title: Axonal remodeling in the corticospinal tract after stroke: how does rehabilitative training modulate it?
abstract: Stroke causes long-term disability, and rehabilitative training is commonly used to improve the consecutive functional recovery. Following brain damage, surviving neurons undergo morphological alterations to reconstruct the remaining neural network. In the motor system, such neural network remodeling is observed as a motor map reorganization. Because of its significant correlation with functional recovery, motor map reorganization has been regarded as a key phenomenon for functional recovery after stroke. Although the mechanism underlying motor map reorganization remains unclear, increasing evidence has shown a critical role for axonal remodeling in the corticospinal tract. In this study, we review previous studies investigating axonal remodeling in the corticospinal tract after stroke and discuss which mechanisms may underlie the stimulatory effect of rehabilitative training. Axonal remodeling in the corticospinal tract can be classified into three types based on the location and the original targets of corticospinal neurons, and it seems that all the surviving corticospinal neurons in both ipsilesional and contralesional hemisphere can participate in axonal remodeling and motor map reorganization. Through axonal remodeling, corticospinal neurons alter their output selectivity from a single to multiple areas to compensate for the lost function. The remodeling of the corticospinal axon is influenced by the extent of tissue destruction and promoted by various therapeutic interventions, including rehabilitative training. Although the precise molecular mechanism underlying rehabilitation-promoted axonal remodeling remains elusive, previous data suggest that rehabilitative training promotes axonal remodeling by upregulating growth-promoting and downregulating growth-inhibiting signals.
authors.affiliation: Second Department of Physiology, Kawasaki Medical School 577, Matsushima, Kurashiki City, Okayama, Japan.
authors.forename: Naohiko
authors.identifier: 0000-0002-7690-6947
authors.initials: N
authors.lastname: Okabe
authors.affiliation: Second Department of Physiology, Kawasaki Medical School 577, Matsushima, Kurashiki City, Okayama, Japan.
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Narita
authors.affiliation: Second Department of Physiology, Kawasaki Medical School 577, Matsushima, Kurashiki City, Okayama, Japan.
authors.forename: Osamu
authors.initials: O
authors.lastname: Miyamoto
keywords: axonal remodeling; corticospinal tract; functional compensation; growth inhibitory signal; growth promoting signal; motor map reorganization; motor system; neural activity; neurotrophic factor; rehabilitative training; stroke; task-specific training