Association between mild behavioral impairment and hippocampal structural covariance in amnestic mild cognitive impairment

Abstract

AbstractBackgroundOur previous work reported that mild cognitive impairment (MCI) patients with multiple mild behavioral impairment (MBI) domain symptoms (complex group) revealed a higher risk of developing Alzheimer’s disease (AD) compared with those with no MBI symptoms (asymptomatic group) and cortical thinning in the parietal and frontal areas. However, MCI patients with only affective dysregulation (affective dysregulation group) were not associated with the risk of AD and revealed relative cortical thickening (Yoon EJ, Front Aging Neurosci 2023). To clarify relationships of cortical thickness changes and risk of progression to AD in MCI patients, we compared structural covariance patterns between hippocampal volume and cortical thickness among the MBI subgroups.MethodA total 201 older adults with amnestic MCI were classified based on profiles of MBI domain symptoms into asymptomatic, affective dysregulation, and complex groups. The FreeSurfer was used to estimate cortical thickness and volumes of hippocampal subfields (Fig 1). A vertex‐wise general linear interaction model was used to compare group map of covariance between volumes of hippocampus subfields and thickness at each of vertices. Correlations between the thickness in regions showing significant group differences and mini‐mental state examination (MMSE) scores were also assessed.ResultIn the affective dysregulation group, the structural covariance of left CA1, CA4/DG and molecular layer were increased in the left superior and inferior parietal cortex (Fig 2a), and the thickness of this region showed positive correlation with MMSE (spearman’s rho = 0.302, p‐value = 0.046). The structural covariance of left hippocampal tail for the affective dysregulation group was increased in left lateral occipital cortex, and those for the complex group was increased in left inferior parietal and lateral occipital cortex compared with the asymptomatic group (Fig 2b). Also, the complex group revealed decreased structural covariance of right subiculum with left rostral middle frontal cortex (Fig 2c).ConclusionOur findings suggest that the lateral parietal area might have an important role in compensatory mechanisms in the affective dysregulation group. On the other hand, the complex group may be associated with more advanced stages of disease in which the patterns of increased covariance of hippocampal subfields were disappeared or inversed.