"Motor Imagery", Journal of Physiology - Paris (2006) by Martin Lotze and Ulrike Halsband
Part 2 'Training motor skill with imagery' (pp 389-393)
The article begins with a quote from an article by Jackson et al. (2001) that is too good for me to summarize. So I shall quote it in its entirety right here:
... contrary to the conditions in which a motor task can be learned implicitly with physical practice, mental practice with mental imagery requires that subjects have all the necessary declarative knowledge about the different components o the task before practicing. However, as with physical practice, the rehearsing of the task with mental imagery can also give access to the non-conscious processes involved in learning the skilled behaviour ...
... internally driven images which promote the kinesthetical [sic] feeling of movements would best activate the different non-conscious processes involved during motor task training.
It seems that only highly specialized, professional athletes and musicians use motor imagery techniques in their training, implying that only those with a high level of execution training can use the imagery techniques effectively.
Obviously motor imagery training does not lead to increased muscle mass, but increased strength in isometric movements is observed, as well as dynamic motor performance (e.g. movement trajectories) improvements.
The article breaks down motor imagery training effects on three separate groups: athletes, musicians and patients. For obvious reasons, I shall focus on the section concerning musicians.
Motor Imagery Training in Musicians
Langheim et al. (2002) report no cerebral activations in the primary motor cortex during kinesthetic motor imagery of simple movements, but report an "activated network of lateral cerebellar, superior parietal and superior frontal activation", leading to the conclusion that "this network is likely to coordinate the complex spatial and timing components of musical performance". The authors of the article hypothesize that with increasing experience in motor imagery, activation sites may move from the motor-centered internal representation areas of the brain to the more abstract areas.
Pascual-Leone et al. (1995) report that a study of five days of training performers using both motor imagery and movement execution results in the performers who use movement execution to train achieve a greater increase in performance than those who use motor imagery. Except (and here's the interesting part) those trained using motor imagery showed the same increase in performance level as those using movement execution to train when the motor imagery group trained for one extra session. Obviously, this points to the importance of combining motor imagery training with movement execution training for optimal performance results.
A study comparing fMRI-activation maps of professional violinists to those of amateurs during imagined performances of a piece shows the professionals with lower activations and the amateurs with widely distributed activations, regardless of the amateurs scoring the vividness of their imagined movement lower. It's possible this indicates a more efficient retrieval of sensorimotor information by the professionals, as well as a more efficient shaping of the timed motor responses.
Another fairly dense article that answers a few questions but really just serves to show how much more room there is for research on this topic. Until technology exists to monitor brains during actual performance (like, with an audience and everything!), any claim of improvement in performance is not necessarily realistic. Performance in an examination room is missing the very elements that make a performer less likely to perform well (and, it could be argued, those that make a performer more likely to give an excellent performance). Regardless, it seems that there is definitely a place for motor imagery in the practice routine of the professional musician.
by Shannon Coates