Possible anatomical basis of recovery of function after neonatal frontal lesions in rats.

Rats given medial frontal lesions on Postnatal Day 1 or Day 10 were trained on the Morris water task on Days 19-21 or Days 56-58. The operated groups were equally impaired at the water task on Days 19-21, but the Day 10 rats had recovered by 56 days. Dendritic arborization and spine density were analyzed in parietal layer II-III pyramidal cells. At Day 60, but not at Day 22, the Day 10 animals had more dendritic spines per unit dendritic length than did the controls or Day 1 rats. Thus, there was functional recovery rather than sparing after frontal lesions at 10 days, and the recovery was correlated with an increase in dendritic spines.