Abstract
Motor imagery, that is the mental rehearsal of a motor skill, can lead to improvements when performing the same skill. Here we show a powerful and complementary role, in which motor imagery of different movements after actually performing a skill allows learning that is not possible without imagery. We leverage a well-studied motor learning task in which subjects reach in the presence of a dynamic (force-field) perturbation. When two opposing perturbations are presented alternately for the same physical movement, there is substantial interference, preventing any learning. However, when the same physical movement is associated with follow-through movements that differ for each perturbation, both skills can be learned. Here we show that when subjects perform the skill and only imagine the follow-through, substantial learning occurs. In contrast, without such motor imagery there was no learning. Therefore, motor imagery can have a profound effect on skill acquisition even when the imagery is not of the skill itself. Our results suggest that motor imagery may evoke different neural states for the same physical state, thereby enhancing learning.
Highlights
ResultsFive groups of participants performed a motor learning task. Participants grasped the handle of a robotic interface and made reaching movements from one of four starting locations through a perturbing force field to a central target (see Methods)
The ability to acquire new motor skills without disrupting existing ones is critical to the development of a broad motor repertoire
Our results suggest that motor imagery can have a profound effect on skill acquisition and the representation of motor memories, even when the imagery is not of the skill itself
Summary
Five groups of participants performed a motor learning task. Participants grasped the handle of a robotic interface and made reaching movements from one of four starting locations through a perturbing force field to a central target (see Methods). The first group of participants were required to make a second unperturbed follow through movement to the secondary target immediately after arriving at the central target (Fig. 1A, Follow through) This follow through movement was predictive of the field direction. To encourage the planning of the entire movement, this group (like all other groups) made full follow through movements on channel trials (Fig. 1B, left) Both these groups showed significant learning of the two force fields (adaptation increases of 42.9 ± 7.5%, t(7) = 5.92, p = 5.9e-4 and 41.9 ± 4.8%, t(7) = 9.87, p = 2.3e−5 for the follow though and planning groups, respectively), reaching approximately 40% of full compensation (Fig. 2A, blue and grey). Our results suggest that just imagining the follow through movement allows the separation of motor memories
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