Article

The loss of independent joint control, clinically referred to as limb synergies,
is prevalent in the paretic upper limb of individuals with chronic hemiparetic
stroke. To understand the underlying neural mechanisms, we previously reported
that an increased overlap of cortical representations of shoulder/elbow could
contribute to the abnormal poststroke synergies. However, these previous results
were limited to a fixed time window just before the onset of motor tasks.
Questions such as (1) how this overlap develops during motor preparation and (2)
whether such development is also linked to upper limb synergies, remain unclear.
To answer these questions, we investigated cortical overlap during motor
preparation of isometric shoulder and elbow torque generation tasks in healthy
individuals (n = 8), and individuals with moderate to severe chronic hemiparesis
following a subcortical stroke (n = 12). We found a significant group difference
in how the cortical overlap developed. In the healthy control and moderately
impaired stroke groups, cortical overlap between shoulder and elbow motor tasks
decreased during the motor preparation; however, this overlap increased in
individuals with severe stroke. Furthermore, the rate of cortical overlap
decrease/increase was linked to the upper limb Fugl-Meyer scores and limb
synergies. These results demonstrate, for the first time, that the increase in
overlap of the cortical activity during motor preparation is associated with the
expression of synergies in the paretic upper limb of severely impaired poststroke
individuals.

Langue : ANGLAIS