Objectives: Older adults presenting with mild cognitive impairment (MCI) have a higher risk of developing dementia and also demonstrate impairments in social cognition. This study sought to establish whether in people with MCI, poorer theory of mind (ToM) was associated with volumetric changes in the amygdala and hippocampus, as well as early changes in behaviour.
Methods: One hundred and fourteen people with MCI and fifty-two older adult controls completed the Reading the Mind in the Eyes Test (RMET), while close informants (e.g., spouse/family member/friend/carer) described any current behavioural changes using the Revised Cambridge Behavioural Inventory (CBI-R). A subsample of participants completed structural magnetic resonance imaging (MRI).
Results: The MCI group showed poorer performance on all neuropsychological tests administered, and moderate reductions on the RMET compared to the control group (d = .44), with greater reduction observed in those with amnestic compared to non-amnestic MCI (p = .03). While a robust correlation was identified between poorer RMET performance and smaller hippocampal volume in the control group (ρ = .53, p = .01), this relationship was not apparent in the MCI group (ρ = .21, p = .11). In the MCI group, poorer RMET performance was associated with poorer everyday skills (ρ = -.26, p = .01) assessed by the CBI-R.
Conclusions: Our findings cross-validate previous reports that social cognitive deficits in ToM are a feature of MCI and also suggest that disruptions to broader neural networks are likely to be implicated. Furthermore, ToM deficits in MCI are associated with a decline in everyday skills such as writing or paying bills.
Keywords: Amygdala; CBI-R; Hippocampus; Mild cognitive impairment (MCI); RMET; Social cognition; Theory of mind (ToM).