title: Square or sine: finding a waveform with high success rate of eliciting SSVEP.
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.
authors.affiliation: Department of Computer and Information Science, University of Mississippi, MS 38677, USA. feiyesdropship@yahoo.com.cn
authors.forename: Fei
authors.initials: F
authors.lastname: Teng
authors.forename: Yixin
authors.initials: Y
authors.lastname: Chen
authors.forename: Aik Min
authors.initials: AM
authors.lastname: Choong
authors.forename: Scott
authors.initials: S
authors.lastname: Gustafson
authors.forename: Christopher
authors.initials: C
authors.lastname: Reichley
authors.forename: Pamela
authors.initials: P
authors.lastname: Lawhead
authors.forename: Dwight
authors.initials: D
authors.lastname: Waddell
mesh_terms: D000465:Algorithms; D004569:Electroencephalography / Q000379:methods*; D004594:Electrophysiology / Q000379:methods; D005074:Evoked Potentials, Visual / Q000502:physiology*; D006801:Humans; D008959:Models, Neurological; D010775:Photic Stimulation / Q000379:methods*; D012815:Signal Processing, Computer-Assisted; D012984:Software; D014584:User-Computer Interface; D014793:Visual Cortex / Q000502:physiology; D014795:Visual Pathways / Q000502:physiology