The Interplay of Social Cognition Sub-domains in Frontotemporal Dementia

Changes in moral processing occur frequently in frontotemporal dementia (FTD) and represent one of several social cognitive domains that are affected in this population. Recently, Strikwerda-Brown et al. investigated moral reasoning in FTD using hypothetical scenarios consisting of moral dilemmas. To act on these, participants were presented a utilitarian action which they could either endorse or decline. Although the patients displayed normal probabilities of endorsing utilitarian actions, they felt less negative about their response, compared to controls. Interestingly, this group difference was specific for scenarios with a direct active involvement of the agent (‘personal’ dilemmas) and for which the proposed action contained a highly aversive emotional act (‘high-conflict’ dilemmas). The post-decision effect was associated with grey matter volume of the anterior temporal lobe (ATL), medial prefrontal cortex (mPFC) and insula (Ins). The blunted emotional response was associated with social conceptual knowledge and with the structural integrity of the uncinate fasciculus. Furthermore, the association between the emotional response and the structural integrity of the uncinate fasciculus was partially explained by social conceptual knowledge. The authors proposed that ‘knowledge of social norms, stored in the ATL, is conveyed to the mPFC where it is incorporated in the production of an emotional response to personal, highly conflictual moral dilemmas’. Two previous FTD studies used the same set of moral dilemmas. Chiong et al. reported an increased utilitarian response bias specifically towards personal dilemmas. They also used functional MRI and revealed that the causal influence from the salience network to the default mode network that they observed in healthy controls during moral reasoning, is significantly reduced in FTD. We also visually presented these dilemma’s verbally (18 non-moral, e.g. driving once or twice to bring home a number of plants; 11 impersonal, e.g. recommending an effective vaccine with a low probability of side-effects, 8 low-conflict, e.g. leaving an injured man by the side of the road to preserve leather upholstery of a car, and 13 high-conflict, e.g. smothering one’s child in order to save oneself and others) on a computer screen and asked participants to indicate by a button press whether they would endorse a proposed action or not. We observed that moral changes in FTD are associated with facial emotion recognition abilities and resting-state activity in the main afferent node of the salience network, i.e. the anterior insula. These findings support an interactive account among social-cognitive subdomains at the neural and psychological level. Here, we follow-up on the suggestions for future research by Strikwerda-Brown et al. and investigate the association of moral reasoning with other social cognition domains. Furthermore, we performed a functional validation test of their structural connectivity findings. We re-analysed our FTD dataset and focused on high-conflict dilemmas. Considering the modest sample size (controls: N1⁄4 19, 11 male; FTD: N1⁄4 12, 9 male), non-parametric testing was performed on the behavioural data. Between-group differences, within-group differences and associations were investigated by means of Mann–Whitney U tests, Wilcoxon Signed Rank tests and Spearman correlation coefficients, respectively. Voxel-wise whole-brain neuroimaging analyses