Facilitation of motor skill learning by callosal denervation or forced forelimb use in adult rats.
Unilateral forelimb sensorimotor cortex lesions in adult rats produce a compensatory hyper-reliance on the forelimb ipsilateral to the lesion and temporally related glial and neural plasticity in the contralateral homotopic cortex. Recently, we found that these lesions enhance acquisition of a motor skills task with the ipsilateral, non-impaired, forelimb in comparison to shams. This effect might be related to a denervation-induced facilitation of neuroplastic changes in the motor cortex opposite the lesion and/or to the lesion-induced hyper-reliance on the non-impaired forelimb. The present study assessed whether increased forelimb use, denervation of motor cortical callosal afferents, or a combination of the two influences acquisition of a skilled reaching task. Adult rats with partial corpus callosum transections or sham procedures were either forced to rely on one forelimb or permitted normal forelimb use for 8 days. Rats were then trained for 14 days with their previously non-preferred forelimb (and the forced-use limb) on a unilateral pellet retrieval task. Compared to shams, transections produced a greater acquisition rate and asymptotic performance level on the task. Forced-use improved reaching performance relative to controls, but this effect was less enduring than the improvements produced by transections alone. The addition of forced-use to transections did not further enhance performance. These findings suggest that denervation-induced changes are likely to be a major contributor to the enhanced learning observed after unilateral sensorimotor cortex lesions.
Bury
Scott D
SD
Department of Psychology, University of Washington, Seattle, WA 98195, USA. sbury@uci.edu
Jones
Theresa A
TA
D000818:Animals; D003337:Corpus Callosum / Q000033:anatomy & histology / Q000502:physiology*; D003714:Denervation; D005552:Forelimb / Q000502:physiology*; D007839:Functional Laterality / Q000502:physiology; D007858:Learning / Q000502:physiology*; D008297:Male; D009044:Motor Cortex / Q000502:physiology; D009048:Motor Skills / Q000502:physiology*; D051381:Rats; D020318:Rats, Long-Evans; D013028:Space Perception / Q000502:physiology