Electrophysiological analysis of motor cortical plasticity after cortical lesions in newborn rats.

Intracortical microstimulation of the motor cortex in normal adult rats evoked low threshold contralateral forelimb movements and high threshold ipsilateral movements. Ablation of the opposite sensorimotor cortex in adult animals did not alter these thresholds. However, stimulation of the unablated hemisphere in adult rats that sustained unilateral sensorimotor cortical lesions as neonates elicited low threshold ipsilateral forelimb movements that were similar to contralateral movements. These low threshold ipsilateral movements may be mediated via aberrant corticofugal pathways which are known to develop following neonatal cortical lesions.