IOP Journal of Neural Engineering Journal of Neural Engineering J. Neural Eng. J. Neural Eng. 15 (2018) 016002 (16pp) https://doi.org/10.1088/1741-2552/aa8235 15 Inferring imagined speech using EEG 2018 signals: a new approach using Riemannian © 2017 IOP Publishing Ltd manifold features JNEIEZ Chuong H Nguyen, George K Karavas and Panagiotis Artemiadis1 016002 School for Engineering of Matter, Transport and Energy, Arizona State University, Tempe, AZ 85287, United States of America C H Nguyen et al E-mail:
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[email protected] Received 25 March 2017, revised 22 July 2017 Inferring imagined speech using EEG signals: a new approach using Riemannian manifold features Accepted for publication 26 July 2017 Published 1 December 2017 Printed in the UK Abstract Objective. In this paper, we investigate the suitability of imagined speech for brain–computer JNE interface (BCI) applications. Approach. A novel method based on covariance matrix descriptors, which lie in Riemannian manifold, and the relevance vector machines classifer is proposed. The method is applied on electroencephalographic (EEG) signals and tested in 10.1088/1741-2552/aa8235 multiple subjects. Main results. The method is shown to outperform other approaches in the feld with respect to accuracy and robustness. The algorithm is validated on various categories of speech, such as imagined pronunciation of vowels, short words and long words. The Paper classifcation accuracy of our methodology is in all cases signifcantly above chance level, reaching a maximum of 70% for cases where we classify three words and 95% for cases of two 1741-2552 words.