Prof.Dr.C.Dettmers

Kliniken Schmieder Konstanz, Konstanz, Germany; Faculty of Psychology, University Konstanz, Konstanz, Germany.

Mental training has been widely recommended for stroke rehabilitation (Sharma, Pomeroy, & Baron, 2006). The potential value of motor imagery is derived from musicians and particularly from the field of sports sciences. In these areas – when combined with physical practice – mental training has been shown to have an additional effect on skills, power and speed. Functional imaging studies confirmed the wide activation of the motor association cortex (particularly premotor and parietal cortex) during motor imagery and motor observation – almost as much as during motor execution (Nedelko et al., 2010). The discovery and wide spread discussion of a mirror neuron system encouraged the application of action observation and action imagery in neurorehabilitation. Beside its physiological arguments the method seems to have a particular – almost mysterious – attraction for scientists. May be they are hoping that the field of motor science turns out to be a cognitive field or cognition finally proves to be superior to the swamps of the motor system. In any event, some type of irrational attitude exists. Moreover, regarding the topic of mental training there is some secret attraction or it is becoming fashionable scientifically. Despite some pilot studies small randomized controlled trials and some reviews surprisingly a recent study did not find any effectiveness of motor imagery after stroke (three times a week, one hour, for six weeks) when it is performed in isolation, and not combined with physical training (Ietswaart et al., 2011).

Regarding mental training’s application in rehabilitation we wanted to know: Can stroke patients still imagine a movement, which they cannot execute (Dettmers, Benz, Liepert, & Rockstroh, 2012)? One difficulty approaching this topic is that imagery appears to be a complex, multidimensional cognitive process, which is not easy to define and identify by a single test. You might have to perform different tests (questionnaires concerning vividness of imagery, mental version of the Box&Block Test (Liepert, Greiner, Nedelko, & Dettmers, 2012)) to define the imagery capacity in an individual stroke patient. The study found out – which is not really surprising – that the impairment for imagery is very different in each patient – probably dependent on the size and location (and sensory impairment!) of the infarct.
On the one hand, a sub observation in this study was, that patients, who have been confined to a wheel chair due to muscular dystrophy for years, were not capable of imagining themselves performing knee bends. This observation confirms the tide coupling between imagery and reality: Motor imagery is not a process in fantasy, but motor experience shapes motor imagery.
On the other hand, motor imagery appears to be represented in both hemispheres and more often preserved or recovered (de, Tepper, Otten, & Mulder, 2011) than the motor executive system. This might explain its potential usefulness in neurorehabilitation.
Finally, motor imagery may be applicable in people experienced in imagery before stroke. It may be challenging for some patients and requests attention and cognitive capacity and also supervision through an experienced therapist.
Action observation (video training) may be an alternative form of mental training suitable for neurorehabilitation (Ertelt et al., 2007). It appears to be easier for patients to perform. Recently, we completed a monocentric, randomized study with two control groups, investigating the effect of home-based video training for six weeks, one hour daily (V. Nedelko, Dissertation, Faculty of Psychology, University Konstanz). Patients were highly satisfied with this method. Results clearly showed an advantage of the intervention group compared to the control group. A multicenter study has just recently begun (Ertelt, Hemmelmann, Dettmers, Ziegler, & Binkofski, 2012). Whether action imagery or action observation is more advantageous in stroke rehabilitation, is not yet settled. It appears that the challenge for the coming years is to identify the right patients at the right time in the right context to integrate action observation and imagery into existing procedures in stroke rehabilitation.

Reference List

de, V. S., Tepper, M., Otten, B., & Mulder, T. (2011). Recovery of motor imagery ability in stroke patients. Rehabil Res.Pract., 2011, 283840.
Dettmers, C., Benz, M., Liepert, J., & Rockstroh, B. (2012). Motor imagery in stroke patients, or plegic patients with spinal cord or peripheral diseases. Acta Neurol Scand., 126, 238-247.
Ertelt, D., Hemmelmann, C., Dettmers, C., Ziegler, A., & Binkofski, F. C. (2012). Observation and execution of upper-limb movements as a tool for rehabilitation of motor deficits in paretic stroke patients: protocol of a randomized clinical trial. BMC.Neurol, 12, 42.
Ertelt, D., Small, S., Solodkin, A., Dettmers, C., McNamara, A., Binkofski, F. et al. (2007). Action observation has a positive impact on rehabilitation of motor deficits after stroke. Neuroimage., 36 Suppl 2, T164-T173.
Ietswaart, M., Johnston, M., Dijkerman, H. C., Joice, S., Scott, C. L., MacWalter, R. S. et al. (2011). Mental practice with motor imagery in stroke recovery: randomized controlled trial of efficacy. Brain, 134, 1373-1386.
Liepert, J., Greiner, J., Nedelko, V., & Dettmers, C. (2012). Reduced Upper Limb Sensation Impairs Mental Chronometry for Motor Imagery After Stroke : Clinical and Electrophysiological Findings. Neurorehabil Neural Repair.
Nedelko, V., Hassa, T., Hamzei, F., Weiller, C., Binkofski, F., Schoenfeld, M. A. et al. (2010). Age-independent activation in areas of the mirror neuron system during action observation and action imagery. A fMRI study. Restor.Neurol.Neurosci., 28, 737-747.
Sharma, N., Pomeroy, V. M., & Baron, J. C. (2006). Motor imagery: a backdoor to the motor system after stroke? Stroke, 37, 1941-1952.