Abstract
Background.
Severe poststroke arm impairment is associated with greater activation
of the nonlesioned hemisphere during movement of the affected arm. The
circumstances under which this activation may be adaptive or maladaptive
remain unclear.
Objective.
To identify the functional relevance
of key lesioned and nonlesioned hemisphere motor areas to reaching
performance in patients with mild versus severe arm impairment.
Methods.
A total of 20 participants with chronic stroke performed a reaching
response time task with their affected arm. During the reaction time
period, a transient magnetic stimulus was applied over the primary (M1)
or dorsal premotor cortex (PMd) of either hemisphere, and the effect of
the perturbation on movement time (MT) was calculated.
Results.
For perturbation of the nonlesioned hemisphere, there was a significant
interaction effect of Site of perturbation (PMd vs M1) by Group (mild vs
severe; P < .001). Perturbation of PMd had a greater effect
on MT in the severe versus the mild group. This effect was not observed
with perturbation of M1. For perturbation of the lesioned hemisphere,
there was a main effect of site of perturbation (P < .05), with perturbation of M1 having a greater effect on MT than PMd.
Conclusions.
These results demonstrate that, in the context of reaching movements,
the role of the nonlesioned hemisphere depends on both impairment
severity and the specific site that is targeted. A deeper understanding
of these individual-, task-, and site-specific factors is essential for
advancing the potential usefulness of neuromodulation to enhance
poststroke motor recovery.
No comments:
Post a Comment