Abstract
Background.
Although the effect of rehabilitation is influenced by aspects of the
training protocol, such as initiation time and intensity of training, it
is unclear whether training protocol modifications affect the
corticospinal projections.
Objective. The present study was
designed to investigate how modification of initiation time
(time-dependency) and affected forelimb use (use-dependency) influence
the effects of rehabilitation on functional recovery and corticospinal
projections.
Methods. The time-dependency of rehabilitation was
investigated in rats forced to use their impaired forelimb immediately,
at 1 day, and 4 days after photothrombotic stroke. The use-dependency of
rehabilitation was investigated by comparing rats with affected
forelimb immobilization (forced nonuse), unaffected forelimb
immobilization (forced use), and a combination of forced use and skilled
forelimb training beginning at 4 days after stroke.
Results.
Although forced use beginning 1 day or 4 days after stroke caused
significant functional improvement, immediate forced limb use caused no
functional improvement. On the other hand, a combination of forced use
and skilled forelimb training boosted functional recovery in multiple
tasks compared to simple forced use treatment. Histological examination
showed that no treatment caused brain damage. However, a retrograde
tracer study revealed that immediate forced use and combination
training, including forced use and skilled forelimb training, increased
corticospinal projections from the contralesional and ipsilesional motor
cortex, respectively.
Conclusions. These results indicate that
although both very early initiation time and enhanced skilled forelimb
use increased corticospinal projections, premature initiation time
hampers the functional improvement induced by poststroke rehabilitation.
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