SNR analysis of high-frequency steady-state visual evoked potentials from the foveal and extrafoveal regions of Human Retina

Abstract

With brain-computer interface (BCI) applications in mind, we analyzed the amplitudes and the signal-to-noise ratios (SNR) of steady-state visual evoked potentials (SSVEP) induced in the foveal and extra-foveal regions of human retina. Eight subjects (age 20-55) have been exposed to 2° circular and 16°-18° annular visual stimulation produced by white LED lights flickering between 5Hz and 65Hz in 5Hz increments. Their EEG signals were recorded using a 64-channel NeuroScan system and analyzed using non-parametric spectral and canonical convolution techniques. Subjects' perception of flickering and their levels of comfort towards the visual stimulation were also noted. Almost all subjects showed distinctively higher SNR in their foveal SSVEP responses between 25Hz and 45Hz. They also noticed less flickering and felt more comfortable with the visual stimulation between 30Hz and 45Hz. These empirical evidences suggest that lights flashing above the critical flicker fusion rates (CFF) of human vision may be used as effective and comfortable stimuli in SSVEP BCI applications.

Tradeoff between User Experience and BCI Classification Accuracy with Frequency Modulated Steady-State Visual Evoked Potentials

“…Moreover, these already small stimuli fall onto the retinal periphery when only covert spatial attention is directed towards them. The smaller anatomical representation of peripheral locations in early visual areas may have led to even lower, undetectable in our case, SSVEP amplitudes for peripheral stimuli (Lin et al, 2012). A third reason could lie in the mechanisms of SSVEP generation.…”

“…Since high frequency stimulation tends to be less annoying (Lin et al, 2012) and FM stimulation with a high frequency carrier is less perceptible (Dreyer and Herrmann, 2015), our hypothesis was that FM stimulation would on average be more comfortable than SIN stimulation. We first compared the ratings in the two blocks for each condition separately with paired sample t -tests.…”

“…Several studies using SSVEPs have reported users experiencing fatigue, annoyance or discomfort due to the flicker stimulation (Ortner et al, 2011; Lin et al, 2012; Cao et al, 2014). Therefore, our second aim was to show that FM-SSVEP stimulation would be more comfortable for the user.…”

“…In fact, Cao et al (2014) showed increasing levels of fatigue after SSVEP stimulation by using subjective as well as physiological measures and Ortner et al (2011) report that their subjects disliked flickering light stimuli. Additionally, it has been shown that low frequency flicker is more perceptible and more irritating for the user (Lin et al, 2012). Stimulation with higher frequencies reduces discomfort (Sakurada et al, 2015) but decreases BCI performance and increases the rate of BCI illiteracy (Volosyak et al, 2011).…”

Assessing the quality of steady-state visual-evoked potentials for moving humans using a mobile electroencephalogram headset

“…However, it is worth mentioning that due to the non-identical channel locations (wet: O1 and O2; dry: PO1 and PO2) used in the comparison, the detectability gap might not be fully attributed to the electrode types. It could be partially attributed to the fact that the occipital electrodes over the visual cortex have better SNR than those at the parieto-occipital areas (Wang et al, 2006; Lin et al, 2012). The 4-ch comparison (c.f.…”