Emotion perception in Behavior frontotemporal dementia and Alzheimer’s disease: the parahippocampal conundrum

Introduction: Emotional perception has been described as the capacity which enables humans to correctly identify cues that guide interpersonal interaction, forming the basis for social behavior. The parahippocampal cortex seems to be a key player in mediating the association between context and emotion, thus helping perceiving emotions in others. Behavioral Variant Frontotemporal Dementia (bvFTD) and Alzheimer’s Disease (AD) patients appear to exhibit deficits in this process. Studying how emotion perception is impaired in these patients may provide insights into social cognition mechanisms, emphasizing the parahippocampal role in social behavior. Methods: We have included convenience samples of 29 bvFTD, 25 AD and 15 controls. Extensive[IS1] [RM2] neuropsychological assessment was performed, complemented with the Comprehensive Affect Testing System (CATS) thus enabling a nuanced evaluation of emotion perception process. Multiple regression analysis was used to assess the relation between CATS main quotients scores and parahippocampal thickness (p £ 0,001). Results: BvFTD patients obtained higher scores in cognitive tests than AD but had a more severe deficit in social behavior. Interestingly, the bvFTD group revealed a significant deficit in all three emotional quotients (face, prosody and global) evaluated by the CATS battery, with a statistically significant relation with parahippocampal thickness. AD group displayed milder deficits in all three emotion quotients, although facial emotion recognition deficits were close to reaching statistical significance. Conclusion: Our data suggest a profound emotion perception deficit in bvFTD, supporting the pivotal role of the parahippocampal gyrus in context associations. Targeted rehabilitation with the objective of reducing these emotion deficits might be valuable.