Post-traumatic functional recovery and reorganization in animal models: a theoretical and methodological challenge.

Studies addressing cerebral functional localization face methodological and theoretical problems. Lesion experiments expect that when a functionally specialized structure is missing, its function can be deduced from the resulting impairments. Mostly, however, initial impairments are partially or fully eliminated through functional recovery. Apparently, such a recovery contradicts the notion of functional localization. In order to understand the mechanisms of recovery, improved methodology and a new theoretical framework are required. Insights into the mechanisms of recovery can be achieved by using "challenge" techniques, where functionally recovered individuals are exposed to organic and behavioral challenges, e.g. pharmacological manipulations or additional lesions, as well as modified test situations. Using such methods, a number of principles of functional recovery have emerged. We evaluate some of the available theories of post-traumatic recovery against these principles and find that none of them can account for the principles. Finally, we present a new conceptual framework - the Reorganization of Elementary Functions (REF) model. This model reconceptualizes the term "function", suggests mechanisms of post-traumatic reorganizations, and resolves the contradiction between localization and functional recovery.