Optimized inter-stimulus interval (ISI) and content design for evoking better visual evoked potential (VEP) in brain-computer interface applications

Brain-computer interfaces have been adopting visual evoked potential (VEP) signals to evaluate real-time cognitive responses, which have been shown to differ depending on the system's panel design and inter-stimulus interval (ISI). The objective of this study was to determine the optimal ISI and display contents for improved VEP signals. The panel contents consisted of six Korean texts or symbols from a television remote controller, and three levels of ISI were used. Subjects concentrated on a target stimulus while the panel randomly flashed different texts or symbols. Six local areas were measured by electroencephalogram based on the Extended International 10-20 system. P3 and N1 amplitudes and latencies were analyzed to determine the optimal combination of panel contents and ISI. Text-based panels were found to produce superior P3 and N1 responses compared with symbol-based panels. The ISI of 300 ms induced the best ERP responses for both text and symbol panels.