Facial Emotion Recognition Deficits in Alzheimer's Disease Are Associated With Bilateral Uncinate Fasciculus...

Alzheimer's disease (AD) is associated with memory impairment and social cognitive dysfunction, including facial emotion recognition (FER) deficits. Our previous diffusion tensor imaging (DTI) study linked poor recognition of negative facial emotions in patients with AD to increased mean diffusivity (MD) in the left uncinate fasciculus (UF). Whether FER deficits in AD reflect microstructural alterations in related grey matter regions remains unclear.

In this cross-sectional study, 74 patients with AD and 28 cognitively normal (CN) subjects underwent behavioural assessments using the Facial Emotion Selection Test (FEST). A subset of 67 AD patients and 23 CN patients underwent magnetic resonance imaging. DTI was used to assess the fractional anisotropy (FA) and MD of the bilateral UF, and neurite orientation dispersion and density imaging (NODDI) was used to evaluate the neurite density index (NDI) and orientation dispersion index (ODI) of the insula, amygdala and temporal lobe.

Patients with AD showed significantly lower FEST total, negative emotion, positive emotion and neutral expression scores. DTI revealed significantly lower FA and higher MD in the bilateral UF. In the AD group, higher bilateral UF MD was significantly associated with lower total FEST and negative emotional scores. NODDI analyses demonstrated significantly lower ODI in the insula, amygdala and temporal lobe in the AD group, whereas no significant between-group differences were observed in the NDI. In the uncorrected analyses, ODI showed trend-level positive associations with FEST performance; however, these associations did not remain significant after false discovery rate correction. Bilateral UF MD was negatively correlated with ODI in the insula and temporal lobes.

FER is broadly impaired in AD and is associated with bilateral UF abnormalities and reduced ODI in the frontotemporal-limbic regions. These findings suggest that social cognitive dysfunction in AD involves broader frontotemporal-limbic network disruption than isolated white matter abnormalities.