Article

The purpose of this study was to investigate the ways in which
stroke-induced posterior parietal cortex (PPC) lesions affect reactive postural
responses and whether providing auditory cues modulates these responses. DESIGN:
Seventeen hemiparetic patients after stroke, nine with PPC lesions (PPCLesion)
and eight with intact PPCs (PPCSpared), and nine age-matched healthy adults
completed a lateral-pull perturbation experiment under noncued and cued
conditions. The activation rates of the gluteus medius muscle ipsilateral (GMi)
and contralateral to the pull direction, the rates of occurrence of three types
of GM activation patterns, and the GMi contraction latency were investigated.
RESULTS: In noncued pulls toward the paretic side, of the three groups, the
PPCLesion group exhibited the lowest activation rate (56%) of the GMi (P < 0.05),
which is the primary postural muscle involved in this task, and the highest rate
of occurrence (33%) of the gluteus medius muscle contralateral-activation-only
pattern (P < 0.05), which is a compensatory activation pattern. In contrast, in
cued pulls toward the paretic side, the PPCLesion group was able to increase the
activation rate of the GMi to a level (81%) such that there became no significant
differences in activation rate of the GMi among the three groups (P > 0.05).
However, there were no significant differences in the GM activation patterns and
GMi contraction latency between the noncued and cued conditions for the PPCLesion
group (P > 0.05). CONCLUSIONS: The PPCLesion patients had greater deficits in
recruiting paretic muscles and were more likely to use the compensatory muscle
activation pattern for postural reactions than the PPCSpared patients, suggesting
that PPC is part of the neural circuitry involved in reactive postural control in
response to lateral perturbations. The auditory cueing used in this study,
however, did not significantly modify the muscle activation patterns in the
PPCLesion patients. More research is needed to explore the type and structure of
cueing that could effectively improve patterns and speed of postural responses in
these patients.

Langue : ANGLAIS