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

BackgroundCompared to other components of social cognition, knowledge of social norms has received less attention, even more so in Alzheimers disease (AD). While semantic memory deficits have been identified early in the course of AD, no study has delved into the knowledge of social norms at these preliminary stages, although evidence suggests it shares common ground with semantic memory. In addition, it is unclear whether the knowledge of social norms in AD is associated socioemotional deficits, as seen in the behavioral variant of frontotemporal dementia (bvFTD). Finally, how social norms knowledge impairments predict behaviours in real-world settings remains unknown in the context of AD. MethodsThis study included 286 participants with mild cognitive impairment (MCI), 157 with AD, 285 with bvFTD along with 384 older healthy controls. All participants were selected from the National Alzheimers Coordinating Center. They completed the Social Norms Questionnaire, 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. ResultsBetween-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, and predicted insensitivity and disinhibition severity in patients. ConclusionsThis study suggests that declines in semantic memory likely play a key role in social norms knowledge decreases and that these decreases predict behavioural tendencies.