Deficits in the knowledge of social norms and their underlying mechanisms in Alzheimer's disease

Compared to other components of social cognition, knowledge of social norms has received less attention, even more in AD. While semantic memory deficits have been identified early in the AD disease course, no study has delved into the knowledge of social norms at these preliminary stages, although evidence suggests it shares common ground with semantic memory. Additionally, it is unclear whether the knowledge of social norms in AD is associated with deficits in social cognition, as seen in behavioral variant bvFTD. Finally, how social norms knowledge impairments predicts behaviours in real-world settings remains unknown in the context of AD. This study included 286 individuals suffering with MCI, 157 with AD, 285 with bvFTD along with 384 cognitively unimpaired older healthy controls (HC). Participants were selected from the National Alzheimers Coordinating Center. Participants completed the Social Norms Questionnaire (SNQ) which assesses the tendency to break or overadhere to social norms. They also completed tests assessing executive, semantic and socioemotional functions, along with tests measuring spontaneous interpersonal behaviours. Between-group comparisons show that individuals with AD and MCI break and overadhere to social norms significantly more than HC, while they perform better than individuals with bvFTD. Knowledge of social norms was mainly associated with semantic knowledge across groups (controlling for age, sex, education, and disease severity), and predicted insensitivity and disinhibition severity in patients. Altogether, this study extends findings of previous studies by focusing on social norms knowledge underlying mechanisms.