Motor imagery

Motor imagery is a mental process by which an individual rehearses or simulates a given action. It is widely used in sport training (AKA, Mental Practice of Action), neurological rehabilitation, and has also been employed as a research paradigm in cognitive neuroscience and cognitive psychology to investigate the content and the structure of covert processes (i.e., unconscious) that precede the execution of action.^{[1] [2]}

Definition

Motor imagery can be defined as a dynamic state during which an individual mentally simulates a given action. This type of phenomenal experience implies that the subject feels herself/himself performing the action.^[3] It corresponds to the so called internal imagery (or first person perspective) of sport psychologists.^[4]

Functional equivalence of motor preparation and motor imagery

Converging empirical evidence indicates a functional equivalence between action execution and motor imagery.

Motor imagery has been studied using the classical methods of introspection and mental chronometry. These methods have revealed that motor images retain many of the properties, in terms of temporal regularities, programming rules and biomechanical constraints, which are observed in the corresponding real action when it comes to execution. For instance, in an experiment participants were instructed to walk mentally through gates of a given apparent width positioned at different apparent distances. The gates were presented to the participants with a 3-D visual display (a virtual reality helmet) which involved no calibration with external cues and no possibility for the subject to refer to a known environment. Participants were asked to indicate the time they started walking and the time they passed through the gate. Mental walking time was found to increase with increasing gate distance and decreasing gate width. Thus, it took the participant longer to walk mentally through a narrow gate than to walk through a larger gate placed at the same distance.^{[5] [6]} This finding led neurophysiologists Marc Jeannerod and Jean Decety to propose that there is a similarity in mental states between action simulation and execution.^{[7] [8] [9]} The functional equivalence between action and imagination goes beyond motor movements. For instance similar cortical networks mediate music performance and music imagery in pianists.^[10]

Neurophysiological mechanisms

Activation in the motor cortex during motor imagery amounts about 30 % of the level observed during actual performance; Roth et al., 1996.

A large number of functional neuroimaging studies have demonstrated that motor imagery is associated with the specific activation of the neural circuits involved in the early stage of motor control (i.e., motor programming). This circuits includes the supplementary motor area, the primary motor cortex, the inferior parietal cortex, the basal ganglia, and the cerebellum.^{[11] [12]} Such physiological data gives strong support about common neural mechanisms of imagery and motor preparation.^[13]

Measurements of cardiac and respiratory activity during motor imagery and during actual motor performance revealed a covariation of heart rate and pulmonary ventilation with the degree of imagined effort.^{[14] [15] [16]} Motor imagery activates motor pathways. Muscular activity often increases with respect to rest, during motor imagery. When this is the case, EMG activity is limited to those muscles that participate in the simulated action and tends to be proportional to the amount of imagined effort.^[17]

The effects of motor imagery

Motor imagery is now widely used as a technique to enhance motor learning and to improve neurological rehabilitation in patients after stroke. Its effectiveness has been demonstrated in musicians.^[18]

• On motor learning: Motor imagery is an accepted procedure in the preparation of athletes. Such practice usually covers a warming up period, relaxation and concentration, and then mental simulation of the specific movement.^[19]

• In neurological rehabilitation: There is some evidence to suggest that motor imagery provides additional benefits to conventional physiotherapy or occupational therapy.^[20] However, a recent systematic review indicates that there is modest evidence supporting the additional benefit of motor imagery compared to only conventional physiotherapy in patients with stroke.^[21] These authors concluded that motor imagery appears to be an attractive treatment opinion, easy to learn and to apply and the intervention is neither physically exhausting nor harmful. Therefore, motor imagery may generate additional benefit for patients.

Simulation and understanding mental states

Motor imagery is close to the notion of simulation used in cognitive and social neuroscience to account for different processes. An individual who is engaging in simulation may replay her own past experience in order to extract from it pleasurable, motivational or strictly informational properties. Such a view was clearly described by the Swedish physiologist Hesslow.^[22] For this author, the simulation hypothesis states that thinking consists of simulated interaction with the environment, and rests on the following three core assumptions: (1) Simulation of actions: we can activate motor structures of the brain in a way that resembles activity during a normal action but does not cause any overt movement; (2) Simulation of perception: imagining perceiving something is essentially the same as actually perceiving it, only the perceptual activity is generated by the brain itself rather than by external stimuli; (3) Anticipation: there exist associative mechanisms that enable both behavioral and perceptual activity to elicit other perceptual activity in the sensory areas of the brain. Most importantly, a simulated action can elicit perceptual activity that resembles the activity that would have occurred if the action had actually been performed.

Mental simulation may also be a representational tool to understand the self and others. Philosophy of mind and developmental psychology also draw on simulation to explain our capacity to mentalize, i.e., to understand mental states (intentions, desires, feelings, and beliefs) of others (aka theory of mind). In this context, the basic idea of simulation is that the attributor attempts to mimic the mental activity of the target by using her own psychological resources.^[23] In order to understand the mental state of another when observing the other acting, the individual imagines herself/himself performing the same action, a covert simulation that does not lead to an overt behavior. One critical aspect of the simulation theory of mind is the idea that in trying to impute mental states to others, an attributor has to set aside her own current mental states, and substitutes those of the target.^[24]

Further readings

• Decety, J., & Stevens, J. (2009). Action representation and its role in social interaction. In K.D. Markman, W.M.P. Klein & J.A. Suhr (Eds.). The Handbook of Imagination and Mental Simulation. New York: Psychology Press.
• Decety, J., & Grezes, J. (2006). The power of simulation: Imagining one's own and other's behavior. Brain Research, 1079, 4-14.
• Jeannerod, M. (1997). The Cognitive Neuroscience of Action. Wiley-Blackwell.
• Morsella, E., Bargh, J.A., & Gollwitzer, P.M. (Eds.) (2009). Oxford Handbook of Human Action. New York: Oxford University Press.

