Functional Connectivity Disruption in Subjective Cognitive Decline and Mild Cognitive Impairment: A Common Pattern of Alterations

Abstract

Functional connectivity (FC) alterations represent a key feature in Alzheimer's Disease (AD) and provide a useful tool to characterize and predict the course of the disease. Those alterations have been also described in Mild Cognitive Impairment (MCI), a prodromal stage of AD. There is a growing interest in detecting AD pathology in the brain in the very early stages of the disorder. Subjective Cognitive Decline (SCD) could represent a preclinical asymptomatic stage of AD but very little is known about this population. In the present work we assessed whether FC disruptions are already present in this stage, and if they share any spatial distribution properties with MCI alterations (a condition known to be highly related to AD). To this end, we measured electromagnetic spontaneous activity with MEG in 39 healthy control elders, 41 elders with SCD and 51 MCI patients. The results showed FC alterations in both SCD and MCI compared to the healthy control group. Interestingly, both groups exhibited a very similar spatial pattern of altered links: a hyper-synchronized anterior network and a posterior network characterized by a decrease in FC. This decrease was more pronounced in the MCI group. These results highlight that elders with SCD present FC alterations. More importantly, those disruptions affected AD typically related areas and showed great overlap with the alterations exhibited by MCI patients. These results support the consideration of SCD as a preclinical stage of AD and may indicate that FC alterations appear very early in the course of the disease.

Network Disruption in the Preclinical Stages of Alzheimer’s Disease: From Subjective Cognitive Decline to Mild Cognitive Impairment

“…Besides, these results are compatible with previous work from our group reporting a dual pattern change in the FC profile of both MCI and SCD showing anterior hypersynchronization and FC reduction over similar posterior brain regions. 84 Interestingly, we did not find in the present work such a pattern in the nodal degree of SCD group, which could indicate that even though significant synchronization alterations are already present in this group, degree distribution seems to be still relatively preserved compared to MCI patients. Furthermore, SCD group exhibited increased nodal strength in a postcentral node in the theta band.…”

Recurrent and Concurrent Patterns of Regional BOLD Dynamics and Functional Connectivity Dynamics in Cognitive Decline

“…[32]. Moreover, SCD showed intermediate changes of DMN connectivity between MCI and HC[31][33]. Analogously, this study found that SCD showed intermediate changes of DMN-dominated FC/fALFF states, which was in line with previous reports.…”

Functional neuroimaging in subjective cognitive decline: current status and a research path forward

“…However, many groups have also observed lower connectivity between these regions in individuals with SCD [18,[76][77][78][79]. Others have reported no difference from control [60], or intricate patterns of greater and lower functional connectivity in individuals with SCD [51][52][53][54][55], suggesting that a complex reorganization of processing responsibilities across network nodes may occur. Multifaceted patterns of increased and decreased connectivity between regions could reflect breakdown in processing within a subnetwork that shifts processing load to more intact components of the broader network.…”