Recovery from early cortical damage in rats, VIII. Earlier may be worse: behavioural dysfunction and abnormal cerebral morphogenesis following perinatal frontal cortical lesions in the rat.

The size of cortical removal was varied in rats that were given medial frontal lesions on postnatal day 2. In adulthood, the animals were trained on the Morris water task and Whishaw reaching task following which the brains were harvested and dendritic arborization and spine density was examined in the layer III pyramidal cells in Zilles' area Par1. There was a small relationship between lesion size and behavioral outcome as smaller lesions produced somewhat smaller deficits. In contrast, both small and large lesions produced large reductions in brain weight, dendritic arborization, and spine density. The cortex of newborn rats appears to be especially vulnerable to even restricted injury. This contrasts to the effects of similar injury a week later when animals show extensive functional recovery and anatomical compensation.