The role of corpus callosum sub‐regional volume and its association to interhemispheric functional connectivity in Alzheimer’s disease (AD) and amyloid mild cognitive impairment (amyMCI)

Abstract

AbstractBackgroundPrevious studies demonstrated that when compare to healthy control (HC), patients with AD and amnesic mild cognitive impairment suffered degeneration in corpus callosum (CC) [2], [3]. The volume of CC and its sub‐regions associate with cognitive impairment in AD and MCI[3].Method52 participants (25 healthy controls HC, 16 AD, 11 amyloid MCI), were recruited to undergo structural MRI and Resting state functional MRI (rs‐fMRI) scanning. Data Acquisition T1W Images MRI images were acquired using a Phillips Achieva 3T equipped with 32‐channel phased‐array head coil (Department of Diagnostic Radiology, the University of Hong Kong). A T1W MPRAGE and rs‐fMRI images were obtained. Voxel Mirrored Homotopic Connectivity (VMHC) was calculated based on the method used by Kelly et al 2011 [4] and Zuo et al 2010 [5]. Two‐sample T‐tests were done between diseased groups with HC and VMHC map were created using DPARSF v4.0. CC was segmented and its subregional volume were calculated by Freesurfer (v. 7.1), and were compared using ANCOVA analysis, with age, gender and total intracranial volume as covariates. Association between regional IFC and CC sub‐regional volume were calculated based on the Spearman’s correlation test, with same covariates, using SPSS (v.25.0).ResultCC subregional volume were compared among AD, amyloid MCI and HC groups. There was no significant different in CC volume for AD group. For amyMCI group, the mid‐anterior CC (480.9mm3) was significantly larger than that of the AD (399mm3, p<0.001) and HC (419.8mm3, p <0.05)) group respectively. Also, the whole CC volume of amyMCI (3176.4mm3) was significantly larger than that of HC (2933.8mm3, p<0.05).In correlation analysis between subregional CC volume and regional IFC, the amyMCI group demonstrated significant positive correlation between ant‐CC volume and IFC at inferior frontal operculum gyrus (r=0.827, p=0.022) and inferior frontal triangular gyrus (r=0.844, p=0.017). Positive correlation between Mid‐ant CC volume and IFC at rolandic operculum (r=0.764, p=0.046).ConclusionThe findings demonstrated that anterior and mid‐ant CC volumes and regional IFC are positively correlated. We speculate that CC subregional volume increase promotes the regional IFC to compensate for cognitive deterioration due to amyloid deposition.