We study how the brain processes time in the range of the hundreds of milliseconds (millisecond timing). This timing range is involved in muscular coordination, speech perception and production, dance and music synchronization, working memory, etc. Our experimental paradigm is sensorimotor synchronization: the mostly specifically human ability to move in synchrony with an external periodic stimulus. The simplest task to study this behavior is paced finger tapping, that is tapping to a beat as in keeping pace with music. We perform experiments with perturbations, for example a tempo change, and record both behavior and central activity (EEG). We develop mathematical models to describe behavior in a unified way and make qualitative and quantitative predictions both at the behavioral and central processing levels.