Visual Evoked Potential

A visual evoked potential (VEP) is an electrical signal generated by the brain's visual cortex in response to a visual stimulus, typically a flash of light or a pattern change. VEPs are measured using electrodes placed over the occipital lobe and extracted from background EEG activity. The magnitude of the VEP is strongly dependent on the stimulus's distance from the center of vision, making it useful for determining gaze direction. In assistive technology, VEP-based interfaces allow users to make selections by fixating on flashing screen elements — the system detects which element the user is looking at by measuring the evoked response. VEP systems provide absolute gaze position information but are slower than EOG-based tracking, with typical selection rates around 1.2 seconds.