What is the typical latency of the P300 component in EEG-based BCIs?

• A. About 50 ms
• B. About 150 ms
• C. About 300 ms
• D. About 600 ms

Answer: (C)

The timing being tested is when the P300 ERP tends to peak after a stimulus. The P300 is a late positive potential that reflects the brain recognizing a target in an oddball-type task. It typically peaks around 300 milliseconds after the stimulus, which is the hallmark latency used in EEG-based BCIs like the P300 speller. There is some natural variability, often in the range of about 250–350 ms, and it can shift a bit with factors such as attention, stimulus modality, and task demands. This 300 ms timing distinguishes the P300 from earlier sensory components that occur closer to 100–200 ms and from much later potentials near 600 ms. So, the typical latency is about 300 milliseconds.