EEG data offline and online during motor imagery for standing and sitting
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The experiments were conducted in an acoustically isolated room where only the participant and the experimenter were present. Participants voluntarily signed an informed consent form in accordance with the experimental protocol approved by the ethics committee of the Universidad Antonio Nariño. The participant was seated in a chair in a posture that was comfortable for him/her but did not affect data collection. In front of the participant, a 40-inch TV screen was placed at about 3 m. On this screen, a graphical user interface (GUI) displayed images that guided the participant through the experiment. Each experimental session was divided into two phases: an offline phase and an online phase. The offline experiments consisted of recording participants´ EEG signals during motor imagery trials for standing and sitting that were guided by the GUI presented on the TV screen. Six offline runs were conducted in which the participants were standing in three runs and sitting in the other three runs. In each run, the participant had to repeat a block of 30 trials of mental tasks indicated by visual cues continuously presented on the screen in a pseudo-random sequence. The first phase of the experimental session was conducted to construct the offline parts of the dataset: (A) Sit-to-stand and (B) Stand-to-sit. The participant´s EEG data were collected from 90 sequences for part A (45 trials of MotorImageryA tasks and 45 trials of IdleStateA tasks) and 90 sequences for part B (45 trials of MotorImageryB tasks and 45 trials of IdleStateB tasks). For each participant, the two machine learning models obtained in the offline phase were used to carry out the online experiment parts of the dataset: (C) Sit-to-stand and (D) Stand-to-sit. Each participant was instructed to select, in no particular order, 30 sequences for part C (15 trials of MotorImageryA tasks and 15 trials of IdleStateA tasks) and 30 other sequences for part D (15 trials of MotorImageryB tasks and 15 trials of IdleStateB tasks). Each trial was unique and was generated pseudo-randomly before the experiment. The database consisted of 32 electroencephalographic files corresponding to the 32 participants. All recordings were collected on channels F3, Fz, F4, FC5, FC1, FC2, FC6, C3, Cz, C4, CP5, CP1, CP2, CP6, P3, Pz, and P4 according to the 10-20 EEG electrode placement standard, grounded to AFz channel and referenced to right mastoid (M2). Each data file contained the data stream in a 2D matrix where rows corresponded to channels and columns corresponded to time samples with a sampling frequency of 250Hz. The following marker numbers encoded information about the execution of the experiment. Marker numbers 200, 201, 202, and 203, indicated the beginning and end of the four steps of the sequence in a trial (resting, fixation, action observation, and imagining). Marker numbers 1, 2, 3, and 4, indicated the figure activated on the screen to the participant perform the task corresponding to 1. actively imagining the sit-to-stand movement (labeled as MotorImageryA), 2. sitting motionless without imagining the sit-to-stand movement (labeled as IdleStateA), 3. standing motionless while actively imagining the stand-to-sit movement (labeled as MotorImageryB), or 4. standing motionless without imagining the stand-to-sit movement (labeled as IdleStateB). Finally, marker numbers 101, 102, 103, and 104, indicated the task detected by the BCI in real time during the online experiment: 101. MotorImageryA, 102. IdleStateA, 103. MotorImageryB, or 104. IdleStateB.
本实验在声学隔离房间内开展，房间内仅包含被试与实验人员两名人员。被试自愿签署知情同意书，该流程符合安东尼奥·纳里尼奥大学（Universidad Antonio Nariño）伦理委员会批准的实验方案。被试将以舒适且不影响数据采集的姿势坐在椅子上。被试前方约3米处放置一台40英寸电视屏幕，屏幕上的图形用户界面（Graphical User Interface, GUI）将展示引导被试完成实验的图像。每场实验分为两个阶段：离线阶段与在线阶段。 离线实验环节为记录被试在执行站立、坐姿运动想象任务时的脑电图（Electroencephalogram, EEG）信号，该任务由电视屏幕上展示的GUI引导完成。实验共开展6组离线运行，其中3组被试处于站立状态，另外3组处于坐姿状态。每组运行中，被试需重复执行由屏幕以伪随机序列连续呈现的视觉提示所指定的30次心理任务试次。 实验的第一阶段用于构建数据集的离线部分：(A) 从坐到站（Sit-to-stand）与(B) 从站到坐（Stand-to-sit）。被试的EEG数据共采集90组序列对应任务A：其中45次为运动想象A任务（MotorImageryA），45次为空闲状态A任务（IdleStateA）；另有90组序列对应任务B：45次为运动想象B任务（MotorImageryB），45次为空闲状态B任务（IdleStateB）。 针对每名被试，将使用离线阶段得到的两个机器学习模型，开展数据集的在线实验部分：(C) 从坐到站与(D) 从站到坐。实验要求被试以无特定顺序选取30组序列对应任务C（15次运动想象A任务与15次空闲状态A任务），以及另外30组序列对应任务D（15次运动想象B任务与15次空闲状态B任务）。所有任务序列均为唯一，并在实验前以伪随机方式生成。 该数据库包含对应32名被试的32份脑电图文件。所有采集信号均遵循10-20脑电图电极放置标准，覆盖通道F3、Fz、F4、FC5、FC1、FC2、FC6、C3、Cz、C4、CP5、CP1、CP2、CP6、P3、Pz与P4，以AFz通道作为接地端，以右侧乳突（M2）作为参考电极。每份数据文件以二维矩阵形式存储数据流：行对应电极通道，列对应时间采样点，采样频率为250Hz。 下述标记编号用于编码实验执行过程中的各类信息。标记200、201、202、203分别表示单次实验序列中四个步骤的开始与结束：休息、注视、动作观察与动作想象。标记1、2、3、4分别表示屏幕上激活的、供被试执行对应任务的图标：1. 主动想象从坐到站动作（标记为MotorImageryA），2. 保持坐姿静止且不想象从坐到站动作（标记为IdleStateA），3. 保持站立静止且主动想象从站到坐动作（标记为MotorImageryB），4. 保持站立静止且不想象从站到坐动作（标记为IdleStateB）。最终，标记101、102、103、104分别表示在线实验中脑机接口（Brain-Computer Interface, BCI）实时检测到的任务：101对应MotorImageryA，102对应IdleStateA，103对应MotorImageryB，104对应IdleStateB。
