Square or Sine: Finding a Waveform with High Success Rate of Eliciting SSVEP

Fei Teng,Scott Gustafson,Pamela Lawhead,Dwight Waddell,Aik Min Choong,Yixin Chen,Christopher Reichley

doi:10.1155/2011/364385

Fei Teng, Scott Gustafson + Show 5 more

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https://doi.org/10.1155/2011/364385

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Abstract

Steady state visual evoked potential (SSVEP) is the brain's natural electrical potential response for visual stimuli at specific frequencies. Using a visual stimulus flashing at some given frequency will entrain the SSVEP at the same frequency, thereby allowing determination of the subject's visual focus. The faster an SSVEP is identified, the higher information transmission rate the system achieves. Thus, an effective stimulus, defined as one with high success rate of eliciting SSVEP and high signal-noise ratio, is desired. Also, researchers observed that harmonic frequencies often appear in the SSVEP at a reduced magnitude. Are the harmonics in the SSVEP elicited by the fundamental stimulating frequency or by the artifacts of the stimuli? In this paper, we compare the SSVEP responses of three periodic stimuli: square wave (with different duty cycles), triangle wave, and sine wave to find an effective stimulus. We also demonstrate the connection between the strength of the harmonics in SSVEP and the type of stimulus.

Highlights

A brain-computer interface (BCI) translates brain activities into commands that control external devices
Three types of neuronal signals are most commonly used in EEG-based BCI systems: event-related potentials (ERP) [6, 8, 9], motor-imagery-related brain activity [10, 11], and steady state visual evoked potentials (SSVEP) [12,13,14,15,16,17,18,19,20]
System can correctly respond, a higher information throughput [28]. As it is currently unknown whether the choice of a square wave, triangle wave, or sine wave light signal affects the strength of the elicited SSVEP, these three waveforms were compared in Section 3 for their success rate in eliciting an SSVEP response

Summary

Introduction

A brain-computer interface (BCI) translates brain activities into commands that control external devices. The faster an SSVEP is identified, the faster a BCI system can correctly respond, a higher information throughput [28] As it is currently unknown whether the choice of a square wave, triangle wave, or sine wave light signal affects the strength of the elicited SSVEP, these three waveforms (square wave with different duty cycles) were compared in Section 3 for their success rate in eliciting an SSVEP response. We explore the SSVEP responses of three periodic stimuli: square waves with different duty cycles, triangle waves, and sine waves This group of waveforms provides us with the flexibility to adjust the strength of harmonics in a stimulus, allowing us to investigate the effects of artifact on SSVEPs. The remainder of the paper is organized as follows.

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