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. 2008 Feb;119(2):399-408.
doi: 10.1016/j.clinph.2007.09.121.

Towards an independent brain-computer interface using steady state visual evoked potentials

Brendan Z Allison  1 , Dennis J McFarland, Gerwin Schalk, Shi Dong Zheng, Melody Moore Jackson, Jonathan R Wolpaw
Affiliations

Towards an independent brain-computer interface using steady state visual evoked potentials

Brendan Z Allison et al. Clin Neurophysiol. 2008 Feb.

Abstract

Objective: Brain-computer interface (BCI) systems using steady state visual evoked potentials (SSVEPs) have allowed healthy subjects to communicate. However, these systems may not work in severely disabled users because they may depend on gaze shifting. This study evaluates the hypothesis that overlapping stimuli can evoke changes in SSVEP activity sufficient to control a BCI. This would provide evidence that SSVEP BCIs could be used without shifting gaze.

Methods: Subjects viewed a display containing two images that each oscillated at a different frequency. Different conditions used overlapping or non-overlapping images to explore dependence on gaze function. Subjects were asked to direct attention to one or the other of these images during each of 12 one-minute runs.

Results: Half of the subjects produced differences in SSVEP activity elicited by overlapping stimuli that could support BCI control. In all remaining users, differences did exist at corresponding frequencies but were not strong enough to allow effective control.

Conclusions: The data demonstrate that SSVEP differences sufficient for BCI control may be elicited by selective attention to one of two overlapping stimuli. Thus, some SSVEP-based BCI approaches may not depend on gaze control. The nature and extent of any BCI's dependence on muscle activity is a function of many factors, including the display, task, environment, and user.

Significance: SSVEP BCIs might function in severely disabled users unable to reliably control gaze. Further research with these users is necessary to explore the optimal parameters of such a system and validate online performance in a home environment.

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Figures

Figure 1
Figure 1
The top row presents the three images used in the BW linebox condition, and the middle row contains three images used in the color linebox condition. The four images used in the BW checkerbox condition are on the bottom row.
Figure 2
Figure 2
Spectral power and R2 values for subject R. Panels A and C show the power spectra over sites O1 and O2 from 0−65 Hz when the subject focused on the 6 Hz checkerbox (solid line) or the 15 Hz checkerbox (dotted line). Panels B and D show the R2 between the two lines in panels A and C. Panel E shows a topographic map of R2 differences at all sites for that subject over six frequencies: the two stimulation frequencies (6 and 15 Hz) and the second and third harmonics of each. Please note that this figure presents data derived with different stimulation frequencies than the subsequent figures.
Figure 3
Figure 3
Spectral power and R2 values for subject J. Panels A and C show the power spectra over sites O1 and O2 from 0−65 Hz when the subject focused on the black and white 10 Hz linebox (solid line) or the 12 Hz linebox (dotted line). Panels B and D show the R2 between the two lines in panels A and C. Panel E shows a topographic map of R2 differences at all sites for that subject over six frequencies: the two stimulation frequencies (10 and 12 Hz) and the second and third harmonics of each.
Figure 4
Figure 4
Spectral power and R2 values for subject A. Panels A and B show the power spectra over sites O1 and O2 from 0−65 Hz when the subject focused on the colored 10 Hz linebox (solid line) or the 12 Hz linebox (dotted line). Panels C and D show the R2 between the two lines in panels A and C. Panel E shows a topographic map of R2 differences at all sites for that subject over six frequencies: the two stimulation frequencies (10 and 12 Hz) and the second and third harmonics of each.
Figure 5
Figure 5
Spectral power and R2 values for subject K. Panels A and C show the power spectra over sites O1 and O2 from 0−65 Hz when the subject focused on the colored 10 Hz linebox (solid line) or the 12 Hz linebox (dotted line). Panels B and D show the R2 between the two lines in panels A and C. Panel E shows a topographic map of R2 differences at all sites for that subject over six frequencies: the two stimulation frequencies (10 and 12 Hz) and the second and third harmonics of each.
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References

    1. Allison BZ. P3 or not P3: Toward a Better P300 BCI. La Jolla; UC San Diego: 2003.
    1. Allison BZ, Pineda JA. ERPs evoked by different matrix sizes: Implications for a brain computer interface (BCI) system. IEEE Trans Neural Syst Rehabil Eng. 2003 Jun;11(2):110–113. - PubMed
    1. Allison BZ, Pineda JA. Effects of SOA and flash pattern manipulations on ERPs, performance, and preference: Implications for a BCI system. International Journal of Psychophysiology. 2006 Feb;59(2):127–140. - PubMed
    1. Allison BZ, Boccanfuso JB, Agocs C, McCampbell LA, Leland DS, Gosch C, Moore Jackson M. Sustained use of an SSVEP BCI under adverse conditions. Journal of Cognitive Neuroscience Supplement. 2006:129.
    1. Allison BZ, Wolpaw EW, Wolpaw JR. Poll E, editor. Brain computer interface systems: Progress and prospects. British review of medical devices. Jul;4(4):463–474. - PubMed

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