Long Range Dependence in Human Sensorimotor Coordination

When humans coordinate their limb movements with a periodic stimulus train (e.g. a rhythmic metronome) by either tapping on the beat (synchronizing) or tapping off the beat (syncopating), their performance is variable and the inevitable timing error from each cycle constitutes a stochastic time series. The analysis of this time series is an important step toward understanding how the human brain controls rhythmic movement. Experimental psychologists have studied this simple task for nearly a century [1]. Early work focused on the mean and variance of the timing errors, but it did not study the possible sequential aspects of the cycle-to-cycle fluctuations. Subsequent researchers attempted to relate correlations among timing errors to the performance strategy [2]. The current prevailing model assumes that the human subject perceives the timing error and makes local corrective adjustments, resulting in short-range correlated timing errors [3],[4].