Yue Liang, Xiao Xiaolin, Xu Minpeng, Chen Long, Wang Yijun, Jung Tzyy-Ping, Ming Dong
Annu Int Conf IEEE Eng Med Biol Soc. 2020 Jul;2020:3090-3093. doi: 10.1109/EMBC44109.2020.9176855.
Steady State Visual Evoked Potentials (SSVEPs) have been widely used in Brain-Computer Interfaces (BCIs). SSVEP-BCIs have advantages of high classification accuracy, high information transfer rate, and strong anti-interference ability. Traditional studies mostly used low/medium frequency SSVEPs as system control signals. However, visual flickers with low/medium frequencies are uncomfortable, and even cause visual fatigue and epilepsy seizure. High-frequency SSVEP is a promising approach to solve these problems, but its miniature amplitude and low signal-to-noise ratio (SNR) would pose great challenges for target recognition. This study developed an innovative BCI paradigm to enhance the SNR of high-frequency SSVEP, which is named Steady-State asymmetrically Visual Evoked Potential (SSaVEP). Ten characters were encoded by ten couples of asymmetric flickers whose durations only lasted one second and frequencies ranged from 31 to 40 Hz with a step of 1 Hz. Discriminative canonical pattern matching (DCPM) was used to decode the high-frequency SSaVEP signals. Four subjects participated in the offline experiment. As a result, the accuracy achieved an average of 87.5% with a peak of 97.1%. The simulated online information transfer rate reached 87.2 bits/min on average and 111.2 bits/min for maximum. The results of this study demonstrate the high-frequency SSaVEP paradigm is a promising approach to alleviate the discomfort caused by visual stimuli and thereby can broaden the applications of BCIs.
稳态视觉诱发电位（SSVEPs）已在脑机接口（BCIs）中得到广泛应用。基于SSVEP的脑机接口具有分类准确率高、信息传输速率高和抗干扰能力强等优点。传统研究大多使用低/中频SSVEPs作为系统控制信号。然而，低/中频的视觉闪烁会让人感到不适，甚至会导致视觉疲劳和癫痫发作。高频SSVEP是解决这些问题的一种有前景的方法，但其微小的幅度和低信噪比（SNR）会给目标识别带来巨大挑战。本研究开发了一种创新的脑机接口范式，以提高高频SSVEP的信噪比，该范式被称为稳态不对称视觉诱发电位（SSaVEP）。十个字符由十对不对称闪烁编码，其持续时间仅为一秒，频率范围为31至40Hz，步长为1Hz。采用判别式规范模式匹配（DCPM）对高频SSaVEP信号进行解码。四名受试者参与了离线实验。结果，准确率平均达到87.5%，最高达到97.1%。模拟在线信息传输速率平均达到87.2比特/分钟，最高达到111.2比特/分钟。本研究结果表明，高频SSaVEP范式是一种有前景的方法，可以减轻视觉刺激引起的不适，从而拓宽脑机接口的应用范围。
