The method was applied to simultaneous EEG-fMRI recordings from 13 healthy subjects (all right-handed males, age 19–26 years). The study was approved by the local Institutional Ethics Committee. All participants signed a written informed consent before the experiment. They performed a visual oddball task. The stimuli were yellow (frequent events, 80% presentation times) and blue disks (rare events, 20% presentation times), appearing on a black background with 200 ms duration, and randomly presented every 2500 ms. The acquisition lasted about 8 minutes, for a total of 154 frequent and 38 rare events.
