Editors' ChoiceNeurodegenerative Disease

A change of heart: Altered cardiac reactivity in frontotemporal dementia

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Science Translational Medicine  16 May 2018:
Vol. 10, Issue 441, eaat8531
DOI: 10.1126/scitranslmed.aat8531

Abstract

Cardiac response to emotional stimuli differs by frontotemporal dementia subtype.

The term frontotemporal dementia (FTD) refers to a group of neurodegenerative conditions characterized by progressive atrophy of the brain's frontal or temporal lobes. In affected individuals, these anatomic features are associated with changes in personality and behavior, including disregard for social conventions and loss of empathy. Progressive deterioration of language and motor function may also occur. Since FTD presents heterogeneous symptomatology, affected individuals are classified into subtypes based upon predominant clinical features. Neuropsychiatric testing can help diagnose and characterize FTD; however, the behavioral and language deficits may make such testing challenging to perform and difficult to interpret.

Marshall et al.’s study investigates the autonomic and anatomic correlates of emotional responsiveness in individuals with defined FTD subtypes compared with healthy controls. Participants watched videos of emotional facial expressions while an electrocardiogram (ECG) monitored their cardiac electrical activity. The authors also used magnetic resonance imaging to quantify gray matter volume loss in prespecified regions known to regulate autonomic function. All individuals with FTD demonstrated deficits in naming emotions, but only two of four FTD subtypes also exhibited reduced cardiac reactivity. Reduced physiologic cardiac response to emotion was present in patients with atrophy of the frontoinsular region of the brain, part of a network implicated in central autonomic control, leading the authors to posit a reciprocity between physiologic response to emotion and perceived emotional state.

As a proof-of-principle study, the authors’ goal was to show that cardiac reactivity, a marker for autonomic health, differed across FTD subtypes. However, although mean cardiac reactivity scores were statistically different, the range of individual scores overlapped substantially. Moreover, cardiac reactivity was assessed only in response to facial expressions. Whether observed differences were specific to emotions or part of a global autonomic dysfunction remains to be evaluated. Despite the inherent limitations of the study, cardiac reactivity shows promise as a noninvasive adjunct to current diagnostic strategies for FTD—a condition that, because of its cognitive and psychological effects, is notoriously difficult to evaluate. Beyond this, Marshall et al.’s work reinforces the complex interplay between the cognitive and physical experience of emotion, as well as the importance and vulnerability of the connections between brain and heart.

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