Abnormalities in cortical and subcortical morphology after neonatal neocortical lesions in rats.

The brain weight, cortical thickness, cross-sectional areas of subcortical structures, and various retrograde changes were compared in rats with neonatal or adult ablation of all or part of the neocortex. Neonatal lesions produced a widespread reduction in brain size accompanied by a variety of major structural changes including modification of the thickness of the residual cortex, necrosis and calcification of subcortical structures, and gross distortion of the structure of the hippocampus. The modification of the cortical thickness, but not the other changes, depended on the site and extent of cortical removal: neonatal frontal cortex ablation reduced the thickness of the remaining neocortex, neonatal posterior cortex ablation had no significant effect upon the thickness of the remaining neocortex, and neonatal hemidecortication increased the thickness of the remaining neocortex.