Changes in Resting-state Functional Connectivity and Its Relationship with Memory Test Performance in Cognitively Normal and Amnestic Mild Cognitive Impairment Individuals

Abstract

Amnestic Mild Cognitive Impairment (aMCI) is associated with increased risk of progression to Alzheimer’s Disease (AD). Individuals with aMCI primarily present with impairments in memory, particularly delayed recall of verbal and visual material. Resting-state functional connectivity within the Default Mode Network, the prefrontal cortex, posterior cingulate and hippocampus is disturbed in aMCI compared to cognitively normal groups. However, no studies have separately examined the relationship between resting-state functional connectivity, and delayed memory recall performance within both verbal and visual memory domains in cognitively normal and aMCI groups. To examine these relations we used behaviour partial least squares (PLS) analyses with target seed regions in the posterior cingulate cortex and bilateral anterior, middle and posterior hippocampus. Additionally, we also tested for group differences in resting-state functional connectivity with the same seeds. The study cohort comprised 87 participants, who fell into of four clinical groups: control older adult (n =16), subjective cognitive decline (n = 18), aMCI (n =46), and early probable AD (n = 7). Our results revealed decreased resting-state functional connectivity in aMCI and early probable AD compared to control and SCD groups, largely driven by the group differences in right middle hippocampal functional connectivity. For behavioural PLS analyses, the control older adult and subjective cognitive decline groups were combined as cognitively normal group. These results indicated that in the cognitively normal group, functional connectivity between all hippocampal seeds and temporal and parietal regions showed differential relationships between verbal and visual memory performance. These differential relationships were reduced in the aMCI group. It was also found that regions in the frontoparietal and visual networks were functionally connected to the bilateral anterior and posterior hippocampus seeds. These seeds were associated with verbal and visual memory performance in the aMCI group, but not in the cognitively normal group. These results suggest the changes in memory performance assessed by memory tests in the aMCI group were associated with changes in resting-state functional connectivity patterns in the brain. Resting-state functional connectivity in regions located within different networks of the brain have specialised relationships with memory performance in the cognitively normal and aMCI groups.