Tactile stimulation after frontal or parietal cortical injury in infant rats facilitates functional recovery and produces synaptic changes in adjacent cortex

Rats with bilateral lesions (and sham controls) of the medial frontal or posterior parietal cortex on postnatal days 2-4 were treated with tactile stimulation for 15 min three times daily for two weeks following injury. In adulthood they were trained in a spatial navigation task and a skilled reaching task, their brains were removed, and dendritic length and spine density were analyzed in layer III pyramidal neurons in area Par 1. Tactile stimulation significantly reduced the behavioral impairments after early cortical injury. Neonatal lesions decreased dendritic length and this was reversed by stimulation in rats with parietal, but not frontal, lesions. Both lesions decreased spine density and tactile stimulation reversed this loss in frontal but not parietal lesion animals. In addition, tactile stimulation decreased spine density in control animals. The results suggest that early intervention with tactile stimulation after cortical injury may be important for stimulating plastic changes in the cortex that can underlie functional recovery and that different mechanisms of synaptic change may occur after different injuries. (C) 2010 Elsevier B.V. All rights reserved.