Disturbance of Emotion Processing in Frontotemporal Dementia: A Synthesis of Cognitive and Neuroimaging Findings

Accurate processing of emotional information is a critical component of appropriate social interactions and interpersonal
relationships. Disturbance of emotion processing is present in frontotemporal dementia (FTD) and is a clinical feature in
two of the three subtypes: behavioural-variant FTD and semantic dementia. Emotion processing in progressive nonfluent aphasia,
the third FTD subtype, is thought to be mostly preserved, although current evidence is scant. This paper reviews the literature
on emotion recognition, reactivity and expression in FTD subtypes, although most studies focus on emotion recognition. The
relationship between patterns of emotion processing deficits and patterns of neural atrophy are considered, by integrating
evidence from recent neuroimaging studies. The review findings are discussed in the context of three contemporary theories
of emotion processing: the limbic system model, the right hemisphere model and a multimodal system of emotion. Results across
subtypes of FTD are most consistent with the multimodal system model, and support the presence of somewhat dissociable neural
correlates for basic emotions, with strongest evidence for the emotions anger and sadness. Poor emotion processing is evident
in all three subtypes, although deficits are more widespread than what would be predicted based on studies in healthy cohorts.
Studies that include behavioural and imaging data are limited. Future investigations combining these approaches will help
improve the understanding of the neural network underlying emotion processing. Presently, longitudinal investigations of emotion
processing in FTD are lacking, and studies investigating emotion processing over time are critical to understand the clinical
manifestations of disease progression in FTD.