Emotional Dysregulation in Mild Behavioral Impairment Is Associated with Reduced Cortical Thickness in the Right Supramarginal Gyrus

Background: Mild behavioral impairment (MBI) has attracted attention as a possible precursor symptom of dementia, but its neural basis has not been fully investigated. Objective: We aimed to investigate the relationship between MBI and surface area, cortical thickness, and volume in the temporal and parietal lobes, which are strongly associated with dementia and emotional disorders. Methods: This retrospective study evaluated 123 participants: 90 with mild cognitive impairment (MCI), 13 with subjective cognitive decline (SCD), and 20 cognitively healthy (CH). Using analysis of covariance (ANCOVA) with sex, age, and MMSE score as covariates, cortical thickness, surface area, and volume in 10 regions were compared between groups with and without MBI. Groups with MBI emotional dysregulation were also compared with groups without MBI. Results: ANCOVA revealed significantly smaller cortical thickness in the MBI group’s right parahippocampal ( p = 0.01) and supramarginal gyri ( p = 0.002). After multiple comparison correction, only the right supramarginal gyrus was significantly smaller ( p = 0.02). When considering only MBI emotional dysregulation, the right parahippocampal and supramarginal gyrus’ cortical thicknesses were significantly smaller in this MBI group ( p = 0.03, 0.01). However, multiple comparison correction identified no significant differences ( p = 0.14, 0.11). Conclusion: Overall MBI and the emotional dysregulation domains were associated with reduced cortical thickness in the right parahippocampal and supramarginal gyri. Since neurodegeneration in the medial temporal and parietal lobe precedes early Alzheimer’s disease (AD), MBI, particularly emotion dysregulation, may predict early AD below the diagnostic threshold.