Preliminary study for extraction of P300 and SSVEP by stimulus presentation using phase inversion technique in hybrid BCI
Preliminary study for extraction of P300 and SSVEP by stimulus presentation using phase inversion technique in hybrid BCI
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DOI：
10.1109/embc.2015.7318301
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发表时间：
2015-11
期刊：
影响因子：
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通讯作者：
T. Fukami;Kazuyoshi Ishihara;F. Ishikawa
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文献类型：
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作者：
T. Fukami;Kazuyoshi Ishihara;F. Ishikawa
在这项研究中，我们提出了一种新的刺激呈现方法的混合BCI的P300和稳态视觉诱发电位（SSVEP）有效地分离两个组件。该方法通过在刺激频率对应的SSVEP分量中产生相位差为π弧度的两个时间点的P300来产生分离。假设连续的两个P300响应是相同的，并且SSVEP是正弦的，通过抑制SSVEP，可以将P300提取为上述两个响应的总和。此外，SSVEP可以通过减去上述两个响应来检测。相应地，该方法通过由上述两个刺激组成的刺激对来实现。在EEG实验中，我们分别使用棋盘格刺激和字符呈现来获得SSVEP和P300。棋盘的刺激频率被指定为5 Hz和3 Hz，以从两个给定的字符中分类目标字符。结果表明，一个突出的P300组件的外观，从只有一对刺激，即使SSVEP的基频和谐波频率分量较低的刺激频率不是很稳定。这是因为SSVEP的正电位和负电位不对称。使用与P300频带重叠的刺激频率是一个好主意，因为这种方法不会通过EEG频率差将P300和SSVEP分离。此外，它减少了测量时间（即，它缩短了P300估计所需的平均数），因为如果SSVEP是正弦的，则SSVEP被抵消。我们认为，这将是一个有用的方法，从这些方面同时估计P300和SSVEP。
In this study, we propose a novel stimulation presentation method for the hybrid BCI of the P300 and steady state visual evoked potential (SSVEP) to separate the two components efficiently. The method produces the separation by generating the P300 at two time points whose phase difference is π radians in the SSVEP component corresponding to stimulus frequency. Assuming that the consecutive two P300 responses are identical and the SSVEP is sinusoidal, the P300 can be extracted as a summation of the above two responses by suppressing the SSVEP. Also, the SSVEP can be detected by the subtraction of the above two responses. Accordingly, this method is realized by a stimulus pair consisting of the above two stimuli. In an EEG experiment, we used a checkerboard stimulus and character presentation for obtaining the SSVEP and P300, respectively. The stimulus frequencies of the checkerboard were assigned to 5 Hz and 3 Hz to classify the target character from the two given characters. The results showed the appearance of a prominent P300 component from only one pair of stimuli, even though the fundamental and harmonic frequency components of the SSVEP for lower stimulus frequencies are not very stable. This is because of the asymmetry of the positive and negative potentials for the SSVEP. It is a good idea to use a stimulus frequency that overlaps with the P300 frequency band, because this method does not separate the P300 and SSVEP by EEG frequency difference. Moreover, it reduces the measurement time (i.e., it shortens the number of averagings required for P300 estimation) because the SSVEP cancels out if it is sinusoidal. We consider that this will be a useful method to estimate the P300 and SSVEP simultaneously from these aspects.