高頻率穩態視覺誘發電位對人眼視網膜中央窩與其外圍的反應

Abstract

在腦機介面(brain-computer interface, BCI)的領域，穩態視覺誘發電位(SSVEP)是其中一種被實現的應用技術：不同的頻率閃爍刺激人類視覺，擷取其腦電訊號(electroencephalogram, EEG)去辨識使用者凝視的刺激物，執行其相對應的指令。本研究將探討穩態視覺誘發電位的現象，從頻率5 Hz到65 Hz以5 Hz為間隔的白光二極體(LED)閃爍，刺激視網膜中央窩(視角2牵)和其外圍(視角16-18牵)。8位受測者(年齡20~55歲)參與本實驗，戴著64電極腦波帽收集腦電訊號。實驗過程中，受測者主觀對於刺激物的閃爍和舒適度的感覺將會被記錄，並做進一步的探討。在頻譜分析和標準關係數分析的結果中，顯示頻率25 Hz至45 Hz之間仍然有相當好的訊雜比(signal-to-noise ratio, SNR)。另外，大部分的受測者對30 Hz至45 Hz之間的頻率感到舒適和較少的閃爍。本次實驗研究證明，燈光閃爍在人類視覺閃爍融合的閾值以上仍可作為有效且舒適的視覺刺激，提供穩定視覺誘發電位在腦機介面實際應用上的重要參考。

To understanding the brain functions via the brain-computer interface (BCI), here, we studied the steady-state visual evoked potentials (SSVEP) from retinal fovea and extrafoveal in response to a 2牵 circular and a 16牵–18牵 annular white light stimuli flickering between 5 and 65 Hz by 5 Hz increments. Eight subjects (age 20~55 years old) participated in this experiment. Their EEG signals were recorded using a commercial 64-channel NeuroScan system. Their flickering perception and comfort levels were also studied. Spectral and canonical correlation analyses of SSVEP signals collected from nine EEG channels in the occipital area showed distinctively higher signal-to-noise ratios (SNR) in the foveal responses between 25 and 45 Hz. The findings from the subjects also indicate that the less flickering and felt are more comfortable with stimulation flickering between 30 and 45 Hz. These empirical evidences suggest that lights flashing above human vision flicker fusion thresholds can be potentially used as an effective visual stimuli tool in SSVEP BCI applications.