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杭州电子科技大学硕士学位论文
I
摘 要
经颅直流电刺激(Transcranial Direct Current Stimulation, tDCS)和运动想象
(Motor Imagery, MI)联合疗法可以调控脑皮层活跃度,进而促进神经元重塑,加
速运动功能康复。然而在这种联合疗法中,tDCS 刺激时长参数设置的标准尚未
明确。针对该问题,本文首先设计实验方案,再搭建实验所需环境,并采集脑
电信号(Electroencephalogram, EEG)。通过小样本实验数据验证事件相关去同步
(Event-related Desynchronization, ERD)、样本熵(Sample Entropy, SampEn)、功率
谱密度(Power Spectral Density, PSD)以及瞬时能量(Instantaneous Energy, IE)四个
脑电特征在本次实验中作为脑皮层活跃度的测度的可行性。接着,本文通过自
研的基于 Web 的特征提取工具对本次实验采集到的 600 份数据进行批量处理。
最后结合配对样本 t 检验和单因素方差分析研究三种电流强度下的 tDCS 刺激时
长对脑运动皮层活跃度的影响。本文主要的研究内容如下:
(1) 构建实验环境。本文设计 3 种电流强度下(1、1.5 和 2 mA)的刺激时长实
验,每个实验包括 4 种不同时长(10、15、20 和 25 min)的阳极刺激,通过采集刺
激前后 C3 区的脑电信号分析不同刺激时长对运动皮层活跃度的影响。本文使用
脑电信号采集仪采集经颅直流电刺激前后的脑电信号,并通过经颅直流电刺激
仪对 C3 区施加阳极电刺激。通过构建的实验环境获取到 EEG 数据,再利用
EEGLab 和 Matlab 对实验数据进行预处理。最后得到的 EEG 信号可以为特征提
取提供数据基础。
(2) 特征选择研究。本文选择四个特征作为 tDCS 和 MI 联合实验中量化皮层
活跃度的测度,并基于 50 份小样本实验数据验证两个特征值在本次联合实验中
量化皮层活跃度的有效性。通过 Matlab 提取刺激前后 EEG 信号对应的特征值后
进行配对 t 检验分析。结果发现,刺激后的四个特征值均显著大于刺激前
(P<0.05),满足阳极刺激增强皮层活跃度的规律,证实所选四个特征在本次联合
实验中作为测度的有效性。
(3) 批量特征提取。本文对本次实验所需的四种 EEG 信号特征提取功能研发
了基于 Web 应用的特征提取工具。将该工具对小样本实验数据提取到的特征值
与 Matlab 提取到的特征值进行比较,结果完全一致,证实本次工具的特征提取
功能有效且结果可信。最后,本文利用该工具对全部的实验数据进行特征提取,
为后续的统计分析做好准备。
(4) 阳极 tDCS 刺激时长对脑运动皮层活跃度的影响研究。对刺激时长实验
杭州电子科技大学硕士学位论文
II
的脑电数据进行特征提取,并计算每种特征在刺激前后的变化量,再通过单因
素方差分析对特征变化量数据进行统计分析,得出不同电流强度下的刺激时长
对皮层活跃度的影响规律一致,均为非线性。其中,在 10 到 20 min 内,刺激时
长参数与阳极 tDCS 对皮层活跃度的增强效果之间呈正相关,而 25 min 刺激对
皮层活跃度的提升效果减弱,并出现抑制皮层活跃度的现象。因此,在 10 到 20
min 范围内,阳极 tDCS 刺激时长参数选择 20 min 最佳。此外,在 1 到 2 mA 的
电流范围内,电流强度与阳极 tDCS 对皮层活跃度的增强效果之间也呈正相关。
而且,在 1 到 2 mA 的电流范围和 10 到 20 min 的时长范围组成的刺激参数空间
内,2 mA 和 20 min 的阳极刺激对皮层活跃度的增强效果最佳。
通过上述研究,本文研究结果有望为使用 tDCS 和 MI 联合技术的运动功能
康复疗法的刺激时长设置提供有意义的参考,同时研发的基于 Web 应用的特征
提取工具可以为后续研究提供帮助。
关键词:经颅直流电刺激时长,运动想象,脑电信号,特征提取,运动皮层活
跃度
杭州电子科技大学硕士学位论文
III
ABSTRACT
The combination of Transcranial Direct Current Stimulation (tDCS) and Motor
Imagery (MI) can modulate the activity of cerebral cortex, thus promoting neuronal
remodeling and accelerating the recovery of motor function. However, the criteria for
setting tDCS stimulation duration parameters in this combination therapy are not yet
clear. To address this problem, this paper first designs the experimental protocol, then
builds the required environment for the experiment and acquires EEG signals
(Electroencephalogram, EEG). The feasibility of the four EEG features, event-related
desynchronization (ERD), sample entropy (SampEn), power spectral density (PSD) and
instantaneous energy (IE), as measures of cortical activity in this experiment was
verified using small sample data. Then, the 600 data collected in this experiment were
batch processed by a self-developed web-based feature extraction tool. Finally, paired-
sample t-test and one-way ANOVA were combined to investigate the effect of tDCS
stimulation duration on brain motor cortex activity at three current intensities. The main
research components of this paper are as follows:
(1) Setting up the experimental environment. We designed experiments with three
current intensities (1, 1.5 and 2 mA), each including four different anodal stimulation
durations (10, 15, 20 and 25 min), and analyzed the effects of different stimulation
durations on motor cortex activity by collecting EEG signals from C3 area before and
after stimulation. In this paper, the EEG signals before and after transcranial direct
current stimulation were acquired using an EEG signal acquisition device, and anodal
electrical stimulation was applied to the C3 area by transcranial direct current stimulator.
