臺灣博碩士論文加值系統

本篇論文探討聽覺穩態反應的腦磁圖活動源造影的問題，因為給受試者的兩耳相似的聽覺刺激，其腦波訊號特性經常會有完全相關的神經活動。在傳統的空間濾波器，因為其假設活動源都是不相關的，所以無法估算正確的完全相關活動源，本篇論文研究方法主要採用雙核波束成形器，目前已有不少論文討論其特性與限制，唯獨完全相關活動源的空間擴展未被納入討論。在模擬實驗中，分別探究各種雜訊活動源與完全相關活動源的空間擴展對DCBF的定位影響。從本篇論文的結果，可發現定位器NAI相較定位器K可找出正確的位置，定位器NAI在空間擴展的標準差5 mm以下都不會影響其定位準確度，但定位器K在空間擴展的標準差1 mm以下才會有正確的定位估計，而且，從實驗可以看出定位器NAI的偽像範圍較小，且比較能壓低其他地區的活化程度估值。

This thesis focus on the problem in source imaging of auditory steady-state responses in MEG signals. When an audio stimulus is simultaneously presented to the ears of a subject, the brain waves recorded from the subject often have fully correlated sources. Conventional spatial filters cannot accurately estimate correlated sources because it’s assumed that all sources are not cross-correlated. The method in this thesis is dual-core beamformer (DCBF). There are some papers discussing the limitation of DCBF, but the effect of spatial extent on the performance of DCBF remains unknown. The effects of noise types of background sources, and of spatial extents of correlated sources on DCBF localizers are investigated in this thesis. In results, localizer-NAI is better than localizer-K. When the standard deviations of spatial extents of correlated sources are less than 5 mm, localizer-NAI is not affected. But localizer-K only works well when the standard deviations of spatial extents of correlated sources are less than 1 mm. Furthermore, localizer-NAI has much smaller range of artifacts, which means localizer-NAI can suppress the estimation of other source locations than localizer-K.

中文摘要 i
英文摘要 ii
誌謝 ii
目錄 iii
表目錄 iv
圖目錄 v
一、緒論 1
1.1 研究動機 1
1.2 腦磁圖設備介紹與製造廠簡介 3
1.3 MEG的訊號特性 5
1.4 聽覺神經科學簡介 6
1.4.1 聽覺穩態響應 6
二、 神經產生電磁場原理與正向模型 7
2.1 活動源模型──電流偶極子 9
2.2 正向模型的磁場積分 11
2.3 球狀顱部模型 13
2.3.1 MEG在球狀顱部正向模型的限制 15
2.4 正向模型對逆問題的影響與其對實驗設計的啟發 16
2.5 分佈式偶極子活動源模型 18
三、 逆問題與腦波訊號的波束成形器 20
3.1 逆問題與活動源模型的數學關係 20
3.1.1 正向模型對MEG或EEG活動源重建的影響與比較 21
3.2 波束成形器 22
3.2.1 線性約束最小變異波束成形器 23
3.3 完全相關活動源的重建問題 25
四、 可重建完全相關活動源的波束成形器 27
4.1 論文回顧 27
4.2 雙核波束成形器 28
4.2.1 雙核波束成形器的兩種定位器 28
4.2.2 雙核波束成形器的限制 29
五、 電腦模擬與雙核波束成形器的計算結果 30
5.1 電腦模擬 30
5.1.1 模擬1 完全相關的活動源但沒有在空間上擴展 31
5.1.2 模擬2 空間擴展的且完全相關活動源 32
5.1.3 模擬3 比較不同空間擴展範圍且完全相關的活動源 32
5.2 雙核波束成形器的計算結果 34
5.2.1 雙核波束成形器對模擬1的計算結果 35
5.2.2 雙核波束成形器對模擬2的計算結果 36
5.2.3 雙核波束成形器對模擬3的計算結果 37
六、 結論 39
七、 未來展望 40
參考文獻 41

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