Independence of amplitude-frequency and phase calibrations in an SSVEP-based BCI using stepping delay flickering sequences

Hsiang Chih Chang*, Po Lei Lee, Men Tzung Lo, I. Hui Lee, Ting Kuang Yeh, Chun Yen Chang

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)


This study proposes a steady-state visual evoked potential (SSVEP)-based brain-computer interface (BCI) independent of amplitude-frequency and phase calibrations. Six stepping delay flickering sequences (SDFSs) at 32-Hz flickering frequency were used to implement a six-command BCI system. EEG signals recorded from Oz position were first filtered within 29-35 Hz, segmented based on trigger events of SDFSs to obtain SDFS epochs, and then stored separately in epoch registers. An epoch-average process suppressed the inter-SDFS interference. For each detection point, the latest six SDFS epochs in each epoch register were averaged and the normalized power of averaged responses was calculated. The visual target that induced the maximum normalized power was identified as the visual target. Eight subjects were recruited in this study. All subjects were requested to produce the "563241" command sequence four times. The averaged accuracy, command transfer interval, and information transfer rate (mean ± std.) values for all eight subjects were 97.38 ± 5.97%, 3.56 ± 0.68 s, and 42.46 ± 11.17 bits/min, respectively. The proposed system requires no calibration in either the amplitude-frequency characteristic or the reference phase of SSVEP which may provide an efficient and reliable channel for the neuromuscular disabled to communicate with external environments.

Original languageEnglish
Article number6112237
Pages (from-to)305-312
Number of pages8
JournalIEEE Transactions on Neural Systems and Rehabilitation Engineering
Issue number3
Publication statusPublished - 2012


  • Brain-computer interface (BCI)
  • electroencephalography (EEG)
  • steady-state visual evoked potential (SSVEP)
  • stepping delay flickering sequence (SDFS)

ASJC Scopus subject areas

  • Internal Medicine
  • General Neuroscience
  • Biomedical Engineering


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