N200-speller using motion-onset visual response
Objective: This study presents a brain-computer interface (BCI) named N200-speller. A matrix of motion stimuli are displayed for inducing the motion-onset visual response that allows the subject to spell out a message by scalp EEG. Methods: The brief motion of chromatic visual objects embedded in a 36 virtual button onscreen interface is employed to evoke a motion-onset specific N200 component. The user focuses attention on the button labeled with the letter to be communicated and performs color recognition task. The computer determines the target letter by identifying the attended row and column respectively. A support vector machine (SVM) is used in the target detection procedures of the BCI system. Results: Ten subjects participated in this study. The neurophysiological characteristics of the N200-speller were compared with the classical P300-speller. The two paradigms elicit components with distinct spatio-temporal patterns. Classification of the data registered from all subjects reveals that the N200-speller achieves a comparable target detection accuracy with that of the P300-speller, given the same number of trials considered. Conclusions: With the advantages of low contrast and luminance tolerance, the proposed motion-onset stimulus presentation paradigm can be applied to brain-computer interface. Significance: A novel motion-onset paradigm N200-speller is proposed and assessed for BCI spelling application. © 2009 International Federation of Clinical Neurophysiology.