Effort avoidance as a core mechanism of apathy in frontotemporal dementia.

Apathy is a core symptom in patients with behavioural variant frontotemporal dementia (bvFTD). It is defined by the observable reduction in goal-directed behaviour, but the underlying mechanisms are poorly understood. According to decision theory, engagement in goal-directed behaviour depends on a cost-benefit optimization trading off the estimated effort (related to the behaviour) against the expected reward (related to the goal).