Disentangling motor execution from motor imagery with the phantom limb.
Patients suffering phantom limb pain sometimes receive visual feedback training as therapy, often being asked to recreate a movement in their amputated limb. Many patients report that they are able to distinguish between imaginedmovement and executed movement (that does not occur due to missing limb.)
14 upper limb amputees’ baseline voluntary movement ability was tested in the amputated limb. Training was then given to practice imagining (i.e. no muscle contraction) as well as executing opening and closing each hand. The activity was repeated with participants in MRI scanner to monitor brain activity, while forearm or stump muscular activity was monitored to ensure contraction/ no contraction.
Although both executing and imagining showed signal changes in some common brain areas each was unique and could be clearly differentiated from the other. Further to this both phantom and intact hand imagination recruited brain areas typically recruited during motor imagery in healthy subjects.
This study provides the first physiological evidence that amputees perform two distinct tasks when executing and imagining a movement with their phantom limb. The authors suggest future studies investigating the efficacy of behavioral techniques for pain reduction also monitor executed motor tasks by using functional imaging. > From: Raffin et al., Brain 135 (2012) 582–595. All rights reserved to The Author.
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