After the data were acquired, the experimental data were pre-processed by EEGLab and
Matlab. The final pure EEG signal obtained can provide the data basis for feature
extraction.
(2) Feature selection study. In this paper, four features were selected as the
measures for quantifying cortical activity in the joint experiment of tDCS and MI, and
the validity of two feature values for quantifying cortical activity in this joint
experiment was verified based on 50 small samples of experimental data. Paired t-test
analysis was performed after extracting the corresponding eigenvalues of EEG signals
before and after stimulation by Matlab. It was found that the four feature values after
stimulation were significantly larger than those before stimulation (P<0.05), which
杭州电子科技大学硕士学位论文
IV
satisfied the law of cortical activity enhancement by anodal stimulation and confirmed
the validity of the selected four features as a measure in this joint experiment.
(3) Batch feature extraction. A web application-based feature extraction tool was
developed for the four EEG signal feature extraction functions required for this
experiment. The feature values extracted by this tool for small sample experimental
data are compared with those extracted by Matlab, and the results are in complete
agreement, confirming that the feature extraction function of this tool is effective and
the results are credible. Finally, this paper uses the tool to extract features from all the
experimental data to prepare for the subsequent statistical analysis.
(4) Study of the effect of anodal tDCS stimulation duration on brain motor cortex
activity. The EEG data from the stimulation duration experiments were subjected to
feature extraction, and the amount of change of each feature before and after stimulation
was calculated, and then the data on the amount of feature change were statistically
analyzed by one-way ANOVA, and it was concluded that the effect of stimulation
duration on cortical activity at different current intensities was consistent and non-linear.
Among them, there was a positive correlation between the stimulation duration
parameter and the enhancement effect of anodic tDCS on cortical activity in the range
of 10 to 20 min, while the enhancement effect of 25 min stimulation on cortical activity
diminished and appeared to inhibit cortical activity. Therefore, in the range of 10 to 20
min, the anodal tDCS stimulation duration parameter of 20 min is the optimal choice.
In addition, there is a positive correlation between current intensity and the
enhancement effect of anodal tDCS on cortical activity in the current range of 1 to 2
mA. Furthermore, in the stimulation parameter space consisting of a current range of 1
to 2 mA and a duration range of 10 to 20 min, anodal stimulation at 2 mA and 20 min
has the best effect on the enhancement of cortical activity.
With the above studies, the results of this paper are expected to provide meaningful
references for the stimulation duration settings of motor function rehabilitation therapy
using the combined tDCS and MI techniques, while the developed Web application-
based feature extraction tool can be helpful for subsequent studies.
Keywords: Transcranial direct current stimulation duration, Motor imagery,
Electroencephalogram, Feature extraction, Motor cortex activity
目 录
第 1 章 绪论............................................................................................... 1
1.1 研究背景和意义 ............................................................................... 1
1.2 经颅直流电刺激概述 ....................................................................... 2
1.2.1 即刻效应 ..................................................................................... 3
1.2.2 后效应 ......................................................................................... 3
1.3 运动想象与 t DCS 联合方法概述 ................................................... 4
1.3.1 刺激时长概述 ............................................................................. 5
1.3.2 研究方法概述 ............................................................................. 7
1.4 主要研究内容与本文组织结构 ...................................................... 7
第 2 章 tDCS 与 MI 联合的实验环境构建 ........................................ 10
2.1 脑电信号概述 ................................................................................. 10
2.1.1 大脑结构及功能分区 ............................................................... 10
2.1.2 脑电信号分类与选取 ............................................................... 11
2.2 实验范式设计及实施 ..................................................................... 12
2.2.1 实验对象 ................................................................................... 12
2.2.2 实验范式设计 ........................................................................... 13
2.2.3 实验设备及参数设置 ............................................................... 13
2.2.4 实验实施 ................................................................................... 14
2.3 脑电信号预处理 ............................................................................. 15
2.4 本章小结 ......................................................................................... 20
第 3 章 EEG 特征提取 ............................................................................ 21
3.1 特征选取 ......................................................................................... 21
3.1.1 ERD/ERS ................................................................................... 21
3.1.2 功率谱密度 ............................................................................... 22
3.1.3 样本熵 ....................................................................................... 23
3.1.4 平均瞬时能量 ........................................................................... 24
3.2 基于 Matlab 验证所选特征作为测度的有效性 ......................... 25
3.2.1 Matlab 实现流程 ...................................................................... 26
3.2.2 数据结果分析 ........................................................................... 26
3.3 基于 Web 应用的特征提取系统需求分析 ................................... 28
3.4 系统设计 ......................................................................................... 29
3.4.1 前端设计 ................................................................................... 29
3.4.2 后端设计 ................................................................................... 30
3.4.3 前后端数据交互设计 ............................................................... 32
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