Linking gray matter structure to trust in mild cognitive impairment: a voxel-based morphometry study

Older adults with mild cognitive impairment (MCI) exhibit a reduction in trust propensity (TP), which is correlated with heightened affective sensitivity to betrayal. However, the mediating role of this affective component in declining TP in MCI and the influence of structural brain alterations on reduced TP via affect warrant further investigation. We conducted multiple mediation analyses to assess whether differences in TP between MCI and normal healthy controls (NHCs) were mediated by affect, motivation, executive function, and social cognition. Whole-brain mediation analyses identified neural substrates and moderated mediation analyses examined whether structural brain changes influenced TP via affect differently between the two groups. Our results revealed a significant mediating effect of affect on the group difference in TP. Atrophy within the thalamus and anterior insula (AI) in the MCI group was found to contribute to their diminished TP. Furthermore, moderated mediation analysis showed that the influence of the thalamus and AI on TP was mediated by affect within the MCI group but not NHCs. These findings suggest that reduced TP in MCI is primarily driven by the increased sensitivity to betrayal, which is underpinned by structural alterations within salience network regions rather than alterations in other trust-related cognitive domains.