| Accounting for phase drifts in SSVEP based BCIs by means of biphasic stimulation. | |
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MedLine Citation:
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PMID: 21193370 Owner: NLM Status: Publisher |
Abstract/OtherAbstract:
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This study proposes a novel biphasic stimulation technique to solve the issue of phase drifts in SSVEPs in phase-tagged systems. Phase calibration was embedded in stimulus sequences using a biphasic flicker, which is driven by a sequence with alternating reference and phase-shift states. Nine subjects were recruited to participate in offline and online tests. Signals were band-pass filtered and segmented by trigger signals into reference and phase-shift epochs. Frequency components of SSVEP in the reference and phase-shift epochs were extracted using the Fourier method with a 50% overlapped sliding-window. The real and imaginary parts of the SSVEP frequency components were organized into complex vectors in each epoch. The Hotelling's t square test was used to determine the significances of non-zero mean vectors. The rejection of noisy data segments and the validation of gaze detections were made based on p values. The phase difference between the valid mean vectors of reference and phase-shift epochs was used to identify user's gazed targets in this system. Data showed an average information transfer rate of 44.55 and 38.21 bits/min in offline and online tests, respectively. |
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Authors:
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H-Y Wu; P-L Lee; H-C Chang; J-C Hsieh |
Publication Detail:
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Type: JOURNAL ARTICLE Date: 2010-12-30 |
Journal Detail:
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Title: IEEE transactions on bio-medical engineering Volume: - ISSN: 1558-2531 ISO Abbreviation: - Publication Date: 2010 Dec |
Date Detail:
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Created Date: 2011-1-3 Completed Date: - Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 0012737 Medline TA: IEEE Trans Biomed Eng Country: - |
Other Details:
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Languages: ENG Pagination: - Citation Subset: - |
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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