[Minimal early childhood brain damage and the compensation capacity of the nervous system]

The concept of infantile cerebral lesion with later behavioral and learning disorders remains unclear and controversial, despite the voluminous literature on the subject. Neuropathologic data are lacking and the neurologic findings are often hard to interpret. Indirect access to this problem is provided by animal experiments in which the sequelae (neurologic and behavioral) of early and late, circumscribed cerebral lesions are compared. They have provided evidence that early--usually neonatal--lesions in particular areas of the central nervous system can be largely compensated. This may involve assumption of the function by the undamaged contralateral side, or sprouting of intact axons reinnervates denervated neurons. In this process, incorrect "switching" is not out of the question. Moreover, subcortical areas may retain their functions if cortical areas which normally take over their functions are damaged. Compensation following early lesions frequently produces intact, but biologically different, nervous systems. For this reason the behavior they generate may diverge from the norm. In many cases these deviations are apparent only in quite specific situations and otherwise remain latent.