The Mental Stage: Exploring the Cognitive and Neural Mechanisms of Envisaged Scenes and Social Perception in Neurodegenerative Disorders

Abstract

Imagination has long been proposed to serve an important evolutionary purpose in supporting human cognition. More recently, research investigating the cognitive and neural correlates pertaining to the capacity to envisage mental scenes has revealed extensive associations between mental imagery and a range of everyday cognitive processes. Exploring the role of mental imagery in relation to social cognition, however, is only now gaining momentum. This thesis expands current clinical and theoretical understanding of the cognitive architecture of mental simulation by examining task performance across two dementia syndromes: behavioural variant frontotemporal dementia (bvFTD) which presents as a profound change in personality and behaviour; and Alzheimer’s disease (AD), more commonly characterized by severe episodic memory deficits. Results arising from four separate studies demonstrate that the capacity for mental imagery is significantly disrupted across dementia syndromes, appearing to result from divergent cognitive and neural contributions. Importantly, discrete classes of mental simulation emerge, dependent on the sociality and congruency of the scene cues, resulting in disproportionately disrupted task performance largely in the bvFTD group. Specifically, social simulation was particularly impaired in bvFTD and significantly related to broader social perception, knowledge, and behavioural changes in this group. Interestingly, modifying the semantic loading of the scene task appears to increase the capacity for mental construction in bvFTD, at least in some respects. Identification of discrete classes of scene construction expands current conceptions of imagination and further elucidates the clinical profile of dementia syndromes. Furthermore, characterizing the potential cognitive underpinnings of social deficits in bvFTD paves the way for improved diagnosis and behavioural management.