Surmounting the ceiling effect of motor expertise by novel sensory experience with a hand exoskeleton

For trained individuals such as athletes and musicians, learning often plateaus after extensive training (i.e., “ceiling effect”). One bottleneck to overcome it is no prior physical experience of the skill to be learned. Here we challenge this issue through having expert pianists passively experience fast and complex finger movements that cannot be performed voluntarily, by using a novel hand exoskeleton-robot that can move individual fingers fast and independently. Although the skill plateaued through weeks of practice, passive exposure to otherwise impossible complex finger movements generated by the exoskeleton-robot at a speed faster than their fastest one enabled the pianists to play faster. Neither a training undergoing fast but simple finger movements nor one undergoing slow but complex movements enhanced the overtrained motor skill. Passive training with one hand also improved the motor skill of the untrained contra-lateral hand, demonstrating the inter-manual transfer effect. The training altered patterns of coordinated activities across multiple finger muscles during piano playing, but not in general motor and somatosensory functions nor in anatomical characteristics of the hand. Patterns of the multi-finger movements evoked by transcranial magnetic stimulation over the left motor cortex were also changed through passive exposure to fast and complex finger movements. The results demonstrate evidence that somatosensory exposure to an unexperienced motor skill allows for surmounting the ceiling effect in a task-specific but effector-independent manner.