Abstract
BackgroundSteady-state visually evoked potentials (SSVEPs) can be elicited by repetitive stimuli and extracted in the frequency domain with satisfied performance. However, the temporal information of such stimulus is often ignored. In this study, we utilized repetitive visual stimuli with missing events to present a novel hybrid BCI paradigm based on SSVEP and omitted stimulus potential (OSP).MethodsFour discs flickering from black to white with missing flickers served as visual stimulators to simultaneously elicit subject’s SSVEPs and OSPs. Key parameters in the new paradigm, including flicker frequency, optimal electrodes, missing flicker duration and intervals of missing events were qualitatively discussed with offline data. Two omitted flicker patterns including missing black/white disc were proposed and compared. Averaging times were optimized with Information Transfer Rate (ITR) in online experiments, where SSVEPs and OSPs were identified using Canonical Correlation Analysis in the frequency domain and Support Vector Machine (SVM)-Bayes fusion in the time domain, respectively.Results and conclusionsThe online accuracy and ITR (mean ± standard deviation) over nine healthy subjects were 79.29 ± 18.14 % and 19.45 ± 11.99 bits/min with missing black disc pattern, and 86.82 ± 12.91 % and 24.06 ± 10.95 bits/min with missing white disc pattern, respectively. The proposed BCI paradigm, for the first time, demonstrated that SSVEPs and OSPs can be simultaneously elicited in single visual stimulus pattern and recognized in real-time with satisfied performance. Besides the frequency features such as SSVEP elicited by repetitive stimuli, we found a new feature (OSP) in the time domain to design a novel hybrid BCI paradigm by adding missing events in repetitive stimuli.
Highlights
Steady-state visually evoked potentials (SSVEPs) can be elicited by repetitive stimuli and extracted in the frequency domain with satisfied performance
10 and 12 Hz were chosen because both SSVEP and omitted stimulus potential (OSP) features are prominent enough to be extracted in the time or frequency domain
As a preliminary study of hybrid Brain Computer Interface (BCI) paradigm based on SSVEP and OSP, one possible limitation is that we only present four visual stimulators on the screen, which limits the Information Transfer Rate (ITR) of the proposed BCI paradigm
Summary
Steady-state visually evoked potentials (SSVEPs) can be elicited by repetitive stimuli and extracted in the frequency domain with satisfied performance. We utilized repetitive visual stimuli with missing events to present a novel hybrid BCI paradigm based on SSVEP and omitted stimulus potential (OSP). Most studies developed P300-based BCI based on oddball paradigm [15,16,17,18,19,20,21,22,23,24] Classifiers such as linear discriminant analysis (LDA) [15,16,17], support vector machine (SVM) [18] and Bayesian fusion [19, 20] were proved to be efficient in P300 classification
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