See also

• Empathy
• Common coding theory
• Mental Practice of Action
• Motor cognition
• Sport psychology
• Theory of mind

References

1. ^ Decety, J., & Ingvar, D. H. (1990). Brain structures participating in mental simulation of motor behavior: A neuropsychological interpretation. Acta Psychologica, 73, 13-24.
2. ^ Decety, J., & Stevens, J. (2009). Action representation and its role in social interaction. In K.D. Markman, W.M.P. Klein & J.A. Suhr (Eds.), The Handbook of Imagination and Mental Simulation. New York: Psychology Press.
3. ^ Decety, J. (1996). Do executed and imagined movements share the same central structures? Cognitive Brain Research, 3, 87-93.
4. ^ Mahoney, M..J., & Avener, M. (1987). Psychology of the elite athlete. Cognitive Therapy Research, 1, 135-141.
5. ^ Decety, J., & Jeannerod, M. (1996). Fitts' law in mentally simulated movements. Behavioral Brain Research, 72, 127-134.
6. ^ Decety, J., Jeannerod, M., & Prablanc, C. (1989). The timing of mentally represented actions. Behavioural Brain Research, 34, 35-42.
7. ^ Decety, J., & Jeannerod, M. (1995). L’imagerie mentale et son substrat neurologique. Revue Neurologique, 151, 474-479.
8. ^ Jeannerod, M. (1994). The representing brain: Neural correlates of motor intention and imagery. Behavioral and Brain Sciences, 17, 187-245.
9. ^ Decety, J. (1996). Neural representations for action. Reviews in the Neurosciences, 7, 285-297.
10. ^ Meister, I.G., Krings, T., Foltys, H., Boroojerdi, B., Muller, M., Topper, R. R., & Thron, A. (2004). Playing piano in the mind - an fMRI study on music imagery and performance in pianists. Cognitive Brain Research, 19, 219-228.
11. ^ Decety, J., Perani, D., Jeannerod, M., Bettinardi, V., Tadary, B., Woods, R., et al. (1994). Mapping motor representations with PET. Nature, 371, 600-602.
12. ^ Roth, M., Decety, J. et al. (1996). Possible involvement of primary motor cortex in mentally simulated movement: A functional magnetic resonance imaging study. NeuroReport, 7, 1280-1284.
13. ^ Jeannerod, M. (2001). Neural simulation of action: A unifying mechanism for motor cognition. NeuroImage, 14, 103-109.
14. ^ Decety, J., Jeannerod, M., Durozard, D., & Baverel, G. (1993). Central activation of autonomic effectors during mental simulation of motor actions in man. Journal of Physiology, 461, 549-563.
15. ^ Wang, Y. & Morgan, W.P. (1992). The effect of imagery perspectives on the psychophysiological responses to imagined exercise. Behavioral Brain Research, 52, 167-174.
16. ^ Wuyam, B., Moosavi, S.H., Decety, J., Adams, L., Lansing, R.W., & Guz, A. (1995). Imagination of dynamic exercise produced ventilatory responses which were more apparent in competitive sportsmen, Journal of Physiology, 482, 713-724.
17. ^ Wehner, T., Vogt, S., & Stadler, M. (1984). Task-specific EMG characteristics during mental training. Psychological Research, 46, 389-401.
18. ^ Lotze, M., Scheler, G. et al. (2003). The musician's brain: functional imaging of amateurs and professionals during performance and imagery. Neuroimage, 20, 1817-1829.
19. ^ Suinn, R.M. (1984). Imagery and sports. In W.F. Straub and J,M, Williams (eds,). Cognitive Sport Psychology. Lansing, NY: Sport Science Associates.
20. ^ Jackson, P. et al. (2001). Potential role of mental practice using motor imagery in neurologic rehabilitation. Archives of Physical Medical Rehabilitation, 83, 1133-1141.
21. ^ Zimmermann-Schlatter, A. et al. (2008). Efficacy of motor imagery in post-stroke rehabilitation: a systematic review. Journal of Neuroengineering and Rehabilitation, 5,8.
22. ^ Hesslow, G. (2002). Conscious thought as simulation of behavior and perception. Trends in Cognitive Sciences, 6, 242-247.
23. ^ Goldman, A.I. (2002). Simulation theory and mental concepts. In J. Dokic & J. Proust (Eds.), Simulation and Knowledge of Action (pp. 1-19.).
24. ^ Goldman, A.I. (2005). Imitation, mind reading, and simulation. In S. Hurley & N. Chater (Eds.), Perspective on Imitation, from Neuroscience to Social Science, Volume 2 (pp. 79-93). Cambridge: MIT press.