Brain optimization, compensation and plasticity

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Damage to the adult brain usually has permanent behavioural and anatomical consequences. A major effect of brain damage is to cause loss of movement capacity. Most individuals, over time, develop compensatory movement strategies that substitute for lost motor capacity. Compensatory strategies are clearly recognizable and distinguishable from original movements. My work has shown that most recovery after brain injury represents compensation of the lost motor function rather than restoration of original movements. Therefore, I propose the brain optimization theory stating that the adult brain functions at the best possible level, and that any form of injury permanently disrupts its original function. Thus, lost function is replaced by alternative, compensatory movement strategies over time. My research is directed toward identifying compensatory strategies and associated plasticity by using skilled movement analysis. In the proposed research, I will use laboratory rats to (1) characterize compensatory strategies used to overcome primary motor disability after injury, (2) quantify compensatory adjustments made by distal and proximal body parts, (3) determine the neural basis of compensation of motor function. The model will then be used to describe (1) how compensatory strategies change with different kinds of injury, (2) how experience can facilitate compensation or genuine restoration, (3) how physiological influences affect compensation. I will also pursue comparative analysis of compensatory behaviour in rats and human subjects. The overall hypothesis of this research is that, unless the lost tissue is replaced, compensatory strategies mediate recovery of function. These studies will elucidate mechanisms of how the brain and behaviour change in response to injury. Because compensation may be mediated by the same neural mechanisms as those that contribute to behavioural development and healthy aging, an understanding of compensation can lead to insights into nervous system function more generally.