Effects of variable practice and declarative knowledge on sensorimotor adaptation to rotated visual feedback.

It has been shown before that sensorimotor adaptation to rotated vision is more generalized when subjects point at eight, rather than at four or less targets. Here we evaluate whether an even more variable practice has additional benefits. One group of subjects pointed at eight targets, and another group executed unconstrained arm movements throughout the workspace. We found no advantage of the latter group with respect to adaptive progress, persistence of adaptation without visual feedback, or transfer of adaptation to a new motor task. We therefore concluded that eight targets are sufficient to yield generalized adaptation. To determine the role of declarative knowledge for sensorimotor adaptation, subjects from both above groups were questioned regarding the nature of the distortion after they completed the experiment. We found that correct responders showed better adaptive progress, more persistence, but the same transfer as incorrect responders. We therefore concluded that the benefit of declarative knowledge is task-specific and short-lived, and is therefore probably related to strategic control rather than to an adaptive recalibration of the sensorimotor system.