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Localization and Quantification Study of Visual Cortex Function by fMRI in Visual Normal Human

Author: WangHao
Tutor: YinZhengQin
School: Third Military Medical University
Course: Ophthalmology
Keywords: fMRI Normal people Sight Figure thorn stimulation Visual cortex Voxel
CLC: R445.2
Type: Master's thesis
Year: 2010
Downloads: 59
Quote: 1
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Abstract

There are still a lot of existing medical technology clinical incurable disease that can lead to blindness in both eyes: If serious eye injuries result in loss of vision or eye; optic atrophy caused by glaucoma and multiple types of retinal degenerative diseases. However, the visual cortex of these patients and no deaths. Therefore, the visual image directly convert electrical signals pass visual cortical neurons, rebuilding visual one way. To visual image is converted into electrical signals of visual cortical neurons understanding, we must first know visually normal subjects in graphics when stimulated, depending on the reaction of cortical neurons in the graphics space distribution pattern, the functional orientation area and the reaction strength. We can use the reaction mode to guide the design of the visual cortex stimulation mode blind people in order to be able to produce the reaction mode corresponding graphical visual experience. In this study, functional magnetic resonance imaging blood oxygen level dependent (blood oxygenation leveldependent-functional magnetic resonance imaging, BOLD-fMRI) technology to study the response of the visual cortex in visual normal viewing graphics. The basic principles for the detection of subjects due to changes in blood flow to the brain caused by external stimuli, which found that a region of the brain is increased activity in the stimulus conditions, the correlation between this part of the brain area and stimulate. Due to its non-invasive, non-injury, non-radiation, and many other advantages, has a high level of security, has been widely used for the study of brain function. In this study, first of all take advantage of this technology visually normal people to be more sensitive to what stimulus pattern, after using this stimulus pattern experiment to get brain stimulation of brain activation graphics database for this. Database information to reconstruct the three-dimensional model of the visual cortex was activated regions, observed depending on the correlation between the spatial distribution of cortical activation region of the stimulus pattern. Anatomical regions after extraction of the amount of each anatomical region of the visual cortex is activated voxels of the voxel, and further activation intensity of these voxels, to study the amount of each anatomical region is activated in the voxel and activated between the total intensity correlation. The study included three parts: the first part: Visual normal people graphics stimulus the fMRI image recording and analysis, circular stimulation graphic visual cortex activation can cause visual normal person larger range and higher strength, is an ideal visual stimuli. 2, collected four subjects ring graphic fMRI images, analyze brain activation information database, the average amount of activated voxels of the four volunteers were 1, 21478, 2, 4777, 3, 8843, the 4th 21 603 described the stimulus pattern can cause the brain is activated, the experiment is successful, a data base for further analysis, the data provided. Part II: Visual related regional activation information extraction and retinal and apparent topology correspondence between the cortex between to using XJview software the first part of the brain activated database screening process off the negative activation has nothing to do with the visual stimulation ; excluding non-occipital positive activation, four volunteers were excluded non-occipital lobe positive activation in the activation of the total average percentage: 15.20%, 14.87% in the 2nd and the 3rd 9.08 % 4 42.85%. The description of the activation of the occipital lobe parts accounted for a considerable proportion, after striking out to obtain accurate occipital lobe activation information. 2, the use of retaining only the occipital lobe brain activation of positive activation information database into depending on the three-dimensional reconstruction of the cortical activation to obtain three-dimensional reconstruction of the visual cortex activation Figure. Visual cortex was observed activated three-dimensional spatial distribution and stimulate the relationship between the graphics, found their distribution correspond to the retina to the visual cortex corresponding to the spatial topology relationship, indicating the activation of the visual cortex is indeed caused by the stimulus pattern, the first portion of the visual stimulation experiments is successful. Part III: the visual cortex of the activation area to locate and quantitative research, the primary visual cortex area the Brodmann 17,18 and 19 District mask database using this database to extract the number of voxels activated in each anatomical region contrast the average amount of activation of the various anatomical regions can be found in the least Brodmann17 Average amount of activated voxels, 205; Brodmann18 Average amount of activated voxels up to 1105, Brodmann19 area is also more 892. Stimulus pattern of activation of different brain regions is different, its main activation area is distributed in Brodmann18 areas and 19 districts. Using AFNI software to obtain the reaction of various anatomical regions voxel intensity distribution analysis found that: 1) with a good reproducibility of the volunteers three replicates of the same anatomical regions, repeatability between different volunteers obvious. 2) the activation of voxel intensity is strongest in Brodmann 18 districts, 19 districts, followed by the weakest in the 17th District. 3) Brodmann, 18 District voxels activated the highest density of 19 districts, followed by the lowest density of Area 17. 3, three anatomical regions of the visual cortex repeatability: 1) volunteers repeatability best, followed by the 4th and the 3rd, the worst on the 2nd of volunteers. 2) Brodmann17 area repeatability better than 18 districts and 19 districts. But generally speaking, activation of the body with the three experiments of the same anatomical region of a subject are prime reaction between the intensity, there is a common trend, but the trend of change in intensity of the voxels between different people poor repeatability. So to find the link between the data of different people for the next focus of the study. 4, using three anatomical regions of the linear model analysis visual cortex voxel Activity amount and activation of the relationship between the total intensity and found living amount of the voxels in the three anatomical regions and activation between the total intensity are linear related linear equation respectively: Brodmann, 17 y = 0.111x 57.50 R2 = 0.942, Brodmann, 18 District, y = 0.146x 96.16 R2 = 0.971, Brodmann, 19 y = 0.170x 75.00 R2 = 0.974. Comparison between the three districts, of Brodmann18 and 19 districts better goodness of fit (R2 gt; 0.97) and Brodmann17 district goodness of fit relative bit weak (R2 = 0.942). But this is the goodness of fit of the three regions in the 0.942 to 0.974 between voxel reaction between different subjects is the inherent link, which provides the foundation for the future establishment of the standard response mode of these anatomical regions. The conclusions of this study: 1, ring stimulating graphics are used to study the visual cortex of the ideal visual stimuli graphical reaction. 2, creating an ideal anatomic region voxel extraction method, i.e. first establish the anatomical regions of the mask database, then the mask with activation database comparison, the voxel belonging to the anatomical region is extracted from the active database, while these voxel intensity of reaction, and reach the positioning, the purpose of the quantitative analysis. 3, through the visual cortex anatomical region voxel activation volume and intensity for each comparison, the reaction patterns of each anatomical region of the visual cortex of the same pattern in the experiment was repeated with a subjects better repeatability of the different subject test between repeatability is not obvious. 4, the different subjects of the same graphics stimulate visual stimulation, the visual cortex of each anatomical region positive linear relationship between the amount of activated voxels with activation of the total strength.

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