Knowledge of Performance is Insufficient for Implicit Visuomotor Rotation Adaptation

ABSTRACT

The ability to adapt is a fundamental and vital characteristic of the motor system. The authors altered the visual environment and focused on the ability of humans to adapt to a rotated environment in a reaching task, in the absence of continuous visual information about their hand location. Subjects could not see their arm but were provided with post trial knowledge of performance depicting hand path from movement onset to final position. Subjects failed to adapt under these conditions. The authors sought to find out whether the lack of adaptation is related to the number of target directions presented in the task, and planned 2 protocols in which subjects were gradually exposed to 22.5° visuomotor rotation. These protocols differed only in the number of target directions: 8 and 4 targets. The authors found that subjects had difficulty adapting without the existence of continuous visual feedback of their performance regardless of the number of targets presented in task. In the 4-target protocol, some of the subjects noticed the rotation and explicitly aimed to the correct direction. The results suggest that real-time feedback is required for motor adaptation to visual rotation during reaching movements.

Keywords:

• knowledge of performance
• motor learning
• reaching movements
• visuomotor rotation adaptation
• visual feedback

ACKNOWLEDGMENTS

The authors wish to thank Pierre Baraduc for useful discussions about early protocols in which we observed the first evidence for lack of adaptation without continuous feedback. This study was supported by the Ministry of Science, Culture and Sport, Israel; the United States–Israel Bi-National Science Foundation (BSF), Jerusalem, Israel; and the Israel Science Foundation (ISF, grant No. 1018/08).