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Absence of impairments or recovery mediated by the uncrossed pyramidal tract in the rat versus enduring deficits produced by the crossed pyramidal tract.

Abstract：

:The pyramidal tract of the rat consists of at least two components. A majority of the fibers cross in the lower medulla and descend through the spinal cord in the ventral portion of the dorsal funiculus. The remaining 5% of the corticospinal projection does not cross and descends in the ipsilateral ventral funiculus into the cervical spinal region where its projections terminate in the internuncial portions of the spinal gray matter. The anatomical origin and terminal distribution of the ipsilateral component suggests that it may be involved in the control of the ipsilateral limb, but the possible contribution of the ipsilateral corticospinal tract has not been systematically examined. To determine whether the ipsilateral corticospinal tract makes a contribution to skilled movement, the corticospinal tract was severed unilaterally at the medullary level rostral to the decussation, thus severing both the crossed component of the tract as well as the ipsilateral component. Performance of the ipsilateral and the contralateral limbs of rats were then evaluated on tests of limb posture, preference, placing, and use in two skilled reaching tasks. No impairments on any quantitative or qualitative measure of performance were detected in the use of the limb ipsilateral to the lesion but severe, enduring impairments on all qualitative and quantitative measures were obtained in use of the limb contralateral to the lesion. Thus, the study finds: (1) no evidence that the ipsilateral portion of the corticospinal tract makes a contribution to skilled movement of the kind made by the contralateral portion of the corticospinal tract, and (2) no evidence that the remaining uncrossed portion of the tract contributes to recovery of symptoms produced by severing the crossed portion of the tract.

journal_name

Behav Brain Res

journal_title

Behavioural brain research

authors

Whishaw IQ,Metz GA

doi

10.1016/s0166-4328(02)00051-7

subject

Has Abstract

pub_date

2002-08-21 00:00:00

pages

323-36

issue

1-2

eissn

0166-4328

issn

1872-7549

pii

S0166432802000517

journal_volume

134

pub_type

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Absence of impairments or recovery mediated by the uncrossed pyramidal tract in the rat versus enduring deficits produced by the crossed pyramidal tract.