Functional connectivity changes in two cortico-hippocampal networks of Alzheimer's disease continuum and their correlations with cognition: A SILCODE study.

Background: The anterior-temporal (AT) and posterior-medial (PM) networks have been proposed to play pivotal roles in the memory processing associated with Alzheimer's disease (AD). Nevertheless, these two networks' intrinsic functional coupling characteristics are still vague in different AD stages.

Objective: To explore the functional connectivity (FC) alterations within and across the AT&PM networks in patients with dementia of the Alzheimer's type (DAT), mild cognitive impairment (MCI), subjective cognitive decline (SCD), and normal controls (NC).

Methods: A total of 368 participants over 50 years old from the SILCODE study were recruited, including 99 NC, 134 SCD, 67 MCI, and 68 DAT patients. All the participants underwent a resting-state functional magnetic resonance imaging scan and a battery of neuropsychological tests. The 56 regions-of-interest of the AT&PM networks were defined broadly following existing literature. The FCs were calculated using DPABINet and compared among these four groups. Correlation analyses were performed on FCs and cognitive tests.

Results: Analysis of variance of all four groups showed significant alteration, mainly in the PM networks. Compared to NC, globally decreased FCs regarding AT&PM networks were observed in DAT and MCI patients, while globally increased FCs regarding AT&PM networks were observed in SCD. The decreased FCs in DAT were significantly correlated with the neuropsychological test on the memory domain.

Conclusions: The FC alteration showed different patterns across the AD continuum, especially in individuals with SCD. The elevated FCs in the AT&PM networks of SCD may implicate certain compensating processes in the early stage of AD.