Study of the Influences of Stimuli Characteristics in the Implementation of Steady State Visual Evoked Potentials Based Brain Computer Interface Systems

Frequency-tagging of spatial attention using periliminal flickers

“…Thus, a more plausible explanation for the higher SSVEP response elicited by the flicker presented on the right area may be due to the difference in flicker frequency between the left and right flickers. Indeed, several studies have systematically characterized SSVEP responses over ranges of frequencies, highlighting that frequencies of 14Hz and 16Hz elicited SSVEP response with notably higher SNR than 12Hz flickers (Murillo López et al, 2021;Ladouce et al, 2021Ladouce et al, , 2022. Moreover, several studies reported a local maximum SSVEP response at 15Hz, at which flickers elicited stronger SSVEP responses than at neighboring frequencies (Tsoneva et al, 2023;Jukiewicz and Cysewska-Sobusiak, 2016).…”

“…The systematic investigation of subliminal SSVEP response over a wide range of frequencies carried by (Tsoneva et al, 2023) suggests that both lower and higher frequencies may be used in imperceptible frequency-tagging to tag specific neural networks. Future frequency-tagging studies are however needed to provide empirical evidence supporting the validity of this approach at frequencies that are not within the range of frequencies at which SSVEP responses are maximal (12 to 20 Hz, see Ladouce et al (2022); Tsoneva et al (2023); Murillo López et al (2021)). Another issue pertains to the ecological validity of the target detection task performed by the participants which may be considered rather artificial and transient with regard to its pacing.…”

“…The trial was concluded by the brief presentation of performance feedback displayed at the center of the screen indicating whether the response was correct or not and the reaction time for the last trial. Throughout the three phases of each trial (fixation, cueing, target), the left and right sides of the screen (partitioned into three equally sized panels) were flickering at frequencies of 13Hz and 15Hz, respectively ((Murillo López et al, 2021; Ladouce et al, 2022)). The participants completed a block of 30 trials per condition for a total of 90 trials for the whole experiment (lasting about 15 minutes).…”

“…Increasing flicker frequencies over 30Hz therefore may be a solution to address SSVEP safety issues. While previous studies using LEDs have demonstrated that SSVEP responses can be elicited over frequencies up to 90 Hz (Herrmann, 2001a;Pastor et al, 2003), their signal-to-noise ratios (SNR) decrease drastically over 30Hz (Murillo López et al, 2021;Chen et al, 2019b). Although the reduction in SNR limits the application of high-frequency flickers within the frame of BCI (Ladouce et al, 2021), flickers were reportedly less intrusive (Hoffmann et al, 2009) and deemed more visually comfortable (Ladouce et al, 2022) as a function of frequency.…”