Motor imagery

Journal of Physiology - Paris 99 (2006) 386–395

doi:10.1016/j.jphysparis.2006.03.012

Martin Lotze a,*, Ulrike Halsband b
a Institute of Medical Psychology and Behavioral Neurobiology, Eberhard-Karls-University of Tu¨ bingen, Gartenstraße 29, D-72074 Tu¨ bingen, Germany
b Neuropsychology, Department of Psychology, University of Freiburg, Germany

Abstract
We describe general concepts about motor imagery and differences to motor execution. The problem of controlling what the subject actually does during imagery is emphasized. A major part of the chapter is dealing with mental training by imagery and the usage of motor imagination in athletes, musicians and during rehabilitation. Data of altered representations of the body after loss of afferent information and motor representation due to limb amputation or complete spinal cord injury are demonstrated and discussed. Finally we provide an outlook on additional work about motor imagery important for further understanding of the topic.

According to Jeannerod (1994, 1995) motor imagery
(MI) represents the result of conscious access to the content
of the intention of a movement, which is usually performed
unconsciously during movement preparation. He concluded
that conscious motor imagery and unconscious
motor preparation share common mechanisms and are
functionally equivalent. This may be the reason why mental
practice using MI training results in motor performance
improvements (review in athletes: Feltz and Landers,
1983).
Therefore a high overlap of active brain regions for
movement execution (ME) and imagery is not astonishing.
Interestingly, a clear image of an intended action can be
present even without the limb involved in movement execution
as it has been demonstrated in patients after traumatic
limb amputation (Schilder, 1935) or deafferentation of half
of the body after complete thoracic spinal cord injury (SCI,
Decety and Boisson, 1990).
In this chapter the recent literature on motor imagery is
reviewed. We describe results on imagery in patients with
cerebral, spinal and peripheral damage of the nervous system.
Furthermore, we will provide insight in recent results
about imagery training and relate knowledge of imagery to
other fields such as movement observation.
1.2. The relation between motor execution and imagination
James (1890) and Jacobsen (1930) described that the
mental image of a movement is always followed by discharges
of its target muscles. In order to discriminate
between movement execution and imagery these discharges
have to be avoided. Therefore, subjects are instructed not
to execute any movements of the target muscles and this
is controlled by electromyography (EMG) feedback. By
inhibiting the execution of a movement a conscious access
of motor preparation may be possible (Jeannerod, 1994).
Nevertheless, imagery training in athletes, musicians
and in stroke patients is usually associated with increased
EMG activation of the target muscles as compared to rest.
On the physiological basis an execution of a movement
and its imagery show several parallels.