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Towards an optimization of stimulus parameters for brain-computer interfaces based on steady state visual evoked potentials.

Duszyk A, Bierzyńska M, Radzikowska Z, Milanowski P, Kuś R, Suffczyński P, Michalska M, Łabęcki M, Zwoliński P, Durka P - PLoS ONE (2014)

Bottom Line: Brighter colours and larger dimensions of flickering fields resulted in a significantly stronger SSVEP response.The distance between stimulation fields and the presence or absence of the fixation point had no significant effect on the response.Contrary to a popular belief, these results suggest that absence of the fixation point does not reduce the magnitude of SSVEP response.

View Article: PubMed Central - PubMed

Affiliation: University of Social Sciences and Humanities, Warsaw, Poland.

ABSTRACT
Efforts to construct an effective brain-computer interface (BCI) system based on Steady State Visual Evoked Potentials (SSVEP) commonly focus on sophisticated mathematical methods for data analysis. The role of different stimulus features in evoking strong SSVEP is less often considered and the knowledge on the optimal stimulus properties is still fragmentary. The goal of this study was to provide insight into the influence of stimulus characteristics on the magnitude of SSVEP response. Five stimuli parameters were tested: size, distance, colour, shape, and presence of a fixation point in the middle of each flickering field. The stimuli were presented on four squares on LCD screen, with each square highlighted by LEDs flickering with different frequencies. Brighter colours and larger dimensions of flickering fields resulted in a significantly stronger SSVEP response. The distance between stimulation fields and the presence or absence of the fixation point had no significant effect on the response. Contrary to a popular belief, these results suggest that absence of the fixation point does not reduce the magnitude of SSVEP response. However, some parameters of the stimuli such as colour and the size of the flickering field play an important role in evoking SSVEP response, which indicates that stimuli rendering is an important factor in building effective SSVEP based BCI systems.

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Related in: MedlinePlus

Relative power increase for SSVEP response to different colours of stimuli.Mean computed for all the subjects. Error bars indicate standard error of the mean (SEM). Horizontal lines above the bars indicate statistically significant differences on the level of p<0.001 (***), p<0.01 (**), and p<0.05 (*).
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pone-0112099-g002: Relative power increase for SSVEP response to different colours of stimuli.Mean computed for all the subjects. Error bars indicate standard error of the mean (SEM). Horizontal lines above the bars indicate statistically significant differences on the level of p<0.001 (***), p<0.01 (**), and p<0.05 (*).

Mentions: The impact of colours presented in Experiment I on mean SSVEP was examined using the Friedman test, indicating significant differences across all frequencies (χ2(4)  = 29.96; p<0.001). Mean ERSP for all participants (Fig. 2) showed that the weakest response is evoked by blue stimuli.


Towards an optimization of stimulus parameters for brain-computer interfaces based on steady state visual evoked potentials.

Duszyk A, Bierzyńska M, Radzikowska Z, Milanowski P, Kuś R, Suffczyński P, Michalska M, Łabęcki M, Zwoliński P, Durka P - PLoS ONE (2014)

Relative power increase for SSVEP response to different colours of stimuli.Mean computed for all the subjects. Error bars indicate standard error of the mean (SEM). Horizontal lines above the bars indicate statistically significant differences on the level of p<0.001 (***), p<0.01 (**), and p<0.05 (*).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4232393&req=5

pone-0112099-g002: Relative power increase for SSVEP response to different colours of stimuli.Mean computed for all the subjects. Error bars indicate standard error of the mean (SEM). Horizontal lines above the bars indicate statistically significant differences on the level of p<0.001 (***), p<0.01 (**), and p<0.05 (*).
Mentions: The impact of colours presented in Experiment I on mean SSVEP was examined using the Friedman test, indicating significant differences across all frequencies (χ2(4)  = 29.96; p<0.001). Mean ERSP for all participants (Fig. 2) showed that the weakest response is evoked by blue stimuli.

Bottom Line: Brighter colours and larger dimensions of flickering fields resulted in a significantly stronger SSVEP response.The distance between stimulation fields and the presence or absence of the fixation point had no significant effect on the response.Contrary to a popular belief, these results suggest that absence of the fixation point does not reduce the magnitude of SSVEP response.

View Article: PubMed Central - PubMed

Affiliation: University of Social Sciences and Humanities, Warsaw, Poland.

ABSTRACT
Efforts to construct an effective brain-computer interface (BCI) system based on Steady State Visual Evoked Potentials (SSVEP) commonly focus on sophisticated mathematical methods for data analysis. The role of different stimulus features in evoking strong SSVEP is less often considered and the knowledge on the optimal stimulus properties is still fragmentary. The goal of this study was to provide insight into the influence of stimulus characteristics on the magnitude of SSVEP response. Five stimuli parameters were tested: size, distance, colour, shape, and presence of a fixation point in the middle of each flickering field. The stimuli were presented on four squares on LCD screen, with each square highlighted by LEDs flickering with different frequencies. Brighter colours and larger dimensions of flickering fields resulted in a significantly stronger SSVEP response. The distance between stimulation fields and the presence or absence of the fixation point had no significant effect on the response. Contrary to a popular belief, these results suggest that absence of the fixation point does not reduce the magnitude of SSVEP response. However, some parameters of the stimuli such as colour and the size of the flickering field play an important role in evoking SSVEP response, which indicates that stimuli rendering is an important factor in building effective SSVEP based BCI systems.

Show MeSH
Related in: MedlinePlus