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    Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/7415


    Title: 腦磁源之定位與源強度還原的若干方法;Some procedures for solving the Magnetoencephalography inverse problem
    Authors: 白宏益;Hung-I Pai
    Contributors: 物理研究所
    Keywords: 資訊處理法;磁腦圖;最大熵法;information process;Maximum entropy;MEG;Magnetoencephalography
    Date: 2008-07-04
    Issue Date: 2009-09-22 10:57:32 (UTC+8)
    Publisher: 國立中央大學圖書館
    Abstract: 腦磁圖 (Magnetoencephalograph , MEG) 提供一個做非侵入式觀察人腦皮質上神經元集之間活動的測量。具有所有腦影像技術裡最高的毫秒的時間解析度。但是由於可能的神經源 (訊號源) 的數目遠大於MEG探測器的數目,所以無法直接從MEG的資料反推回去發出訊號源的精確的位置和強度,這又稱為病態的反問題 (ill-posed inverse problem)。再加上全部訊號源都被塞在半徑只有大約10公分的頭殼裡,更加難從外面的探測器的資料分辨發出訊號的位置。但是利用一些和腦相關的先前知識 (prior) 和腦皮質結構上的限制,我們發展出一套資訊處理的方法,可以估算出最有可能的發出訊號的源的位置。這程序包含對先前知識(prior) 的位置做處理的部分:分群、前向式過濾法 (forward filtering) 、後向式過濾法 (backward filtering)。還有對源的強度做微調的部分。 從跟聽覺有關的一小塊皮質做模擬實驗的開始。大小是長40毫米,寬15毫米。模擬其中一個小區域的激發。當限制住空間源的分佈和縮小假陽性 (false positive),我們的方法計算出的陽性 (P) 區域和真實激發的區域 (T) 的誤差是毫米大小的尺度。 Magnetoencephalography (MEG) provides dynamic spatial-temporal insight of neural activities in the cortex. Because the number of possible sources is far greater than the number of MEG detectors, the proposition to localize sources directly from MEG data is notoriously ill-posed. Here we develop an approach based on data processing procedures including clustering, forward and backward filtering, and the method of maximum entropy. We show that taking as a starting point the assumption that the sources lie in the general area of the auditory cortex (an area of about 40 mm by 15 mm), our approach is capable of achieving reasonable success in pinpointing active sources concentrated in an area of a few mm's across, while limiting the spatial distribution and number of false positives.
    Appears in Collections:[Graduate Institute of Physics] Electronic Thesis & Dissertation

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