臺灣博碩士論文加值系統

想像運動一直是腦機介面的應用中備受重視的一個主題，本研究藉由觀察想像左右手運動的腦電波在C3和C4之特定頻帶範圍內的能量變化，讓個別受試者使用此二通道在此頻率範圍內能量的相減(C3-C4)作為各自的左與右的判斷標準，並且通過LabVIEW軟體與OpenBCI腦波儀建構一個即時的游標操控系統。此游標控制系統也在受試者自由左右控制之前，提供一個半控制的訓練，只會對判斷正確的腦波有反應，供受試者專注在產生正確的腦波以控制游標移動，並且在實驗的過程中將逐步調整判斷標準，以提升受試者對此系統與腦波的控制。
共十位受試者參與本研究，受試者的表現優劣存在個體之間的差異，我們提出r-F圖作為選定Mu與Beta頻帶範圍內相對重要的頻率的方法。也提出FA index作為判斷左右手能量差(power difference)分布圖的差異程度與mean correlation coefficient作為左與右手的能量差(power difference)大小關係。 並且發現在沒有回饋階段收到的受試者腦波計算出的FA index和mean correlation coefficient分別對有回饋控制的表現優劣均有著線性關係，此線性關係可用以預期受試者在做想像運動的表現狀況。

Motor Imagery has been an important role in developing the application of Brain Computer Interface. Based on the power changes at C3 and C4 in the task of left hand and right hand motor imagery, we developed an EEG-based real-time cursor control system based on LabVIEW and OpenBCI amplifier. The recognizing criteria of left hand and right hand motor imagery was computed from the power at C3 minus that at C4 in specific frequency band. The experimental protocol consisted of no-feedback stage, semi-control stage and self-control stage. In the no-feedback stage, the cursor moved in constant speed and subjects were asked to conduct motor imagery, pretending the cursor was controlled by themselves. In the semi-control stage, the cursor moved toward the correct direction only when the direction of imaged movement was correctly recognized, otherwise the cursor stayed stationary. The purpose of such a design was to encourage subjects to focus on the correctly recognized imaged movement and ignore the incorrect ones. In the self-control stage, the cursor movement was totally controlled by subjects.
Ten subjects participated in this study, and there exists individual difference among subjects. We found that, in the no feedback stage, the mean correlation coefficients across the selected frequency band in the r-F plots, and the FA index that measured the separation of two distributions of the task power difference can be two effective indexes to predict the subject performance in the semi-control stage because of the linearity between these two indexes and accuracy of semi-control.

致謝...i
中文摘要...ii
Abstract...iii
Contents...iv
List of Figures...vi
List of Tables...vii

Chapter 1 Introduction...1
1.1 Brain Computer Interface(BCI)...1
1.2 Electroencephalographic...2
1.3 Motor Imagery...3
1.4 Aims of this Thesis...5
1.5 Thesis Organization...5

Chapter 2 Material and Methods...6
2.1 Subjects...6
2.2 Data Acquisition...6
2.3 Equipment...7
2.4 Experimental Description and Protocol...8
2.5 Data Processing...13
2.5.1 Autoregressive model (AR model)...14
2.5.2 correlation coefficient – frequency plot (r-F plot)...15
2.5.3 Frequency Selection and Classification...17
2.5.4 Far-Apart index (FA index)...18

Chapter 3 Results...20
3.1 The Results in no-feedback stage of each subject...20
3.2 The 2 indexes from No-Feedback are both linear with performance
of each subject in the Semi-Control stage...26
3.3 The Accuracy in the Self-Control stage is generally smaller than
Semi-Control stage...31
3.4 The frequency response(FR) of AR model of each segment...33

Chapter 4 Discussion...39
4.1 Three Stages of experiment...39
4.2 The r-F plots are different in each subject...39

Chapter 5 Conclusions...41

Chapter 6 Future Work...42

References...43

Appendix...46



List of Figures

Figure 1-1 10-20 system...3
Figure 1-2 ERD/ERS of different subjects...4
Figure 2.1 Bipolar montage of electrodes...7
Figure 2.2 The experimental equipment...8
Figure 2.3 The display of cursor feedback experiment...9
Figure 2.4 Flow diagram of three stages in the one-day experiment...11
Figure 2.5 Task in one trial of No-Feedback...12
Figure 2.6 r-F plot...16
Figure 2.7 Histogram of task power differences in imaging left and right movement...18
Figure 3.1 Positively linear relation between FA index and accuracy in semi-control stage...29
Figure 3.2 Negatively linear relation between averaged correlation coefficient and accuracy in semi-control stage...29
Figure 3.3 Positively linear relation between FA index and the best mean accuracy in semi-control stage...30
Figure 3.4 Negatively linear relation between averaged correlation coefficient and beast mean accuracy in semi-control stage...30
Figure 3.5 Best performance in Semi-Control and Self-Control stages...33



List of Tables

Table 3.1 r-F plot and histogram of each subject...24
Table 3.2 Results in No-Feedback stage...25
Table 3.3 Mean value of task power difference of each subject in no-feedback stage...25
Table 3.4 Performance in the semi-control stage...27
Table 3.5 Best performance in Semi-Control stage...28
Table 3.6 Performance in Self-Control stage...32
Table 3.7 Description of the plots in the Table 3.8...34
Table 3.8 Average of frequency response of left and right motor imagery at C3 and C4 in no-feedback stage...38

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