The neuroimaging basis of apathy: Empirical findings and conceptual challenges.

Apathy, usually defined as loss of motivation, is common in both neurodegenerative conditions such as Alzheimer's disease, and acute neurological disorders such as stroke. Neuroradiological studies on the imaging correlates of apathy have used a variety of methods such as structural and functional magnetic resonance imaging, diffusion tensor imaging, and single photon and positron emission tomography to assess brain metabolic activity and specific synaptic receptors. Dysfunction of the anterior cingulate cortex (ACC) is the strongest anatomical correlate of apathy in Alzheimer's disease, whereas lesions of the basal ganglia are the most common correlates of apathy in cerebrovascular disorders. These findings should be considered in the context of important conceptual and empirical limitations. There are diverging definitions of apathy, and this behavioural disorder has not yet been validated in most neurological conditions. Moreover, apathy may be related not only to specific brain dysfunction, but to relevant contextual confounders which deserve further study.