在一起,形成柱状的功能结构。皮层的细胞组织具有精确的视网膜-皮层拓扑对应关系。在本论文的第一部分,我们首先利用基于脑内源信号的光学成像和二维互相关分析的方法,分析了猫的初级视皮层的功能,研究内容主要围绕在三个方面:第一,即对猫初级视皮层 17 区的视野拓扑离心度(即视网膜-皮层拓扑关系)进行了精确测量。第二,利用视网膜-皮层的拓扑对应关系以及皮层 17 区和 18 区边界的细胞感受野的特殊特性,对皮层 17 区和 18 区的边界作了标定。第三,利用不同的空间频率的正弦光栅为视觉刺激,分析了初级视皮层的空间频率特性。在这部分论文中,我们对“利用光学记录研究初级视皮层特性”这个课题进行了新的尝试,研究结果为大面积地确定视皮层细胞感受野在视野中的位置提供了一种快速和较准确的方法;从一个新的角度为确定 17 区和 18 区的边界提供了一种快速的方法;获得了皮层的空间频率特性功能图的,为我们以后的实验研究(如眼压升高对初级视皮层功能的影响,21a 区反馈对 17 区的功能影响等)打下了基础。(二)急性青光眼和眼内压升高对视觉系统的影响是国际眼科学的前沿课题。以往关于急性眼内压升高对视觉系统的影响的研究很少涉及皮层细胞的功能。以往本实验室在皮层下的研究显示,急性眼内压升高对视网膜和外膝体的不同类型神经元的影响有明显差异。在本论文的第二和第三部分,利用光学成像和电生理方法,我们对皮层细胞的功能在急性眼内压升高前后的变化进行了研究。结果显示,在眼内压升高时,光学功能图的反应强度下降,单细胞的反应也降低。这种下降依赖于灌注压的降低而非绝对的眼内压升高。在眼压升高时,高空间频率光栅刺激获得的方位功能图反应强度下降的更为显著,同时最优空间频率高的细胞比最优空间频率低的细胞反应下降得更为明显,皮层简单细胞较复杂细胞反应下降得更为明显。然而,尽管功能图反应强度下降和单细胞的方位选择性强度均有所下降,但方位功能图的基本模式没有因眼压升高而发生变化,细胞的最优方位也没有显著变化。 22<WP=26>复旦大学博士学位论文摘要本工作用光学记录和电生理记录的方法第一次揭示了皮层细胞的功能在急性眼内压升高前后的变化,为了解和研究急性眼内压升高对高级视觉中枢的影响提供了丰富的实验数据和一个典型的动物模型。表明正常的眼内压对维持视觉皮层细胞正常功能是非常重要的。由于我们实验中所采用的急性眼内压升高的生理状态和在我国人群中比例较大的急性闭角性青光眼发作时的生理状态相似,因此,本研究对临床也有一定的指导意义。更多还原

【Abstract】 I ) There are many inherent properties of functional organization of neurons inprimary visual cortex. The neurons with similar properties are organized together,forming the columnar structure which is very accurate in the retinotopic topographyof the visual cortex. In the first part of this thesis, using optical imaging method andplanar cross correlation analysis, the function of primary visual cortex of the cat wasinvestigated. Three aspects were observed. Firstly, the retinotopic topography of area17 in cat was measured accurately. Secondly, the border of area 17 and area 18 wasdemarcated based on the properties of single neuron’s receptive field in this borderand the relationship between the retina and retinotopic topography of visual cortex.Thirdly, the spatial frequency properties of orientation maps were analyzed in primaryvisual cortex when animals were stimulated by sinusoidal gratings of different spatialfrequencies. In this part, the properties of visual cortex were investigated using optical imagingmethod. The results of the research provided a fast and relatively accurate method tocalculate the retinotopic eccentricities in a large cortical area of the visual cortex;furthermore, the border of area 17 and 18 was demarcated in a newly developed way;and finally, the overall spatial frequency properties of primary visual cortex wereanalyzed based on the spatial frequency maps revealed by optical imaging, whichestablished the foundation of the subsequent researches, such as studies on the effectof elevation of intraocular pressure (IOP) on the function of visual cortex and thefunction of the feedback of high-order visual cortical areas (7, 21a, PMLS) tolower-order areas 17 and 18.II ) The effects of acute glaucoma and elevation of IOP on the structure andfunction in the visual system is one of several important tasks in ophthalmology. Allthe past studies on the effect of short time elevation of IOP on the visual system havenot involved the function of neurons in visual cortex. The previous researches in ourlaboratory have showed that the effects of elevation of IOP on the different types of 24<WP=28>复旦大学博士学位论文 摘要neurons were different in the retinal ganglion cells and LGN cells in the cat. In thesecond and third parts of this thesis, using optical imaging and electrophysiologicalsingle unit recording methods, we studied the neurons’ response before and duringelevation of IOP in the visual cortex of the cat. The results showed that, during elevation of IOP, both the responses amplitude offunctional orientation maps and the responses of single neurons decreased. However,the effect of elevation of IOP on simple cells was more significant than complex cells.The decrease in response was dependent on the retinal perfusion pressure but not onthe absolute IOP. Interestingly, the blurring or loss of the pattern of the orientationmaps caused by elevation of IOP was most severe in appearance of the posterior partof the exposed cortex when high-spatial-frequency gratings were used. On the otherhand, the responses of the cortical neurons with high preferred spatial frequencydecreased more than those of low spatial frequency during elevation of IOP. However,the basic patterns of the orientation maps remained unchanged and the preferredorientation of single neurons did not change as well. To our best of knowledge, this isa first studied on the function of visual cortex cells during elevation of IOP whichshows that a stable normal IOP is essential for maintaining normal functions of thevisual cortex. The animal’s eye condition in the experiments was similar to that ofacute angle-closure glaucoma at the breaking-out stage mostly seen in Chinesepopulation, which results in a sharp decrease of visual acuity and even rapidly causesblindness, thus, the results shown here have a clinical significance更多还原