(University of Oxford, United Kingdom)
When the spark goes out. The neurology of apathy and motivation
Disorders of motivation are common across brain disorders. One extreme is the syndrome of pathological loss of motivation – apathy. Unfortunately, we understand very little about the mechanisms underlying this condition. In this talk, I’ll put forward a conceptual framework to understand apathy by considering the processes that normally underlie motivated, goal-directed behavior. In particular, I’ll focus on the ability to generate options for behavior and effort-based decision making for rewards. Several lines of evidence suggest that when we make decisions about how much effort we might invest to initiate actions, we weigh up the costs involved against the potential rewards to be obtained. Functional imaging in healthy people reveals both medial frontal and ventral striatal involvement when we make such decisions. In patients with apathy, this evaluation is altered. They show blunted sensitivity to rewards and less inclination to invest effort for low rewards. Both these factors can be improved by dopaminergic medication in some cases. These findings support the view that it is possible to provide a mechanistic account of apathy and also obtain better understanding of brain systems underpinning normal human motivation to generate actions.