The results of experiments with noninvasive monitoring techniques give us ideas about strategies used by the brain during recovery of function. They have their limitations, however, in that they do not allow us to work out underlying mechanism for such recovery. This can only be done by exact physiologic investigations, which can be performed most rigorously in monkeys or other animals. We hope that advances in comparative anatomy and physiology between different primates, including humans, will allow us to combine our knowledge about functional changes in the brain with more fundamental knowledge about their mechanisms. In the future this knowledge may indicate in which way such mechanisms can be modulated either pharmacologically or by physiotherapy to lead to a better outcome for patients.