Transcranial Magnetic Stimulation of the Lateral Cerebellum Enhances Prediction During Manual Tracking of a Moving Visual Target.

The present study examined whether the lateral cerebellum contributes to prediction of a sudden change in target movement direction during manual tracking of a moving visual target. A target circle, indicating the target force, moved horizontally from left to right at a constant velocity. Participants increased the right index finger flexion force to track the target movement with a force circle. The target circle then suddenly changed its movement direction, corresponding to the target peak force. In response to this direction change, participants changed the direction of force modulation from increasing to decreasing. Transcranial magnetic stimulation was delivered to the right lateral cerebellum 100, 200, 300, or 400 ms before the target peak force. The peak force was delayed relative to the target peak force due to central delays in processing visual information about target movement. As a result of this delay, the peak force overshot the target peak force. Both the overshoot of the peak force and the delay in peak force timing were reduced when transcranial magnetic stimulation was applied over the lateral cerebellum. In particular, stimulation delivered 300 or 400 ms before the target peak force decreased the force increase velocity immediately before the target peak force. These findings are most likely explained by enhanced online prediction of the timing of the target movement direction change induced by transcranial magnetic stimulation over the lateral cerebellum.