Subjects control the position of one or two cursors on a screen using one or two fingers. They perform tracking or pointing tasks according to what they see on the screen. During the single-task experiment only one task is presented on the screen. During the dual-task experiment, two tasks are presented on the screen. Subjects perform either the single-task or dual-task experiment, but not both. The fMRI lasts about 90 minutes, with subjects asked to lie still during the scan for up to 9 minutes at a time.