. Uncovering Neuroanatomical Networks Responsible for Abnormal Eating Behavior in Frontotemporal Dementia. JAMA Neurol. 2016 Mar 1;73(3):267-8. PubMed.

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  1. Although it has been recognized for some time that changes in eating behavior and food preferences are salient features of frontotemporal dementia and semantic dementia (indeed, this is included among the defining consensus criteria for behavioral variant frontotemporal dementia), the biology of these changes and the brain basis for them has not been well defined. The work of Ahmed and colleagues takes significant steps forward in studying the eating behaviors of FTD quantitatively under carefully controlled conditions with test meals (rather than simply by historical reports), in a well-characterized patient cohort, with detailed structural neuroanatomical (MRI) correlation. Their study design has allowed the authors to present one of the most comprehensive and neurobiologically relevant delineations to date of the brain networks that mediate abnormal eating behavior. These networks show some specificity for particular syndromes (behavioral variant frontotemporal dementia and semantic dementia), which may hold a clue to the clinical profiles these patients present. However, the networks implicated are very extensive, including areas involved in the sensory processing of food, associating it with biological and emotional meaning, monitoring internal homeostatic signals (such as hunger and satiety), and programming complex behavioral responses such as food-seeking. The work should provide a platform for a more systematic and physiologically informed study of these complex and highly clinically relevant behavioral changes.

    At the same time the work raises a number of further questions—such as, can even more biologically specific eating signatures be identified (for example, in association with particular genetic mutations), how early in the course do eating changes signal FTD, how do the structural brain changes relate to dynamic functional changes in brain networks, and can the latter be measured in a way that would allow us to assess the impact of interventions on underlying physiology and metabolism, while damage is still recoverable? Addressing these questions will require longitudinal study of larger (including genetic) FTD cohorts, ideally with task-based as well as task-free functional MRI so that we capture the brain at work. We will also need to remain alert to clinical observations made in individual patients.

    Some of the work from our group on this topic complements the work of Ahmed and colleagues. For example, we have shown that some patients with FTD lose the meaning of flavors and food more generally (Piwnica-Worms et al., 2010; Omar et al., 2013). Patients with Alzheimer's disease often seem to show reduced appetite and lose weight for reasons that are not clear, and we have recently seen two patients with semantic dementia who have food aversion rather than overeating. Observations like these will need to be reconciled with the data from Ahmed and colleagues if we are to arrive at a really comprehensive picture of eating behavior in different dementias.

    References:

    . Flavour processing in semantic dementia. Cortex. 2010 Jun;46(6):761-8. Epub 2009 Jul 14 PubMed.

    . Flavour identification in frontotemporal lobar degeneration. J Neurol Neurosurg Psychiatry. 2013 Jan;84(1):88-93. PubMed.

    View all comments by Jason Warren

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  1. Brain Imaging Gets the Scoop on Eating Disorders in FTD