Constructing the social world: impaired capacity for social simulation in dementia

Scene construction refers to the capacity to imagine richly detailed scenes in one's mind's eye and has been demonstrated to be compromised across a range of clinical disorders in which episodic memory processes are also affected. It remains unclear however, how task demands modulate the content of the to-be-simulated scenes. Here, we sought to investigate the capacity for social forms of scene construction in the behavioural-variant of frontotemporal dementia (bvFTD), a progressive neurodegenerative disorder characterised by pronounced social cognitive and executive dysfunction, alongside episodic memory impairments. Twenty bvFTD patients, 14 Alzheimer's disease (AD) patients, and 20 healthy controls completed a scene construction task involving imagining social (e.g., busy restaurant, crowded train), and non-social (e.g., forest, abandoned warehouse) scenes, as well as a comprehensive neuropsychological battery. Relative to Controls, patient groups provided significantly fewer contextual details during scene construction, irrespective of condition, with no difference between the patient groups. A significant group by condition interaction reflected the fact that bvFTD patients were disproportionately impaired on social relative to non-social scenes, whereas performance was comparable across conditions within Control and AD groups. Social construction impairments correlated with response inhibition and verbal episodic memory in bvFTD, with no such associations emerging in the AD group. A multiple regression confirmed that response inhibition and verbal episodic memory were significant predictors of social construction capacity, accounting for ~54% of the overall variance on the task. Our findings suggest that the capacity to simulate social scenes represents a special class of mental construction that relies upon a number of interacting cognitive processes, including aspects of executive function and episodic memory. How the process of social construction relates to acts of prosocial behaviour or empathy will be important for future studies to address.