Article

In healthy adults, hand movements are controlled largely by the contralateral primary motor cortex. Following amputation, however, movements of
the intact hand are accompanied by increased activity in the sensorimotor
cortices of both cerebral hemispheres. OBJECTIVE:
The authors tested whether use
of the intact hand reactivates the cortical territory formerly devoted to the now
missing hand and whether these effects can be augmented by motor imagery (MI)
and/or exposure to illusory visual "feedback" (VF) of the absent hand created
with a mirror. METHODS: Functional magnetic resonance imaging (fMRI) was used to
delineate the boundaries of normative sensorimotor hand representations in
healthy controls. Brain activity from 11 unilateral hand amputees was recorded
while they performed aurally paced thumb-finger sequencing movements with their
intact hands under 4 conditions: (1) motor execution of the intact hand alone
(ME), (2) ME with corresponding MI of the amputated hand, (3) ME with VF of the
amputated hand, and (4) ME with MI and VF. RESULTS: Intact hand movements
increased activity specifically within the former sensorimotor hand territory
during all conditions, an effect that may be attributable to decreased levels of
interhemispheric inhibition and/or use-dependent functional reorganization
following amputation.
This effect was not significantly increased by the addition
of VF and/or MI of the amputated hand. However, in amputees,
MI was associated
with an expansion of this ipsilateral response into parietal, premotor, and
presupplementary motor areas. CONCLUSION: Active engagement of the intact hand
may be critical for therapies seeking to stimulate the former hand territory.

Langue : ANGLAIS