Evaluation of a Compact Hybrid Brain-Computer Interface System

Figure 2

Timing sequence diagram of a single trial for the Stroop word-picture matching test. The whole process was done twice consecutively for congruent and incongruent tasks, which comprised a single trial. “Congruent first-incongruent later” and “incongruent first-congruent later” tasks were randomly presented. At the task presentation, the left- or right-side picture was sequentially selected. The name of either picture was displayed for 2 s. At initial mental arithmetic (MA) problem presentation, an example of a three-digit number minus a one-digit number (6 to 9) was shown instead of the name for 2 s. In a task period starting with a short beep (250 ms) and black fixation cross, subjects performed MA or baseline (BL) task if the word and picture were matched (congruent) or mismatched (incongruent), respectively. After 10 s, a rest period started with a short beep (250 ms), and a large black fixation cross was displayed at the center of the screen.