Towards a domain-general mechanistic model of fatigue: application to Functional Neurological Disorder.

Fatigue is a central symptom in individuals with functional neurological disorder (FND), yet few studies have investigated fatigue in this population. While this may be surprising, given the importance of fatigue in FND, it is nevertheless understandable, given that fatigue has historically been difficult to study. However, the tools of cognitive neuroscience have allowed researchers to begin to understand fatigue as never before. Here, I review recent advances in the field of fatigue research, ranging from experimental design to objective and subjective measures of fatigue to a network of brain areas that has shown sensitivity to fatigue. Taken together, these metrics support the idea that fatigue is a signal the brain generates when the reward received no longer merits the effort required. I conclude by arguing that the application of this domain-general mechanistic model of fatigue, using objective and subjective dependent measures, is likely to provide important insights into the fatigue that is so pervasive in FND. This article is part of the discussion meeting issue 'Digital healthcare for the management of functional neurological disorders'.