Behavioral and anatomical effects of complex rearing after day 7 neonatal frontal lesions vary with sex

Rats received medial frontal lesions, or sham surgery, on postnatal day 7 (P7), and were placed in complex environments or standard lab housing at weaning. Three months later the animals were tested in a spatial learning task and in a skilled reaching task. Rats with P7 lesions had smaller deficits in spatial learning than similar adult operates, and males performed better than females. Complex housing further improved the performance of male, but not female, lesion rats. The opposite was seen in motor performance as female lesion rats performed better than males and benefited from experience whereas males did not. There was a correlation between behavior and dendritic change as complex housing reversed lesion-induced dendritic atrophy, an effect that was greater in males. P7 frontal males, but not females, showed an increase in spine density that was reversed by complex housing. Experience thus can affect functional and anatomical outcome after early brain injury, but the effects vary with sex.