Differences in functional connectivity amongst older adults with mild cognitive impairment, subjective cognitive decline or normal cognition

Abstract

AbstractBackgroundSubjective cognitive decline (SCD), hypothesized as a preclinical stage of Alzheimer’s disease (AD), describes individuals with subjective cognitive concerns despite normal performance on cognitive tests (Jessen et al., 2014). The reduced ability of the salience network (SN) to control switching between the central executive network (CEN) and the default mode network (DMN) has been linked to deterioration of cognitive functioning in normal aging, mild cognitive impairment (MCI) and AD dementia (He et al., 2014). Since alterations in functional connectivity between these networks have been implicated in MCI and AD, we compared connectivity of the SN with CEN and DMN amongst SCD, MCI and older adults who were cognitively unimpaired (CU). We predicted that SCD would show reduced SN connectivity between CEN and DMN networks compared to CU, but greater connectivity compared to MCI.MethodParticipants were 72 older adults [39 females, mean age=71.5] who were classified as either CU (n=26), SCD (n=29), or MCI (n=17). CU reported no memory concerns and performed within normal limits on neuropsychological (NP) assessments. SCD was established by affirmative responses to “Do you feel like your memory is becoming worse?” “If so, are you worried?” and normal NP test performance. MCI was based on the presence of subjective cognitive concerns and impairment on ≥ 2 NP measures within a cognitive domain, and functional independence. Participants underwent resting state functional magnetic resonance imaging (rs‐fMRI) for 6 minutes in an awake state with their eyes closed using gradient‐echo EPI BOLD at 3T (TR=2000ms, TE=30ms). Imaging data were processed using CONN toolbox. Seed‐based analysis using left and right frontoinsular cortices as seeds, which are key nodes in the SN network (MNI coordinates: ‐34,24‐,6 and 38,16,6, respectively), was conducted to measure connectivity between SN and the other two networks, CEN and DMN, within each group.ResultGroups did not differ in age, years of education, or sex distribution [F(2,69)=0.415, p=0.66;F(2,69)=2.20, p=0.12;X2(2, N=72)=1.89, p=0.39, respectively]. Results from imaging data analyses will be presented.ConclusionExamination of functional connectivity in SCD can be conducted using rs‐fMRI and may provide a window to the neurobiology of SCD.