Anticipation and motor control on repetitive tooth tapping produced by open-close jaw movements

This study was designed to evaluate the relationship between the temporal anticipation effects and motor control on repetitive tooth tapping movements (tooth tapping produced by open-close jaw movements) commanded by six frequencies of acoustic signals. Ten dentulous young adults were asked to perform tooth tapping movements to acoustic command signals at constant frequencies of 0.3, 0.8, 1.3, 1.8, 2.3 and 2.8 Hz. Surface electromyograms of the Masseter muscles, vertical component of the Mandibular kinesiograph, and acoustic signals were simultaneously recorded. Some parameters were measured for tappings at the last signal (TL) and surplus tappings without signals after the last signal (TL(n)) in each frequency command signal. The results showed that changes in the strategy for tapping movement controls occurred between 0.3 and 0.8 Hz. Between 0.8 and 2.8 Hz, each tooth tapping was automatically initiated before the confirmation of the signal; initiation and control of repetitive tapping movements were apparently based on effector anticipation (predicting the duration of internal processes for a planned movement so that it can be made coincidental to some anticipated external event) and receptor anticipation (anticipation of the arrival of a stimulus due to sensory information about its time of arrival). However, at 0.3 Hz, the movement initiation was delayed, such that each tooth tapping was initiated after the confirmation of the signal. Therefore, tappings at 0.3 Hz showed less dependence on receptor anticipation. These changes in motor control strategy are considered to be a reasonable way to prevent incorrect movements and to minimize erroneous movements.