The AR Workbench: A Complete Co-located Reach-in Mirror-Based ...

Marlon Richert, Master’s Thesis, Friday, 23 February, 2007
that subjects generate, the more effective their mental practice is [33]. Apparently,
access to motor imagery that is more intensive leads to bigger improvements in
motor skill learning. Therefore, to maximize the effectiveness of mental practice, it
clearly is important to stimulate the use of intensive motor imagery as much as
possible [20]. The reported vividness of motor imagery, however, does not appear
to correlate with the effectiveness of mental practice. Vividness is very important for
visual imagery, but not for motor imagery, for which being able to control what you
are imagining is much more important.
2.2.3 Post-Stroke Rehabilitation
Post-stroke rehabilitation involves helping patients relearn skills they lost due to
stroke. Well-focused, repetitive practice is the most important ingredient for poststroke
rehabilitation, experts agree [26]. Since many post-stroke patients are
hemiplegic, initial treatment immediately focuses on promoting independent
movement using passive or active practice. The difference between these two types
of practice is that in passive practice the therapist actively assists the patient in
moving impaired limbs in nonspecific ways, while in active practice the patient
performs task-specific activities without receiving any physical help. Post-stroke
rehabilitation generally focuses on goal-directed tasks, since they promote
coordination.
Traditionally, post-stroke rehabilitation has used repeated physical practice,
consisting mostly of compensatory training of the healthy arm and passive practice
of the disabled arm to improving motor activity and stimulate brain plasticity [26]. A
problem with this approach is that its effectiveness depends on the performance of
the disabled limb [37]. In addition, since spontaneous recovery from stroke shows a
plateau after three months, traditional stroke rehabilitation only focuses on those
first three months [40].
Using active practice through forced use of the impaired arm, researchers have
demonstrated that stroke patients can achieve functional gains and brain plasticity
long after the three-month spontaneous recovery period [1]. Through the forced use
of the affected arm, patients can significantly increase the functional ability and daily
use of their weakened arm [40]. Auditory cueing can further enhance active
practice, allowing forced-use task-oriented repetitive training to treat successfully
much more severe cases of stroke than would otherwise be possible [38].
Mental practice is a form of active practice that is a cost-efficient and effective
means of assisting motor recovery in stroke patients [17]. Indeed, mentally
practicing a motor skill can result in the same kind of brain plasticity that would
occur because of physically acquiring the skill [10, 13, 20, 42]. To stimulate the
production of motor imagery involving the disabled limb in patients with UEH,
therapists can use either video or a mirror box [37]. In the first case, patients watch
a computer-generated movie showing a moving arm from varying angles and at
varying speeds, after which they immediately have to perform the same movement
mentally. When they have completed the imagined movement, they have to tap the
space bar, enabling the therapist to obtain the time used to complete each
movement. In the second case, patients sit at a table with a vertical mirror
positioned in front of them in such a way that the reflection of the healthy arm
visually replaces the disabled arm. The therapist instructs the patients to imagine
that the reflection is in fact their disabled limb, moving around freely. Patients spent
the first week learning to do this, after which they have to perform relatively simple
exercises in the next two weeks, and complex maneuvers in the final week. At the
end of the four weeks, patients will have made significant improvements in both
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