Objective Steady-state visual evoked potential ( SSVEP ) is the response of brain elicited by periodic visual stimulation, and is widely used in electroencephalography ( EEG ) based brain-computer interface ( BCI) . SSVEP frequency-response functions are usually obtained by using a light emitting diode ( LED) as a visual stimulator. Recently, the computer monitor is widely used for producing flickering stimuli. However, there are few existing studies that have attempted to investigate computer monitor-based SSVEP frequency-response functions. Therefore, this study investigated computer monitor-based SSVEP frequency-response characteristic. Methods We used the sampled sinusoidal encoded method to realize 42 stimulation frequencies ranging from 4 Hz to 45 Hz on a conventional LCD screen. We collected an EEG dataset from 10 healthy subjects and investigated the relationship between SSVEP amplitude/signal-to-noise ratio ( SNR ) and stimulation frequencies. Results Strong SSVEPs were observed over occipital area. The SSVEP amplitude of the fundamental frequency exhibited strong peak at 10 Hz and weaker secondary maximum at 20 Hz. The SSVEP amplitude of the second harmonic was maximal for the stimulation frequency of 6 Hz and smaller for higher stimulation frequencies. The SSVEP SNR of the fundamental frequency in the low-and medium-frequency bands was comparable. Conclusions These results could provide a basis for frequency selection of computer screen-based SSVEP-BCIs.%目的 稳态视觉诱发电位(steady-state visual evoked potential,SSVEP)是大脑对周期性视觉刺激产生的响应,已广泛应用于基于脑电(electroencephalogram,EEG)的脑-机接口(brain-computer interface,BCI).SSVEP频率响应曲线通常是以发光二极管(light emitting diode,LED)作为视觉刺激器的方式获得的.近年来,计算机显示器广泛用于产生闪烁刺激,然而基于计算机显示器的SSVEP频率响应曲线少有研究.为此,本文研究了基于计算机显示器的SSVEP频率响应特性.方法 利用采样正弦编码方法在普通LCD显示器上产生了42个刺激频率(频率范围4～45 Hz),并收集了10位健康受试者的脑电数据,以研究SSVEP幅值/信噪比(signal-to-noise ratio,SNR)与刺激频率的关系.结果 较强SSVEP响应出现在大脑枕区.SSVEP基频幅值的峰值出现在10 Hz处,且第二峰值出现在20 Hz处.SSVEP二次谐波幅值的峰值出现在6 Hz且在高刺激频率处幅值较小.低、中频段的SSVEP基频信噪比处于相当的水平.结论 本文的实验结果可以为基于计算机显示器的SSVEP-BCIs的频率选择提供依据.
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