Optical Imaging And Electrophysiological Methods Of Cat Visual Cortex And Acute Elevation Of Intraocular Pressure Of The Impact Of Its Functions

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...