What is learned in mental practice?

Content of research project: Mental practice designates the systematic and repetitive use of motor imagery (the imagination of movements without their actual execution) with the aim to improve performance. It is unclear, what aspects of a task are learned in mental practice and whether this is similar to physical practice. One way to investigate this is to test intermanual transfer, that is transfer of a skill learned with one hand to the other hand. An example of intermanual transfer is when one is used to changing gears with the right hand but then drives a British car in which one has to change gears with the left hand. Research question: It has been argued that movement representations are more flexible after mental practice than after physical practice. Does this result in more intermanual transfer after mental practice than after physical practice? Does this depend on how long the skill has been practiced? Is intermanual transfer easier when spatially same movements or when mirror movements are performed? Is intermanual transfer similar from the dominant to the non-dominant hand and the reverse? Does the focus during mental practice (primarily on vision or kinesthesis) have an influence on intermanual transfer? Is subthreshold muscle activity during mental practice related to intermanual transfer? Does intermanual transfer depend on the type of task? Methods: In several experiments, participants will either perform physical practice, mental practice, or control practice. In some experiments two different types of mental practice (visual and kinesthetic) will be performed. Practice will occur with either the dominant or nondominant hand. In all experiments, the first four sessions (three to four days apart) will start with transfer tests followed by practice. Session 5 (two weeks after Session 1) will include the usual tests and additional tests. To assess the stability of training effects participants will be tested again one month later. Different tasks will be used. Behavioural data (reaction times, movement times, and errors) and (subthreshold) muscle activity will be recorded. Scientific innovation: Mental practice is widely used in sports and has recently been applied to motor rehabilitation. However, little is known about the underlying processes of skill acquisition during mental practice and what exactly is learned. Results from this project will significantly enhance the understanding of mental practice and contribute to a solid theoretical and empirical basis for applications of mental practice.

Action imagery practice (AIP), also called mental practice, entails the systematic and repetitive use of the imagination of movements without their actual execution with the aim to improve performance. Major aims of the project were to investigate what kind of representations (i.e., internal codes of the external reality) are learned in AIP and action execution practice (AEP), the time course how different representations develop, whether practicing with the dominant or nondominant hand matters, and whether focusing on visual or kinesthetic aspects of a task matters. Several experiments were conducted to investigate those questions. In all experiments, AIP was effective for learning new tasks. Learning effects remained stable even after practiced had ceased, which was observed in follow-up tests, conducted about one month later. Though AIP was sometimes less effective than AEP, in most tasks similar representations were acquired in AIP and AEP and the times course of learning was similar. The type of acquired representations were however task-specific. Some subtle differences between AIP and AEP were observed. For instance, in one task, effector-independent visual-spatial representations (i.e., representation of a movement sequence in visual space) were acquired in both, AEP and AEP. However, effector-dependent representations (i.e., representation of the movement sequence entailing the effectors used during practice) were acquired only in AEP. These results indicate that in some tasks AIP may replace AEP to acquire effector-independent visual-spatial representations, but not to acquire effector-dependent representations. Representations acquired in AEP and AIP were not differently affected by the hand used for practice. When participants were instructed to attend to visual or kinesthetic aspects of the task, they adhered to instructions (i.e., they showed relatively more focus on the instructed modality), but still used both modalities. Similar representations were acquired under both modality instructions. Thus, task characteristics, not modality instructions, may determine to a large degree which representations are acquire. However, in one task, attention to visual aspects of the task in AIP resulted in effector effector-independent visual-spatial representations which were not observed in AEP. This finding represents may indicate that it may be of advantageous to perform visual AIP (for instance in addition to AEP) to promote the development of such representations in tasks in which they are not easily acquired. The results from the project deepen the understanding of the mechanisms underlying AIP. They are relevant for applications of AIP, which is used for instance in sports and rehabilitation (e.g., after stroke).