P2‐353: Signal Coherence in the Hippocampus Is Related to Its Functional Isolation, Preclinical Alzheimer's Disease Pathology and Memory in Aging
Year: 2019
Type: article
Study design: Observational Study
Abstract: The hippocampus is targeted by tau pathology in aging and Alzheimer's disease. We used measures of hippocampal local resting state fMRI (rs-fMRI) signal synchrony and functional connectivity, combined with PET measures of amyloid (PiB) and tau (FTP) to explore mechanisms through which tau may disrupt normal function and cognition in the aging brain. Eighty-nine older adults (OA; 77±6.1 years, 63% F, 44% PiB+) and 50 young adults (YA; 25±4.4 years, 50% F) underwent 3T rs-fMRI; OA also had PiB and FTP scans. rs-fMRI data were processed to calculate voxelwise regional homogeneity (ReHo), a measure of local functional synchrony, and for conventional functional connectivity (FC) and variability analyses. Mean group ReHo images were created for YA and OA using DARTEL tools for normalization and ReHo was measured in native space with FreeSurfer-derived ROIs. Hippocampal BOLD variability was also quantified in native space. Global PiB DVR and partial volume corrected FTP SUVR regional values were calculated for OA. Memory performance was measured using an episodic memory domain score. In YA, areas of high ReHo include lateral parietotemoporal junction, lateral frontal, precuneus and primary visual areas (Fig. 1A). In contrast, high ReHo regions in OA include the temporal lobe (Fig. 1B). ROI data also reveal that ReHo increases with age in the temporal lobe, including the hippocampus (r=0.35, p<0.001). Higher hippocampal ReHo is predicted by PiB (p=0.02) and FTP (p=0.01) in models adjusting for age, sex and hippocampal volume (Fig. 2AandB). Higher hippocampal ReHo is associated with lower hippocampal BOLD signal variability (r=−0.21, p=0.047) and lower FC between hippocampus tau-vulnerable temporal regions (r=−0.28 p=0.007; Fig. 3). In OA, worse memory performance is predicted by higher hippocampal ReHo (r=−0.29, p=0.01, Fig. 4). In YA, hippocampal ReHo was not related to memory or functional connectivity measures.
Source: Alzheimer s & Dementia
Language: English
Subfield: Cognitive Neuroscience
Field: Neuroscience
Domain: Life Sciences
Open Access status: bronze
OpenAlex ID: W2980395286