Affiliations: Psychology Department, The University of Texas,
Austin, TX, USA | Institute for Neuroscience, The University of Texas,
Austin, TX, USA
Note: [] Corresponding author: T.A. Jones, University of Texas,
Psychology and Neuroscience Institute, 1 University Station A8000, Austin, TX
78712, USA. Tel.: +1 512 475 7763; Fax: +1 512 475 7765; E-mail:
tj@psy.utexas.edu
Abstract: Purpose: Unilateral lesions of the sensorimotor cortex (SMC) in
adult rats cause major behavioral changes in the ipsilesional, "less-affected"
forelimb. An increase in function and reliance on this forelimb can aid
compensation for contralesional impairments, but may also promote disuse and
reduced functionality of the impaired forelimb. We hypothesized that training
focused on the ipsilesional forelimb following a unilateral SMC lesion would
reduce the efficacy of later motor rehabilitative training of the impaired
forelimb. Methods: Rats with ischemic SMC lesions were trained on a skilled
reaching task with the ipsilesional forelimb (PriorT) or received control
procedures (Cont) for 10 days. Both groups were then trained with the impaired
forelimb on the same reaching task for 10 days. Results: In comparison with Cont, PriorT rats had little improvement
on the reaching task with the impaired forelimb and had a more enduring disuse
of the impaired forelimb for postural support behaviors. Lesion sizes were
similar between groups. Conclusions: Behavioral experience with the less-affected forelimb
early after unilateral SMC lesions has the potential to increase disuse and
dysfunction of the impaired forelimb, consistent with a training-induced
exacerbation of learned non-use. These findings are suggestive of competitive
processes in experience-dependent neural restructuring after brain damage.
Keywords: Ischemia, caudal forelimb representation area, motor cortex, motor rehabilitation, skilled reaching, learned non-use
