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Simultaneous Decoding of Eccentricity and Direction Information for a Single-Flicker SSVEP BCI

1
Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing 100084, China
2
Department of Neurophysiology and Pathophysiology, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
3
State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100864, China
4
Department of Psychology, School of Social Sciences, Tsinghua University, Beijing 100084, China
*
Author to whom correspondence should be addressed.
Electronics 2019, 8(12), 1554; https://doi.org/10.3390/electronics8121554
Received: 11 October 2019 / Revised: 3 December 2019 / Accepted: 3 December 2019 / Published: 17 December 2019
The feasibility of a steady-state visual evoked potential (SSVEP) brain–computer interface (BCI) with a single-flicker stimulus for multiple-target decoding has been demonstrated in a number of recent studies. The single-flicker BCIs have mainly employed the direction information for encoding the targets, i.e., different targets are placed at different spatial directions relative to the flicker stimulus. The present study explored whether visual eccentricity information can also be used to encode targets for the purpose of increasing the number of targets in the single-flicker BCIs. A total number of 16 targets were encoded, placed at eight spatial directions, and two eccentricities (2.5° and 5°) relative to a 12 Hz flicker stimulus. Whereas distinct SSVEP topographies were elicited when participants gazed at targets of different directions, targets of different eccentricities were mainly represented by different signal-to-noise ratios (SNRs). Using a canonical correlation analysis-based classification algorithm, simultaneous decoding of both direction and eccentricity information was achieved, with an offline 16-class accuracy of 66.8 ± 16.4% averaged over 12 participants and a best individual accuracy of 90.0%. Our results demonstrate a single-flicker BCI with a substantially increased target number towards practical applications. View Full-Text
Keywords: steady-state visual evoked potential; brain–computer interface; direction; eccentricity; canonical correlation analysis steady-state visual evoked potential; brain–computer interface; direction; eccentricity; canonical correlation analysis
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Chen, J.; Maye, A.; Engel, A.K.; Wang, Y.; Gao, X.; Zhang, D. Simultaneous Decoding of Eccentricity and Direction Information for a Single-Flicker SSVEP BCI. Electronics 2019, 8, 1554.

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