在本文中是使用多重聚焦法以及視覺功能性磁振造影來來找出視網膜拓樸，並應用視網膜拓樸，來想辦法重建辨識人眼所見的視覺影像。多重聚焦法是將刺激影像分成好幾個刺激單元，並用彼此獨立的刺激序列，同時給予受試者刺激。在合理刺激時間內，能夠同時收集大數量刺激單元所引起的訊號。除了視覺功能性磁振造影外，這個方法也用在如視網膜電圖或是視覺誘發電位的研究上，可用來作為臨床眼電生理檢查的工具。
本研究利用多重聚焦法，找出受試者的視網膜拓樸後，再利用不同的圖案給予受試者視覺刺激並進行功能性磁振造影實驗。最後試圖依靠磁振造影實驗的資料，重建出受試者所觀察到的圖案形狀。在重建影像的過程中，本研究使用通用線性模型來分析功能性磁振造影的訊號，並可得到一統計t值用來判斷視覺皮質區是否有反應。然而對於「是否」有反應這件事，牽涉到t值的閥值選擇。本研究發現閥值選擇對於視覺重建的精確度有很大的影響。因此，我們提出了利用接收者操作特徵分析，來找出能獲得最大精確度的最佳閥值。本研究共進行了五名受試者實驗，使用了兩種視覺圖案。經過最佳化的閥值選擇後，我們得到了平均80%的精確度。
本研究成功的完成了視覺影像的重建實驗。而相較於前人的研究，我們認為最大的貢獻在於提出最佳化的方法，能夠找出應用在所有受試者上的相同閥值。如此一來，能夠使得整套視覺重建自動化。讓利用功能性磁振造影來進行視覺重建的研究往前邁進了一步。

This thesis describes a study exploiting multi-focal functional MRI(fMRI) for retinotopic mapping, or retinotopy, in the primary visual cortex. We tried to reconstruct visual image according the retinotopy and brain activities obtained by fMRI. Multi-focal method divides the visual field into several blocks and each block has its own paradigm for the visual experiment. Using this method, researchers show that they are able to distinguish the brain areas corresponding to each block simultaneously. Despite visual fMRI, this method is also applied electrophysiological analysis of visual system.
In this study, we performed a visual fMRI experiment using a specific pattern after multi-focal retinotopy. We then attempt to reconstruct the visual image by combining the results of visual fMRI and retinotopy. The study applied general linear model to analyze the fMRI signal and produced a t value to justify the existence of stimuli-related brain activities. However, judging the “existence” required selecting a threshold of the t value. We empirically found that the accuracy of the reconstructed visual image largely depended on the threshold selection. Therefore, this study proposed an approach to find the optimal t threshold according to a receiver operating characteristic analysis. The results obtained with 5 volunteers using the optimized t thresholds demonstrated an average accuracy of 80%.
In conclusion, we successfully reconstructed the visual image by the fMRI technique. Compared to previous investigations, we regard the contributions of this thesis are the optimization method for visual image reconstruction. This method leads to a completely automatic reconstruction procedure and takes visual reconstruction a step forward.

1. Engel, S.A., D.E. Rumelhart, B.A. Wandell, A.T. Lee, G.H. Glover, E.J. Chichilnisky, and M.N. Shadlen, fMRI of human visual cortex. Nature, 1994. 369(6481): p. 525.
2. Wandell, B.A., S.O. Dumoulin, and A.A. Brewer, Visual field maps in human cortex. Neuron, 2007. 56(2): p. 366-83.
3. DeYoe, E.A., G.J. Carman, P. Bandettini, S. Glickman, J. Wieser, R. Cox, D. Miller, and J. Neitz, Mapping striate and extrastriate visual areas in human cerebral cortex. Proc Natl Acad Sci U S A, 1996. 93(6): p. 2382-6.
4. Dumoulin, S.O., R.D. Hoge, C.L. Baker, Jr., R.F. Hess, R.L. Achtman, and A.C. Evans, Automatic volumetric segmentation of human visual retinotopic cortex. Neuroimage, 2003. 18(3): p. 576-87.
5. Engel, S.A., G.H. Glover, and B.A. Wandell, Retinotopic organization in human visual cortex and the spatial precision of functional MRI. Cereb Cortex, 1997. 7(2): p. 181-92.
6. Sereno, M.I., A.M. Dale, J.B. Reppas, K.K. Kwong, J.W. Belliveau, T.J. Brady, B.R. Rosen, and R.B. Tootell, Borders of multiple visual areas in humans revealed by functional magnetic resonance imaging. Science, 1995. 268(5212): p. 889-93.
7. Wandell, B.A., A.A. Brewer, and R.F. Dougherty, Visual field map clusters in human cortex. Philos Trans R Soc Lond B Biol Sci, 2005. 360(1456): p. 693-707.
8. Warnking, J., M. Dojat, A. Guerin-Dugue, C. Delon-Martin, S. Olympieff, N. Richard, A. Chehikian, and C. Segebarth, fMRI retinotopic mapping--step by step. Neuroimage, 2002. 17(4): p. 1665-83.
9. Vanni, S., L. Henriksson, and A.C. James, Multifocal fMRI mapping of visual cortical areas. Neuroimage, 2005. 27(1): p. 95-105.
10. Dumoulin, S.O. and B.A. Wandell, Population receptive field estimates in human visual cortex. Neuroimage, 2008. 39(2): p. 647-60.
11. Baseler, H.A. and E.E. Sutter, M and P components of the VEP and their visual field distribution. Vision Res, 1997. 37(6): p. 675-90.
12. Baseler, H.A., E.E. Sutter, S.A. Klein, and T. Carney, The topography of visual evoked response properties across the visual field. Electroencephalogr Clin Neurophysiol, 1994. 90(1): p. 65-81.
13. Slotnick, S.D., S.A. Klein, T. Carney, and E.E. Sutter, Electrophysiological estimate of human cortical magnification. Clin Neurophysiol, 2001. 112(7): p. 1349-56.
14. Sutter, E.E., Imaging visual function with the multifocal m-sequence technique. Vision Res, 2001. 41(10-11): p. 1241-55.
15. Sutter, E.E. and D. Tran, The field topography of ERG components in man--I. The photopic luminance response. Vision Res, 1992. 32(3): p. 433-46.
16. Miyawaki, Y., H. Uchida, O. Yamashita, M.A. Sato, Y. Morito, H.C. Tanabe, N. Sadato, and Y. Kamitani, Visual image reconstruction from human brain activity using a combination of multiscale local image decoders. Neuron, 2008. 60(5): p. 915-29.
17. Brainard, D.H., The Psychophysics Toolbox. Spat Vis, 1997. 10(4): p. 433-6.
18. Dale, A.M., B. Fischl, and M.I. Sereno, Cortical surface-based analysis. I. Segmentation and surface reconstruction. Neuroimage, 1999. 9(2): p. 179-94.