Author:

Keywords:

Science & Technology, Technology, Life Sciences & Biomedicine, Engineering, Biomedical, Neurosciences, Engineering, Neurosciences & Neurology, VISUAL-EVOKED POTENTIALS, BCI, FREQUENCY, RESPONSES, SELECTION, SYSTEMS, Adult, Brain Mapping, Brain-Computer Interfaces, Event-Related Potentials, P300, Evoked Potentials, Visual, Female, Fuzzy Logic, Humans, Male, Pattern Recognition, Automated, Photic Stimulation, Reproducibility of Results, Sample Size, Sensitivity and Specificity, User-Computer Interface, 0903 Biomedical Engineering, 1103 Clinical Sciences, 1109 Neurosciences, Biomedical Engineering, 3209 Neurosciences, 4003 Biomedical engineering

Abstract:

OBJECTIVE: The performance and usability of brain-computer interfaces (BCIs) can be improved by new paradigms, stimulation methods, decoding strategies, sensor technology etc. In this study we introduce new stimulation and decoding methods for electroencephalogram (EEG)-based BCIs that have targets flickering at the same frequency but with different phases. APPROACH: The phase information is estimated from the EEG data, and used for target command decoding. All visual stimulation is done on a conventional (60-Hz) LCD screen. Instead of the 'on/off' visual stimulation, commonly used in phase-coded BCI, we propose one based on a sampled sinusoidal intensity profile. In order to fully exploit the circular nature of the evoked phase response, we introduce a filter feature selection procedure based on circular statistics and propose a fuzzy logic classifier designed to cope with circular information from multiple channels jointly. MAIN RESULTS: We show that the proposed visual stimulation enables us not only to encode more commands under the same conditions, but also to obtain EEG responses with a more stable phase. We also demonstrate that the proposed decoding approach outperforms existing ones, especially for the short time windows used. SIGNIFICANCE: The work presented here shows how to overcome some of the limitations of screen-based visual stimulation. The superiority of the proposed decoding approach demonstrates the importance of preserving the circularity of the data during the decoding stage.