Effect of Alzheimer’s pathology on the functional architecture of memory networks during rest and task states in aging

Abstract

AbstractBackgroundIntrinsic brain networks are relatively consistently organized between rest and task states in young individuals. We performed this study in order to determine whether the same is true in aging, and whether measures of AD pathology affect this relationship.MethodWe used task‐based (mnemonic discrimination task with object and scene stimuli) and rest fMRI to measure functional connectivity (FC) in an anterior temporal (AT) and posteromedial (PM) network in older (OA; N=49, 74±5 years, 31F) and younger adults (YA; N=24, 27±4 years, 9F). We calculated the correlation between rest and task FC states by conducting a Pearson’s correlation between the rest and task FC matrices for each participant. We used PiB‐PET to measure global Aβ (using threshold of 1.065 to classify OA as PiB+/‐) and FTP‐PET to measure tau within an AT and PM composite ROI in OA. We also measured recognition memory performance during the mnemonic discrimination task requiring discrimination of repeated stimuli from lures.ResultResting state and task FC in the ATPM network were less correlated in older compared to younger adults. In addition, less correlated rest vs. task FC was associated with higher levels of FTP in ATPM networks in PiB+ older adults. Finally, less correlated rest vs. task FC was associated with worse recognition performance (among all participants and OA alone) during the object trials.ConclusionThese findings link AD pathology to disruption of the functional architecture of intrinsic brain networks during rest and memory task states in OA. They also suggest that memory decline in some older adults may be influenced by the extent of change in functional architecture between rest and task demands. Overall, dynamic FC changes from rest to task may provide a novel mechanism in which aging impacts cognition.